Design, synthesis and preliminary antimicrobial evaluation of n-alkyl chain tethered c-5 functionalized bis-isatins

USDA-ARS?s Scientific Manuscript database

A series of N-alkyl tethered C-5 functionalized bis-isatins were synthesized and evaluated for antimicrobial activity against pathogenic microorganisms. The preliminary evaluation studies revealed the compound 4t, with an optimal combination of bromo-substituent at the C-5 position of isatin ring al...

Extended 3{beta}-alkyl steranes and 3-alkyl triaromatic steroids in crude oils and rock extracts

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dahl, J.; Moldowan, J.M.; Summons, R.E.

1995-09-01

In oils and Precambian- to Miocene-age source rocks from varying depositional environments, we have conclusively identified several novel 3-alkyl sterane and triaromatic steroid series, including (1) 3{beta}-n-pentyl steranes, (2) 3{beta}-isopentyl steranes, (3) 3{beta}-n-hexyl steranes, (4) 3{beta}-n-hepatyl steranes, (5) 3,4-dimethyl steranes, (6) 3{beta}-butyl,4-methyl steranes, (7) triaromatic 3-n-pentyl steroids, and (8) triaromatic 3-isopentyl steroids. We have also tentatively identified additional homologs with 3-alkyl substituents as large as C{sub 11}. The relative abundances of these compounds vary substantially between samples, as indicated by (1) the ratio of 3{beta}-n-pentyl steranes to 3{beta}-isopentyl steranes and (2) the ratio of 3-n-pentyl triaromatic steroids to 3-isopentyl triaromaticmore » steroids. These data suggest possible utility for these parameters as tools for oil-source rock correlations and reconstruction of depositional environments. Although no 3-alkyl steroid natural products are currently known, several lines of evidence suggest that 3{beta}-alkyl steroids result from bacterial side-chain additions to diagenetic {delta}{sup 2}-sterenes.« less

Binding of alkylphenols and alkylated non-phenolics to the rainbow trout (Oncorhynchus mykiss) plasma sex steroid-binding protein.

PubMed

Tollefsen, K-E

2007-09-01

Alkylphenols are well-known endocrine disrupters, mediating effects through the estrogen receptor (ER). Although the estrogenic properties of the alkylphenols are well documented, alternative mechanisms of action are poorly described. In the present work, the interaction of a range of alkyl-substituted phenols and alkyl-substituted non-phenolics with the rainbow trout (Oncorhynchus mykiss) sex steroid-binding protein (rtSBP) were determined by competitive ligand-binding studies. The role of alkyl chain length and branching, substituent position, number of alkylated groups, and the requirement of a phenolic ring structure were assessed. The results showed that the rtSBP binds to most chemical structures tested, although the highest affinity was obtained for mono-substituted alkylphenols with a chain length of four to eight methyl groups. Interestingly, rtSBP binding was also observed for non-phenolic compounds such as 4-t-butylcyclohexanol and 4-t-butylnitrobenzene suggesting that the rtSBP has a broad binding specificity for alkylphenols and alkylated non-phenolics.

Influence of alkyl chain length compatibility on microemulsion structure and solubilization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bansal, V.K.; O'Connell, J.P.; Shah, D.O.

1980-06-01

The water solubilization capacity of water/oil microemulsions is studied as a function of alkyl chain length of oil (C/sub 8/ to C/sub 16/), surfactant (C/sub 14/ and C/sub 18/ fatty acid soaps), and alcohol (C/sub 4/ to C/sub 7/). Sodium stearate and sodium myristate were used as surfactants. For n-butanol microemulsions the maximum amount of water solubilized in the microemulsion decreased continuously with increasing oil chain length; for n-heptanol it increased continuously. For n-pentanol and n-hexanol systems, water solubilization reached a maximum when the oil chain length plus alcohol chain length was equal to that of the surfactant. The electricmore » resistance and dielectric constant of the microemulsions also are measured as a function of alkyl chain length of the oil. 48 references.« less

A Concentration-Dependent Insulin Immobilization Behavior of Alkyl-Modified Silica Vesicles: The Impact of Alkyl Chain Length.

PubMed

Zhang, Jun; Zhang, Long; Lei, Chang; Huang, Xiaodan; Yang, Yannan; Yu, Chengzhong

2018-05-01

The insulin immobilization behaviors of silica vesicles (SV) before and after modification with hydrophobic alkyl -C 8 and -C 18 groups have been studied and correlated to the grafted alkyl chain length. In order to minimize the influence from the other structural parameters, monolayered -C 8 or -C 18 groups are grafted onto SV with controlled density. The insulin immobilization capacity of SV is dependent on the initial insulin concentrations (IIC). At high IIC (2.6-3.0 mg/mL), the trend of insulin immobilization capacity of SV is SV-OH > SV-C 8 > SV-C 18 , which is determined mainly by the surface area of SV. At medium IIC (0.6-1.9 mg/mL), the trend changes to SV-C 8 ≥ SV-C 18 > SV-OH as both the surface area and alkyl chain length contribute to the insulin immobilization. At an extremely low IIC, the hydrophobic-hydrophobic interaction between the alkyl group and insulin molecules plays the most significant role. Consequently, SV-C 18 with longer alkyl groups and the highest hydrophobicity show the best insulin enrichment performance compared to SV-C 8 and SV-OH, as evidenced by an insulin detection limit of 0.001 ng/mL in phosphate buffered saline (PBS) and 0.05 ng/mL in artficial urine determined by mass spectrometry (MS).

The 3,7-diazabicyclo[3.3.1]nonane scaffold for subtype selective nicotinic acetylcholine receptor (nAChR) ligands. Part 1: the influence of different hydrogen bond acceptor systems on alkyl and (hetero)aryl substituents.

PubMed

Eibl, Christoph; Tomassoli, Isabelle; Munoz, Lenka; Stokes, Clare; Papke, Roger L; Gündisch, Daniela

2013-12-01

3,7-Diazabicyclo[3.3.1]nonane is a naturally occurring scaffold interacting with nicotinic acetylcholine receptors (nAChRs). When one nitrogen of the 3,7-diazabicyclo[3.3.1]nonane scaffold was implemented in a carboxamide motif displaying a hydrogen bond acceptor (HBA) functionality, compounds with higher affinities and subtype selectivity for α4β2(∗) were obtained. The nature of the HBA system (carboxamide, sulfonamide, urea) had a strong impact on nAChR interaction. High affinity ligands for α4β2(∗) possessed small alkyl chains, small un-substituted hetero-aryl groups or para-substituted phenyl ring systems along with a carboxamide group. Electrophysiological responses of selected 3,7-diazabicyclo[3.3.1]nonane derivatives to Xenopus oocytes expressing various nAChR subtypes showed diverse activation profiles. Compounds with strongest agonistic profiles were obtained with small alkyl groups whereas a shift to partial agonism/antagonism was observed for aryl substituents. Copyright © 2013 Elsevier Ltd. All rights reserved.

Tunneling conductance of amine-linked alkyl chains.

PubMed

Prodan, Emil; Car, Roberto

2008-06-01

The tunneling transport theory developed in ref 9 (Phys. Rev. B 2007, 76, 115102) is applied to molecular devices made of alkyl chains linked to gold electrodes via amine groups. Using the analytic expression of the tunneling conductance derived in our previous work, we identify the key physical quantities that characterize the conductance of these devices. By investigating the transport characteristics of three devices, containing four, six, and eight methyl groups, we extract the dependence of the tunneling conductance on the chain's length, which is an exponential decay law in agreement with recent experimental data.

Aryl sulfonate based anticancer alkylating agents.

PubMed

Sheikh, Hamdullah Khadim; Arshad, Tanzila; Kanwal, Ghazala

2018-05-01

This research work revolves around synthesis of antineoplastic alkylating sulfonate esters with dual alkylating sites for crosslinking of the DNA strands. These molecules were evaluated as potential antineoplastic cross linking alkylating agents by reaction with the nucleoside of Guanine DNA nucleobase at both ends of the synthesized molecule. Synthesis of the alkylating molecules and the crosslinking with the guanosine nucleoside was monitored by MALDITOF mass spectroscopy. The synthesized molecule's crosslinking or adduct forming rate with the nucleoside was compared with that of 1,4 butane disulfonate (busulfan), in form of time taken for the appearance of [M+H] + . It was found that aryl sulfonate leaving group was causing higher rate of nucleophilic attack by the Lewis basic site of the nucleobase. Furthermore, the rate was also found to be a function of electron withdrawing or donating nature of the substituent on the aryl ring. Compound with strong electron withdrawing substituent on the para position of the ring reacted fastest. Hence, new alkylating agents were synthesized with optimized or desired reactivity.

Effect of alkyl chain length on the rotational diffusion of nonpolar and ionic solutes in 1-alkyl-3-methylimidazolium-bis(trifluoromethylsulfonyl)imides.

PubMed

Gangamallaiah, V; Dutt, G B

2013-10-10

Rotational diffusion of a nonpolar solute 9-phenylanthracene (9-PA) and a cationic solute rhodamine 110 (R110) has been examined in a series of 1-alkyl-3-methylimidazolium (alkyl = octyl, decyl, dodecyl, tetradecyl, hexadecyl, and octadecyl) bis(trifluoromethylsulfonyl)imides to understand the influence of alkyl chain length on solute rotation. In this study, reorientation times (τr) have been measured as a function of viscosity (η) by varying the temperature (T) of the solvents. These results have been analyzed using the Stokes-Einstein-Debye (SED) hydrodynamic theory along with the ones obtained for the same solutes in 1-alkyl-3-methylimidazolium (alkyl = methyl, ethyl, propyl, butyl, and hexyl) bis(trifluoromethylsulfonyl)imides (Gangamallaiah and Dutt, J. Phys. Chem. B 2012, 116, 12819-12825). It has been noticed that the data for 9-PA and R110 follows the relation τr = A(η/T)(n) with A being the ratio of hydrodynamic volume of the solute to the Boltzmann constant and n = 1 as envisaged by the SED theory. However, upon increasing the alkyl chain length from methyl to octadecyl significant deviations from the SED theory have been observed especially from the octyl derivative onward. From methyl to octadecyl derivatives, the value of A decreases by a factor of 3 for both the solutes and n by a factor of 1.4 and 1.6 for 9-PA and R110, respectively. These observations have been rationalized by taking into consideration the organized structure of the ionic liquids, whose influence appears to be pronounced when the number of carbon atoms in the alkyl chain attached to the imidazolium cation exceeds eight.

Understanding the effect of alkyl chains of gemini cations on the physicochemical and cellular properties of polyurethane micelles.

PubMed

Pan, Zhicheng; Fang, Danxuan; Song, Yuanqing; Song, Nijia; Ding, Mingming; Li, Jiehua; Luo, Feng; Li, Jianshu; Tan, Hong; Fu, Qiang

2018-06-06

Cationic gemini quaternary ammonium (GQA) has been used as a cell internalization promoter to improve the permeability of the cell membrane and enhance the cellular uptake. However, the effect of the alkyl chain length on the cellular properties of nanocarriers has not been elucidated yet. In this study, we developed a series of polyurethane micelles containing GQAs with various alkyl chain lengths. The alteration of the gemini alkyl chain length was found to change the distribution of GQA surfactants in the micellar structure and affect the surface charge exposure, stability, and the protein absorption properties of nanocarriers. Moreover, we also clarified the role of the alkyl chain length in tumor cell internalization and macrophage uptake of polyurethane micelles. This work provides a new understanding on the effect of the GQA alkyl chain length on the physicochemical and biological properties of nanomedicines, and offers guidance on the rational design of effective drug delivery systems where the issue of functional group exposure at the micellar surface should be considered.

Self-Assembly and Drug Release Capacities of Organogels via Some Amide Compounds with Aromatic Substituent Headgroups

PubMed Central

Zhang, Lexin; Jiao, Tifeng; Ma, Kai; Xing, Ruirui; Liu, Yamei; Xiao, Yong; Zhou, Jingxin; Zhang, Qingrui; Peng, Qiuming

2016-01-01

In this work, some amide compounds with different aromatic substituent headgroups were synthesized and their gelation self-assembly behaviors in 22 solvents were characterized as new gelators. The obtained results indicated that the size of aromatic substituent headgroups in molecular skeletons in gelators showed crucial effect in the gel formation and self-assembly behavior of all compounds in the solvents used. Larger aromatic headgroups in molecular structures in the synthesized gelator molecules are helpful to form various gel nanostructures. Morphological investigations showed that the gelator molecules can self-assembly and stack into various organized aggregates with solvent change, such as wrinkle, belt, rod, and lamella-like structures. Spectral characterizations suggested that there existed various weak interactions including π-π stacking, hydrogen bonding, and hydrophobic forces due to aromatic substituent headgroups and alkyl substituent chains in molecular structures. In addition, the drug release capacities experiments demonstrated that the drug release rate in present obtained gels can be tuned by adjusting the concentrations of dye. The present work would open up enormous insight to design and investigate new kind of soft materials with designed molecular structures and tunable drug release performance. PMID:28773663

Multidimensional Self-Assembled Structures of Alkylated Cellulose Oligomers Synthesized via in Vitro Enzymatic Reactions.

PubMed

Yataka, Yusuke; Sawada, Toshiki; Serizawa, Takeshi

2016-10-04

The self-assembly of biomolecules into highly ordered nano-to-macroscale structures is essential in the construction of biological tissues and organs. A variety of biomolecular assemblies composed of nucleic acids, peptides, and lipids have been used as molecular building units for self-assembled materials. However, crystalline polysaccharides have rarely been utilized in self-assembled materials. In this study, we describe multidimensional self-assembled structures of alkylated cellulose oligomers synthesized via in vitro enzymatic reactions. We found that the alkyl chain length drastically affected the assembled morphologies and allomorphs of cellulose moieties. The modulation of the intermolecular interactions of cellulose oligomers by alkyl substituents was highly effective at controlling their assembly into multidimensional structures. This study proposes a new potential of crystalline oligosaccharides for structural components of molecular assemblies with controlled morphologies and crystal structures.

Ultrasonic Relaxation Study of 1-Alkyl-3-methylimidazolium-Based Room-Temperature Ionic Liquids: Probing the Role of Alkyl Chain Length in the Cation.

PubMed

Zorębski, Michał; Zorębski, Edward; Dzida, Marzena; Skowronek, Justyna; Jężak, Sylwia; Goodrich, Peter; Jacquemin, Johan

2016-04-14

Ultrasound absorption spectra of four 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imides were determined as a function of the alkyl chain length on the cation from 1-propyl to 1-hexyl from 293.15 to 323.15 K at ambient pressure. Herein, the ultrasound absorption measurements were carried out using a standard pulse technique within a frequency range from 10 to 300 MHz. Additionally, the speed of sound, density, and viscosity have been measured. The presence of strong dissipative processes during the ultrasound wave propagation was found experimentally, i.e., relaxation processes in the megahertz range were observed for all compounds over the whole temperature range. The relaxation spectra (both relaxation amplitude and relaxation frequency) were shown to be dependent on the alkyl side chain length of the 1-alkyl-3-methylimidazolium ring. In most cases, a single-Debye model described the absorption spectra very well. However, a comparison of the determined spectra with the spectra of a few other imidazolium-based ionic liquids reported in the literature (in part recalculated in this work) shows that the complexity of the spectra increases rapidly with the elongation of the alkyl chain length on the cation. This complexity indicates that both the volume viscosity and the shear viscosity are involved in relaxation processes even in relatively low frequency ranges. As a consequence, the sound velocity dispersion is present at relatively low megahertz frequencies.

Vapor pressures of 1,3-dialkylimidazolium bis(trifluoromethylsulfonyl)imide ionic liquids with long alkyl chains

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rocha, Marisa A. A., E-mail: lbsantos@fc.up.pt, E-mail: marisa.alexandra.rocha@gmail.com; Department of Chemical Engineering and Chemistry, Eindhoven University of Technology, Den Dolech 2, 5612 AZ Eindhoven; Coutinho, João A. P.

2014-10-07

This work presents the vapor pressure at several temperatures for the 1,3-dialkylimidazolium bis(trifluoromethylsulfonyl)imide series, [C{sub N/2}C{sub N/2}im][NTf{sub 2}] (N = 14, 16, 18, and 20), measured by a Knudsen effusion method combined with a quartz crystal microbalance. The thermodynamic properties of vaporization of the ionic liquids under study are analysed together with the results obtained previously for the shorter alkyl chain length [C{sub N/2}C{sub N/2}im][NTf{sub 2}] (N = 2, 4, 6, 8, 10, and 12), in order to evaluate the effect of the alkyl side chains of the cation and to get additional insights concerning the nanostructuration of ionic liquids.more » The symmetry effect is explored, based on the comparison with the asymmetric imidazolium based ionic liquids, [C{sub N-1}C{sub 1}im][NTf{sub 2}]. A trend shift on the thermodynamic properties of vaporization along the alkyl side chains of the extended symmetric ionic liquids, around [C{sub 6}C{sub 6}im][NTf{sub 2}], was detected. An intensification of the odd-even effect was observed starting from [C{sub 6}C{sub 6}im][NTf{sub 2}], with higher enthalpies and entropies of vaporization for the odd numbered ionic liquids, [C{sub 7}C{sub 7}im][NTf{sub 2}] and [C{sub 9}C{sub 9}im][NTf{sub 2}]. Similar, but less pronounced, odd-even effect was found for the symmetric ionic liquids with lower alkyl side chains length, [C{sub N/2}C{sub N/2}im][NTf{sub 2}] (with N = 4, 6, 8, 10, and 12). This effect is related with the predominant orientation of the terminal methyl group of the alkyl chain to the imidazolium ring and their influence in the cation-anion interaction. The same Critical Alkyl length at the hexyl, (C{sub 6}C{sub 1}and C{sub 6}C{sub 6}) was found for both asymmetric and symmetric series indicating that the nanostructuration of the ionic liquids is related with alkyl chain length.« less

Mechanism of the protective effects of long chain n-alkyl glucopyranosides against ultrasound-induced cytolysis of HL-60 cells.

PubMed

Cheng, Jason Y; Riesz, Peter

2007-07-01

Recently it has been shown that long chain (C5-C8) n-alkyl glucopyranosides completely inhibit ultrasound-induced cytolysis [J.Z. Sostaric, N. Miyoshi, P. Riesz, W.G. DeGraff, and J.B. Mitchell, Free Radical Biol. Med., 39 (2005) 1539]. This protective effect has possible applications in HIFU (high intensity focused ultrasound) for tumor treatment, and in ultrasound assisted drug delivery and gene therapy. n-Alkyl glucopyranosides with hexyl (5mM), heptyl (3mM), octyl (2mM) n-alkyl chains protected 100% of HL-60 cells in vitro from 1.057 MHz ultrasound-induced cytolysis under a range of conditions that resulted in 35-100% cytolysis in the absence of glucopyranosides. However the hydrophilic methyl-beta-d-glucopyranoside did not protect cells. The surface active n-alkyl glucopyranosides accumulate at the gas-liquid interface of cavitation bubbles. The OH radicals and H atoms formed in collapsing cavitation bubbles react by H-atom abstraction from either the n-alkyl chain or the glucose moiety of the n-alkyl glucopyranosides. Owing to the high concentration of the long chain surfactants at the gas-liquid interface of cavitation bubbles, the initially formed carbon radicals on the alkyl chains are transferred to the glucose moieties to yield radicals which react with oxygen leading to the formation of hydrogen peroxide. In this work, we find that the sonochemically produced hydrogen peroxide yields from oxygen-saturated solutions of long chain (hexyl, octyl) n-alkyl glucopyranosides at 614 kHz and 1.057 MHz ultrasound increase with increasing n-alkyl glucopyranoside concentration but are independent of concentration for methyl-beta-D-glucopyranoside. These results are consistent with the previously proposed mechanism of sonoprotection [J.Z. Sostaric, N. Miyoshi, P. Riesz, W.G. DeGraff, and J.B. Mitchell, Free Radical Biol. Med., 39 (2005) 1539]. This sequence of events prevents sonodynamic cell killing by initiation of lipid peroxidation chain reactions in cellular

The effect of the cation alkyl chain branching on mutual solubilities with water and toxicities.

PubMed

Kurnia, Kiki A; Sintra, Tânia E; Neves, Catarina M S S; Shimizu, Karina; Canongia Lopes, José N; Gonçalves, Fernando; Ventura, Sónia P M; Freire, Mara G; Santos, Luís M N B F; Coutinho, João A P

2014-10-07

The design of ionic liquids has been focused on the cation-anion combinations but other more subtle approaches can be used. In this work the effect of the branching of the cation alkyl chain on the design of ionic liquids (ILs) is evaluated. The mutual solubilities with water and toxicities of a series of bis(trifluoromethylsulfonyl)-based ILs, combined with imidazolium, pyridinium, pyrrolidinium, and piperidinium cations with linear or branched alkyl chains, are reported. The mutual solubility measurements were carried out in the temperature range from (288.15 to 323.15) K. From the obtained experimental data, the thermodynamic properties of the solution (in the water-rich phase) were determined and discussed. The COnductor like Screening MOdel for Real Solvents (COSMO-RS) was used to predict the liquid-liquid equilibrium. Furthermore, molecular dynamic simulations were also carried out aiming to get a deeper understanding of these fluids at the molecular level. The results show that the increase in the number of atoms at the cation ring (from five to six) leads to a decrease in the mutual solubilities with water while increasing their toxicity, and as expected from the well-established relationship between toxicities and hydrophobicities of ILs. The branching of the alkyl chain was observed to decrease the water solubility in ILs, while increasing the ILs solubility in water. The inability of COSMO-RS to correctly predict the effect of branching alkyl chains toward water solubility on them was confirmed using molecular dynamic simulations to be due to the formation of nano-segregated structures of the ILs that are not taken into account by the COSMO-RS model. In addition, the impact of branched alkyl chains on the toxicity is shown to be not trivial and to depend on the aromatic nature of the ILs.

Effect of Partially Fluorinated N-Alkyl-Substituted Piperidine-2-carboxamides on Pharmacologically Relevant Properties.

PubMed

Vorberg, Raffael; Trapp, Nils; Zimmerli, Daniel; Wagner, Björn; Fischer, Holger; Kratochwil, Nicole A; Kansy, Manfred; Carreira, Erick M; Müller, Klaus

2016-10-06

The modulation of pharmacologically relevant properties of N-alkyl-piperidine-2-carboxamides was studied by selective introduction of 1-3 fluorine atoms into the n-propyl and n-butyl side chains of the local anesthetics ropivacaine and levobupivacaine. The basicity modulation by nearby fluorine substituents is essentially additive and exhibits an exponential attenuation as a function of topological distance between fluorine and the basic center. The intrinsic lipophilicity of the neutral piperidine derivatives displays the characteristic response noted for partially fluorinated alkyl groups attached to neutral heteroaryl systems. However, basicity decrease by nearby fluorine substituents affects lipophilicities at neutral pH, so that all partially fluorinated derivatives are of similar or higher lipophilicity than their non-fluorinated parents. Aqueous solubilities were found to correlate inversely with lipophilicity with a significant contribution from crystal packing energies, as indicated by variations in melting point temperatures. All fluorinated derivatives were found to be somewhat more readily oxidized in human liver microsomes, the rates of degradation correlating with increasing lipophilicity. Because the piperidine-2-carboxamide core is chiral, pairs with enantiomeric N-alkyl groups are diastereomeric. While little response to such stereoisomerism was observed for basicity or lipophilicity, more pronounced variations were observed for melting point temperatures and oxidative degradation. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Exploring Alkyl Chains in Benzobisthiazole-Naphthobisthiadiazole Polymers: Impact on Solar-Cell Performance, Crystalline Structures, and Optoelectronics.

PubMed

Al-Naamani, Eman; Gopal, Anesh; Ide, Marina; Osaka, Itaru; Saeki, Akinori

2017-11-01

The shapes and lengths of the alkyl chains of conjugated polymers greatly affect the efficiencies of organic photovoltaic devices. This often results in a trade-off between solubility and self-organizing behavior; however, each material has specific optimal chains. Here we report on the effect of alkyl side chains on the film morphologies, crystallinities, and optoelectronic properties of new benzobisthiazole-naphthobisthiadiazole (PBBT-NTz) polymers. The power conversion efficiencies (PCEs) of linear-branched and all-branched polymers range from 2.5% to 6.6%; the variations in these PCEs are investigated by atomic force microscopy, two-dimensional X-ray diffraction (2D-GIXRD), and transient photoconductivity techniques. The best-performing linear-branched polymer, bearing dodecyl and decyltetradecyl chains (C12-DT), exhibits nanometer-scale fibers along with the highest crystallinity, comprising predominant edge-on and partial face-on orientations. This morphology leads to the highest photoconductivity and the longest carrier lifetime. These results highlight the importance of long alkyl chains for inducing intermolecular stacking, which is in contrast to observations made for analogous previously reported polymers.

Critical role of alkyl chain branching of organic semiconductors in enabling solution-processed N-channel organic thin-film transistors with mobility of up to 3.50 cm² V(-1) s(-1).

PubMed

Zhang, Fengjiao; Hu, Yunbin; Schuettfort, Torben; Di, Chong-an; Gao, Xike; McNeill, Christopher R; Thomsen, Lars; Mannsfeld, Stefan C B; Yuan, Wei; Sirringhaus, Henning; Zhu, Daoben

2013-02-13

Substituted side chains are fundamental units in solution processable organic semiconductors in order to achieve a balance of close intermolecular stacking, high crystallinity, and good compatibility with different wet techniques. Based on four air-stable solution-processed naphthalene diimides fused with 2-(1,3-dithiol-2-ylidene)malononitrile groups (NDI-DTYM2) that bear branched alkyl chains with varied side-chain length and different branching position, we have carried out systematic studies on the relationship between film microstructure and charge transport in their organic thin-film transistors (OTFTs). In particular synchrotron measurements (grazing incidence X-ray diffraction and near-edge X-ray absorption fine structure) are combined with device optimization studies to probe the interplay between molecular structure, molecular packing, and OTFT mobility. It is found that the side-chain length has a moderate influence on thin-film microstructure but leads to only limited changes in OTFT performance. In contrast, the position of branching point results in subtle, yet critical changes in molecular packing and leads to dramatic differences in electron mobility ranging from ~0.001 to >3.0 cm(2) V(-1) s(-1). Incorporating a NDI-DTYM2 core with three-branched N-alkyl substituents of C(11,6) results in a dense in-plane molecular packing with an unit cell area of 127 Å(2), larger domain sizes of up to 1000 × 3000 nm(2), and an electron mobility of up to 3.50 cm(2) V(-1) s(-1), which is an unprecedented value for ambient stable n-channel solution-processed OTFTs reported to date. These results demonstrate that variation of the alkyl chain branching point is a powerful strategy for tuning of molecular packing to enable high charge transport mobilities.

Long alkyl-chain imidazolium ionic liquids: Antibiofilm activity against phototrophic biofilms.

PubMed

Reddy, G Kiran Kumar; Nancharaiah, Y V; Venugopalan, V P

2017-07-01

Biofilm formation is problematic and hence undesirable in medical and industrial settings. In addition to bacteria, phototrophic organisms are an integral component of biofilms that develop on surfaces immersed in natural waters. 1-Alkyl-3-methyl imidazolium ionic liquids (IL) with varying alkyl chain length were evaluated for their influence on the formation of monospecies (Navicula sp.) and multispecies biofilms under phototrophic conditions. An IL with a long alkyl side chain, 1-hexadecyl-3-methylimidaazolium chloride ([C 16 (MIM)][Cl]) retarded growth, adhesion and biofilm formation of Navicula sp. at concentrations as low as 5μM. Interestingly, [C 16 (MIM)][Cl] was very effective in preventing multispecies phototrophic biofilms on fibre reinforced plastic surfaces immersed in natural waters (fresh and seawater). SYTOX ® Green staining and chlorophyll leakage assay confirmed that the biocidal activity of the IL was exerted through cell membrane disruption. The data show that [C 16 (MIM)][Cl] is a potent inhibitor of phototrophic biofilms at micromolar concentrations and a promising agent for biofilm control in re-circulating cooling water systems. This is the first report that ionic liquids inhibit biofilm formation by phototrophic organisms which are important members of biofilms in streams and cooling towers. Copyright © 2017 Elsevier B.V. All rights reserved.

Microbial biodegradation of aromatic alkanoic naphthenic acids is affected by the degree of alkyl side chain branching

PubMed Central

Johnson, Richard J; Smith, Ben E; Sutton, Paul A; McGenity, Terry J; Rowland, Steven J; Whitby, Corinne

2011-01-01

Naphthenic acids (NAs) occur naturally in oil sands and enter the environment through natural and anthropogenic processes. NAs comprise toxic carboxylic acids that are difficult to degrade. Information on NA biodegradation mechanisms is limited, and there are no studies on alkyl branched aromatic alkanoic acid biodegradation, despite their contribution to NA toxicity and recalcitrance. Increased alkyl side chain branching has been proposed to explain NA recalcitrance. Using soil enrichments, we examined the biodegradation of four aromatic alkanoic acid isomers that differed in alkyl side chain branching: (4′-n-butylphenyl)-4-butanoic acid (n-BPBA, least branched); (4′-iso-butylphenyl)-4-butanoic acid (iso-BPBA); (4′-sec-butylphenyl)-4-butanoic acid (sec-BPBA) and (4′-tert-butylphenyl)-4-butanoic acid (tert-BPBA, most branched). n-BPBA was completely metabolized within 49 days. Mass spectral analysis confirmed that the more branched isomers iso-, sec- and tert-BPBA were transformed to their butylphenylethanoic acid (BPEA) counterparts at 14 days. The BPEA metabolites were generally less toxic than BPBAs as determined by Microtox assay. n-BPEA was further transformed to a diacid, showing that carboxylation of the alkyl side chain occurred. In each case, biodegradation of the carboxyl side chain proceeded through beta-oxidation, which depended on the degree of alkyl side chain branching, and a BPBA degradation pathway is proposed. Comparison of 16S rRNA gene sequences at days 0 and 49 showed an increase and high abundance at day 49 of Pseudomonas (sec-BPBA), Burkholderia (n-, iso-, tert-BPBA) and Sphingomonas (n-, sec-BPBA). PMID:20962873

Alkyl chain interaction at the surface of room temperature ionic liquids: systematic variation of alkyl chain length (R = C(1)-C(4), C(8)) in both cation and anion of [RMIM][R-OSO(3)] by sum frequency generation and surface tension.

PubMed

Santos, Cherry S; Baldelli, Steven

2009-01-29

The gas-liquid interface of halide-free 1,3-dialkylimidazolium alkyl sulfates [RMIM][R-OSO(3)] with R chain length from C(1)-C(4) and C(8) has been studied systematically using the surface-specific sum frequency generation (SFG) vibrational spectroscopy and surface tension measurements. From the SFG spectra, vibrational modes from the methyl group of both cation and anion are observed for all ionic liquid samples considered in the present study. These results suggest the presence of both ions at the gas-liquid interface, which is further supported by surface tension measurements. Surface tension data show a decreasing trend as the alkyl chain in the imidazolium cation is varied from methyl to butyl chain, with a specific anion. A similar trend is observed when the alkyl chain of the anion is modified and the cation is fixed.

Connecting Structural and Transport Properties of Ionic Liquids with Cationic Oligoether Chains

DOE PAGES

Lall-Ramnarine, Sharon I.; Zhao, Man; Rodriguez, Chanele; ...

2017-06-01

We used X-ray diffraction and molecular dynamics simulations to probe the structures of two families of ionic liquids containing oligoether tails on the cations. Imidazolium and pyrrolidinium bis(trifluoromethylsulfonyl)amide ILs with side chains ranging from 4 to 10 atoms in length, including both linear alkyl and oligo-ethylene oxide tails, were prepared. Furthermore, their physical properties, such as viscosity, conductivity and thermal profile, were measured and compared for systematic trends. Consistent with earlier literature, a single ether substituent substantially decreases the viscosity of pyrrolidinium and imidazolium ILs compared to their alkyl congeners. Remarkably, as the number of ether units in the pyrrolidiniummore » ILs increases there is hardly any increase in the viscosity, in contrast to alkylpyrrolidinium ILs where the viscosity increases steadily with chain length. Viscosities of imidazolium ether ILs increase with chain length but always remain well below their alkyl congeners. To complement the experimentally determined properties, molecular dynamics simulations were run on the two ILs with the longest ether chains. Our results point to specific aspects that could be useful for researchers designing ILs for specific applications.« less

Sources and proxy potential of long chain alkyl diols in lacustrine environments

NASA Astrophysics Data System (ADS)

Rampen, Sebastiaan W.; Datema, Mariska; Rodrigo-Gámiz, Marta; Schouten, Stefan; Reichart, Gert-Jan; Sinninghe Damsté, Jaap S.

2014-11-01

Long chain 1,13- and 1,15-alkyl diols form the base of a number of recently proposed proxies used for climate reconstruction. However, the sources of these lipids and environmental controls on their distribution are still poorly constrained. We have analyzed the long chain alkyl diol (LCD) composition of cultures of ten eustigmatophyte species, with three species from different families grown at various temperatures, to identify the effect of species composition and growth temperature on the LCD distribution. The results were compared with the LCD distribution of sixty-two lake surface sediments, and with previously reported LCD distributions from marine environments. The different families within the Eustigmatophyceae show distinct LCD patterns, with the freshwater family Eustigmataceae most closely resembling LCD distributions in both marine and lake environments. Unlike the other two eustigmatophyte families analyzed (Monodopsidaceae and Goniochloridaceae), C28 and C30 1,13-alkyl diols and C30 and C32 1,15-alkyl diols are all relatively abundant in the family Eustigmataceae, while the mono-unsaturated C32 1,15-alkyl diol was below detection limit. In contrast to the marine environment, LCD distributions in lakes did not show a clear relationship with temperature. The Long chain Diol Index (LDI), a proxy previously proposed for sea surface temperature reconstruction, showed a relatively weak correlation (R2 = 0.33) with mean annual air temperature used as an approximation for annual mean surface temperature of the lakes. A much-improved correlation (R2 = 0.74, p-value <0.001) was observed applying a multiple linear regression analysis between LCD distributions and lake temperatures reconstructed using branched tetraether lipid distributions. The obtained regression model provides good estimates of temperatures for cultures of the family Eustigmataceae, suggesting that algae belonging to this family have an important role as a source for LCDs in lacustrine

Interplay between alkyl chain asymmetry and cholesterol addition in the rigid ion pair amphiphile bilayer systems

NASA Astrophysics Data System (ADS)

Huang, Fong-yin; Chiu, Chi-cheng

2017-01-01

Ion pair amphiphile (IPA), a molecular complex composed of a pair of cationic and anionic surfactants, has been proposed as a novel phospholipid substitute. Controlling the physical stability of IPA vesicles is important for its application developments such as cosmetic and drug deliveries. To investigate the effects of IPA alkyl chain combinations and the cholesterol additive on the structural and mechanical properties of IPA vesicular bilayers, we conducted a series of molecular dynamics studies on the hexadecyltrimethylammonium-dodecylsulfate (HTMA-DS) and dodecyltrimethylammonium-hexadecylsulfate (DTMA-HS) IPA bilayers with cholesterol. We found that both IPA bilayers are in the gel phase at 298 K, consistent with experimental observations. Compared with the HTMA-DS system, the DTMA-HS bilayer has more disordered alkyl chains in the hydrophobic region. When adding cholesterol, it induces alkyl chain ordering around its rigid sterol ring. Yet, cholesterol increases the molecular areas for all species and disturbs the molecular packing near the hydrophilic region and the bilayer core. Cholesterol also promotes the alkyl chain mismatch between the IPA moieties, especially for the DTMA-HS bilayer. The combined effects lead to non-monotonically enhancement of the membrane mechanical moduli for both IPA-cholesterol systems. Furthermore, cholesterol can form H-bonds with the alkylsulfate and thus enhance the contribution of alkylsulfate to the overall mechanical moduli. Combined results provide valuable molecular insights into the roles of each IPA component and the cholesterol on modulating the IPA bilayer properties.

N-alkyl functionalised expanded ring N-heterocyclic carbene complexes of rhodium(I) and iridium(I): structural investigations and preliminary catalytic evaluation.

PubMed

Dunsford, Jay J; Tromp, Dorette S; Cavell, Kingsley J; Elsevier, Cornelis J; Kariuki, Benson M

2013-05-28

A series of new N-alkyl functionalised 6- and 7-membered expanded ring N-heterocyclic carbene (NHC) pro-ligands 3-6 and their corresponding complexes of rhodium(I) and iridium(I), [M(NHC)(COD)Cl] 7-14 and [M(NHC)(CO)2Cl] 15-22 are described. The complexes have been characterised by (1)H and (13)C{(1)H} NMR, mass spectrometry, IR and X-ray diffraction. It is noted from X-ray diffraction studies that the N-alkyl substituents are found to orientate themselves away from the metal centre due to unfavourable steric interactions resulting in low percent buried volume (%V(bur)) values in the solid state. The heterocycle ring size is also found to dictate the spatial orientation of the N-alkyl substituents in the neopentyl functionalised derivatives 10 and 14. The 7-membered derivative 14 allows for a conformational 'twist' of the heterocycle ring with the N-alkyl substituents adopting a mutually trans configuration with respect to each other, while the more rigid 6-membered system 10 does not allow for this conformational 'twist' and consequently the N-alkyl substituents adopt a mutually cis configuration. The σ-donor function of this new class of expanded ring NHC ligand has also been probed by measured IR stretching frequencies of the [M(NHC)(CO)2Cl] complexes 15-22. A preliminary catalytic survey of the hydrogenation of functionalised alkenes with molecular hydrogen under mild conditions has also been undertaken with complex , affording an insight into the application of large ring NHC ancillary ligands bearing N-alkyl substituents in hydrogenation transformations.

Parallel and automated library synthesis of 2-long alkyl chain benzoazoles and azole[4,5-b]pyridines under microwave irradiation.

PubMed

Martínez-Palou, Rafael; Zepeda, L Gerardo; Höpfl, Herbert; Montoya, Ascensión; Guzmán-Lucero, Diego J; Guzmán, Javier

2005-01-01

A versatile route to 40-membered library of 2-long alkyl chain substituted benzoazoles (1 and 2) and azole[4,5-b]pyridines (3 and 4) via microwave-assisted combinatorial synthesis was developed. The reactions were carried out in both monomode and multimode microwave oven. With the latter, all reactions were performed in high-throughput experimental settings consisting of an 8 x 5 combinatorial library designed to synthesize 40 compounds. Each step, from the addition of reagents to the recovery of final products, was automated. The microwave-assisted N-long chain alkylation reactions of 2-alkyl-1H-benzimidazole (1) and 2-alkyl-1H-benzimidazole[4,5-b] pyridines (3) were also studied.

Effects of alkyl chain length and solvents on thermodynamic dissociation constants of the ionic liquids with one carboxyl group in the alkyl chain of imidazolium cations.

PubMed

Chen, Yuehua; Wang, Huiyong; Wang, Jianji

2014-05-01

Thermodynamic dissociation constants of the Brønsted acidic ionic liquids (ILs) are important for their catalytic and separation applications. In this work, a series of imidazolium bromides with one carboxylic acid substitute group in their alkyl chain ([{(CH2)nCOOH}mim]Br, n = 1,3,5,7) have been synthesized, and their dissociation constants (pKa) at different ionic strengths have been determined in aqueous and aqueous organic solvents at 0.1 mole fraction (x) of ethanol, glycol, iso-propanol, and dimethyl sulfoxide by potentiometric titrations at 298.2 K. The standard thermodynamic dissociation constants (pKa(T)) of the ILs in these solvents were calculated from the extended Debye-Hückel equation. It was found that the pKa values increased with the increase of ionic strength of the media and of the addition of organic solvent in water. The pKa(T) values also increased with the increase of the alkyl chain length of cations of the ILs. In addition, the effect of solvent nature on pKa(T) values is interpreted from solvation of the dissociation components and their Gibbs energy of transfer from water to aqueous organic solutions.

Pseudomonas aeruginosa cytochrome c551 denaturation by five systematic urea derivatives that differ in the alkyl chain length.

PubMed

Kobayashi, Shinya; Fujii, Sotaro; Koga, Aya; Wakai, Satoshi; Matubayasi, Nobuyuki; Sambongi, Yoshihiro

2017-07-01

Reversible denaturation of Pseudomonas aeruginosa cytochrome c 551 (PAc 551 ) could be followed using five systematic urea derivatives that differ in the alkyl chain length, i.e. urea, N-methylurea (MU), N-ethylurea (EU), N-propylurea (PU), and N-butylurea (BU). The BU concentration was the lowest required for the PAc 551 denaturation, those of PU, EU, MU, and urea being gradually higher. Furthermore, the accessible surface area difference upon PAc 551 denaturation caused by BU was found to be the highest, those by PU, EU, MU, and urea being gradually lower. These findings indicate that urea derivatives with longer alkyl chains are stronger denaturants. In this study, as many as five systematic urea derivatives could be applied for the reversible denaturation of a single protein, PAc 551 , for the first time, and the effects of the alkyl chain length on protein denaturation were systematically verified by means of thermodynamic parameters.

Activated-Sludge Nitrification in the Presence of Linear and Branched-Chain Alkyl Benzene Sulfonates

PubMed Central

Baillod, Charles R.; Boyle, W. C.

1968-01-01

The effects of biodegradable linear alkyl benzene sulfonate and branched-chain alkyl benzene sulfonate detergents on activated-sludge nitrification were investigated by administering a synthetic waste containing up to 23 mg of each detergent per liter to eight bench-scale, batch, activated-sludge units. It was found that both detergents tended to promote complete oxidation of ammonia to nitrate, whereas control units produced approximately equal amounts of nitrite and nitrate. Various hypotheses are offered to explain the phenomenon. PMID:5636474

Effect of the alkyl chain length on the rotational dynamics of nonpolar and dipolar solutes in a series of N-alkyl-N-methylmorpholinium ionic liquids.

PubMed

Khara, Dinesh Chandra; Kumar, Jaini Praveen; Mondal, Navendu; Samanta, Anunay

2013-05-02

Rotational dynamics of two dipolar solutes, 4-aminophthalimide (AP) and 6-propionyl-2-dimethylaminonaphthalene (PRODAN), and a nonpolar solute, anthracene, have been studied in N-alkyl-N-methylmorpholinium (alkyl = ethyl, butyl, hexyl, and octyl) bis(trifluoromethansulfonyl)imide (Tf2N) ionic liquids as a function of temperature and excitation wavelength to probe the microheterogeneous nature of these ionic liquids, which are recently reported to be more structured than the imidazolium ionic liquids (Khara and Samanta, J. Phys. Chem. B2012, 116, 13430-13438). Analysis of the measured rotational time constants of the solutes in terms of the Stokes-Einstein-Debye (SED) hydrodynamic theory reveals that with increase in the alkyl chain length attached to the cationic component of the ionic liquids, AP shows stick to superstick behavior, PRODAN rotation lies between stick and slip boundary conditions, whereas anthracene exhibits slip to sub slip behavior. The contrasting rotational dynamics of these probe molecules is a reflection of their location in distinct environments of the ionic liquids thus demonstrating the heterogeneity of these ionic liquids. The microheterogeneity of these media, in particular, those with the long alkyl chain, is further evidence from the excitation wavelength dependence study of the rotational diffusion of the dipolar probe molecules.

Metabolic engineering of Saccharomyces cerevisiae for production of fatty acid short- and branched-chain alkyl esters biodiesel.

PubMed

Teo, Wei Suong; Ling, Hua; Yu, Ai-Qun; Chang, Matthew Wook

2015-01-01

Biodiesel is a mixture of fatty acid short-chain alkyl esters of different fatty acid carbon chain lengths. However, while fatty acid methyl or ethyl esters are useful biodiesel produced commercially, fatty acid esters with branched-chain alcohol moieties have superior fuel properties. Crucially, this includes improved cold flow characteristics, as one of the major problems associated with biodiesel use is poor low-temperature flow properties. Hence, microbial production as a renewable, nontoxic and scalable method to produce fatty acid esters with branched-chain alcohol moieties from biomass is critical. We engineered Saccharomyces cerevisiae to produce fatty acid short- and branched-chain alkyl esters, including ethyl, isobutyl, isoamyl and active amyl esters using endogenously synthesized fatty acids and alcohols. Two wax ester synthase genes (ws2 and Maqu_0168 from Marinobacter sp.) were cloned and expressed. Both enzymes were found to catalyze the formation of fatty acid esters, with different alcohol preferences. To boost the ability of S. cerevisiae to produce the aforementioned esters, negative regulators of the INO1 gene in phospholipid metabolism, Rpd3 and Opi1, were deleted to increase flux towards fatty acyl-CoAs. In addition, five isobutanol pathway enzymes (Ilv2, Ilv5, Ilv3, Aro10, and Adh7) targeted into the mitochondria were overexpressed to enhance production of alcohol precursors. By combining these engineering strategies with high-cell-density fermentation, over 230 mg/L fatty acid short- and branched-chain alkyl esters were produced, which is the highest titer reported in yeast to date. In this work, we engineered the metabolism of S. cerevisiae to produce biodiesels in the form of fatty acid short- and branched-chain alkyl esters, including ethyl, isobutyl, isoamyl and active amyl esters. To our knowledge, this is the first report of the production of fatty acid isobutyl and active amyl esters in S. cerevisiae. Our findings will be useful for

Nickel-Catalyzed Reductive Allylation of Tertiary Alkyl Halides with Allylic Carbonates.

PubMed

Chen, Haifeng; Jia, Xiao; Yu, Yingying; Qian, Qun; Gong, Hegui

2017-10-09

The construction of all C(sp 3 ) quaternary centers has been successfully achieved under Ni-catalyzed cross-electrophile coupling of allylic carbonates with unactivated tertiary alkyl halides. For allylic carbonates bearing C1 or C3 substituents, the reaction affords excellent regioselectivity through the addition of alkyl groups to the unsubstituted allylic carbon terminus. The allylic alkylation method also exhibits excellent functional-group compatibility, and delivers the products with high E selectivity. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

The Identification of Two Arabinosyltransferases from Tomato Reveals Functional Equivalency of Xyloglucan Side Chain Substituents1[W][OPEN

PubMed Central

Schultink, Alex; Cheng, Kun; Park, Yong Bum; Cosgrove, Daniel J.; Pauly, Markus

2013-01-01

Xyloglucan (XyG) is the dominant hemicellulose present in the primary cell walls of dicotyledonous plants. Unlike Arabidopsis (Arabidopsis thaliana) XyG, which contains galactosyl and fucosyl substituents, tomato (Solanum lycopersicum) XyG contains arabinofuranosyl residues. To investigate the biological function of these differing substituents, we used a functional complementation approach. Candidate glycosyltransferases were identified from tomato by using comparative genomics with known XyG galactosyltransferase genes from Arabidopsis. These candidate genes were expressed in an Arabidopsis mutant lacking XyG galactosylation, and two of them resulted in the production of arabinosylated XyG, a structure not previously found in this plant species. These genes may therefore encode XyG arabinofuranosyltransferases. Moreover, the addition of arabinofuranosyl residues to the XyG of this Arabidopsis mutant rescued a growth and cell wall biomechanics phenotype, demonstrating that the function of XyG in plant growth, development, and mechanics has considerable flexibility in terms of the specific residues in the side chains. These experiments also highlight the potential of reengineering the sugar substituents on plant wall polysaccharides without compromising growth or viability. PMID:23893172

Rotational diffusion of nonpolar and ionic solutes in 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imides: is solute rotation always influenced by the length of the alkyl chain on the imidazolium cation?

PubMed

Gangamallaiah, V; Dutt, G B

2012-10-25

In an attempt to find out whether the length of the alkyl chain on the imidazolium cation has a bearing on solute rotation, temperature-dependent fluorescence anisotropies of three structurally similar solutes have been measured in a series of 1-alkyl-3-methylimidazolium (alkyl = methyl, ethyl, propyl, butyl, and hexyl) bis(trifluoromethylsulfonyl)imides. Solute-solvent coupling constants obtained from the experimentally measured reorientation times with the aid of Stokes-Einstein-Debye hydrodynamic theory indicate that there is no influence of the length of the alkyl chain on the rotation of nonpolar, anionic, and cationic solutes 9-phenylanthracene (9-PA), fluorescein (FL), and rhodamine 110 (R110), respectively. It has also been noticed that the rotational diffusion of 9-PA is closer to the predictions of slip hydrodynamics, whereas the rotation of negatively charged FL and positively charged R110 is almost identical and follows stick hydrodynamics in these ionic liquids. Despite having similar shape and size, ionic solutes rotate slower by a factor of 3-4 compared to the nonpolar solute. Interplay of specific and electrostatic interactions between FL and the imidazolium cation of the ionic liquids, and between R110 and the bis(trifluoromethylsulfonyl)imide anion, appear to be responsible for the observed behavior. These results are an indication that the length of the alkyl chain on the imidazolium cation does not alter their physical properties in a manner that has an effect on solute rotation.

C2-Selective Branched Alkylation of Benzimidazoles by Rhodium(I)-Catalyzed C-H Activation.

PubMed

Tran, Gaël; Confair, Danielle; Hesp, Kevin D; Mascitti, Vincent; Ellman, Jonathan A

2017-09-01

Herein, we report a Rh(I)/bisphosphine/K 3 PO 4 catalytic system allowing for the first time the selective branched C-H alkylation of benzimidazoles with Michael acceptors. Branched alkylation with N,N-dimethyl acrylamide was successfully applied to the alkylation of a broad range of benzimidazoles incorporating a variety of N-substituents and with both electron-rich and -poor functionality displayed at different sites of the arene. Moreover, the introduction of a quaternary carbon was achieved by alkylation with ethyl methacrylate. The method was also shown to be applicable to the C2-selective branched alkylation of azabenzimidazoles.

Molecular structure, supramolecular organization and thermotropic phase behavior of N-acylglycine alkyl esters with matched acyl and alkyl chains.

PubMed

Reddy, S Thirupathi; Swamy, Musti J

2017-11-01

N-Acylglycines (NAGs), the endogenous single-tailed lipids present in rat brain and other mammalian tissues, play significant roles in cell physiology and exhibit interesting pharmacological properties. In the present study, a homologous series of N-acylglycine alkyl esters (NAGEs) with matched chains were synthesized and characterized. Results of differential scanning calorimetric studies revealed that all NAGEs exhibit a single sharp phase transition and that the transition enthalpy and entropy show a linear dependence on the N-acyl and ester alkyl chain length. The structure of N-myristoylglycine myristyl ester (NMGME), solved by single-crystal X-ray diffraction, showed that the molecule adopts a linear geometry and revealed that the structure of N-myristoyl glycyl moiety in NMGME is identical to that in N-myristoylglycine. The molecules are packed in layers with the polar functional groups of the ester and amide functionalities located at the center of the layer. The crystal packing is stabilized by NH⋯O hydrogen bonds between the amide CO and NH groups of adjacent molecules as well as by CH⋯O hydrogen bonds between the amide carbonyl and the methylene CH adjacent to the ester carbonyl of neighboring molecules as well as between ester carbonyl and methylene group of the glycine moiety of adjacent molecules. Powder X-ray diffraction studies showed a linear dependence of the d-spacings on the acyl chain length, suggesting that all NAGEs adopt a structure similar to the packing exhibited in the crystal lattice of NMGME. Copyright © 2017 Elsevier B.V. All rights reserved.

Impact of the alkyl chain length on binding of imidazolium-based ionic liquids to bovine serum albumin

NASA Astrophysics Data System (ADS)

Zhang, Mengyue; Wang, Ying; Zhang, Hongmei; Cao, Jian; Fei, Zhenghao; Wang, Yanqing

2018-05-01

The effects of six imidazolium-based ionic liquids (ILs) with different alkyl chain length ([CnMim]Cl, n = 2, 4, 6, 8, 10, 12) on the structure and functions of bovine serum albumin (BSA) were studied by multi-spectral methods and molecular docking. ILs with the longer alkyl chain length have the stronger binding interaction with BSA and the greater conformational damage to protein. The effects of ILs on the functional properties of BSA were further studied by the determination of non-enzyme esterase activity, β-fibrosis and other properties of BSA. The thermal stability of BSA was reduced, the rate of the formation of beta sheet structures of BSA was lowered, and the esterase-like activity of BSA were decreased with the increase of ILs concentration. Simultaneous molecular modeling technique revealed the favorable binding sites of ILs on protein. The hydrophobic force and polar interactions were the mainly binding forces of them. The calculated results are in a good agreement with the spectroscopic experiments. These studies on the impact of the alkyl chain length on binding of imidazolium-based ionic liquids to BSA are of great significance for understanding and developing the application of ionic liquid in life and physiological system.

Certain Chemical Substances Containing Varying Carbon Chain Lengths (Alkyl Ranges Using the Cx-y Notation) on the TSCA Inventory

EPA Pesticide Factsheets

This paper explains the conventions that are applied to certain listings of chemical substances containing ranges of alkyl chain lengths (i.e., carbon chains of varying lengths) for chemical substances on the Toxic Substances Control Act (TSCA)

Polyethylenimine-impregnated mesoporous silica: effect of amine loading and surface alkyl chains on CO2 adsorption.

PubMed

Heydari-Gorji, Aliakbar; Belmabkhout, Youssef; Sayari, Abdelhamid

2011-10-18

Poly(ethyleneimine) (PEI) supported on pore-expanded MCM-41 whose surface is covered with a layer of long-alkyl chains was found to be a more efficient CO(2) adsorbent than PEI supported on the corresponding calcined silica and all PEI-impregnated materials reported in the literature. The layer of surface alkyl chains plays an important role in enhancing the dispersion of PEI, thus decreasing the diffusion resistance. It was also found that at low temperature, adsorbents with relatively low PEI contents are more efficient than their highly loaded counterparts because of the increased adsorption rate. Extensive CO(2) adsorption-desorption cycling showed that the use of humidified feed and purge gases affords materials with enhanced stability, despite limited loss due to amine evaporation. © 2011 American Chemical Society

Molecular design of boronic acid-functionalized squarylium cyanine dyes for multiple discriminant analysis of sialic acid in biological samples: selectivity toward monosaccharides controlled by different alkyl side chain lengths.

PubMed

Ouchi, Kazuki; Colyer, Christa L; Sebaiy, Mahmoud; Zhou, Jin; Maeda, Takeshi; Nakazumi, Hiroyuki; Shibukawa, Masami; Saito, Shingo

2015-02-03

We designed a new series of boronic acid-functionalized squarylium cyanine dyes (SQ-BA) with different lengths of alkyl chain residues, suitable for multiple discriminant analysis (MDA) of sialic acid (Neu5Ac) in biological samples. The SQ-BA dyes form aggregates based on hydrophobic interactions, which result in quenched fluorescence in aqueous solutions. When the boronic acid binds with saccharides, the fluorescence intensity increases as a result of dissociation to the emissive monomeric complex. We inferred that different dye aggregate structures (H-aggregates and J-aggregates) were induced depending on the alkyl chain length, so that monosaccharides would be recognized in different ways (especially, multipoint interaction with J-aggregates). A distinctive emission enhancement of SQ-BA dyes with shorter-alkyl-chains in the presence of Neu5Ac was observed (2.4-fold fluorescence enhancement; with formation constant 10(1.7) M(-1)), with no such enhancement for SQ-BA dyes with longer-alkyl-chain. In addition, various enhancement factors for other monosaccharides were observed depending on the alkyl chain length. Detailed thermodynamic and NMR studies of the SQ-BA complexes revealed the unique recognition mechanism: the dye aggregate with a shorter-alkyl-chain causes the slipped parallel structure and forms a stable 2:1 complex with Neu5Ac, as distinct from longer-alkyl-chain dyes, which form a 1:1 monomeric complex. MDA using the four SQ-BA dyes was performed for human urine samples, resulting in the successful discrimination between normal and abnormal Neu5Ac levels characteristic of disease. Thus, we successfully controlled various responses to similar monosaccharides with a novel approach that chemically modified not the boronic acid moiety itself but the length of the alkyl chain residue attached to the dye in order to generate specificity.

Asymmetric Alkyl Side-Chain Engineering of Naphthalene Diimide-Based n-Type Polymers for Efficient All-Polymer Solar Cells.

PubMed

Jia, Tao; Li, Zhenye; Ying, Lei; Jia, Jianchao; Fan, Baobing; Zhong, Wenkai; Pan, Feilong; He, Penghui; Chen, Junwu; Huang, Fei; Cao, Yong

2018-02-13

The design and synthesis of three n-type conjugated polymers based on a naphthalene diimide-thiophene skeleton are presented. The control polymer, PNDI-2HD, has two identical 2-hexyldecyl side chains, and the other polymers have different alkyl side chains; PNDI-EHDT has a 2-ethylhexyl and a 2-decyltetradecyl side chain, and PNDI-BOOD has a 2-butyloctyl and a 2-octyldodecyl side chain. These copolymers with different alkyl side chains exhibit higher melting and crystallization temperatures, and stronger aggregation in solution, than the control copolymer PNDI-2HD that has the same side chain. Polymer solar cells based on the electron-donating copolymer PTB7-Th and these novel copolymers exhibit nearly the same open-circuit voltage of 0.77 V. Devices based on the copolymer PNDI-BOOD with different side chains have a power-conversion efficiency of up to 6.89%, which is much higher than the 4.30% obtained with the symmetric PNDI-2HD. This improvement can be attributed to the improved charge-carrier mobility and the formation of favorable film morphology. These observations suggest that the molecular design strategy of incorporating different side chains can provide a new and promising approach to developing n-type conjugated polymers. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Synthetic Method for Oligonucleotide Block by Using Alkyl-Chain-Soluble Support.

PubMed

Matsuno, Yuki; Shoji, Takao; Kim, Shokaku; Chiba, Kazuhiro

2016-02-19

A straightforward method for the synthesis of oligonucleotide blocks using a Cbz-type alkyl-chain-soluble support (Z-ACSS) attached to the 3'-OH group of 3'-terminal nucleosides was developed. The Z-ACSS allowed for the preparation of fully protected deoxyribo- and ribo-oligonucleotides without chromatographic purification and released dimer- to tetramer-size oligonucleotide blocks via hydrogenation using a Pd/C catalyst without significant loss or migration of protective groups such as 5'-end 4,4'-dimethoxtrityl, 2-cyanoethyl on internucleotide bonds, or 2'-TBS.

Comprehensive Study on the Impact of the Cation Alkyl Side Chain Length on the Solubility of Water in Ionic Liquids.

PubMed

Kurnia, Kiki A; Neves, Catarina M S S; Freire, Mara G; Santos, Luís M N B F; Coutinho, João A P

2015-10-01

A comprehensive study on the phase behaviour of two sets of ionic liquids (ILs) and their interactions with water is here presented through combining experimental and theoretical approaches. The impact of the alkyl side chain length and the cation symmetry on the water solubility in the asymmetric [C N- 1 C 1 im][NTf 2 ] and symmetric [C N- 1 C N- 1 im][NTf 2 ] series of ILs ( N up to 22), from 288.15 K to 318.15 K and at atmospheric pressure, was studied. The experimental data reveal that the solubility of water in ILs with an asymmetric cation is higher than in those with the symmetric isomer. Several trend shifts on the water solubility as a function of the alkyl side chain length were identified, namely at [C 6 C 1 im][NTf 2 ] for asymmetric ILs and at [C 4 C 4 im][NTf 2 ] and [C 7 C 7 im][NTf 2 ] for the symmetric ILs. To complement the experimental data and to further investigate the molecular-level mechanisms behind the dissolution process, Density Functional Theory calculations, using the Conductor-like Screening Model for Real Solvents (COSMO-RS) and the Electrostatic potential-derived CHelpG, were performed. The COSMO-RS model is able to qualitatively predict water solubility as function of temperature and alkyl chain lengths of both symmetric and asymmetric cations. Furthermore, the model is also capable to predict the somewhat higher water solubility in the asymmetric cation, as well as the trend shift as function of alkyl chain lengths experimentally observed. Both COSMO-RS and the electrostatic potential-derived CHelpG show that the interactions of water and the IL cation take place on the IL polar region, namely on the aromatic head and adjacent methylene groups what explains the differences in water solubility observed for cations with different chain lengths. Furthermore, the CHelpG calculations for the isolated cations in the gas phase indicates that the trend shift of water solubility as function of alkyl chain lengths and the difference of water

Development of Long Chain Alkyl Diol δD as a Paleohydrological Proxy

NASA Astrophysics Data System (ADS)

Neary, A.; Russell, J. M.; Cordero, D.

2017-12-01

Understanding past hydroclimate is important to better understand and prepare for future climate changes. Past hydrological change is often studied through δD of lipid biomarkers preserved in sediment. Long chain alkyl diols are lipid biomarkers that are widely distributed in lake and marine sediments. These compounds are produced by certain species of diatoms and algae (Eustigmatophytes). Diol δD is expected to record relative precipitation and evaporation, and other lake surface processes. This would be a valuable addition to the repertoire of organic compounds used for hydrologic reconstruction, such as leaf waxes which record precipitation. While long chain alkyl diols present an opportunity to expand the range of compounds available for compound specific isotope analysis, studies of diol δD are scarce. This study aims to compare diol and leaf wax δD records from Lake Tanganyika spanning approximately the past 20 kyrs in order to elucidate the controlling factors on diol δD values and evaluate the effectiveness of such a record as a paleohydrological proxy. If viable, diol δD records could be used to gain a deeper understanding of past climates. δD leaf wax records have been previously measured in Lake Tanganyika cores (Tierney et al., 2008). This study measures δD of long chain alkyl diols from the same cores in order to compare records. Our current measurements show significant deviations of the diol record from the leaf wax record at times when large magnitude changes in the leaf wax record are occurring, such as a less pronounced Younger Dryas and a more gradual decrease in δD values after Heinrich 1 than the sudden shift expressed by the leaf wax record. In addition to generating a diol δD record through time at Lake Tanganyika, we have also measured diol δD in surface sediments from several east African lakes in order to examine the potential for a proxy calibration. A positive correlation between diol and lake water δD has been observed

Influence of different amino substituents in position 1 and 4 on spectroscopic and acid base properties of 9,10-anthraquinone moiety

NASA Astrophysics Data System (ADS)

Wcisło, Anna; Niedziałkowski, Paweł; Wnuk, Elżbieta; Zarzeczańska, Dorota; Ossowski, Tadeusz

2013-05-01

A series of novel 1-amino and 1,4-diamino-9,10-anthraquinones, substituted with different alkyl groups, were synthesized as the result of alkylation with amino substituents. All the obtained aminoanthraquinone derivatives were characterized by NMR, IR spectroscopy and mass spectrometry. The spectroscopic properties of these compounds were determined by using UV-Vis spectroscopy in acetonitrile, and in the mixture of acetonitrile and methanol at different pH ranges. The effects of various substituents present in the newly developed anthraquinone derivatives and their ability to form hydrogen bonds between the carbonyl oxygen atom of anthraquinone moiety and nitrogen atom of N-H group in 1-aminoanthraquinone (1-AAQ) and 1,4-diaminoanthraquinone (1,4-DAAQ) were studied. Additionally, the effects of hydrogen bond formation between O-H group in hydroxyethylamino substituent and the carbonyl oxygen atom of anthraquinone were investigated. The spectroscopic behavior of the studied derivatives strongly depended on the solvent-solute interactions and the nature of solvent. The values of pKa for the new anthraquinones were determined by the combined potentiometric and spectrophotometric titration methods.

Alkyl substituent effects on gas-phase acidities - The influence of hybridization.

NASA Technical Reports Server (NTRS)

Brauman, J. I.; Blair, L. K.

1971-01-01

Exploration of the effect on acidity of alkyl groups bonded to trigonal and digonal carbon. Some results on the relative acidities of toluene and p-xylene, and acetylene and substitute acetylenes, as determined by ion cyclotron resonance (icr) spectroscopy, are described. Some limitations of the CNDO/2 calculation method are discussed.

How Does the Alkyl Chain Length of an Ionic Liquid Influence Solute Rotation in the Presence of an Electrolyte?

PubMed

Prabhu, Sugosh R; Dutt, G B

2016-12-29

Fluorescence anisotropies of a nonpolar solute, 9-phenylanthracene (9-PA), have been measured in 1-alkyl-3-methylimidazolium (alkyl = methyl, butyl, octyl, and dodecyl) bis(trifluoromethylsulfonyl)imides ([RMIM][Tf 2 N]) with varying amounts (0-0.3 mole fraction) of lithium bis(trifluoromethylsulfonyl)imide (LiTf 2 N). This study has been carried out to understand how the length of the alkyl chain and the concentration of the electrolyte influence the rotational diffusion of a nonpolar solute. It has been observed that the addition of an electrolyte to the ionic liquid increases the bulk viscosity of the system significantly, as the Li + cations strongly coordinate with the [Tf 2 N] anions in the polar domains. The reorientation times of 9-PA have been analyzed with the aid of Stokes-Einstein-Debye hydrodynamic (SED) theory, and they fall within the broad limits set by the hydrodynamic slip and stick boundary conditions. However, deviations from the SED theory have been noticed upon addition of LiTf 2 N, and the influence of the electrolyte is more pronounced in the case of ionic liquids with shorter alkyl chains. The observed trends have been rationalized in terms of electrolyte-induced structural changes in these ionic liquids.

Chain length effects on the vibrational structure and molecular interactions in the liquid normal alkyl alcohols

NASA Astrophysics Data System (ADS)

Kiefer, Johannes; Wagenfeld, Sabine; Kerlé, Daniela

2018-01-01

Alkyl alcohols are widely used in academia, industry, and our everyday lives, e.g. as cleaning agents and solvents. Vibrational spectroscopy is commonly used to identify and quantify these compounds, but also to study their structure and behavior. However, a comprehensive investigation and comparison of all normal alkanols that are liquid at room temperature has not been performed, surprisingly. This study aims at bridging this gap with a combined experimental and computational effort. For this purpose, the alkyl alcohols from methanol to undecan-1-ol have been analyzed using infrared and Raman spectroscopy. A detailed assignment of the individual peaks is presented and the influence of the alkyl chain length on the hydrogen bonding network is discussed. A 2D vibrational mapping allows a straightforward visualization of the effects. The conclusions drawn from the experimental data are backed up with results from Monte Carlo simulations using the simulation package Cassandra.

Influence of different amino substituents in position 1 and 4 on spectroscopic and acid base properties of 9,10-anthraquinone moiety.

PubMed

Wcisło, Anna; Niedziałkowski, Paweł; Wnuk, Elżbieta; Zarzeczańska, Dorota; Ossowski, Tadeusz

2013-05-01

A series of novel 1-amino and 1,4-diamino-9,10-anthraquinones, substituted with different alkyl groups, were synthesized as the result of alkylation with amino substituents. All the obtained aminoanthraquinone derivatives were characterized by NMR, IR spectroscopy and mass spectrometry. The spectroscopic properties of these compounds were determined by using UV-Vis spectroscopy in acetonitrile, and in the mixture of acetonitrile and methanol at different pH ranges. The effects of various substituents present in the newly developed anthraquinone derivatives and their ability to form hydrogen bonds between the carbonyl oxygen atom of anthraquinone moiety and nitrogen atom of N-H group in 1-aminoanthraquinone (1-AAQ) and 1,4-diaminoanthraquinone (1,4-DAAQ) were studied. Additionally, the effects of hydrogen bond formation between O-H group in hydroxyethylamino substituent and the carbonyl oxygen atom of anthraquinone were investigated. The spectroscopic behavior of the studied derivatives strongly depended on the solvent-solute interactions and the nature of solvent. The values of pKa for the new anthraquinones were determined by the combined potentiometric and spectrophotometric titration methods. Copyright © 2013 Elsevier B.V. All rights reserved.

Exploring backbone-cation alkyl spacers for multi-cation side chain anion exchange membranes

NASA Astrophysics Data System (ADS)

Zhu, Liang; Yu, Xuedi; Hickner, Michael A.

2018-01-01

In order to systematically study how the arrangement of cations on the side chain and length of alkyl spacers between cations impact the performance of multi-cation AEMs for alkaline fuel cells, a series of polyphenylene oxide (PPO)-based AEMs with different cationic side chains were synthesized. This work resulted in samples with two or three cations in a side chain pendant to the PPO backbone. More importantly, the length of the spacer between cations varied from 3 methylene (-CH2-) (C3) groups to 8 methylene (C8) groups. The highest conductivity, up to 99 mS/cm in liquid water at room temperature, was observed for the triple-cation side chain AEM with pentyl (C5) or hexyl (C6) spacers. The multi-cation AEMs were found to have decreased water uptake and ionic conductivity when the spacer chains between cations were lengthened from pentyl (C5) or hexyl (C6) to octyl (C8) linking groups. The triple-cation membranes with pentyl (C5) or hexyl (C6) groups between cations showed greatest stability after immersion in 1 M NaOH at 80 °C for 500 h.

(E)-3-(2-Alkyl-10H-phenothiazin-3-yl)-1-arylprop-2-en-1-ones: Preparative, IR, NMR and DFT study on their substituent-dependent reactivity in hydrazinolysis and sonication-assisted oxidation with copper(II)nitrate.

PubMed

Găină, Luiza; Csámpai, Antal; Túrós, György; Lovász, Tamás; Zsoldos-Mády, Virág; Silberg, Ioan A; Sohár, Pál

2006-12-07

A series of novel 3(5)-aryl/ferrocenyl-5(3)-phenothiazinylpyrazoles and pyrazolines were obtained by substituent-dependent regioselective condensation of the corresponding (E)-3-(2-alkyl-10H-phenothiazin-3-yl)-1-aryl/ferrocenylprop-2-en-1-one with hydrazine or methylhydrazine in acetic acid. The different propensity of the primary formed beta-hydrazino adducts to undergo competitive retro-Mannich reaction was interpreted in terms of tautomerisation equilibrium constants calculated by DFT using a solvent model. The regioselectivity of the cyclisation reactions with methylhydrazine and the substituent-dependent redox properties of pyrazolines were also rationalized by comparative DFT calculations performed for simplified model molecules. On the effect of ultrasound-promoted oxidation with copper(II)nitrate phenothiazine-containing pyrazolines, enones and oxo-compounds were selectively transformed into sulfoxides. Only one sulfoxide enone was partially converted into an oxirane derivative. The structure of the novel products was determined by IR and NMR spectroscopy including COSY, HSQC, HMBC and DNOE measurements.

Density functional theory with van der waals corrections study of the adsorption of alkyl, alkylthiol, alkoxyl, and amino-alkyl chains on the H:Si(111) surface.

PubMed

Arefi, Hadi H; Nolan, Michael; Fagas, Giorgos

2014-11-11

Surface modification of silicon with organic monolayers tethered to the surface by different linkers is an important process in realizing future miniaturized electronic and sensor devices. Understanding the roles played by the nature of the linking group and the chain length on the adsorption structures and stabilities of these assemblies is vital to advance this technology. This paper presents a density functional theory (DFT) study of the hydrogen passivated Si(111) surface modified with alkyl chains of the general formula H:Si-(CH2)n-CH2 and H:Si-X-(CH2)n-CH3, where X = NH, O, S and n = (0, 1, 3, 5, 7, 9, 11), at half coverage. For (X)-hexane and (X)-dodecane functionalization, we also examined various coverages up to full monolayer grafting in order to validate the result of half covered surface and the linker effect on the coverage. We find that it is necessary to take into account the van der Waals interaction between the alkyl chains. The strongest binding is for the oxygen linker, followed by S, N, and C, irrespective of chain length. The result revealed that the sequence of the stability is independent of coverage; however, linkers other than carbon can shift the optimum coverage considerably and allow further packing density. For all linkers apart from sulfur, structural properties, in particular, surface-linker-chain angles, saturate to a single value once n > 3. For sulfur, we identify three regimes, namely, n = 0-3, n = 5-7, and n = 9-11, each with its own characteristic adsorption structures. Where possible, our computational results are shown to be consistent with the available experimental data and show how the fundamental structural properties of modified Si surfaces can be controlled by the choice of linking group and chain length.

Probing the effects of the ester functional group, alkyl side chain length and anions on the bulk nanostructure of ionic liquids: a computational study.

PubMed

Fakhraee, Mostafa; Gholami, Mohammad Reza

2016-04-14

The effects of ester addition on nanostructural properties of biodegradable ILs composed of 1-alkoxycarbonyl-3-alkyl-imidazolium cations ([C1COOCnC1im](+), n = 1, 2, 4) combined with [Br](-), [NO3](-), [BF4](-), [PF6](-), [TfO](-), and [Tf2N](-) were explored by using the molecular dynamics (MD) simulations and quantum theory of atoms in molecules (QTAIM) analysis at 400 K. Various thermodynamic properties of these ILs were extensively computed in our earlier work (Ind. Eng. Chem. Res., 2015, 54, 11678-11700). Nano-scale segregation analysis demonstrates the formation of a small spherical island-like hydrocarbon within the continuous ionic domain for ILs with short alkyl side chain ([C1COOC1C1im]), and a sponge-like nanostructure for the compound with long alkyl side chain ([C1COOC4C1im]). Ester-functionalized ILs with ethyl side chain ([C1COOC2C1im]) are the turning point between two different morphologies. Non-polar channels were observed for [C1COOC4C1im] ILs composed of smaller anions such as [Br] and [NO3], whereas clustering organization was found for the other anions. Formation of the spherical micelle-like nanostructure was seen for lengthened cations. Finally, the incorporation of an ester group into the alkyl side chain of the cation leads to stronger segregation between charged and uncharged networks, which consequently increased the possibility of self-assembly and micelle formation.

Proton affinity of diastereoisomers of modified prolines using the kinetic method and density functional theory calculations: role of the cis/trans substituent on the endo/exo ring conformation.

PubMed

Mezzache, S; Pepe, C; Karoyan, P; Fournier, F; Tabet, J-C

2005-01-01

The proton affinity (PA) of cis/trans-3-prolinoleucines and cis/trans-3-prolinoglutamic acids have been studied by the kinetic method and density functional theory (DFT) calculations. Several conformations of the neutral and the protonated modified prolines, in particular the endo and exo ring conformations, were analyzed with respect to their contribution to the PA values. When the substituent is an alkyl, both the diastereoisomers have the same PA value. However, the PA values for the diastereoisomers are different when the substituted chain contains functional groups (e.g. a carboxyl group). This variation in PA values could be attributed to the existence of intramolecular hydrogen bonds. Copyright (c) 2005 John Wiley & Sons, Ltd.

Association of 2-acylaminopyridines and benzoic acids. Steric and electronic substituent effect studied by XRD, solution and solid-state NMR and calculations

NASA Astrophysics Data System (ADS)

Ośmiałowski, Borys; Kolehmainen, Erkki; Ejsmont, Krzysztof; Ikonen, Satu; Valkonen, Arto; Rissanen, Kari; Nonappa

2013-12-01

Eight single crystal X-ray structures, solid-state NMR spectroscopic, and theoretical studies utilizing QTAIM methodology were used to characterize the 2-acyl (alkyl in acyl = methyl, ethyl, t-butyl, and 1-adamantyl) amino-6-R-pyridine/4-R‧-benzoic acid (R,R‧ = H or Me) cocrystals. As expected among alkyl groups 1-adamantyl due to its bulkiness has the most significant effect on the relative positions of molecules in cocrystals. In addition, the subtle electronic and steric effects by the methyl substituents were observed. The theoretical calculations with full geometry optimizations are in agreement with the experimental findings (geometry, energy of hydrogen bonds). Based on the crystal structures and calculations it is concluded that p-methyl substituent in benzoic acid increase the hydrogen bond accepting ability of the CO oxygen and decreases the hydrogen bond donating ability of OH proton. The 15N solid-state (CP MAS) NMR chemical shifts prove that molecules in cocrystal are held together by hydrogen bonding. The biggest variation in the 15N chemical shift of acylamino nitrogen can be related with the size of the alkyl group in acyl moiety.

Solvent and substituent effects on aggregation constants of perylene bisimide π-stacks--a linear free energy relationship analysis.

PubMed

Chen, Zhijian; Fimmel, Benjamin; Würthner, Frank

2012-08-14

A series of six perylene bisimides (PBIs) with hydrophilic and hydrophobic side chains at the imide nitrogens were applied for a comparative study of the solvent and structural effects on the aggregation behaviour of this class of dyes. A comparison of the binding constants in tetrachloromethane at room temperature revealed the highest binding constant of about 10(5) M(-1) for a PBI bearing 3,4,5-tridodecyloxyphenyl substituents at the imide nitrogens, followed by 3,4,5-tridodecylphenyl and alkyl-substituted PBIs, whereas no aggregation could be observed in the accessible concentration range for PBIs equipped with bulky 2,6-diisopropylphenyl substituents at the imide nitrogens. The aggregation behaviour of three properly soluble compounds was investigated in 17 different solvents covering a broad polarity range from nonpolar n-hexane to highly polar DMSO and water. Linear free energy relationships (LFER) revealed a biphasic behaviour between Gibbs free energies of aggregation and common empirical solvent polarity scales indicating particularly strong π-π stacking interactions in nonpolar aliphatic and polar alcoholic solvents whilst the weakest binding is observed in dichloromethane and chloroform. Accordingly, PBI aggregation is dominated by electrostatic interactions in nonpolar solvents and by solvophobic interactions in protic solvents. In water, the aggregation constant is increased far beyond LFER expectations pointing at a pronounced hydrophobic effect.

Straight-Chain Alkyl Isocyanides Open the Distal Histidine Gate in Crystal Structures of Myoglobin†

PubMed Central

Smith, Rober D.; Blouin, George C.; Johnson, Kenneth A.; Phillips, George N.; Olson, John S.

2014-01-01

Crystal structures of methyl, ethyl, propyl and butyl isocyanide bound to sperm whale myoglobin (Mb) reveal two major conformations. In the in conformer, His(E7) is in a “closed” position, forcing the ligand alkyl chain to point inward. In the out conformer, His(E7) is in an “open” position, allowing the ligand side chain to point outward. A progressive increase in the population of the out conformer is observed with increasing ligand length in P21 crystals of native Mb at pH 7.0. This switch from in to out with increasing ligand size also occurs in solution as measured by the decrease in the relative intensity of the low (~2075 cm 1) versus high frequency (~2125 cm 1) isocyano bands. In contrast, all four isocyanides in P6 crystals of wild type recombinant Mb occupy the in conformation. However, mutating either His64 to Ala, creating a “hole” to solvent, or Phe46 to Val, freeing rotation of His64, causes bound butyl isocyanide to point completely outward in P6 crystals. Thus, the unfavorable hindrance caused with crowding a large alkyl side chain into the distal pocket appears to be roughly equal to that for pushing open the His(E7) gate and is easily affected by crystal packing. This structural conclusion supports the “side path” kinetic mechanism for O2 release, in which the dissociated ligand first moves toward the protein interior and then encounters steric resistance, which is roughly equal to that for escaping to solvent through the His(E7) channel. PMID:20481504

Theoretical investigation on the kinetics and mechanisms of hydroxyl radical-induced transformation of parabens and its consequences for toxicity: Influence of alkyl-chain length.

PubMed

Gao, Yanpeng; Ji, Yuemeng; Li, Guiying; An, Taicheng

2016-03-15

As emerging organic contaminants (EOCs), the ubiquitous presence of preservative parabens in water causes a serious environmental concern. Hydroxyl radical ((•)OH) is a strong oxidant that can degrade EOCs through photochemistry in surface water environments as well as in advanced oxidation processes (AOPs). To better understand the degradation mechanisms, kinetics, and products toxicity of the preservative parabens in aquatic environments and AOPs, the (•)OH-initiated degradation reactions of the four parabens were investigated systematically using a computational approach. The four studied parabens with increase of alkyl-chain length were methylparaben (MPB), ethylparaben (EPB), propylparaben (PPB), and dibutylparaben (BPB). Results showed that the four parabens can be initially attacked by (•)OH through (•)OH-addition and H-abstraction routes. The (•)OH-addition route was more important for the degradation of shorter alkyl-chain parabens like MPB and EPB, while the H-abstraction route was predominant for the degradation of parabens with longer alkyl-chain for example PPB and BPB. In assessing the aquatic toxicity of parabens and their degradation products using the model calculations, the products of the (•)OH-addition route were found to be more toxic to green algae than original parabens. Although all degradation products were less toxic to daphnia and fish than corresponding parental parabens, they could be still harmful to these aquatic organisms. Furthermore, as alkyl-chain length increased, the ecotoxicity of parabens and their degradation products was found to be also increased. Copyright © 2016 Elsevier Ltd. All rights reserved.

Influence of alkyl chain length and anion species on ionic liquid structure at the graphite interface as a function of applied potential

NASA Astrophysics Data System (ADS)

Li, Hua; Wood, Ross J.; Endres, Frank; Atkin, Rob

2014-07-01

Atomic force microscopy (AFM) force measurements elucidate the effect of cation alkyl chain length and the anion species on ionic liquid (IL) interfacial structure at highly ordered pyrolytic graphite (HOPG) surfaces as a function of potential. Three ILs are examined: 1-hexyl-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate ([HMIM] FAP), 1-ethyl-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate ([EMIM] FAP), and 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([EMIM] TFSA). The step-wise force-distance profiles indicate the ILs adopt a multilayered morphology near the surface. When the surface is biased positively or negatively versus Pt quasireference electrode, both the number of steps, and the force required to rupture each step increase, indicating stronger interfacial structure. At all potentials, push-through forces for [HMIM] FAP are the highest, because the long alkyl chain results in strong cohesive interactions between cations, leading to well-formed layers that resist the AFM tip. The most layers are observed for [EMIM] FAP, because the C2 chains are relatively rigid and the dimensions of the cation and anion are similar, facilitating neat packing. [EMIM] TFSA has the smallest push-through forces and fewest layers, and thus the weakest interfacial structure. Surface-tip attractive forces are measured for all ILs. At the same potential, the attractions are the strongest for [EMIM] TFSA and the weakest for [HMIM] FAP because the interfacial layers are better formed for the longer alkyl chain cation. This means interfacial forces are stronger, which masks the weak attractive forces.

Charge Mobility Enhancement for Conjugated DPP-Selenophene Polymer by Simply Replacing One Bulky Branching Alkyl Chain with Linear One at Each DPP Unit

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Zhijie; Liu, Zitong; Ning, Lu

Here, we demonstrate a simple, but efficient, approach for improving the semiconducting performances of DPP-based conjugated D-A polymers. This approach involves the replacement of one bulky branching alkyl chain with the linear one at each DPP unit in regular polymer PDPPSe-10 and PDPPSe-12. The UV–vis absorption, Raman spectra, PDS data, and theoretical calculations support that the replacement of bulky branching chains with linear ones can weaken the steric hindrance, and accordingly conjugated backbones become more planar and rigid. GIWAXS data show that the incorporation of linear alkyl chains as in PDPPSe-10 and PDPPSe-12 is beneficial for side-chain interdigitation and interchainmore » dense packing, leading to improvement of interchain packing order and thin film crystallinity by comparing with PDPPSe, which contains branching alkyl chains. On the basis of field-effect transistor (FET) studies, charge mobilities of PDPPSe-10 and PDPPSe-12 are remarkably enhanced. Hole mobilities of PDPPSe-10 and PDPPSe-12 in air are boosted to 8.1 and 9.4 cm 2 V –1 s –1, which are about 6 and 7 times, respectively, than that of PDPPSe (1.35 cm 2 V –1 s –1). Furthermore, both PDPPSe-10 and PDPPSe-12 behave as ambipolar semiconductors under a nitrogen atmosphere with increased hole/electron mobilities up to 6.5/0.48 cm 2 V –1 s –1 and 7.9/0.79 cm 2 V –1 s –1, respectively.« less

Charge Mobility Enhancement for Conjugated DPP-Selenophene Polymer by Simply Replacing One Bulky Branching Alkyl Chain with Linear One at Each DPP Unit

DOE PAGES

Wang, Zhijie; Liu, Zitong; Ning, Lu; ...

2018-04-17

Here, we demonstrate a simple, but efficient, approach for improving the semiconducting performances of DPP-based conjugated D-A polymers. This approach involves the replacement of one bulky branching alkyl chain with the linear one at each DPP unit in regular polymer PDPPSe-10 and PDPPSe-12. The UV–vis absorption, Raman spectra, PDS data, and theoretical calculations support that the replacement of bulky branching chains with linear ones can weaken the steric hindrance, and accordingly conjugated backbones become more planar and rigid. GIWAXS data show that the incorporation of linear alkyl chains as in PDPPSe-10 and PDPPSe-12 is beneficial for side-chain interdigitation and interchainmore » dense packing, leading to improvement of interchain packing order and thin film crystallinity by comparing with PDPPSe, which contains branching alkyl chains. On the basis of field-effect transistor (FET) studies, charge mobilities of PDPPSe-10 and PDPPSe-12 are remarkably enhanced. Hole mobilities of PDPPSe-10 and PDPPSe-12 in air are boosted to 8.1 and 9.4 cm 2 V –1 s –1, which are about 6 and 7 times, respectively, than that of PDPPSe (1.35 cm 2 V –1 s –1). Furthermore, both PDPPSe-10 and PDPPSe-12 behave as ambipolar semiconductors under a nitrogen atmosphere with increased hole/electron mobilities up to 6.5/0.48 cm 2 V –1 s –1 and 7.9/0.79 cm 2 V –1 s –1, respectively.« less

Rotational dynamics of imidazolium-based ionic liquids: do the nature of the anion and the length of the alkyl chain influence the dynamics?

PubMed

Prabhu, Sugosh R; Dutt, G B

2014-11-20

The rotational dynamics of 1-alkyl-3-methylimidazolium-based ionic liquids has been investigated by monitoring their inherent fluorescence with the intent to unravel the characteristics of the emitting species. For this purpose, temperature-dependent fluorescence anisotropies of 1-alkyl-3-methylimidazolium (alkyl = ethyl and hexyl) ionic liquids with anions such as tris(pentafluoroethyl)trifluorophosphate ([FAP]), bis(trifluoromethylsulfonyl)imide ([Tf2N]), tetrafluoroborate ([BF4]), and hexafluorophosphate ([PF6]) have been measured. It has been observed that the reorientation times (τr) of the ionic liquids with an ethyl chain scale linearly with viscosity and were found to be independent of the nature of the anion. The experimentally measured τr values are a factor of 3 longer than the ones calculated for 1-ethyl-3-methylimidazolium cation using the Stokes-Einstein-Debye (SED) hydrodynamic theory with stick boundary condition, which suggests that the emitting species is not the imidazolium moiety but some kind of associated species. The reorientation times of ionic liquids with a hexyl chain, in contrast, follow the trend τr([FAP]) > τr([Tf2N]) = τr([BF4]) > τr([PF6]) at a given viscosity (η) and temperature (T). The ability of the ionic liquids with longer alkyl chains to form the organized structure appears to be responsible for the observed behavior considering the fact that significant deviations from linearity have been noticed in the τr versus η/T plots for strongly associating anions [BF4] and [PF6], especially at ambient temperatures.

Influence of solute charge and pyrrolidinium ionic liquid alkyl chain length on probe rotational reorientation dynamics.

PubMed

Guo, Jianchang; Mahurin, Shannon M; Baker, Gary A; Hillesheim, Patrick C; Dai, Sheng; Shaw, Robert W

2014-01-30

In recent years, the effect of molecular charge on the rotational dynamics of probe solutes in room-temperature ionic liquids (RTILs) has been a subject of growing interest. For the purpose of extending our understanding of charged solute behavior within RTILs, we have studied the rotational dynamics of three illustrative xanthene fluorescent probes within a series of N-alkylpyrrolidinium bis(trifluoromethylsulfonyl)imide ([Cnmpyr][Tf2N]) RTILs with different n-alkyl chain lengths (n = 3, 4, 6, 8, or 10) using time-resolved fluorescence anisotropy decay. The rotational dynamics of the neutral probe rhodamine B (RhB) dye lies between the stick and slip boundary conditions due to the influence of specific hydrogen bonding interactions. The rotation of the negatively charged sulforhodamine 640 (SR640) is slower than that of its positively charged counterpart rhodamine 6G (R6G). An analysis based upon Stokes-Einstein-Debye hydrodynamics indicates that SR640 adheres to stick boundary conditions due to specific interactions, whereas the faster rotation of R6G is attributed to weaker electrostatic interactions. No significant dependence of the rotational dynamics on the solvent alkyl chain length was observed for any of the three dyes, suggesting that the specific interactions between dyes and RTILs are relatively independent of this solvent parameter.

CRM1 inhibitory and antiproliferative activities of novel 4'-alkyl substituted klavuzon derivatives.

PubMed

Kanbur, Tuğçe; Kara, Murat; Kutluer, Meltem; Şen, Ayhan; Delman, Murat; Alkan, Aylin; Otaş, Hasan Ozan; Akçok, İsmail; Çağır, Ali

2017-08-15

Klavuzons are 6-(naphthalen-1-yl) substituted 5,6-dihydro-2H-pyran-2-one derivatives showing promising antiproliferative activities in variety of cancer cell lines. In this work, racemic syntheses of nine novel 4'-alkyl substituted klavuzon derivatives were completed in eight steps and anticancer properties of these compounds were evaluated. It is found that size of the substituent has dramatic effect over the potency and selectivity of the cytotoxic activity in cancerous and healthy pancreatic cell lines. The size of the substituent can also effect the CRM1 inhibitory properties of klavuzon derivatives. Strong cytotoxic activity and CRM1 inhibition can be observed only when a small substituent present at 4'-position of naphthalen-1-yl group. However, these substituents makes the molecule more cytotoxic in healthy pancreatic cells rather than cancerous pancreatic cells. Among the tested compounds 1,2,3,4-tetrahydrophenanthren-9-yl substituted lactone was the most cytotoxic compound and its antiproliferative activity was also tested in 3D spheroids generated from HuH-7 cell lines. Copyright © 2017 Elsevier Ltd. All rights reserved.

Crystal structures of 3-methyladenine DNA glycosylase MagIII and the recognition of alkylated bases

PubMed Central

Eichman, Brandt F.; O’Rourke, Eyleen J.; Radicella, J.Pablo; Ellenberger, Tom

2003-01-01

DNA glycosylases catalyze the excision of chemically modified bases from DNA. Although most glycosylases are specific to a particular base, the 3-methyladenine (m3A) DNA glycosylases include both highly specific enzymes acting on a single modified base, and enzymes with broader specificity for alkylation-damaged DNA. Our structural understanding of these different enzymatic specificities is currently limited to crystal and NMR structures of the unliganded enzymes and complexes with abasic DNA inhibitors. Presented here are high-resolution crystal structures of the m3A DNA glycosylase from Helicobacter pylori (MagIII) in the unliganded form and bound to alkylated bases 3,9-dimethyladenine and 1,N6-ethenoadenine. These are the first structures of a nucleobase bound in the active site of a m3A glycosylase belonging to the helix–hairpin–helix superfamily. MagIII achieves its specificity for positively-charged m3A not by direct interactions with purine or methyl substituent atoms, but rather by stacking the base between two aromatic side chains in a pocket that excludes 7-methylguanine. We report base excision and DNA binding activities of MagIII active site mutants, together with a structural comparison of the HhH glycosylases. PMID:14517230

Can 5-methylcytosine analogues with extended alkyl side chains guide DNA methylation?

PubMed

Kotandeniya, D; Seiler, C L; Fernandez, J; Pujari, S S; Curwick, L; Murphy, K; Wickramaratne, S; Yan, S; Murphy, D; Sham, Yuk Y; Tretyakova, N Y

2018-01-25

5-Methylcytosine ( Me C) is an endogenous modification of DNA that plays a crucial role in DNA-protein interactions, chromatin structure, epigenetic regulation, and DNA repair. Me C is produced via enzymatic methylation of the C-5 position of cytosine by DNA-methyltransferases (DNMT) which use S-adenosylmethionine (SAM) as a cofactor. Hemimethylated CG dinucleotides generated as a result of DNA replication are specifically recognized and methylated by maintenance DNA methyltransferase 1 (DNMT1). The accuracy of DNMT1-mediated methylation is essential for preserving tissue-specific DNA methylation and thus gene expression patterns. In the present study, we synthesized DNA duplexes containing MeC analogues with modified C-5 side chains and examined their ability to guide cytosine methylation by the human DNMT1 protein. We found that the ability of 5-alkylcytosines to direct cytosine methylation decreased with increased alkyl chain length and rigidity (methyl > ethyl > propyl ∼ vinyl). Molecular modeling studies indicated that this loss of activity may be caused by the distorted geometry of the DNA-protein complex in the presence of unnatural alkylcytosines.

Bis(thienothiophenyl) diketopyrrolopyrrole-based conjugated polymers with various branched alkyl side chains and their applications in thin-film transistors and polymer solar cells.

PubMed

Shin, Jicheol; Park, Gi Eun; Lee, Dae Hee; Um, Hyun Ah; Lee, Tae Wan; Cho, Min Ju; Choi, Dong Hoon

2015-02-11

New thienothiophene-flanked diketopyrrolopyrrole and thiophene-containing π-extended conjugated polymers with various branched alkyl side-chains were successfully synthesized. 2-Octyldodecyl, 2-decyltetradecyl, 2-tetradecylhexadecyl, 2-hexadecyloctadecyl, and 2-octadecyldocosyl groups were selected as the side-chain moieties and were anchored to the N-positions of the thienothiophene-flanked diketopyrrolopyrrole unit. All five polymers were found to be soluble owing to the bulkiness of the side chains. The thin-film transistor based on the 2-tetradecylhexadecyl-substituted polymer showed the highest hole mobility of 1.92 cm2 V(-1) s(-1) due to it having the smallest π-π stacking distance between the polymer chains, which was determined by grazing incidence X-ray diffraction. Bulk heterojunction polymer solar cells incorporating [6,6]-phenyl-C71-butyric acid methyl ester as the n-type molecule and the additive 1,8-diiodooctane (1 vol %) were also constructed from the synthesized polymers without thermal annealing; the device containing the 2-octyldodecyl-substituted polymer exhibited the highest power conversion efficiency of 5.8%. Although all the polymers showed similar physical properties, their device performance was clearly influenced by the sizes of the branched alkyl side-chain groups.

Theoretical study on the influence of different para-substituents on 13C NMR of the single carbonyl curcumin analogues

NASA Astrophysics Data System (ADS)

Jia, Fei-yun; Ran, Ming; Zhang, Bo

2015-12-01

The structure of eight kinds of different para-substituents curcumin analogues has been optimized at the level of B3LYP/6-31G( d, p), under which the stability has been verified by means of vibration analysis. Moreover, NMR spectra of curcumin analogues compounds have been studied at the level of B3LYP/6-311G( d, p) by GIAO method. The results show that the structure of eight compounds, a larger conjugated system, has good planarity. The effect of ortho-substituents on bond lengths and bond angles is greater than para and meta. Different substituents and different positions of substituents all have different influence on NMR of the single carbonyl curcumin analogues. In general, after the hydrogen atom on the benzene ring is substituted by other groups, the δ value of α-C changes significantly, the δ value of ortho-carbon atom may also have great change, but the δ value change of meta-carbon atoms is not too obvious. The effect of substituent electronegativity on α-C atoms presents obvious regularity, while the influence of conjugate effect on carbon atoms of benzene ring is more complex. Finally, the bigger substituted alkyl is, the more the δ value of α-C increases.

Is the liquid or the solid phase responsible for the low melting points of ionic liquids? Alkyl-chain-length dependence of thermodynamic properties of [C nmim][Tf 2N

NASA Astrophysics Data System (ADS)

Shimizu, Yoshitaka; Ohte, Yoko; Yamamura, Yasuhisa; Saito, Kazuya

2009-03-01

To establish the alkyl-chain-length dependences of thermodynamic properties of typical ionic liquids [C nmim][Tf 2N], the heat capacities of compounds with n = 2 and 18 were measured by adiabatic calorimetry. The comparison with other ionic liquids and typical molecular substances reveals that the low melting point of [C nmim][Tf 2N] with a short alkyl chain mainly originate in the large fusion entropy arising from the low entropy of the crystalline phase.

Towards a physical interpretation of substituent effect: Quantum chemical interpretation of Hammett substituent constants

NASA Astrophysics Data System (ADS)

Varaksin, Konstantin S.; Szatylowicz, Halina; Krygowski, Tadeusz M.

2017-06-01

Quantitative description of substituent effects is of a great importance especially in organic chemistry and QSAR-type treatments. The proposed approaches: substituent effect stabilization energy (SESE) and charge of the substituent active region (cSAR) provide substituent effect characteristics, physically independent of the Hammett's substituent constants, σ. To document abilities of these descriptors the B3LYP/6-311++G(d,p) method is employed to examine changes in properties of a reaction center Y (Y = COOH or COO- groups) and a transmitting moiety (benzene ring) due to substituent effects in a series of meta- and para-X-substituted benzoic acid and benzoate anion derivatives (X = NMe2, NH2, OH, OMe, CH3, H, F, Cl, CF3, CN, CHO, COMe, CONH2, COOH, NO2, NO). The transmitting moiety is described by aromaticity indices HOMA and NICS(1). Furthermore, an advantage of the cSAR characteristic is the ability to use it to describe both electron donating/accepting properties of a substituent as well as a reaction center. It allows demonstration of the reverse substituent effects of COOH and COO- groups on substituent X.

Molecular dynamics study of intermediate phase of long chain alkyl sulfonate/water systems.

PubMed

Poghosyan, Armen H; Arsenyan, Levon H; Shahinyan, Aram A

2013-01-08

Using atomic level simulation we aimed to investigate various intermediate phases of the long chain alkyl sulfonate/water system. Overall, about 800 ns parallel molecular dynamics simulation study was conducted for a surfactant/water system consisting of 128 sodium pentadecyl sulfonate and 2251 water molecules. The GROMACS software code with united atom force field was applied. Despite some differences, the analysis of main structural parameters is in agreement with X-ray experimental findings. The mechanism of self-assembly of SPDS molecules was also examined. At T = 323 K we obtained both tilted fully interdigitated and liquid crystalline-like disordered hydrocarbon chains; hence, the presence of either gel phase that coexists with a lamellar phase or metastable gel phase with fraction of gauche configuration can be assumed. Further increase of temperature revealed that the system underwent a transition to a lamellar phase, which was clearly identified by the presence of fully disordered hydrocarbon chains. The transition from gel-to-fluid phase was implemented by simulated annealing treatment, and the phase transition point at T = 335 K was identified. The surfactant force field in its presented set is surely enabled to fully demonstrate the mechanism of self-assembly and the behavior of phase transition making it possible to get important information around the phase transition point.

Effect of Structure on Transport Properties (Viscosity, Ionic Conductivity, and Self-Diffusion Coefficient) of Aprotic Heterocyclic Anion (AHA) Room Temperature Ionic Liquids. 2. Variation of Alkyl Chain Length in the Phosphonium Cation.

PubMed

Sun, Liyuan; Morales-Collazo, Oscar; Xia, Han; Brennecke, Joan F

2016-06-30

A series of room-temperature ionic liquids (ILs) composed of triethyl(alkyl)phosphonium cations paired with three different aprotic heterocyclic anions (AHAs) (alkyl = butyl ([P2224](+)) and octyl ([P2228](+))) were prepared to investigate the effect of cationic alkyl chain length on transport properties. The transport properties and density of these ILs were measured from 283.15 to 343.15 K at ambient pressure. The dependence of the transport properties (viscosity, ionic conductivity, diffusivity, and molar conductivity) on temperature can be described by the Vogel-Fulcher-Tamman (VFT) equation. The ratio of the molar conductivity obtained from the molar concentration and ionic conductivity measurements to that calculated from self-diffusion coefficients (measured by pulsed gradient spin-echo nuclear magnetic resonance spectroscopy) using the Nernst-Einstein equation was used to quantify the ionicity of these ILs. The molar conductivity ratio decreases with increasing number of carbon atoms in the alkyl chain, indicating that the reduced Coulombic interactions resulting from lower density are more than balanced by the increased van der Waals interactions between the alkyl chains. The results of this study may provide insight into the design of ILs with enhanced dynamics that may be suitable as electrolytes in lithium ion batteries and other electrochemical applications.

Effect of N-substituents on redox, optical, and electronic properties of naphthalene bisimides used for field-effect transistors fabrication.

PubMed

Gawrys, Pawel; Djurado, David; Rimarcík, Ján; Kornet, Aleksandra; Boudinet, Damien; Verilhac, Jean-Marie; Lukes, Vladimír; Wielgus, Ireneusz; Zagorska, Malgorzata; Pron, Adam

2010-02-11

Three groups of naphthalene bisimides were synthesized and comparatively studied, namely, alkyl bisimides, alkylaryl ones, and novel bisimides containing the alkylthienyl moiety in the N-substituent. The experimental absorption spectra measured in CHCl(3) exhibit one intensive absorption band that is uniformly detected in the spectral range of 340 to 400 nm for all studied molecules. This band consists of three or four vibronic peaks. The introduction of an alkylthienyl group results in the appearance of an additional band (in the spectral range from 282 to 326 nm, depending on the position of the substituent) that can be ascribed to the pi-pi* transition in the thienyl chromophore. The minimal substituent effect on the lowest electronic transitions was explained using the quantum chemical calculations based on the time-dependent density functional theory. The investigation of the shapes of frontier orbitals have also shown that the oxidation of bisimides containing thiophene moiety is primary connected with the electron abstraction from the thienyl ring. To the contrary, the addition of an electron in the reduction process leads to an increase in the electron density in the central bisimide core. As shown by the electrochemical measurements, the onset of the first reduction potential (so-called "electrochemically determined LUMO level") is sensitive toward the type of the substituent being shifted from about -3.72 eV for bisimides with alkyl substituents to about -3.83 eV for alkylaryl ones and to about -3.94 eV for bisimides with thienyl groups. The presence of the thienyl ring also lowers the energy difference between the HOMO and LUMO orbitals. These experimental data can be well correlated with the DFT calculations in terms of HOMO/LUMO shapes and energies. Taking into account the low position of their LUMO level and their highly ordered supramolecular organization, the new bisimides are good candidates for the use in n-channel field effect transistors

Access to 6a-Alkyl Aporphines: Synthesis of (±)-N-Methylguattescidine.

PubMed

Ku, Angela F; Cuny, Gregory D

2016-10-21

(-)-N-Methylguattescidine (3) is an alkaloid recently isolated from Fissistigma latifolium and assigned as a rare example of a 6a-alkyl aporphine. Herein, we report the synthesis of (±)-3 and the des-hydroxyl derivative 4 using our previously reported ortho-phenol arylation methodology mediated by the XPhos precatalyst as a key synthetic step. In addition, substituents on the aryl halide portion of the ortho-phenol arylation substrates significantly influenced the formation of an oxidized side product.

Side-Chain Effects on the Thermoelectric Properties of Fluorene-Based Copolymers.

PubMed

Liang, Ansheng; Zhou, Xiaoyan; Zhou, Wenqiao; Wan, Tao; Wang, Luhai; Pan, Chengjun; Wang, Lei

2017-09-01

Three conjugated polymers with alkyl chains of different lengths are designed and synthesized, and their structure-property relationship as organic thermoelectric materials is systematically elucidated. All three polymers show similar photophysical properties, thermal properties, and mechanical properties; however, their thermoelectric performance is influenced by the length of their side chains. The length of the alkyl chain significantly influences the electrical conductivity of the conjugated polymers, and polymers with a short alkyl chain exhibit better conductivity than those with a long alkyl chain. The length of the alkyl chain has little effect on the Seebeck coefficient. Only a slight increase in the Seebeck coefficient is observed with the increasing length of the alkyl chain. The purpose of this study is to provide comprehensive insight into fine-tuning the thermoelectric properties of conjugated polymers as a function of side-chain engineering, thereby providing a novel perspective into the design of high-performance thermoelectric conjugated polymers. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Substituent effects that control conjugated oligomer conformation through non-covalent interactions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sharber, Seth A.; Baral, Rom Nath; Frausto, Fanny

Although understanding the conformations and arrangements of conjugated materials as solids is key to their prospective applications, predictive power over these structural factors remains elusive. In this work, substituent effects tune non-covalent interactions between side-chain fluorinated benzyl esters and main-chain terminal arenes, in turn controlling the conformations and interchromophore aggregation of three-ring phenylene-ethynylenes (PEs). Cofacial fluoroarene–arene (ArF–ArH) interactions cause twisting in the PE backbone, interrupting intramolecular conjugation as well as blocking chromophore aggregation, both of which prevent the typically observed bathochromic shift observed upon transitioning PEs from solution to solid. This work highlights two structural factors that determine whether themore » ArF–ArH interactions, and the resulting twisted, unaggregated chromophores, occur in these solids: (i) the electron-releasing characteristic of substituents on ArH, with more electron-releasing character favoring ArF–ArH interactions, and (ii) the fluorination pattern of the ArF ring, with 2,3,4,5,6-pentafluorophenyl favoring ArF–ArH interactions over 2,4,6-trifluorophenyl. Furthermore, these trends indicate that considerations of electrostatic complementarity, whether through a polar-π or substituent–substituent mechanism, can serve as an effective design principle in controlling the interaction strengths, and therefore the optoelectronic properties, of these molecules as solids.« less

Substituent effects that control conjugated oligomer conformation through non-covalent interactions

DOE PAGES

Sharber, Seth A.; Baral, Rom Nath; Frausto, Fanny; ...

2017-03-31

Although understanding the conformations and arrangements of conjugated materials as solids is key to their prospective applications, predictive power over these structural factors remains elusive. In this work, substituent effects tune non-covalent interactions between side-chain fluorinated benzyl esters and main-chain terminal arenes, in turn controlling the conformations and interchromophore aggregation of three-ring phenylene-ethynylenes (PEs). Cofacial fluoroarene–arene (ArF–ArH) interactions cause twisting in the PE backbone, interrupting intramolecular conjugation as well as blocking chromophore aggregation, both of which prevent the typically observed bathochromic shift observed upon transitioning PEs from solution to solid. This work highlights two structural factors that determine whether themore » ArF–ArH interactions, and the resulting twisted, unaggregated chromophores, occur in these solids: (i) the electron-releasing characteristic of substituents on ArH, with more electron-releasing character favoring ArF–ArH interactions, and (ii) the fluorination pattern of the ArF ring, with 2,3,4,5,6-pentafluorophenyl favoring ArF–ArH interactions over 2,4,6-trifluorophenyl. Furthermore, these trends indicate that considerations of electrostatic complementarity, whether through a polar-π or substituent–substituent mechanism, can serve as an effective design principle in controlling the interaction strengths, and therefore the optoelectronic properties, of these molecules as solids.« less

Equilibration of tert-alkylphenols (thermodynamic analysis of the alkylation of phenols using branched-chain olefins)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nesterova, T.N.; Malova, T.N.; Pil'shchikov, V.A.

1985-09-01

The authors describe the results of a study to evaluate the thermodynamic properties of t-Alk phi. These results, combined with earlier results, have enabled the authors to complete a thermodynamic analysis of the process for preparing tertiary alkylphenols which are widely used as additives in lubricating and fuel oils. Research was conducted over a fairly wide temperature range, in which the median temperature value corresponds to the upper temperature limit for a continuous process utilizing a type KU-2 ion-exchange resin catalyst; continuous operations are currently the most widely used method for industrial preparation of alkylphenols. Experimentally determined values of themore » equilibrium constants in a table indicate that they are influenced primarily by the nature of the reaction, and do not depend on the size of the tertiary alkyl substituents. Data in another table demonstrate that the thermodynamic properties of a given reaction are determined by the reaction type and are independent of the size of the tertiary alkylphenols. It was discovered that in order to increase the yield of the desired tert-alkylphenol product, the process should be carried out at the minimum possible temperature, using catalysts which are sufficiently active to guarantee thermodynamic control.« less

Production of long chain alkyl esters from carbon dioxide and electricity by a two-stage bacterial process.

PubMed

Lehtinen, Tapio; Efimova, Elena; Tremblay, Pier-Luc; Santala, Suvi; Zhang, Tian; Santala, Ville

2017-11-01

Microbial electrosynthesis (MES) is a promising technology for the reduction of carbon dioxide into value-added multicarbon molecules. In order to broaden the product profile of MES processes, we developed a two-stage process for microbial conversion of carbon dioxide and electricity into long chain alkyl esters. In the first stage, the carbon dioxide is reduced to organic compounds, mainly acetate, in a MES process by Sporomusa ovata. In the second stage, the liquid end-products of the MES process are converted to the final product by a second microorganism, Acinetobacter baylyi in an aerobic bioprocess. In this proof-of-principle study, we demonstrate for the first time the bacterial production of long alkyl esters (wax esters) from carbon dioxide and electricity as the sole sources of carbon and energy. The process holds potential for the efficient production of carbon-neutral chemicals or biofuels. Copyright © 2017 Elsevier Ltd. All rights reserved.

Effect of molecular characteristics on cellular uptake, subcellular localization, and phototoxicity of Zn(II) N-alkylpyridylporphyrins.

PubMed

Ezzeddine, Rima; Al-Banaw, Anwar; Tovmasyan, Artak; Craik, James D; Batinic-Haberle, Ines; Benov, Ludmil T

2013-12-20

Tetra-cationic Zn(II) meso-tetrakis(N-alkylpyridinium-2 (or -3 or -4)-yl)porphyrins (ZnPs) with progressively increased lipophilicity were synthesized to investigate how the tri-dimensional shape and lipophilicity of the photosensitizer (PS) affect cellular uptake, subcellular distribution, and photodynamic efficacy. The effect of the tri-dimensional shape of the molecule was studied by shifting the N-alkyl substituent attached to the pyridyl nitrogen from ortho to meta and para positions. Progressive increase of lipophilicity from shorter hydrophilic (methyl) to longer amphiphilic (hexyl) alkyl chains increased the phototoxicity of the ZnP PSs. PS efficacy was also increased for all derivatives when the alkyl substituents were shifted from ortho to meta, and from meta to para positions. Both cellular uptake and subcellular distribution of the PSs were affected by the lipophilicity and the position of the alkyl chains on the periphery of the porphyrin ring. Whereas the hydrophilic ZnPs demonstrated mostly lysosomal distribution, the amphiphilic hexyl derivatives were associated with mitochondria, endoplasmic reticulum, and plasma membrane. A comparison of hexyl isomers revealed that cellular uptake and partition into membranes followed the order para > meta > ortho. Varying the position and length of the alkyl substituents affects (i) the exposure of cationic charges for electrostatic interactions with anionic biomolecules and (ii) the lipophilicity of the molecule. The charge, lipophilicity, and the tri-dimensional shape of the PS are the major factors that determine cellular uptake, subcellular distribution, and as a consequence, the phototoxicity of the PSs.

Effect of Molecular Characteristics on Cellular Uptake, Subcellular Localization, and Phototoxicity of Zn(II) N-Alkylpyridylporphyrins*

PubMed Central

Ezzeddine, Rima; Al-Banaw, Anwar; Tovmasyan, Artak; Craik, James D.; Batinic-Haberle, Ines; Benov, Ludmil T.

2013-01-01

Tetra-cationic Zn(II) meso-tetrakis(N-alkylpyridinium-2 (or -3 or -4)-yl)porphyrins (ZnPs) with progressively increased lipophilicity were synthesized to investigate how the tri-dimensional shape and lipophilicity of the photosensitizer (PS) affect cellular uptake, subcellular distribution, and photodynamic efficacy. The effect of the tri-dimensional shape of the molecule was studied by shifting the N-alkyl substituent attached to the pyridyl nitrogen from ortho to meta and para positions. Progressive increase of lipophilicity from shorter hydrophilic (methyl) to longer amphiphilic (hexyl) alkyl chains increased the phototoxicity of the ZnP PSs. PS efficacy was also increased for all derivatives when the alkyl substituents were shifted from ortho to meta, and from meta to para positions. Both cellular uptake and subcellular distribution of the PSs were affected by the lipophilicity and the position of the alkyl chains on the periphery of the porphyrin ring. Whereas the hydrophilic ZnPs demonstrated mostly lysosomal distribution, the amphiphilic hexyl derivatives were associated with mitochondria, endoplasmic reticulum, and plasma membrane. A comparison of hexyl isomers revealed that cellular uptake and partition into membranes followed the order para > meta > ortho. Varying the position and length of the alkyl substituents affects (i) the exposure of cationic charges for electrostatic interactions with anionic biomolecules and (ii) the lipophilicity of the molecule. The charge, lipophilicity, and the tri-dimensional shape of the PS are the major factors that determine cellular uptake, subcellular distribution, and as a consequence, the phototoxicity of the PSs. PMID:24214973

Optoelectronic functional materials based on alkylated-π molecules: self-assembled architectures and nonassembled liquids.

PubMed

Li, Hongguang; Choi, Jiyoung; Nakanishi, Takashi

2013-05-07

The engineering of single molecules into higher-order hierarchical assemblies is a current research focus in molecular materials chemistry. Molecules containing π-conjugated units are an important class of building blocks because their self-assembly is not only of fundamental interest, but also the key to fabricating functional systems for organic electronic and photovoltaic applications. Functionalizing the π-cores with "alkyl chains" is a common strategy in the molecular design that can give the system desirable properties, such as good solubility in organic solvents for solution processing. Moreover, the alkylated-π system can regulate the self-assembly behavior by fine-tuning the intermolecular forces. The optimally assembled structures can then exhibit advanced functions. However, while some general rules have been revealed, a comprehensive understanding of the function played by the attached alkyl chains is still lacking, and current methodology is system-specific in many cases. Better clarification of this issue requires contributions from carefully designed libraries of alkylated-π molecular systems in both self-assembly and nonassembly materialization strategies. Here, based on recent efforts toward this goal, we show the power of the alkyl chains in controlling the self-assembly of soft molecular materials and their resulting optoelectronic properties. The design of alkylated-C60 is selected from our recent research achievements, as the most attractive example of such alkylated-π systems. Some other closely related systems composed of alkyl chains and π-units are also reviewed to indicate the universality of the methodology. Finally, as a contrast to the self-assembled molecular materials, nonassembled, solvent-free, novel functional liquid materials are discussed. In doing so, a new journey toward the ultimate organic "soft" materials is introduced, based on alkylated-π molecular design.

The Biosynthesis of Nitrogen-, Sulfur-, and High-carbon Chain-containing Sugars†

PubMed Central

Lin, Chia-I; McCarty, Reid M.; Liu, Hung-wen

2013-01-01

Carbohydrates serve many structural and functional roles in biology. While the majority of monosaccharides are characterized by the chemical composition: (CH2O)n, modifications including deoxygenation, C-alkylation, amination, O- and N-methylation, which are characteristic of many sugar appendages of secondary metabolites, are not uncommon. Interestingly, some sugar molecules are formed via modifications including amine oxidation, sulfur incorporation, and “high-carbon” chain attachment. Most of these unusual sugars have been identified over the past several decades as components of microbially produced natural products, although a few high-carbon sugars are also found in the lipooligosaccharides of the outer cell walls of Gram-negative bacteria. Despite their broad distribution in nature, these sugars are considered “rare” due to their relative scarcity. The biosynthetic steps that underlie their formation continue to perplex researchers to this day and many questions regarding key transformations remain unanswered. This review will focus on our current understanding of the biosynthesis of unusual sugars bearing oxidized amine substituents, thio-functional groups, and high-carbon chains. PMID:23348524

The biosynthesis of nitrogen-, sulfur-, and high-carbon chain-containing sugars.

PubMed

Lin, Chia-I; McCarty, Reid M; Liu, Hung-wen

2013-05-21

Carbohydrates serve many structural and functional roles in biology. While the majority of monosaccharides are characterized by the chemical composition (CH2O)n, modifications including deoxygenation, C-alkylation, amination, O- and N-methylation, which are characteristic of many sugar appendages of secondary metabolites, are not uncommon. Interestingly, some sugar molecules are formed via modifications including amine oxidation, sulfur incorporation, and "high-carbon" chain attachment. Most of these unusual sugars have been identified over the past several decades as components of microbially produced natural products, although a few high-carbon sugars are also found in the lipooligosaccharides of the outer cell walls of Gram-negative bacteria. Despite their broad distribution in nature, these sugars are considered "rare" due to their relative scarcity. The biosynthetic steps that underlie their formation continue to perplex researchers to this day and many questions regarding key transformations remain unanswered. This review will focus on our current understanding of the biosynthesis of unusual sugars bearing oxidized amine substituents, thio-functional groups, and high-carbon chains.

Ionic liquids as refolding additives: N′-alkyl and N′-(ω-hydroxyalkyl) N-methylimidazolium chlorides

PubMed Central

Lange, Christian; Patil, Ganesh; Rudolph, Rainer

2005-01-01

The purpose of this work was to investigate the influence of a series of N′-alkyl and N′-(ω-hydroxy-alkyl)-N-methylimidazolium chlorides on the renaturation of two model proteins, namely hen egg white lysozyme and the single-chain antibody fragment ScFvOx. All tested ionic liquids acted as refolding enhancers, with varying efficacies and efficiencies. The results of the refolding screening could be interpreted by taking into account the effect of the studied ionic liquids on protein aggregation, together with the systematic variations of their influence on the stability of native proteins in solution. More hydrophobic imidazolium cations carrying longer alkyl chains were increasingly destabilizing, while terminal hydroxylation of the alkyl chain made the salts more compatible with protein stability. The studied ionic liquids can be classified as preferentially bound, slightly to moderately chaotropic cosolvents for proteins. PMID:16195554

The effects of side-chain-induced disorder on the emission spectra and quantum yields of oligothiophene nano-aggregates. A combined experimental and MD-TDDFT study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hong, Jiyun; Jeon, SuKyung; Kim, Janice J.

2014-07-24

Oligomeric thiophenes are commonly-used components in organic electronics and solar cells. These molecules stack and/or aggregate readily under the processing conditions used to form thin films for these applications, significantly altering their optical and charge-transport properties. To determine how these effects depend on the substitution pattern of the thiophene main chains, nano-aggregates of three sexi-thiophene (6T) oligomers having different alkyl substitution patterns were formed using solvent poisoning techniques and studied using steady-state and time-resolved emission spectroscopy. The results indicate the substantial role played by the side-chain substituents in determining the emissive properties of these species. Both the measured spectral changesmore » and their dependence on substitution are well modeled by combined quantum chemistry and molecular dynamics simulations. The simulations connect the side-chain-induced disorder, which determines the favorable chain packing configurations within the aggregates, with their measured electronic spectra.« less

Stereocontrolled Alkylative Construction of Quaternary Carbon Centers

PubMed Central

Kummer, David A.; Chain, William J.; Morales, Marvin R.; Quiroga, Olga; Myers, Andrew G.

2009-01-01

Protocols for the stereodefined formation of α,α-disubstituted enolates of pseudoephedrine amides are presented followed by the implementation of these in diastereoselective alkylation reactions. Direct alkylation of α,α-disubstituted pseudoephedrine amide substrates is demonstrated to be both efficient and diastereoselective across a range of substrates, as exemplified by alkylation of the diastereomeric pseudoephedrine α-methylbutyramides, where both substrates are found to undergo stereospecific replacement of the α-C-H bond with α-C-alkyl, with retention of stereochemistry. This is shown to arise by sequential stereospecific enolization and alkylation reactions, with the alkyl halide attacking a common π-face of the E- and Z-enolates, proposed to be that opposite the pseudoephedrine alkoxide side-chain. Pseudoephedrine α-phenylbutyramides are found to undergo highly stereoselective but not stereospecific α-alkylation reactions, which evidence suggests is due to facile enolate isomerization. Also, we show that α, α-disubstituted pseudoephedrine amide enolates can be generated in a highly stereocontrolled fashion by conjugate addition of an alkyllithium reagent to the s-cis-conformer of an α-alkyl-α,β-unsaturated pseudoephedrine amide, providing α,α-disubstituted enolate substrates that undergo alkylation in the same sense as those formed by direct deprotonation. Methods are presented to transform the α-quaternary pseudoephedrine amide products into optically active carboxylic acids, ketones, primary alcohols, and aldehydes. PMID:18788739

Diacyltransferase Activity and Chain Length Specificity of Mycobacterium tuberculosis PapA5 in the Synthesis of Alkyl β-Diol Lipids

DOE Office of Scientific and Technical Information (OSTI.GOV)

Touchette, Megan H.; Bommineni, Gopal R.; Delle Bovi, Richard J.

Although classified as Gram-positive bacteria, Corynebacterineae possess an asymmetric outer membrane that imparts structural and thereby physiological similarity to more distantly related Gram-negative bacteria. Like lipopolysaccharide in Gram-negative bacteria, lipids in the outer membrane of Corynebacterineae have been associated with the virulence of pathogenic species such as Mycobacterium tuberculosis (Mtb). For example, Mtb strains that lack long, branched-chain alkyl esters known as dimycocerosates (DIMs) are significantly attenuated in model infections. The resultant interest in the biosynthetic pathway of these unusual virulence factors has led to the elucidation of many of the steps leading to the final esterification of the alkylmore » beta-diol, phthiocerol, with branched-chain fatty acids know as mycocerosates. PapA5 is an acyltransferase implicated in these final reactions. We here show that PapA5 is indeed the terminal enzyme in DIM biosynthesis by demonstrating its dual esterification activity and chain-length preference using synthetic alkyl beta-diol substrate analogues. Applying these analogues to a series of PapA5 mutants, we also revise a model for the substrate binding within PapA5. Finally, we demonstrate that the Mtb Ser/Thr kinase PknB modifies PapA5 on three Thr residues, including two (T196, T198) located on an unresolved loop. These results clarify the DIM biosynthetic pathway and suggest possible mechanisms by which DIM biosynthesis may be regulated by the post-translational modification of PapA5.« less

Solubilization of cyclohexane in aqueous solutions of sodium. cap alpha. -alkyl alkanoates

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sagitani, H.; Suzuki, T.; Nagai, M.

1982-01-01

The effect of branched alkyl chain length and the position of the COONa group on the solubilizing power of n-alkane sodium carboxylates was studied. The lipophilic property and the amount of solubilized cyclohexane increased with the branched chain length of branched soaps, and with the change of the position of the -COONa group from 3 to 7 in the alkyl chain of pentadecane -3, -5, and -7 sodium carboxylates. Alpha-branched soaps having proper branched alkyl chains were better solubilizers for cyclohexane than straight chain compounds. The amount of cyclohexane solublized by C/sub 10/ H/sub 21/ CH(C/sub 6/H/sub 13/) COONa wasmore » about three times greater than the amount solubilized by C/sub 17/ H/sub 35/ COONa. There was a marked increase in the solubilization of cyclohexane replacing ..cap alpha..-branched fatty acid soaps with optimum amount of cosurfactants such as C/sub 8/H/sub 17/ (OCH/sub 2/CH/sub 2/)/sub 2/OH. Namely, solubilization increased markedly at the optimum hydrophile-lipophile balance of mixed surfactant. 21 references.« less

Computational study of chain transfer to monomer reactions in high-temperature polymerization of alkyl acrylates.

PubMed

Moghadam, Nazanin; Liu, Shi; Srinivasan, Sriraj; Grady, Michael C; Soroush, Masoud; Rappe, Andrew M

2013-03-28

This article presents a computational study of chain transfer to monomer (CTM) reactions in self-initiated high-temperature homopolymerization of alkyl acrylates (methyl, ethyl, and n-butyl acrylate). Several mechanisms of CTM are studied. The effects of the length of live polymer chains and the type of monoradical that initiated the live polymer chains on the energy barriers and rate constants of the involved reaction steps are investigated theoretically. All calculations are carried out using density functional theory. Three types of hybrid functionals (B3LYP, X3LYP, and M06-2X) and four basis sets (6-31G(d), 6-31G(d,p), 6-311G(d), and 6-311G(d,p)) are applied to predict the molecular geometries of the reactants, products and transition sates, and energy barriers. Transition state theory is used to estimate rate constants. The results indicate that abstraction of a hydrogen atom (by live polymer chains) from the methyl group in methyl acrylate, the methylene group in ethyl acrylate, and methylene groups in n-butyl acrylate are the most likely mechanisms of CTM. Also, the rate constants of CTM reactions calculated using M06-2X are in good agreement with those estimated from polymer sample measurements using macroscopic mechanistic models. The rate constant values do not change significantly with the length of live polymer chains. Abstraction of a hydrogen atom by a tertiary radical has a higher energy barrier than abstraction by a secondary radical, which agrees with experimental findings. The calculated and experimental NMR spectra of dead polymer chains produced by CTM reactions are comparable. This theoretical/computational study reveals that CTM occurs most likely via hydrogen abstraction by live polymer chains from the methyl group of methyl acrylate and methylene group(s) of ethyl (n-butyl) acrylate.

Poly(ethyleneoxide) functionalization through alkylation

DOEpatents

Sivanandan, Kulandaivelu; Eitouni, Hany Basam; Li, Yan; Pratt, Russell Clayton

2015-04-21

A new and efficient method of functionalizing high molecular weight polymers through alkylation using a metal amide base is described. This novel procedure can also be used to synthesize polymer-based macro-initiators containing radical initiating groups at the chain-ends for synthesis of block copolymers.

Alkyl gallates, intensifiers of beta-lactam susceptibility in methicillin-resistant Staphylococcus aureus.

PubMed

Shibata, Hirofumi; Kondo, Kyoko; Katsuyama, Ryo; Kawazoe, Kazuyoshi; Sato, Yoichi; Murakami, Kotaro; Takaishi, Yoshihisa; Arakaki, Naokatu; Higuti, Tomihiko

2005-02-01

We found that ethyl gallate purified from a dried pod of tara (Caesalpinia spinosa) intensified beta-lactam susceptibility in methicillin-resistant and methicillin-sensitive strains of Staphylococcus aureus (MRSA and MSSA strains, respectively). This compound and several known alkyl gallates were tested with MRSA and MSSA strains to gain new insights into their structural functions in relation to antimicrobial and beta-lactam susceptibility-intensifying activities. The maximum activity of alkyl gallates against MRSA and MSSA strains occurred at 1-nonyl and 1-decyl gallate, with an MIC at which 90% of the isolates tested were inhibited of 15.6 microg/ml. At concentrations lower than the MIC, alkyl gallates synergistically elevated the susceptibility of MRSA and MSSA strains to beta-lactam antibiotics. Such a synergistic activity of the alkyl gallates appears to be specific for beta-lactam antibiotics, because no significant changes were observed in the MICs of other classes of antibiotics examined in this study. The length of the alkyl chain was also associated with the modifying activity of the alkyl gallates, and the optimum length was C5 to C6. The present work clearly demonstrates that the length of the alkyl chain has a key role in the elevation of susceptibility to beta-lactam antibiotics.

A comparison of the solvation structure and dynamics of the lithium ion in linear organic carbonates with different alkyl chain lengths.

PubMed

Fulfer, K D; Kuroda, D G

2017-09-20

The structure and dynamics of electrolytes composed of lithium hexafluorophosphate (LiPF 6 ) in dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate were investigated using a combination of linear and two-dimensional infrared spectroscopies. The solutions studied here have a LiPF 6 concentration of X(LiPF 6 ) = 0.09, which is typically found in commercial lithium ion batteries. This study focuses on comparing the differences in the solvation shell structure and dynamics produced by linear organic carbonates of different alkyl chain lengths. The IR experiments show that either linear carbonate forms a tetrahedral solvation shell (coordination number of 4) around the lithium ion irrespective of whether the solvation shell has anions in close proximity to the carbonates. Moreover, analysis of the absorption cross sections via FTIR and DFT computations reveals a distortion in the angle formed by Li + -O[double bond, length as m-dash]C which decreases from the expected 180° when the alkyl chains of the carbonate are lengthened. In addition, our findings also reveal that, likely due to its asymmetric structure, ethyl methyl carbonate has a significantly more distorted tetrahedral lithium ion solvation shell than either of the other two investigated carbonates. IR photon echo studies further demonstrate that the motions of the solvation shell have a time scale of a few picoseconds for all three linear carbonates. Interestingly, a slowdown of the in place-motions of the first solvation shell is observed when the carbonate has a longer alkyl chain length irrespective of the symmetry. In addition, vibrational energy transfer with a time scale of tens of picoseconds is observed between strongly coupled modes arising from the solvation shell structure of the Li + which corroborates the modeling of these solvation shells in terms of highly coupled vibrational states. Results of this study provide new insights into the molecular structure and dynamics of the

Ruthenium-catalyzed alkylation of indoles with tertiary amines by oxidation of a sp3 C-H bond and Lewis acid catalysis.

PubMed

Wang, Ming-Zhong; Zhou, Cong-Ying; Wong, Man-Kin; Che, Chi-Ming

2010-05-17

Ruthenium porphyrins (particularly [Ru(2,6-Cl(2)tpp)CO]; tpp=tetraphenylporphinato) and RuCl(3) can act as oxidation and/or Lewis acid catalysts for direct C-3 alkylation of indoles, giving the desired products in high yields (up to 82% based on 60-95% substrate conversions). These ruthenium compounds catalyze oxidative coupling reactions of a wide variety of anilines and indoles bearing electron-withdrawing or electron-donating substituents with high regioselectivity when using tBuOOH as an oxidant, resulting in the alkylation of N-arylindoles to 3-{[(N-aryl-N-alkyl)amino]methyl}indoles (yield: up to 82%, conversion: up to 95%) and the alkylation of N-alkyl or N-H indoles to 3-[p-(dialkylamino)benzyl]indoles (yield: up to 73%, conversion: up to 92%). A tentative reaction mechanism involving two pathways is proposed: an iminium ion intermediate may be generated by oxidation of an sp(3) C-H bond of the alkylated aniline by an oxoruthenium species; this iminium ion could then either be trapped by an N-arylindole (pathway A) or converted to formaldehyde, allowing a subsequent three-component coupling reaction of the in situ generated formaldehyde with an N-alkylindole and an aniline in the presence of a Lewis acid catalyst (pathway B). The results of deuterium-labeling experiments are consistent with the alkylation of N-alkylindoles via pathway B. The relative reaction rates of [Ru(2,6-Cl(2)tpp)CO]-catalyzed oxidative coupling reactions of 4-X-substituted N,N-dimethylanilines with N-phenylindole (using tBuOOH as oxidant), determined through competition experiments, correlate linearly with the substituent constants sigma (R(2)=0.989), giving a rho value of -1.09. This rho value and the magnitudes of the intra- and intermolecular deuterium isotope effects (k(H)/k(D)) suggest that electron transfer most likely occurs during the initial stage of the oxidation of 4-X-substituted N,N-dimethylanilines. Ruthenium-catalyzed three-component reaction of N-alkyl/N-H indoles

Metal complexes of alkyl-aryl dithiocarbamates: Structural studies, anticancer potentials and applications as precursors for semiconductor nanocrystals

NASA Astrophysics Data System (ADS)

Andrew, Fartisincha P.; Ajibade, Peter A.

2018-03-01

Dithiocarbamates are versatile ligands able to stabilize wide range of metal ions in their various oxidation states with the partial double bond character of Csbnd N and Csbnd S of thioureide moiety. Variation of the substituents attached to the nitrogen atom of dithiocarbamate moiety generates various intermolecular interactions, which lead to different structural arrangement in the solid state. The presence of bulky substituents on the N atom obviates the supramolecular aggregation via secondary Msbnd S interactions whereas smaller substituents encourage such aggregation that results in their wide properties and applications. Over the past decades, the synthesis and structural studies of metal complexes of dithiocarbamates have received considerable attention as potential anticancer agents with various degree of DNA binding affinity and cytotoxicity and as single molecule precursors for the preparation of semiconductor nanocrystals. In this paper, we review the synthesis, structural studies, anticancer potency and the use of alkyl-phenyl dithiocarbamate complexes as precursors for the preparation of semiconductor nanocrystals. The properties of these compounds and activities are ascribed to be due to either the dithiocarbamate moieties, the nature or type of the substituents around the dithiocarbamate backbone and the central metal ions or combination of these factors.

Effects of alkyl chain length and anion size on thermal and structural properties for 1-alkyl-3-methylimidazolium hexafluorocomplex salts (C(x)MImAF6, x = 14, 16 and 18; A = P, As, Sb, Nb and Ta).

PubMed

Xu, Fei; Matsumoto, Kazuhiko; Hagiwara, Rika

2012-03-28

A series of 1-alkyl-3-methylimidazolium hexafluorocomplex salts (C(x)MImAF(6), x = 14, 16 and 18, A = P, As, Sb, Nb and Ta) have been characterized by thermal analysis, X-ray diffraction and polarized optical microscopy. A liquid crystalline mesophase is observed for all the C(16)MIm and C(18)MIm salts. The C(14)MIm(+) cation gives a liquid crystalline mesophase only with PF(6)(-). The temperature range of the liquid crystalline mesophase increases with an increase in alkyl chain length or with decrease in anion size. Single-crystal X-ray diffraction revealed that all the C(18)MImAF(6) salts (A = P, As, Sb, Nb and Ta) are isostructural with each other in the crystalline phase and have a layered structure. The interdigitated alkyl chain of the cation has a bent shape like a spoon near the imidazolium ring in the crystalline phase at -100 °C and is tilted with respect to the sheets of the imidazolium headgroups and anions. An increase of temperature increases the ratio of an all-trans conformation to the bent conformation in the crystalline phase. X-ray diffraction and polarized optical microscopy suggested that the liquid crystalline mesophase has a smectic A(2) structure. The interlayer distance increases with a decrease in the anion size since the smaller anion has a stronger coulombic interaction with the imidazolium headgroup, resulting in the decrease of the interdigitated part to give a larger layer spacing.

Synthesis of Alkyl-Glycerolipids Standards for Gas Chromatography Analysis: Application for Chimera and Shark Liver Oils

PubMed Central

Pinault, Michelle; Guimaraes, Cyrille; Couthon, Hélène; Thibonnet, Jérôme; Fontaine, Delphine; Chantôme, Aurélie; Chevalier, Stephan; Jaffrès, Paul-Alain; Vandier, Christophe

2018-01-01

Natural O-alkyl-glycerolipids, also known as alkyl-ether-lipids (AEL), feature a long fatty alkyl chain linked to the glycerol unit by an ether bond. AEL are ubiquitously found in different tissues but, are abundant in shark liver oil, breast milk, red blood cells, blood plasma, and bone marrow. Only a few AEL are commercially available, while many others with saturated or mono-unsaturated alkyl chains of variable length are not available. These compounds are, however, necessary as standards for analytical methods. Here, we investigated different reported procedures and we adapted some of them to prepare a series of 1-O-alkyl-glycerols featuring mainly saturated alkyl chains of various lengths (14:0, 16:0, 17:0, 19:0, 20:0, 22:0) and two monounsaturated chains (16:1, 18:1). All of these standards were fully characterized by NMR and GC-MS. Finally, we used these standards to identify the AEL subtypes in shark and chimera liver oils. The distribution of the identified AEL were: 14:0 (20–24%), 16:0 (42–54%) and 18:1 (6–16%) and, to a lesser extent, (0.2–2%) for each of the following: 16:1, 17:0, 18:0, and 20:0. These standards open the possibilities to identify AEL subtypes in tumours and compare their composition to those of non-tumour tissues. PMID:29570630

Synthesis and Pharmacology of 1-Alkyl-3-(1-naphthoyl)indoles: Steric and Electronic Effects of 4- and 8-Halogenated Naphthoyl Substituents.

PubMed Central

Wiley, Jenny L.; Smith, Valerie J.; Chen, Jianhong; Martin, Billy R.; Huffman, John W.

2012-01-01

To develop SAR at both the cannabinoid CB1 and CB2 receptors for 3-(1-naphthoyl)indoles bearing moderately electron withdrawing substituents at C-4 of the naphthoyl moiety, 1-propyl and 1-pentyl-3-(4-fluoro, chloro, bromo and iodo-1-naphthoyl) derivatives were prepared. To study the steric and electronic effects of substituents at the 8-position of the naphthoyl group, the 3-(4-chloro, bromo and iodo-1-naphthoyl)indoles were also synthesized. The affinities of both groups of compounds for the CB1 and CB2 receptors were determined and several of them were evaluated in vivo in the mouse. The effects of these substituents on receptor affinities and in vivo activity are discussed and structure-activity relationships are presented. Although many of these compounds are selective for the CB2 receptor, only three JWH-423, 1-propyl-3-(4-iodo-1-naphthoyl)indole, JWH-422, 2-methyl-1-propyl-3-(4-iodo-1-naphthoyl)indole, the 2-methyl analog of JWH-423 and JWH-417, 1-pentyl-3-(8-iodo-1-naphthoyl)indole, possess the desirable combination of low CB1 affinity and good CB2 affinity. PMID:22341572

Structure-Antibacterial Activity Relationships of Imidazolium-Type Ionic Liquid Monomers, Poly(ionic liquids) and Poly(ionic liquid) Membranes: Effect of Alkyl Chain Length and Cations.

PubMed

Zheng, Zhiqiang; Xu, Qiming; Guo, Jiangna; Qin, Jing; Mao, Hailei; Wang, Bin; Yan, Feng

2016-05-25

The structure-antibacterial activity relationship between the small molecular compounds and polymers are still elusive. Here, imidazolium-type ionic liquid (IL) monomers and their corresponding poly(ionic liquids) (PILs) and poly(ionic liquid) membranes were synthesized. The effect of chemical structure, including carbon chain length of substitution at the N3 position and charge density of cations (mono- or bis-imidazolium) on the antimicrobial activities against both Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) was investigated by determination of minimum inhibitory concentration (MIC). The antibacterial activities of both ILs and PILs were improved with the increase of the alkyl chain length and higher charge density (bis-cations) of imidazolium cations. Moreover, PILs exhibited lower MIC values relative to the IL monomers. However, the antibacterial activities of PIL membranes showed no correlation to those of their analogous small molecule IL monomers and PILs, which increased with the charge density (bis-cations) while decreasing with the increase of alkyl chain length. The results indicated that antibacterial property studies on small molecules and homopolymers may not provide a solid basis for evaluating that in corresponding polymer membranes.

Antioxidant activity of alkyl gallates and glycosyl alkyl gallates in fish oil in water emulsions: relevance of their surface active properties and of the type of emulsifier.

PubMed

González, María J; Medina, Isabel; Maldonado, Olivia S; Lucas, Ricardo; Morales, Juan C

2015-09-15

The antioxidant activity of gallic acid and a series of alkyl gallates (C4-C18) and glycosylated alkyl gallates (C4-C18) on fish oil-in-water emulsions was studied. Three types of emulsifiers, lecithin, Tween-20 and sodium dodecyl sulphate (SDS) were tested. A nonlinear behavior of the antioxidant activity of alkyl gallates when increasing alkyl chain length was observed for emulsions prepared with lecithin. Medium-size alkyl gallates (C6-C12) were the best antioxidants. In contrast, for emulsions prepared with Tween-20, the antioxidants seem to follow the polar paradox. Glucosyl alkyl gallates were shown previously to be better surfactants than alkyl gallates. Nevertheless, they exhibited a worse antioxidant capacity than their corresponding alkyl gallates, in emulsions prepared with lecithin or Tween-20, indicating the greater relevance of having three OH groups at the polar head in comparison with having improved surfactant properties but just a di-ortho phenolic structure in the antioxidant. Copyright © 2015 Elsevier Ltd. All rights reserved.

Effect of the C-2 hydroxyl group on the mesomorphism of alkyl glycosides: synthesis and thermotropic behavior of alkyl 2-deoxy-D-arabino-hexopyranosides.

PubMed

Singh, Madan Kumar; Jayaraman, Narayanaswamy; Rao, D S Shankar; Prasad, S Krishna

2008-10-01

A homologous series of alkyl 2-deoxy-alpha-d-arabino-hexopyranosides and alkyl 2-deoxy-beta-d-arabino-hexopyranosides were synthesized, upon glycosylation of 1-alkanols (from C8 to C18 alkanols) with ethyl 2-deoxy-3,4,6-tri-O-acetyl-1-thio-d-arabino-hexopyranoside, followed by a deprotection. The thermotropic behavior of these new types of alkyl glycosides was investigated. It was observed that the beta-anomers of these alkyl glycosides, bearing nonyl to tetradecyl alkyl chain are mesomorphic, exhibiting monotropic smectic A phase. In contrast, the alpha-anomers are all non-mesomorphic. An effort to identify the liquid crystalline behavior of binary mixtures of the alpha- and beta-anomers was undertaken and it was found that mixtures containing equimolar amounts of the anomers exhibited mesomorphic behavior. A fine balance of the hydrophilic and hydrophobic components within the molecule is also found to be important for the alkyl 2-deoxy glycosides to form the mesophase.

Cu sbnd Al sbnd Fe layered double hydroxides with CO32- and anionic surfactants with different alkyl chains in the interlayer

NASA Astrophysics Data System (ADS)

Trujillano, Raquel; Holgado, María Jesús; González, José Luis; Rives, Vicente

2005-08-01

Layered double hydroxides (LDHs), with the hydrotalcite-like structure containing Cu(II), Al(III) and Fe(III) in the layers, and different alkyl sulfonates in the interlayer, have been prepared and characterized by powder X-ray diffraction, FT-IR spectroscopy, differential thermal analysis and thermogravimetric analysis. Pure crystalline phases have been obtained in all cases. Upon heating, combustion of the organic chain takes place at lower temperature than the corresponding sodium salts.

Membrane-destabilizing activity of pH-responsive cationic lysine-based surfactants: role of charge position and alkyl chain length.

PubMed

Nogueira, Daniele Rubert; Mitjans, Montserrat; Morán, M Carmen; Pérez, Lourdes; Vinardell, M Pilar

2012-09-01

Many strategies for treating diseases require the delivery of drugs into the cell cytoplasm following internalization within endosomal vesicles. Thus, compounds triggered by low pH to disrupt membranes and release endosomal contents into the cytosol are of particular interest. Here, we report novel cationic lysine-based surfactants (hydrochloride salts of N(ε)- and N(α)-acyl lysine methyl ester) that differ in the position of the positive charge and the length of the alkyl chain. Amino acid-based surfactants could be promising novel biomaterials in drug delivery systems, given their biocompatible properties and low cytotoxic potential. We examined their ability to disrupt the cell membrane in a range of pH values, concentrations and incubation times, using a standard hemolysis assay as a model of endosomal membranes. Furthermore, we addressed the mechanism of surfactant-mediated membrane destabilization, including the effects of each surfactant on erythrocyte morphology as a function of pH. We found that only surfactants with the positive charge on the α-amino group of lysine showed pH-sensitive hemolytic activity and improved kinetics within the endosomal pH range, indicating that the positive charge position is critical for pH-responsive behavior. Moreover, our results showed that an increase in the alkyl chain length from 14 to 16 carbon atoms was associated with a lower ability to disrupt cell membranes. Knowledge on modulating surfactant-lipid bilayer interactions may help us to develop more efficient biocompatible amino acid-based drug delivery devices.

Kinetic study of the anaerobic biodegradation of alkyl polyglucosides and the influence of their structural parameters.

PubMed

Ríos, Francisco; Fernández-Arteaga, Alejandro; Lechuga, Manuela; Jurado, Encarnación; Fernández-Serrano, Mercedes

2016-05-01

This paper reports a study of the anaerobic biodegradation of non-ionic surfactants alkyl polyglucosides applying the method by measurement of the biogas production in digested sludge. Three alkyl polyglucosides with different length alkyl chain and degree of polymerization of the glucose units were tested. The influence of their structural parameters was evaluated, and the characteristics parameters of the anaerobic biodegradation were determined. Results show that alkyl polyglucosides, at the standard initial concentration of 100 mgC L(-1), are not completely biodegradable in anaerobic conditions because they inhibit the biogas production. The alkyl polyglucoside having the shortest alkyl chain showed the fastest biodegradability and reached the higher percentage of final mineralization. The anaerobic process was well adjusted to a pseudo first-order equation using the carbon produced as gas during the test; also, kinetics parameters and a global rate constant for all the involved metabolic process were determined. This modeling is helpful to evaluate the biodegradation or the persistence of alkyl polyglucosides under anaerobic conditions in the environment and in the wastewater treatment.

Tuning the nature and stability of self-assemblies formed by ester benzene 1,3,5-tricarboxamides: the crucial role played by the substituents.

PubMed

Desmarchelier, Alaric; Alvarenga, Bruno Giordano; Caumes, Xavier; Dubreucq, Ludovic; Troufflard, Claire; Tessier, Martine; Vanthuyne, Nicolas; Idé, Julien; Maistriaux, Thomas; Beljonne, David; Brocorens, Patrick; Lazzaroni, Roberto; Raynal, Matthieu; Bouteiller, Laurent

2016-09-20

As the benzene 1,3,5-tricarboxamide (BTA) moiety is commonly used as the central assembling unit for the construction of functionalized supramolecular architectures, strategies to tailor the nature and stability of BTA assemblies are needed. The assembly properties of a library of structurally simple BTAs derived from amino dodecyl esters (ester BTAs, 13 members) have been studied, either in the bulk or in cyclohexane solutions, by means of a series of analytical methods (NMR, DSC, POM, FT-IR, UV-Vis, CD, ITC, high-sensitivity DSC, SANS). Two types of hydrogen-bonded species have been identified and characterized: the expected amide-bonded helical rods (or stacks) that are structurally similar to those formed by BTAs with simple alkyl side chains (alkyl BTAs), and ester-bonded dimers in which the BTAs are connected by means of hydrogen bonds linking the amide N-H and the ester C[double bond, length as m-dash]O. MM/MD calculations coupled with simulations of CD spectra allow for the precise determination of the molecular arrangement and of the hydrogen bond pattern of these dimers. Our study points out the crucial influence of the substituent attached on the amino-ester α-carbon on the relative stability of the rod-like versus dimeric assemblies. By varying this substituent, one can precisely tune the nature of the dominant hydrogen-bonded species (stacks or dimers) in the neat compounds and in cyclohexane over a wide range of temperatures and concentrations. In the neat BTAs, stacks are stable up to 213 °C and dimers above 180 °C whilst in cyclohexane stacks form at c* > 3 × 10 -5 M at 20 °C and dimers are stable up to 80 °C at 7 × 10 -6 M. Ester BTAs that assemble into stacks form a liquid-crystalline phase and yield gels or viscous solutions in cyclohexane, demonstrating the importance of controlling the structure of these assemblies. Our systematic study of these structurally similar ester BTAs also allows for a better understanding of how a single atom

Alkyl-substituted phenylamino derivatives of 7-nitrobenz-2-oxa-1,3-diazole as uncouplers of oxidative phosphorylation and antibacterial agents: involvement of membrane proteins in the uncoupling action.

PubMed

Antonenko, Yuri N; Denisov, Stepan S; Khailova, Ljudmila S; Nazarov, Pavel A; Rokitskaya, Tatyana; Tashlitsky, Vadim N; Firsov, Alexander M; Korshunova, Galina A; Kotova, Elena A

2017-03-01

In search for new effective uncouplers of oxidative phosphorylation, we studied 4-aryl amino derivatives of a fluorescent group 7-nitrobenz-2-oxa-1,3-diazol (NBD). In our recent work (Denisov et al., Bioelectrochemistry, 2014), NBD-conjugated alkyl amines (NBD-C n ) were shown to exhibit uncoupling activity. It was concluded that despite a pK a value being about 10, the expected hindering of the uncoupling activity could be overcome by insertion of an alkyl chain. There is evidence in the literature that the introduction of an aryl substituent in the 4-amino NBD group shifts the pK a to neutral values. Here we report the data on the properties of a number of 4-arylamino derivatives of NBD, namely, alkylphenyl-amino-NBD (C n -phenyl-NBD) with varying alkyl chain C n . By measuring the electrical current across planar bilayer lipid membrane, the protonophoric activity of C n -phenyl-NBD at neutral pH grew monotonously from C 1 - to C 6 -phenyl-NBD. All of these compounds increased the respiration rate and reduced the membrane potential of isolated rat liver mitochondria. Importantly, the uncoupling action of C 6 - and C 4 -phenyl-NBD was partially reversed by glutamate, diethyl pyrocarbonate (DEPC), 6-ketocholestanol, and carboxyatractyloside, thus pointing to the involvement of membrane proteins in the uncoupling activity of C n -phenyl-NBD in mitochondria. The pronounced recoupling effect of DEPC, an inhibitor of an aspartate-glutamate carrier (AGC), and that of its substrates for the first time highlighted AGC participation in the action of potent uncouplers on mitochondria. C 6 -phenyl-NBD produced strong antimicrobial effect on Bacillus subtilis, which manifested itself in cell membrane depolarization and suppression of bacterial growth at submicromolar concentrations. Copyright © 2016 Elsevier B.V. All rights reserved.

Theoretical model to investigate the alkyl chain and anion dependent interactions of gemini surfactant with bovine serum albumin

NASA Astrophysics Data System (ADS)

Vishvakarma, Vijay K.; Kumari, Kamlesh; Patel, Rajan; Dixit, V. S.; Singh, Prashant; Mehrotra, Gopal K.; Chandra, Ramesh; Chakrawarty, Anand Kumar

2015-05-01

Surfactants are used to prevent the irreversible aggregation of partially refolded proteins and they also assist in protein refolding. We have reported the design and screening of gemini surfactant to stabilize bovine serum albumin (BSA) with the help of computational tool (iGEMDOCK). A series of gemini surfactant has been designed based on bis-N-alkyl nicotinate dianion via varying the alkyl group and anion. On changing the alkyl group and anion of the surfactant, the value of Log P changes means polarity of surfactant can be tuned. Further, the virtual screening of the gemini surfactant has been carried out based on generic evolutionary method. Herein, thermodynamic data was studied to determine the potential of gemini surfactant as BSA stabilizer. Computational tools help to find out the efficient gemini surfactant to stabilize the BSA rather than to use the surfactant randomly and directionless for the stabilization. It can be confirmed through the experimental techniques. Previously, researcher synthesized one of the designed and used gemini surfactant to stabilize the BSA and their interactions were confirmed through various techniques and computational docking. But herein, the authors find the most competent gemini surfactant to stabilize BSA using computational tools on the basis of energy score. Different from the single chain surfactant, the gemini surfactants exhibit much stronger electrostatic and hydrophobic interactions with the protein and are thus effective at much lower concentrations. Based on the present study, it is expected that gemini surfactants may prove useful in the protein stabilization operations and may thus be effectively employed to circumvent the problem of misfolding and aggregation.

Effect of ionic strength and cationic DNA affinity binders on the DNA sequence selective alkylation of guanine N7-positions by nitrogen mustards

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hartley, J.A.; Forrow, S.M.; Souhami, R.L.

Large variations in alkylation intensities exist among guanines in a DNA sequence following treatment with chemotherapeutic alkylating agents such as nitrogen mustards, and the substituent attached to the reactive group can impose a distinct sequence preference for reaction. In order to understand further the structural and electrostatic factors which determine the sequence selectivity of alkylation reactions, the effect of increase ionic strength, the intercalator ethidium bromide, AT-specific minor groove binders distamycin A and netropsin, and the polyamine spermine on guanine N7-alkylation by L-phenylalanine mustard (L-Pam), uracil mustard (UM), and quinacrine mustard (QM) was investigated with a modification of the guanine-specificmore » chemical cleavage technique for DNA sequencing. The result differed with both the nitrogen mustard and the cationic agent used. The effect, which resulted in both enhancement and suppression of alkylation sites, was most striking in the case of netropsin and distamycin A, which differed from each other. DNA footprinting indicated that selective binding to AT sequences in the minor groove of DNA can have long-range effects on the alkylation pattern of DNA in the major groove.« less

Chemistry of anthracene-acetylene oligomers XXV: on-surface chirality of a self-assembled molecular network of a fan-blade-shaped anthracene-acetylene macrocycle with a long alkyl chain.

PubMed

Tsuya, Takuya; Iritani, Kohei; Tahara, Kazukuni; Tobe, Yoshito; Iwanaga, Tetsuo; Toyota, Shinji

2015-03-27

An anthracene cyclic dimer with two different linkers and a dodecyl group was synthesized by means of coupling reactions. The calculated structure had a planar macrocyclic π core and a linear alkyl chain. Scanning tunneling microscopy observations at the 1-phenyloctane/graphite interface revealed that the molecules formed a self-assembled monolayer that consisted of linear striped bright and dark bands. In each domain, the molecular network consisted of either Re or Si molecules that differed in the two-dimensional chirality about the macrocyclic faces, which led to a unique conglomerate-type self-assembly. The molecular packing mode and the conformation of the alkyl chains are discussed in terms of the intermolecular interactions and the interactions between the molecules and the graphite surface with the aid of MM3 simulations of a model system. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Critical effects of alkyl chain length on fibril structures in benzene-trans(RR)- or (SS)-N,N'-alkanoyl-1,2-diaminocyclohexane gels.

PubMed

Sato, Hisako; Nakae, Takahiro; Morimoto, Kazuya; Tamura, Kenji

2012-02-28

Vibrational circular dichroism (VCD) spectra were recorded on benzene-d(6) gels formed by chiral low molecular mass gelators (LMGs), trans(RR)- or trans(SS)-N,N'-alkanoyl-1,2-diaminocyclohexane (denoted by RR-C(n) or SS-C(n), respectively; n = the number of carbon atoms in an introduced alkanoyl group). Attention was focused on the effects of alkyl chain length on the structures of the gels. When n was changed from 6 to 12, the signs of the coupled peaks around 1550 cm(-1) in the VCD spectra, which were assigned to the symmetric and asymmetric C=O stretching vibrations from the higher to lower wavenumber, respectively, critically depended on the alkyl chain length. In the case of RR-C(n), for example, the signs of the couplet were plus and minus for n = 8, 9, 10 and 12, while the signs of the same couplet were reversed for n = 6 and 7. The conformations of LMGs in fibrils were determined by comparing the observed IR and VCD spectra with those calculated for a monomeric molecule. The observed reversal of signs in the C=O couplet was rationalized in terms of the different modes of hydrogen bonding. In the case of C(8), C(9), C(10) and C(12), gelator molecules were stacked with their cyclohexyl rings in parallel, forming double anti-parallel chains of intermolecular hydrogen bonds using two pairs of >NH and >C=O groups. In case of C(6) and C(7), gelator molecules were stacked through a single chain of intermolecular hydrogen bonds using a pair of >NH and >C=O groups. The remaining pair of >NH and >C=O groups formed an intramolecular hydrogen bond.

Occurrence and Biosynthesis of Alkyl Hydroxycinnamates in Plant Lipid Barriers

PubMed Central

Domergue, Frédéric; Kosma, Dylan K.

2017-01-01

The plant lipid barriers cuticle and suberin represent one of the largest biological interfaces on the planet. They are comprised of an insoluble polymeric domain with associated organic solvent-soluble waxes. Suberin-associated and plant cuticular waxes contain mixtures of aliphatic components that may include alkyl hydroxycinnamates (AHCs). The canonical alkyl hydroxycinnamates are comprised of phenylpropanoids, typically coumaric, ferulic, or caffeic acids, esterified with long chain to very long chain fatty alcohols. However, many related structures are also present in the plant kingdom. Although their functions remain elusive, much progress has been made on understanding the distribution, biosynthesis, and deposition of AHCs. Herein a summary of the current state of knowledge on plant AHCs is provided. PMID:28665304

Synthesis and Antioxidant Activity of Hydroxytyrosol Alkyl-Carbonate Derivatives.

PubMed

Fernandez-Pastor, Ignacio; Fernandez-Hernandez, Antonia; Rivas, Francisco; Martinez, Antonio; Garcia-Granados, Andres; Parra, Andres

2016-07-22

Three procedures have been investigated for the isolation of tyrosol (1) and hydroxytyrosol (2) from a phenolic extract obtained from the solid residue of olive milling. These three methods, which facilitated the recovery of these phenols, were chemical or enzymatic acetylation, benzylation, and carbomethoxylation, and subsequent carbonylation or acetonation reactions. Several new lipophilic alkyl-carbonate derivatives of hydroxytyrosol have been synthesized, coupling the primary hydroxy group of this phenol, through a carbonate linker, using alcohols with different chain lengths. The antioxidant properties of these lipophilic derivatives have been evaluated by different methods and compared with free hydroxytyrosol (2) and also with the well-known antioxidants BHT and α-tocopherol. Three methods were used for the determination of this antioxidant activity: FRAP and ABTS assays, to test the antioxidant power in hydrophilic media, and the Rancimat test, to evaluate the antioxidant capacity in a lipophilic matrix. These new alkyl-carbonate derivatives of hydroxytyrosol enhanced the antioxidant activity of this natural phenol, with their antioxidant properties also being higher than those of the commercial antioxidants BHT and α-tocopherol. There was no clear influence of the side-chain length on the antioxidant properties of the alkyl-carbonate derivatives of 2, although the best results were achieved mainly by the compounds with a longer chain on the primary hydroxy group of this natural phenolic substance.

Substituent Effects in the Benzene Dimer are Due to Direct Interactions of the Substituents with the Unsubstituted Benzene

PubMed Central

Wheeler, Steven E.; Houk, K. N.

2009-01-01

The prevailing views of substituent effects in the sandwich configuration of the benzene dimer are flawed. For example, in the polar/π model of Cozzi and co-workers (J. Am. Chem. Soc. 1992, 114, 5729), electron-withdrawing substituents enhance binding in the benzene dimer by withdrawing electron density from the π-cloud of the substituted ring, reducing the repulsive electrostatic interaction with the non-substituted benzene. Conversely, electron-donating substituents donate excess electrons into the π-system and diminish the π-stacking interaction. We present computed interaction energies for the sandwich configuration of the benzene dimer and 24 substituted dimers, as well as sandwich complexes of substituted benzenes with perfluorobenzene. While the computed interaction energies correlate well with σm values for the substituents, interaction energies for related model systems demonstrate that this trend is independent of the substituted ring. Instead, the observed trends are consistent with direct electrostatic and dispersive interactions of the substituents with the unsubstituted ring. PMID:18652453

Isolation of the antibiotic pseudopyronine B and SAR evaluation of C3/C6 alkyl analogs.

PubMed

Bouthillette, Leah M; Darcey, Catherine A; Handy, Tess E; Seaton, Sarah C; Wolfe, Amanda L

2017-06-15

Natural products are an abundant source of structurally diverse compounds with antibacterial activity that can be used to develop new and potent antibiotics. One such class of natural products is the pseudopyronines. Here we present the isolation of pseudopyronine B (2) from a Pseudomonas species found in garden soil in Western North Carolina, and SAR evaluation of C3 and C6 alkyl analogs of the natural product for antibacterial activity against Gram-positive and Gram-negative bacteria. We found a direct relationship between antibacterial activity and C3/C6 alkyl chain length. For inhibition of Gram-positive bacteria, alkyl chain lengths between 6 and 7 carbons were found to be the most active (IC 50 =0.04-3.8µg/mL) whereas short alkyl chain analogs showed modest activity against Gram-negative bacteria (IC 50 =223-304µg/mL). This demonstrates the potential for this class of natural products to be optimized for selective activity against either Gram-positive or Gram-negative bacteria. Copyright © 2017 Elsevier Ltd. All rights reserved.

Synthesis and evaluation of thermo-rheological behaviour and ionotropic crosslinking of new gellan gum-alkyl derivatives.

PubMed

Agnello, Stefano; Palumbo, Fabio Salvatore; Pitarresi, Giovanna; Fiorica, Calogero; Giammona, Gaetano

2018-04-01

This paper reports the synthesis and the physicochemical characterization of two series of gellan gum (GG) derivatives functionalized with alkyl chains with different number of carbon, from 8 to 18. In particular, low molecular weight gellan gum samples with 52.6 or 96.7 kDa, respectively, were functionalized with octylamine (C 8 ), dodecylamine (C 12 ) and octadecylamine (C 18 ) by using bis(4-nitrophenyl) carbonate (4-NPBC) as a coupling agent. Thermo-rheological and ionotropic crosslinking properties of these gellan gum-alkyl derivatives were evaluated and related to the degree of derivatization in alkyl chains. Results suggested as length and degree of derivatization differently influenced coil-to-helix gelation mechanism of GG derivatives, ionotropic crosslinking, and strength of crosslinked hydrogels obtained in CaCl 2 0.102 M and NaCl 0.15 M. Statement of hypothesis: The insertion of alkyl chains on the gellan gum backbone interferes with coil-to-helix transition mechanism and allows the production of hydrophobically assembled hydrogels. Copyright © 2018 Elsevier Ltd. All rights reserved.

Theoretical model to investigate the alkyl chain and anion dependent interactions of gemini surfactant with bovine serum albumin.

PubMed

Vishvakarma, Vijay K; Kumari, Kamlesh; Patel, Rajan; Dixit, V S; Singh, Prashant; Mehrotra, Gopal K; Chandra, Ramesh; Chakrawarty, Anand Kumar

2015-05-15

Surfactants are used to prevent the irreversible aggregation of partially refolded proteins and they also assist in protein refolding. We have reported the design and screening of gemini surfactant to stabilize bovine serum albumin (BSA) with the help of computational tool (iGEMDOCK). A series of gemini surfactant has been designed based on bis-N-alkyl nicotinate dianion via varying the alkyl group and anion. On changing the alkyl group and anion of the surfactant, the value of Log P changes means polarity of surfactant can be tuned. Further, the virtual screening of the gemini surfactant has been carried out based on generic evolutionary method. Herein, thermodynamic data was studied to determine the potential of gemini surfactant as BSA stabilizer. Computational tools help to find out the efficient gemini surfactant to stabilize the BSA rather than to use the surfactant randomly and directionless for the stabilization. It can be confirmed through the experimental techniques. Previously, researcher synthesized one of the designed and used gemini surfactant to stabilize the BSA and their interactions were confirmed through various techniques and computational docking. But herein, the authors find the most competent gemini surfactant to stabilize BSA using computational tools on the basis of energy score. Different from the single chain surfactant, the gemini surfactants exhibit much stronger electrostatic and hydrophobic interactions with the protein and are thus effective at much lower concentrations. Based on the present study, it is expected that gemini surfactants may prove useful in the protein stabilization operations and may thus be effectively employed to circumvent the problem of misfolding and aggregation. Copyright © 2015 Elsevier B.V. All rights reserved.

Phosphines bearing alkyne substituents: synthesis and hydrophosphination polymerization.

PubMed

Greenberg, Sharonna; Stephan, Douglas W

2009-09-07

A synthetic route is described for a series of phosphines bearing pendant alkyne substituents, from the conversion of BrC(6)H(2)R(2)C[triple bond]CR' (R = Me, i-Pr; R' = Ph, SiMe(3)) to [(mu-Br)Cu(Et(2)N)(2)PC(6)H(2)R(2)C[triple bond]CR'](2) and subsequently to Cl(2)PC(6)H(2)R(2)C[triple bond]CR' and H(2)PC(6)H(2)R(2)C[triple bond]CR'. Lithiation and subsequent alkylation yield the secondary phosphines R(H)PC(6)H(2)(i-Pr)(2)C[triple bond]CPh (R = CH(2)i-Pr, CH(2)Ph). Intermolecular hydrophosphination-polymerization is used to prepare the polymeric species [RPC(6)H(2)(i-Pr)(2)CH=CPh](n), which can then be sulfurized to give [RP(S)C(6)H(2)(i-Pr)(2)CH=CPh](n). The polymeric products were characterized by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and gel permeation chromatography. These data indicate a degree of polymerization (DP(n)) of up to 60. Discussion of the mechanism is augmented with gas-phase density functional theory calculations.

Ion sensing by charge transfer absorption variations of benzocrown-bipyridinium conjugates with an alkyl chain.

PubMed

Kuwabara, Tetsuo; Satake, Ryota; Guo, Haocheng

2015-01-01

Two benzocrown ether-bipyridinium conjugates, 1 and 2, each having a different length of alkyl chains with butyl and dodecyl groups, respectively, have been synthesized for the purpose of developing a new guest-responsive color-change chemosensor. Both 1 and 2 showed yellow colors with broad absorption bands around 400 nm in acetonitrile. These are associated with the intramolecular charge transfer (CT) absorption, in which the benzocrown ether and bipyridinium units act as the donor and acceptor, respectively. Upon addition of the guest; such as Na(+), they faded in color due to the blue shift in their intramolecular charge transfer absorption bands. These are associated with the formation of 1:1 host-guest inclusion complex. Analogues, 3 and 4, both being similar in structure to 1 and 2 with non-crown ether unit, also showed intramolecular CT absorptions around 400 nm, but did not change their absorption spectra upon addition of the guest because of the lack of guest-binding abilities. The guest-induced color change of 1 and 2 can be used for alkali and alkaline metal ion sensing. Both 1 and 2 could detect divalent cations such as Mg(2+) and Ca(2+) rather than univalent ones, Li(+), Na(+), K(+), Rb(+), and Cs(+). Although a marked difference between 1 and 2 was not observed in their guest sensing abilities, the remarkable recognition of 1 and 2 for Mg(2+) and Ca(2+) was found compared with that of 5, which has benzyl unit instead of alkyl chains of 1 and 2. The sensitivity values of 1 and 2 were roughly proportional to their binding constants, as shown by the binding constants with Li(+), Na(+), Mg(2+), and Ca(2+) with the values of 910, 260, 820, and 2300 M(-1) for 1 and 930, 290, 1270, and 2790 M(-1) for 2, while the binding constants of 5 were estimated to be 930, 440, 210, and 1200 M(-1) for Li(+), Na(+), Mg(2+), and Ca(2+), respectively. The limit concentration of detection of 2 for Ca(2+) was estimated to be 0.016 mM, which was the smallest value in this

Conformational explosion: Understanding the complexity of short chain para-dialkylbenzene potential energy surfaces

NASA Astrophysics Data System (ADS)

Mishra, Piyush; Hewett, Daniel M.; Zwier, Timothy S.

2018-05-01

The single-conformation ultraviolet and infrared spectroscopy of three short-chain para-dialkylbenzenes (para-diethylbenzene, para-dipropylbenzene, and para-dibutylbenzene) is reported for the jet-cooled, isolated molecules. The present study builds off previous work on single-chain n-alkylbenzenes, where an anharmonic local mode Hamiltonian method was developed to account for stretch-bend Fermi resonance in the alkyl CH stretch region [D. P. Tabor et al., J. Chem. Phys. 144, 224310 (2016)]. The jet-cooled molecules are interrogated using laser-induced fluorescence (LIF) excitation, fluorescence dip infrared spectroscopy, and dispersed fluorescence. The LIF spectra in the S1 ← S0 origin region show a dramatic increase in the number of resolved transitions with increasing length of the alkyl chains, reflecting an explosion in the number of unique low-energy conformations formed when two independent alkyl chains are present. Since the barriers to isomerization of the alkyl chain are similar in size, this results in an "egg carton" shaped potential energy surface. A combination of electronic frequency shift and alkyl CH stretch infrared spectra is used to generate a consistent set of conformational assignments. Using these experimental techniques in conjunction with computational methods, subsets of origin transitions in the LIF excitation spectrum can be classified into different conformational families. Two conformations are resolved in para-diethylbenzene, seven in para-dipropylbenzene, and about nineteen in para-dibutylbenzene. These chains are largely independent of each other as there are no new single-chain conformations induced by the presence of a second chain. A cursory LIF excitation scan of para-dioctylbenzene shows a broad congested spectrum at frequencies consistent with interactions of alkyl chains with the phenyl π cloud.

Conformational explosion: Understanding the complexity of short chain para-dialkylbenzene potential energy surfaces.

PubMed

Mishra, Piyush; Hewett, Daniel M; Zwier, Timothy S

2018-05-14

The single-conformation ultraviolet and infrared spectroscopy of three short-chain para-dialkylbenzenes (para-diethylbenzene, para-dipropylbenzene, and para-dibutylbenzene) is reported for the jet-cooled, isolated molecules. The present study builds off previous work on single-chain n-alkylbenzenes, where an anharmonic local mode Hamiltonian method was developed to account for stretch-bend Fermi resonance in the alkyl CH stretch region [D. P. Tabor et al., J. Chem. Phys. 144, 224310 (2016)]. The jet-cooled molecules are interrogated using laser-induced fluorescence (LIF) excitation, fluorescence dip infrared spectroscopy, and dispersed fluorescence. The LIF spectra in the S 1 ← S 0 origin region show a dramatic increase in the number of resolved transitions with increasing length of the alkyl chains, reflecting an explosion in the number of unique low-energy conformations formed when two independent alkyl chains are present. Since the barriers to isomerization of the alkyl chain are similar in size, this results in an "egg carton" shaped potential energy surface. A combination of electronic frequency shift and alkyl CH stretch infrared spectra is used to generate a consistent set of conformational assignments. Using these experimental techniques in conjunction with computational methods, subsets of origin transitions in the LIF excitation spectrum can be classified into different conformational families. Two conformations are resolved in para-diethylbenzene, seven in para-dipropylbenzene, and about nineteen in para-dibutylbenzene. These chains are largely independent of each other as there are no new single-chain conformations induced by the presence of a second chain. A cursory LIF excitation scan of para-dioctylbenzene shows a broad congested spectrum at frequencies consistent with interactions of alkyl chains with the phenyl π cloud.

Molecular dynamic simulation of dicationic ionic liquids: effects of anions and alkyl chain length on liquid structure and diffusion.

PubMed

Yeganegi, Saeid; Soltanabadi, Azim; Farmanzadeh, Davood

2012-09-20

Structures and dynamics of nine geminal dicationic ionic liquids (DILs) Cn(mim)2X2, where n = 3, 6, and 9 and X = PF6(-), BF4(-), and Br(-), were studied by molecular dynamic simulations (J. Phys. Chem.B2004, 108, 2038-2047). A force field with a minor modification for C3(mim)2 × 2 was adopted for the simulations. Densities, detailed microscopic structures, mean-square displacements (MSD), and self-diffusivities for various ion pairs from MD simulations have been presented. The calculated densities for C9(mim)2X2 (X = Br(-) and BF4(-)) agreed well with the experimental values. The calculated RDFs show that anions are well organized around the imidazolium rings. The calculated RDFs indicate that, unlike the mono cationic ILs, the anions and cations in DILs distribute homogeneously. Enthalpies of vaporization were calculated and correlated with the structural features of DILs. The local structure of C9(mim)2X2 (X = Br, PF6) was examined by the spatial distribution function (SDF). The calculated SDFs show that similar trends were found by other groups for mono cationic ionic liquids (ILs). The highest probability densities are located around the imidazolium ring hydrogens. The calculated diffusion coefficients show that the ion diffusivities are 1 order of magnitude smaller than that of the mono cationic ionic liquids. The effects of alkyl chain length and anion type on the diffusion coefficient were also studied. The dynamics of the imidazolium rings and the alkyl chain in different time scales have also discussed. The calculated transference numbers show that the anions have the major role in carrying the electric current in a DIL.

Ab initio evaluation of the thermodynamic and electrochemical properties of alkyl halides and radicals and their mechanistic implications for atom transfer radical polymerization.

PubMed

Lin, Ching Yeh; Coote, Michelle L; Gennaro, Armando; Matyjaszewski, Krzysztof

2008-09-24

High-level ab initio molecular orbital calculations are used to study the thermodynamics and electrochemistry relevant to the mechanism of atom transfer radical polymerization (ATRP). Homolytic bond dissociation energies (BDEs) and standard reduction potentials (SRPs) are reported for a series of alkyl halides (R-X; R = CH 2CN, CH(CH 3)CN, C(CH 3) 2CN, CH 2COOC 2H 5, CH(CH 3)COOCH 3, C(CH 3) 2COOCH 3, C(CH 3) 2COOC 2H 5, CH 2Ph, CH(CH 3)Ph, CH(CH 3)Cl, CH(CH 3)OCOCH 3, CH(Ph)COOCH 3, SO 2Ph, Ph; X = Cl, Br, I) both in the gas phase and in two common organic solvents, acetonitrile and dimethylformamide. The SRPs of the corresponding alkyl radicals, R (*), are also examined. The computational results are in a very good agreement with the experimental data. For all alkyl halides examined, it is found that, in the solution phase, one-electron reduction results in the fragmentation of the R-X bond to the corresponding alkyl radical and halide anion; hence it may be concluded that a hypothetical outer-sphere electron transfer (OSET) in ATRP should occur via concerted dissociative electron transfer rather than a two-step process with radical anion intermediates. Both the homolytic and heterolytic reactions are favored by electron-withdrawing substituents and/or those that stabilize the product alkyl radical, which explains why monomers such as acrylonitrile and styrene require less active ATRP catalysts than vinyl chloride and vinyl acetate. The rate constant of the hypothetical OSET reaction between bromoacetonitrile and Cu (I)/TPMA complex was estimated using Marcus theory for the electron-transfer processes. The estimated rate constant k OSET = approximately 10 (-11) M (-1) s (-1) is significantly smaller than the experimentally measured activation rate constant ( k ISET = approximately 82 M (-1) s (-1) at 25 degrees C in acetonitrile) for the concerted atom transfer mechanism (inner-sphere electron transfer, ISET), implying that the ISET mechanism is preferred. For

Effect of substituents on redox, spectroscopic and structural properties of conjugated diaryltetrazines--a combined experimental and theoretical study.

PubMed

Kurach, Ewa; Djurado, David; Rimarčik, Jan; Kornet, Aleksandra; Wlostowski, Marek; Lukeš, Vladimir; Pécaut, Jacques; Zagorska, Malgorzata; Pron, Adam

2011-02-21

Two series of new soluble conjugated compounds containing tetrazine central ring have been synthesized. The three-ring compounds have been synthesized by the reaction of aryl cyanide (where aryl = thienyl, alkylthienyl, phenyl or pyridyl) with hydrazine followed by oxidation of the intermediate product with diethyl azodicarboxylate. The five-ring compounds have been prepared using two pathways: (i) reaction of 5-cyano-2,2'-bithiophene (or its alkyl derivative) with hydrazine; (ii) via Suzuki or Stille coupling of 3,6-bis(5-bromo-2-thienyl)-1,2,4,5-tetrazine with a stannyl or boronate derivative of alkylthiophene. UV-vis spectroscopic properties of the synthesized compounds are strongly dependent on the nature of the aryl group, the position of the solubilizing substituent and the length of the molecule, showing the highest bathochromic shift (λ(max) > 440 nm) for five-ring compounds with alkyl groups attached to C(α) carbon in the terminal thienyl ring. An excellent linear correlation has been found for spectroscopically determined and theoretically calculated (TD-B3LYP/6-31G*) excitation energies. With the exception of dipyridyl derivative, the calculated lowest unoccupied molecular orbital (LUMO) level of the investigated molecules changes within a narrow range (from -2.63 to -2.41 eV), in line with the electrochemical data, which show a reversible reduction process with the redox potential varying from -1.23 V to -1.33 V (vs. Fc/Fc(+)). The electrochemically determined positions of the LUMO levels are consistently lower by 0.9 to 1.2 eV with respect to the calculated ones. All molecules readily crystallize. Single crystal studies of 3,6-bis(2,2'-bithien-5-yl)-1,2,4,5-tetrazine show that it crystallizes in a P2(1)/c space group whose structural arrangement is not very favorable to the charge carriers flow within the crystal. Powder diffraction studies of other derivatives have shown that their structural organization is sensitive to the position of the

Synthesis, docking study and relaxant effect of 2-alkyl and 2-naphthylchromones on rat aorta and guinea-pig trachea through phosphodiesterase inhibition.

PubMed

Rodríguez-Ramos, Fernando; Navarrete, Andrés; González-Andrade, Martín; Alarcón, Carlos; Aguilera-Cruz, Alejandro; Reyes-Ramírez, Adelfo

2013-10-01

Chromone (4), which form the base structure of various flavonoids isolated as natural products, is capable of relaxing smooth muscle. This is relevant to the treatment of high blood pressure, asthma and chronic obstructive pulmonary disease. The former disorder involves the contraction of vascular smooth muscle (VSM), and the latter two bronchoconstriction of airway smooth muscle (ASM). One of the principal mechanisms by which flavonoids relax muscle tissue is the inhibition of phosphodiesterases (PDEs), present in both VSM and ASM. Therefore, a study was designed to analyze the structure-activity relationship of chromone derivatives in vaso- and bronchorelaxation through the inhibition of PDE. Docking studies showed that these chromones bind at the catalytic site of PDEs. Consequently, we synthesized analogs of chromones substituted at position C-2 with alkyl and naphthyl groups. These compounds were synthesized from 2-hydroxyacetophenone and acyl chlorides in the presence of DBU and pyridine, modifying the methodology reported for the synthesis of 3-acylchromones by changing the reaction temperature from 80 to 30°C and using methylene chloride as solvent, yielding the corresponding phenolic esters 10a-10h. These compounds were cyclized with an equivalent of DBU, pyridine as solvent, and heated at reflux temperature, yielding the chromones 11a-11h. Evaluation of the vasorelaxant effect of 4, 11a-11h on rat aorta demonstrated that potency decreases with branched alkyl groups. Whereas the EC50 of compound 11d (substituted by an n-hexyl group) was 8.64±0.39 μM, that of 11f (substituted by an isobutyl group) was 14.58±0.64 μM. Contrarily, the effectiveness of the compound is directly proportional to the length of the alkyl chain, as evidenced by the increase in maximal effect of compound 11c versus 11d (66% versus 100%) and 11e versus 11f (60% versus 96%). With an aromatic group like naphthyl as the C-2 substituent, the effectiveness was only 43%. All compounds

World Wide Web-based system for the calculation of substituent parameters and substituent similarity searches.

PubMed

Ertl, P

1998-02-01

Easy to use, interactive, and platform-independent WWW-based tools are ideal for development of chemical applications. By using the newly emerging Web technologies such as Java applets and sophisticated scripting, it is possible to deliver powerful molecular processing capabilities directly to the desk of synthetic organic chemists. In Novartis Crop Protection in Basel, a Web-based molecular modelling system has been in use since 1995. In this article two new modules of this system are presented: a program for interactive calculation of important hydrophobic, electronic, and steric properties of organic substituents, and a module for substituent similarity searches enabling the identification of bioisosteric functional groups. Various possible applications of calculated substituent parameters are also discussed, including automatic design of molecules with the desired properties and creation of targeted virtual combinatorial libraries.

Designing greener plasticizers: Effects of alkyl chain length and branching on the biodegradation of maleate based plasticizers.

PubMed

Erythropel, Hanno C; Brown, Tobin; Maric, Milan; Nicell, Jim A; Cooper, David G; Leask, Richard L

2015-09-01

The ubiquitous presence of the plasticizer di (2-ethylhexyl) phthalate (DEHP) in the environment is of concern due to negative biological effects associated with it and its metabolites. In particular, the metabolite mono (2-ethylhexyl) phthalate (MEHP) is a potential endocrine disruptor. Earlier work had identified the diester di (2-ethylhexyl) maleate (DEHM) as a potential greener candidate plasticizer to replace DEHP, yet its biodegradation rate was reported to be slow. In this study, we modified the side chains of maleate diesters to be linear (i.e., unbranched) alkyl chains that varied in length from ethyl to n-octyl. The plasticization efficiency of these compounds blended into PVC at 29 wt.% increased with the overall length of the molecule, but all compounds performed as well as or better than comparable samples with DEHP. Tests conducted with the equally long DEHM and dihexyl maleate (DHM) showed that branching has no effect on glass transition temperature (Tg) reduction efficiency. Biodegradation experiments with the common soil bacterium Rhodococcus rhodocrous in the presence of the plasticizer showed acceptable hydrolysis rates of maleates with unbranched side chains, while the branched DEHM showed almost no degradation. The addition of hexadecane as auxiliary carbon source improved hydrolysis rates. Temporary buildup of the respective monoester of the compounds were observed, but only in the case of the longest molecule, dioctyl maleate (DOM), did this buildup lead to growth inhibition of the bacteria. Maleates with linear side chains, if designed and tested properly, show promise as potential candidate plasticizers as replacements for DEHP. Copyright © 2015 Elsevier Ltd. All rights reserved.

The Effect of Lengthening Cation Ether Tails on Ionic Liquid Properties

DOE PAGES

Lall-Ramnarine, S.; Rodriguez, C.; Fernandez, R.; ...

2016-08-30

In order to explore the effect of multiple ether functionalities on ionic liquid properties, a series of ten pyrrolidinium ionic liquids and ten imidazolium ionic liquids bearing ether and alkyl side chains of varying lengths (4 to 10 atoms in length) were prepared for this study. Their physical properties, such as viscosity, conductivity and thermal profile were measured and compared. Consistent with earlier literature, a single ether substituent substantially decreases the viscosity of pyrrolidinium and imidazolium ILs compared to their alkyl congeners. Remarkably, as the number of ether units in the pyrrolidinium ILs increases there is hardly any increase inmore » the viscosity, in contrast to alkylpyrrolidinium ILs where the viscosity increases steadily with chain length. Viscosities of imidazolium ether ILs increase with chain length but always remain well below their alkyl congeners. These results provide significant insight on the choice of starting materials for researchers designing ILs for specific applications.« less

Tailoring Thermal Conductivity of Single-stranded Carbon-chain Polymers through Atomic Mass Modification

PubMed Central

Liao, Quanwen; Zeng, Lingping; Liu, Zhichun; Liu, Wei

2016-01-01

Tailoring the thermal conductivity of polymers is central to enlarge their applications in the thermal management of flexible integrated circuits. Progress has been made over the past decade by fabricating materials with various nanostructures, but a clear relationship between various functional groups and thermal properties of polymers remains to be established. Here, we numerically study the thermal conductivity of single-stranded carbon-chain polymers with multiple substituents of hydrogen atoms through atomic mass modification. We find that their thermal conductivity can be tuned by atomic mass modifications as revealed through molecular dynamics simulations. The simulation results suggest that heavy homogeneous substituents do not assist heat transport and trace amounts of heavy substituents can in fact hinder heat transport substantially. Our analysis indicates that carbon chain has the biggest contribution (over 80%) to the thermal conduction in single-stranded carbon-chain polymers. We further demonstrate that atomic mass modifications influence the phonon bands of bonding carbon atoms, and the discrepancies of phonon bands between carbon atoms are responsible for the remarkable drops in thermal conductivity and large thermal resistances in carbon chains. Our study provides fundamental insight into how to tailor the thermal conductivity of polymers through variable substituents. PMID:27713563

The color tuning of PS-b-P2VP lamellar films with changing the alkyl chain length of 1-iodoalkanes.

PubMed

Shin, Sung-Eui; Kim, Su-Young; Shin, Dong-Myung

2011-05-01

Photonic crystals with tunability in the visible or near-infrared region have drawn increasing attention for controlling and processing light for the active components of future display. We prepared polystyrene-b-poly(2-vinyl pyridine) (PS-b-P2VP) lamellar films which is hydrophobic block-hydrophilic polyelectrolyte block polymer of 57 kg/mol-b-57 kg/mol. The lamellar stacks, which is alternating layer of hydrophilic and hydrophobic moiety of PS-b-P2VP, are obtained by exposing the spin coated film under chloroform vapor. The band gaps of the lamellar films interestingly varied after immersion into the quaternizing solvents containing 5 wt% of iodomethane, iodoethane, 1-iodobutane, 1-iodopentane, 1-iodohexane and 1-iodooctane solubilized in n-hexane. The iodoalkanes reacted with pyridine groups in PS-b-P2VP and generated the alkyl pyridinium salts readily. The degree of quaternization, alkyl chain length of iodoalkane and the salt water concentration affects the spacing of layer structure of PS-b-P2VP. The iodomethane and iodohexane produced similar band gaps and salt concentration dependence. These results are very much dependent on the hydrophobic-hydrophilic characters of PS-b-P2VP lamellar surface.

Nickel-catalyzed coupling reaction of alkyl halides with aryl Grignard reagents in the presence of 1,3-butadiene: mechanistic studies of four-component coupling and competing cross-coupling reactions† †Electronic supplementary information (ESI) available: Detailed experimental and computational results, procedures, characterization data, copies of NMR charts, and crystallographic data. CCDC 1572238. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c7sc04675h

PubMed Central

Fukuoka, Asuka; Yokoyama, Wataru; Min, Xin; Hisaki, Ichiro; Kuniyasu, Hitoshi

2018-01-01

We describe the mechanism, substituent effects, and origins of the selectivity of the nickel-catalyzed four-component coupling reactions of alkyl fluorides, aryl Grignard reagents, and two molecules of 1,3-butadiene that affords a 1,6-octadiene carbon framework bearing alkyl and aryl groups at the 3- and 8-positions, respectively, and the competing cross-coupling reaction. Both the four-component coupling reaction and the cross-coupling reaction are triggered by the formation of anionic nickel complexes, which are generated by the oxidative dimerization of two molecules of 1,3-butadiene on Ni(0) and the subsequent complexation with the aryl Grignard reagents. The C–C bond formation of the alkyl fluorides with the γ-carbon of the anionic nickel complexes leads to the four-component coupling product, whereas the cross-coupling product is yielded via nucleophilic attack of the Ni center toward the alkyl fluorides. These steps are found to be the rate-determining and selectivity-determining steps of the whole catalytic cycle, in which the C–F bond of the alkyl fluorides is activated by the Mg cation rather than a Li or Zn cation. ortho-Substituents of the aryl Grignard reagents suppressed the cross-coupling reaction leading to the selective formation of the four-component products. Such steric effects of the ortho-substituents were clearly demonstrated by crystal structure characterizations of ate complexes and DFT calculations. The electronic effects of the para-substituent of the aryl Grignard reagents on both the selectivity and reaction rates are thoroughly discussed. The present mechanistic study offers new insight into anionic complexes, which are proposed as the key intermediates in catalytic transformations even though detailed mechanisms are not established in many cases, and demonstrates their synthetic utility as promising intermediates for C–C bond forming reactions, providing useful information for developing efficient and straightforward

Synthesis of 6-substituted 6H-indolo[2,3-b]quinolines as novel cytotoxic agents and topoisomerase II inhibitors.

PubMed

Kaczmarek, Lukasz; Luniewski, Wojciech; Zagrodzki, Bogdan; Godlewska, Joanna; Osiadacz, Jarosław; Wietrzyk, Joanna; Opolski, Adam; Peczyńska-Czoch, Wanda

2002-01-01

A systematic investigation into the impact of the substituents introduced into the indolo[2,3-b]quinoline system is described. The findings clearly demonstrate that the compounds bearing a methyl group or a longer aliphatic chain at the N-6 position are inactive against prokaryotic and eukaryotic cells. The introduction of alkyl-amino-alkyl substituent at the N-6 position of indolo[2,3-b]quinoline accounts for the appearance of the antimicrobial and.cytotoxic properties. The cytotoxicity against oral epidermoid carcinoma KB (ID50) is in the range from 2.0 to 9.0 microM, and the antimicrobial activity (MIC) falls between 0.03 and 0.50 mM. The structural relation within 6H-indolo[2,3-b]quinolines, concerning their antimicrobial and cytotoxic activity, corresponds well with their ability to bind DNA and to inhibit topoisomerase II activity.

[Dental plaque microcosm biofilm behavior on a resin composite incorporated with nano-antibacterial inorganic filler containing long-chain alkyl quaternary ammonium salt].

PubMed

Junling, Wu; Qiang, Zhang; Ruinan, Sun; Ting, Zhu; Jianhua, Ge; Chuanjian, Zhou

2015-12-01

To develop a resin composite incorporated with nano-antibacterial inorganic filler containing long-chain alkyl quaternary ammonium salt, and to measure its effect on human dental plaque microcosm biofilm. A novel nano-antibacterial inorganic filler containing long-chain alkyl quaternary ammonium salt was synthesized according to methods introduced in previous research. Samples of the novel nano-antibacterial inorganic fillers were modified by a coupling agent and then added into resin composite at 0%, 5%, 10%, 15% or 20% mass fractions; 0% composite was used as control. A flexural test was used to measure resin composite mechanical properties. Results showed that a dental plaque microcosm biofilm model with human saliva as inoculum was formed. Colony-forming unit (CFU) counts, lactic acid production, and live/dead assay of biofilm on the resin composite were calculated to test the effect of the resin composite on human dental plaque microcosm biofilm. The incorporation of nano-antibacterial inorganic fillers with as much as 15% concentration into the resin composite showed no adverse effect on the mechanical properties of the resin composite (P > 0.05). Resin composite containing 5% or more nano-antibacterial inorganic fillers significantly inhibited the metabolic activity of dental plaque microcosm biofilm, suggesting its strong antibacterial potency (P < 0.05). This novel resin composite exhibited a strong antibacterial property upon the addition of up to 5% nano-antibacterial inorganic fillers, thereby leading to effective caries inhibition in dental application.

Read-across of ready biodegradability based on the substrate specificity of N-alkyl polypropylene polyamine-degrading microorganisms.

PubMed

Geerts, R; van Ginkel, C G; Plugge, C M

2017-04-01

The biodegradation of N-alkyl polypropylene polyamines (NAPPs) was studied using pure and mixed cultures to enable read-across of ready biodegradability test results. Two Pseudomonas spp. were isolated from activated sludge with N-oleyl alkyl propylene diamine and N-coco alkyl dipropylene triamine, respectively. Both strains utilized all NAPPs tested as the sole source of carbon, nitrogen and energy for growth. Mineralization of NAPPs was independent of the alkyl chain length and the size of the polyamine moiety. NAPPs degraded in closed bottle tests (CBTs) using both river water and activated sludge. However, ready biodegradability of NAPPs with alkyl chain lengths of 16-18 carbon atoms and polyamine moieties with three and four nitrogen atoms could not be demonstrated. Biodegradation in the CBT was hampered by their limited bioavailability, making assessment of the true ready biodegradability of these highly adsorptive surfactants impossible. All NAPPs are therefore classified as readily biodegradable through read-across. Read-across is justified by the broad substrate specificity of NAPP-degrading microorganisms, their omnipresence and the mineralization of NAPPs.

pi-Selective stationary phases: (II) Adsorption behavior of substituted aromatic compounds on n-alkyl-phenyl stationary phases

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gritti, Fabrice; Guiochon, Georges A; Mayfield, Kirsty

2010-01-01

The frontal analysis method was used to measure the adsorption isotherms of phenol, 4-chlorophenol, p-cresol, 4-methoxyphenol and caffeine on a series of columns packed with home-made alkyl-phenyl bonded silica particles. These ligands consist of a phenyl ring tethered to the silica support via a carbon chain of length ranging from 0 to 4 atoms. The adsorption isotherm models that fit best to the data account for solute-solute interactions that are likely caused by p-p interactions occurring between aromatic compounds and the phenyl group of the ligand. These interactions are the dominant factor responsible for the separation of low molecular weightmore » aromatic compounds on these phenyl-type stationary phases. The saturation capacities depend on whether the spacer of the ligands have an even or an odd number of carbon atoms, with the even alkyl chain lengths having a greater saturation capacity than the odd alkyl chain lengths. The trends in the adsorption equilibrium constant are also significantly different for the even and the odd chain length ligands.« less

Extra-thermodynamic study on surface diffusion in reversed-phase liquid chromatography using silica gels bonded with alkyl ligands of different chain lengths

DOE Office of Scientific and Technical Information (OSTI.GOV)

Miyabe, Kanji; Guiochon, Georges A

2005-06-01

Surface diffusion on adsorbents made of silica gels bonded to C{sub 1}, C{sub 4}, C{sub 8}, and C{sub 18} alkyl ligands was studied in reversed-phase liquid chromatography (RPLC) from the viewpoints of two extrathermodynamic relationships: enthalpy-entropy compensation (EEC) and linear free-energy relationship (LFER). First, the values of the surface diffusion coefficient (D{sub s}), normalized by the density of the alkyl ligands, were analyzed with the modified Arrhenius equation, following the four approaches proposed in earlier research. This showed that an actual EEC resulting from substantial physicochemical effects occurs for surface diffusion and suggested a mechanistic similarity of molecular migration bymore » surface diffusion, irrespective of the alkyl chain length. Second, a new model based on EEC was derived to explain the LFER between the logarithms of D{sub s} measured under different RPLC conditions. This showed that the changes of free energy, enthalpy, and entropy of surface diffusion are linearly correlated with the carbon number in the alkyl ligands of the bonded phases and that the contribution of the C{sub 18} ligand to the changes of the thermodynamic parameters corresponds to that of the C{sub 10} ligand. The new LFER model correlates the slope and intercept of the LFER to the compensation temperatures derived from the EEC analyses and to several parameters characterizing the molecular contributions to the changes in enthalpy and entropy. Finally, the new model was used to estimate D{sub s} under various RPLC conditions. The values of D{sub s} that were estimated from only two original experimental D{sub s} data were in agreement with corresponding experimental D{sub s} values, with relative errors of {approx}20%, irrespective of some RPLC conditions.« less

Protic ammonium carboxylate ionic liquids: insight into structure, dynamics and thermophysical properties by alkyl group functionalization.

PubMed

Reddy, Th Dhileep N; Mallik, Bhabani S

2017-04-19

This study is aimed at characterising the structure, dynamics and thermophysical properties of five alkylammonium carboxylate ionic liquids (ILs) from classical molecular dynamics simulations. The structural features of these ILs were characterised by calculating the site-site radial distribution functions, g(r), spatial distribution functions and structure factors. The structural properties demonstrate that ILs show greater interaction between cations and anions when alkyl chain length increases on the cation or anion. In all ILs, spatial distribution functions show that the anion is close to the acidic hydrogen atoms of the ammonium cation. We determined the role of alkyl group functionalization of the charged entities, cations and anions, in the dynamical behavior and the transport coefficients of this family of ionic liquids. The dynamics of ILs are described by studying the mean square displacement (MSD) of the centres of mass of the ions, diffusion coefficients, ionic conductivities and hydrogen bonds as well as residence dynamics. The diffusion coefficients and ionic conductivity decrease with an increase in the size of the cation or anion. The effect of alkyl chain length on ionic conductivity calculated in this article is consistent with the findings of other experimental studies. Hydrogen bond lifetimes and residence times along with structure factors were also calculated, and are related to alkyl chain length.

Docking model of the nicotinic acetylcholine receptor and nitromethylene neonicotinoid derivatives with a longer chiral substituent and their biological activities.

PubMed

Nagaoka, Hikaru; Nishiwaki, Hisashi; Kubo, Takuya; Akamatsu, Miki; Yamauchi, Satoshi; Shuto, Yoshihiro

2015-02-15

In the present study, nitromethylene neonicotinoid derivatives possessing substituents that contain a sulfur atom, oxygen atom or aromatic ring at position 5 on the imidazolidine ring were synthesized to evaluate their affinity for the nicotinic acetylcholine receptor (nAChR) and their insecticidal activity against adult female houseflies. Comparing the receptor affinity of the alkylated derivative with the receptor affinity of compounds possessing either ether or thioether groups revealed that conversion of the carbon atom to a sulfur atom did not influence the receptor affinity, whereas conversion to an oxygen atom was disadvantageous for the receptor affinity. The receptor affinity of compounds possessing a benzyl or phenyl group was lower than that of the unsubstituted compound. Analysis of the three-dimensional quantitative structure-activity relationship using comparative molecular field analysis demonstrated that steric hindrance of the receptor should exist around the C3 of an n-butyl group attached at position 5 on the imidazolidine ring. A docking study of the nAChR-ligand model suggested that the ligand-binding region expands as the length of the substituent increases by brushing against the amino acids that form the binding region. The insecticidal activity of the compounds was positively correlated with the receptor affinity by considering logP and the number of heteroatoms, including sulfur and oxygen atoms, in the substituents, suggesting that the insecticidal activity is influenced by the receptor affinity, hydrophobicity, and metabolic stability of the compounds. Copyright © 2015 Elsevier Ltd. All rights reserved.

Synthesis and Tuberculostatic Activity Evaluation of Novel Benzazoles with Alkyl, Cycloalkyl or Pyridine Moiety.

PubMed

Krause, Malwina; Foks, Henryk; Augustynowicz-Kopeć, Ewa; Napiórkowska, Agnieszka; Szczesio, Małgorzata; Gobis, Katarzyna

2018-04-23

Compounds possessing benzimidazole system exhibit significant antituberculous activity. In order to examine how structure modifications affect tuberculostatic activity, a series of benzazole derivatives were synthesized and screened for their antitubercular activity. The compounds 1 ⁻ 20 were obtained by the reaction between o -diamine, o -aminophenol, or o -aminothiophenol with carboxylic acids or thioamides. The newly synthesized compounds were characterized by IR, ¹H-NMR, 13 C-NMR spectra, and elemental analysis. Synthesized benzazoles were evaluated for their tuberculostatic activity toward Mycobacterium tuberculosis strains. Quantum chemical calculations were performed to study the molecular geometry and the electronic structure of benzimidazoles GK-151B, 4 , 6 , and benzoxazole 11 , using the Gaussian 03W software (Gaussian, Inc., Wallingford, CT, USA). Three-dimensional structure of benzimidazoles 1 ⁻ 3 , MC-9, and GK-151B was determined by ab initio calculation using Gamess-US software. The activity of the received benzimidazoles was moderate or good. All of the benzoxazoles and benzothiazoles demonstrated much lower activity. Benzoxazoles were less active by about 50 times, and benzothiazole by 100 times than the benzimidazole analogs. Quantum chemical calculations showed differences in the distribution of electrostatic potential in the benzazole system of benzimidazoles and benzoxazoles. Three-dimensional structure calculations revealed how the parity of the alkyl substituent at the C2 position impacts the activity. Benzimidazole system is essential for the antituberculosis activity that is associated with the presence of the imine nitrogen atom in N-1 position. Its replacement by an oxygen or sulfur atom results in a decrease of the activity. The parity of the alkyl substituent at the C-2 position also modifies the activity.

A novel type of highly effective nonionic gemini alkyl O-glucoside surfactants: a versatile strategy of design.

PubMed

Liu, Songbai; Sang, Ruocheng; Hong, Shan; Cai, Yujing; Wang, Hua

2013-07-09

A novel type of highly effective gemini alkyl glucosides has been rationally designed and synthesized. The gemini surfactants have been readily prepared by glycosylation of the gemini alkyl chains that are synthesized with regioselective ring-opening of ethylene glycol epoxides by the alkyl alcohols. The new gemini alkyl glucosides exhibit significantly better surface activity than the known results. Then rheological, DLS, and TEM studies have revealed the intriguing self-assembly behavior of the novel gemini surfactants. This study has proved the effectiveness of the design of gemini alkyl glucosides which is modular, extendable, and synthetically simple. The new gemini surfactants have great potential as nano carriers in drug and gene delivery.

Synthesis and antifungal activity of natural product-based 6-alkyl-2 3 4 5-tetrahydropyridines

USDA-ARS?s Scientific Manuscript database

Seven 6-alkyl-2,3,4,5-tetrahydropyridines (5a–5g) that mimic the natural products piperideines that were recently identified in the fire ant venom have been synthesized. Compounds 5c–5g with the C-6 alkyl chain lengths from C14 to C18 showed varying degrees of antifungal activities, with 5e (6-hexa...

In vitro analysis of the effect of alkyl-chain length of anionic surfactants on the skin by using a reconstructed human epidermal model.

PubMed

Yamaguchi, Fumiko; Watanabe, Shin-Ichi; Harada, Fusae; Miyake, Miyuki; Yoshida, Masaki; Okano, Tomomichi

2014-01-01

We investigated the effect of the alkyl-chain length of anionic surfactants on the skin using an in vitro model. The evaluated anionic surfactants were sodium alkyl sulfate (AS) and sodium fatty acid methyl ester sulfonate (MES), which had different alkyl-chain lengths (C8-C14). Skin tissue damage and permeability were examined using a reconstructed human epidermal model, LabCyte EPI-MODEL24. Skin tissue damage was examined by measuring cytotoxicity with an MTT assay. Liquid chromatography/tandem mass spectrometry (LC/MS-MS) and liquid chromatography/mass spectrometry (LC/MS) were used to detect surfactants that permeated into the assay medium through an epidermal model. To assess the permeation mechanism and cell damage caused by the surfactants through the epidermis, we evaluated the structural changes of Bovine Serum Albumin (BSA), used as a simple model protein, and the fluidity of 1,2-dipalmitoyl-sn-glycero-3-phosphpcholine (DPPC) liposome, which serves as one of the most abundant phospholipid models of living cell membranes in the epidermis. The effects of the surfactants on the proteins were measured using Circular Dichroism (CD) spectroscopy, while the effects on membrane fluidity were investigated by electron spin resonance (ESR) spectroscopy. ET50 (the 50% median effective time) increased as follows: C10 < C12 < C8 < C14 in AS and C8, C10 < C12 < C14 in MES. The order of permeation through the LabCyte EPI-MODEL24 was C10 > C12 > C14, for both AS and MES. For both AS and MES, the order parameter, which is the criteria for the microscopic viscosity of lipid bilayers, increased as follows: C10 < C12 < C14, which means the membrane fluidity is C10 > C12 > C14. It was determined that the difference in skin tissue damage in the LabCyte EPI-MODEL24 with C10 to C14 AS and MES was caused by the difference in permeation and cell membrane fluidity through the lipid bilayer path in the epidermis.

Surface Photochemistry: 3,3′-Dialkylthia and Selenocarbocyanine Dyes Adsorbed onto Microcrystalline Cellulose

PubMed Central

Vieira Ferreira, Luís F.; Ferreira, Diana P.; Duarte, Paulo; Oliveira, A. S.; Torres, E.; Machado, I. Ferreira; Almeida, P.; Reis, Lucinda V.; Santos, Paulo F.

2012-01-01

In this work, thia and selenocarbocyanines with n-alkyl chains of different length, namely with methyl, ethyl, propyl, hexyl and decyl substituents, were studied in homogeneous and heterogeneous media for comparison purposes. For both carbocyanine dyes adsorbed onto microcrystalline cellulose, a remarkable increase in the fluorescence quantum yields and lifetimes were detected, when compared with solution. Contrary to the solution behaviour, where the increase in the n-alkyl chains length increases to a certain extent the fluorescence emission ΦF and τF, on powdered solid samples a decrease of ΦF and τF was observed. The use of an integrating sphere enabled us to obtain absolute ΦF’s for all the powdered samples. The main difference for liquid homogeneous samples is that the increase of the alkyl chain strongly decreases the ΦF values, both for thiacarbocyanines and selenocarbocyanines. A lifetime distribution analysis for the fluorescence of these dyes adsorbed onto microcrystalline cellulose, evidenced location on the ordered and crystalline part of the substrate, as well as on the more disordered region where the lifetime is smaller. The increase of the n-alkyl chains length decreases the photoisomer emission for the dyes adsorbed onto microcrystalline cellulose, as detected for high fluences of the laser excitation, for most samples. PMID:22312274

Trifluoromethyl ethers – synthesis and properties of an unusual substituent

PubMed Central

Manteau, Baptiste; Vors, Jean-Pierre; Pazenok, Sergiy

2008-01-01

Summary After nitrogen, fluorine is probably the next most favorite hetero-atom for incorporation into small molecules in life science-oriented research. This review focuses on a particular fluorinated substituent, the trifluoromethoxy group, which is finding increased utility as a substituent in bioactives, but it is still perhaps the least well understood fluorine substituent in currency. The present review will give an overview of the synthesis, properties and reactivity of this important substituent. PMID:18941485

Occurrence of fatty acid short-chain-alkyl esters in fruits of Celastraceae plants.

PubMed

Sidorov, Roman A; Zhukov, Anatoly V; Pchelkin, Vasily P; Vereshchagin, Andrei G; Tsydendambaev, Vladimir D

2013-06-01

Small amounts of a mixture of fatty acid short-chain-alkyl esters (FASCAEs) were obtained from the fruits of twelve plant species of Celastraceae family, and in five of them the FASCAEs were present not only in the arils but also in the seeds. These mixtures contained 32 individual FASCAE species, which formed four separate fractions, viz. FA methyl, ethyl, isopropyl, and butyl esters (FAMEs, FAEEs, FAIPEs, and FABEs, resp.). The FASCAE acyl components included the residues of 16 individual C₁₄-C₂₄ saturated, mono-, di-, and trienoic FAs. Linoleic, oleic, and palmitic acids, and, in some cases, also α-linolenic acid predominated in FAMEs and FAEEs, while myristic acid was predominant in FAIPEs. It can be suggested that, in the fruit arils of some plant species, FAMEs and FAEEs were formed at the expense of a same FA pool characteristic of a given species and were strongly different from FAIPEs and FABEs esters regarding the mechanism of their biosynthesis. However, as a whole, the qualitative and quantitative composition of various FASCAE fractions, as well as their FA composition, varied considerably depending on various factors. Therefore, separate FASCAE fractions seem to be synthesized from different FA pools other than those used for triacylglycerol formation. Copyright © 2013 Verlag Helvetica Chimica Acta AG, Zürich.

Direct α-alkylation of ketones with alcohols in water.

PubMed

Xu, Guoqiang; Li, Qiong; Feng, Jiange; Liu, Qiang; Zhang, Zuojun; Wang, Xicheng; Zhang, Xiaoyun; Mu, Xindong

2014-01-01

The direct α-alkylation of ketones with alcohols has emerged as a new green protocol to construct C-C bonds with H2 O as the sole byproduct. In this work, a very simple and convenient Pd/C catalytic system for the direct α-alkylation of ketones with primary alcohols in pure water is developed. Based on this catalytic system, aqueous mixtures of dilute acetone, 1-butanol, and ethanol (mimicking ABE fermentation products) can be directly transformed into C5 -C11 or longer-chain ketones and alcohols, which are precursors to fuels. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Merging Photoredox with 1,2-Metallate Rearrangements: The Photochemical Alkylation of Vinyl Boronate Complexes.

PubMed

Silvi, Mattia; Sandford, Christopher; Aggarwal, Varinder K

2017-04-26

Vinyl boronates react with electron-deficient alkyl iodides in the presence of visible light to give boronic esters in which two new C-C bonds have been created. The reaction occurs by radical addition of an electron-deficient alkyl radical to the vinyl boronate followed by electron transfer with another molecule of alkyl iodide, continuing the chain, and triggering a 1,2-metalate rearrangement. In a number of cases, the use of a photoredox catalyst enhances yields significantly. The scope of the radical precursor includes α-iodo ketones, esters, nitriles, primary amides, α-fluorinated halo-acetates and perfluoroalkyl iodides.

Branched-chain dicationic ionic liquids for fatty acid methyl ester assessment by gas chromatography.

PubMed

Talebi, Mohsen; Patil, Rahul A; Sidisky, Leonard M; Berthod, Alain; Armstrong, Daniel W

2017-12-06

Twelve bis- or dicationic ionic liquids (ILs) including eight based on imidazolium, a single one based on phosphonium, and three based on pyrrolidinium cationic units were prepared with the bis(trifluoromethyl sulfonyl) imide anion. The two identical cationic moieties were attached by different alkyl spacers having three or five carbons and differing alkyl substituents attached to the spacer. The SLB-IL111 column, as the most polar commercial stationary phase known, was included in the study for comparison. Isothermal separations of a rapeseed oil fatty acid methyl ester (FAME) sample were used to study and compare the 12 IL-based column performances and selectivities. The retention times of the most retained methyl esters of lignoceric (C24:0) and erucic (C22:1) acids were used to estimate the IL polarity. The phosphonium dicationic IL column was, by far, the least polar. Imidazolium-based dicationic IL columns were the most polar. Polarity and selectivity for the FAME separation were somewhat related. The separation of a 37-FAME standard mixture allowed the investigation of selectivity variations observed on the 12 IL-based columns under temperature gradients up to 230 °C. The remarkable selectivity of the IL-based columns is demonstrated by the detailed analysis of the cis/trans C18:1 isomers of a partially hydrogenated vegetable oil sample on 30-m columns, separations competing with that done following an "official method" performed on a 100-m column. Graphical abstract Separation of fatty acid methyl esters on a 30-m 3m 2 C 5 (mpy) 2 . 2NTf 2 branched-chain dicationic IL-based column. Branched chain dicationic ILs show great selectivity for separation of cis/trans, ω-3/ω-6, and detailed analysis of cis/trans fats.

Design and synthesis of 2-nitroimidazoles with variable alkylating and acylating functionality.

PubMed

Winters, Thomas; Sercel, Anthony; Suto, Carla; Elliott, William; Leopold, Wilbur; Leopold, Judith; Showalter, Hollis

2014-01-01

The synthesis of a small series of 2-nitroimidazoles in which the β-amino alcohol side chain was amidated with a range of alkylating/acylating functionality is described. Synthetic methodologies were developed that generally provided for selective N-acyl versus N,O-bisacyl products. In vitro, target analogs showed minimal radiosensitization activity, with only a few exhibiting a sensitizer enhancement ratio (SER) >2.0 and C(1.6) values comparable to reference agents RB-6145 and RSU-1069. In an assay to determine potential to alkylate biomolecules, representative analogs showed <1% of the alkylating activity of RSU-1069. In vivo, one analog showed an enhancement ratio of 1.6 relative to vehicle control when tested in B6C3F1 mice with an implanted KHT sarcoma. The data reinforce prior findings that there is a correlation between alkylation potential and in vivo activity.

Alkyl–Alkyl Suzuki Cross-Couplings of Unactivated Secondary Alkyl Chlorides**

PubMed Central

Lu, Zhe; Fu, Gregory C.

2010-01-01

The first method for achieving alkyl–alkyl Suzuki reactions of unactivated secondary alkyl chlorides has been developed. Carbon–carbon bond formation occurs under mild conditions (at room temperature) with the aid of commercially available catalyst components. This method has proved to be versatile: without modification, it can be applied to Suzuki reactions of secondary and primary alkyl bromides and iodides, as well as primary alkyl chlorides. Mechanistic investigations suggest that oxidative addition is not the turnover-limiting step of the catalytic cycle for unactivated secondary alkyl iodides and bromides, whereas it may be (partially) for chlorides. PMID:20715038

Synthesis of novel vitamin K derivatives with alkylated phenyl groups introduced at the ω-terminal side chain and evaluation of their neural differentiation activities.

PubMed

Sakane, Rie; Kimura, Kimito; Hirota, Yoshihisa; Ishizawa, Michiyasu; Takagi, Yuta; Wada, Akimori; Kuwahara, Shigefumi; Makishima, Makoto; Suhara, Yoshitomo

2017-11-01

Vitamin K is an essential cofactor of γ-glutamylcarboxylase as related to blood coagulation and bone formation. Menaquinone-4, one of the vitamin K homologues, is biosynthesized in the body and has various biological activities such as being a ligand for steroid and xenobiotic receptors, protection of neuronal cells from oxidative stress, and so on. From this background, we focused on the role of menaquinone in the differentiation activity of progenitor cells into neuronal cells and we synthesized novel vitamin K derivatives with modification of the ω-terminal side chain. We report here new vitamin K analogues, which introduced an alkylated phenyl group at the ω-terminal side chain. These compounds exhibited potent differentiation activity as compared to control. Copyright © 2017 The Author(s). Published by Elsevier Ltd.. All rights reserved.

Applying Alkyl-Chain Surface Functionalizations in Mesoporous Inorganic Structures: Their Impact on Gas Flow and Selectivity Depending on Temperature.

PubMed

Besser, Benjamin; Ahmed, Atiq; Baune, Michael; Kroll, Stephen; Thöming, Jorg; Rezwan, Kurosch

2016-10-12

Porous inorganic capillary membranes are prepared to serve as model structures for the experimental investigation of the gas transport in functionalized mesopores. The porous structures possess a mean pore diameter of 23 nm which is slightly reduced to 20 nm after immobilizing C 16 -alkyl chains on the surface. Gas permeation measurements are performed at temperatures ranging from 0 to 80 °C using Ar, N 2 , and CO 2 . Nonfunctionalized structures feature a gas transport according to Knudsen diffusion with regard to gas flow and selectivity. After C 16 -functionalization, the gas flow is reduced by a factor of 10, and the ideal selectivities deviate from the Knudsen theory. CO 2 adsorption measurements show a decrease in total amount of adsorbed gas and isosteric heat of adsorption. It is hypothesized that the immobilized C 16 -chains sterically influence the gas transport behavior without a contribution from adsorption effects. The reduced gas flow derives from an additional surface resistance caused by the C 16 -chains spacially limiting the adsorption and desorption directions for gas molecules propagating through the structure, resulting in longer diffusion paths. In agreement, the gas flow is found to correlate with the molecular diameter of the gas species (CO 2 < Ar < N 2 ) increasing the resistance for larger molecules. This affects the ideal selectivities with the relation [Formula: see text]. The influence on selectivity increases with increasing temperature which leads to the conclusion that the temperature induced movement of the C 16 -chains is responsible for the stronger interaction between gas molecules and surface functional groups.

Alkyl Caffeates Improve the Antioxidant Activity, Antitumor Property and Oxidation Stability of Edible Oil

PubMed Central

Wang, Jun; Gu, Shuang-Shuang; Pang, Na; Wang, Fang-Qin; Pang, Fei; Cui, Hong-Sheng; Wu, Xiang-Yang; Wu, Fu-An

2014-01-01

Caffeic acid (CA) is distributed widely in nature and possesses strong antioxidant activity. However, CA has lower solubility in non-polar media, which limits its application in fat-soluble food. To increase the lipophilicity of natural antioxidant CA, a series of alkyl caffeates were synthesized and their antioxidant and antitumor activities were investigated. The antioxidant parameters, including the induction period, acid value and unsaturated fatty acid content, of the alkyl caffeates in edible oil were firstly investigated. The results indicated that alkyl caffeates had a lower DPPH IC50 (14–23 µM) compared to CA, dibutyl hydroxy toluene (BHT) and Vitamin C (24–51 µM), and significantly inhibited four human cancer cells (SW620, SW480, SGC7901 and HepG2) with inhibition ratio of 71.4–78.0% by a MTT assay. With regard to the induction period and acid value assays, methyl and butyl caffeates had higher abilities than BHT to restrain the oxidation process and improve the stability of edible oil. The addition of ethyl caffeate to oil allowed maintenance of a higher unsaturated fatty acid methyl ester content (68.53%) at high temperatures. Overall, the alkyl caffeats with short chain length (n<5) assessed better oxidative stability than those with long chain length. To date, this is the first report to the correlations among the antioxidant activity, anticancer activity and oxidative stability of alkyl caffeates. PMID:24760050

Semiquantitative FMO Analysis of Substituent Effect on the Reaction of Permanganate Ion with Unsymmetrical Alkenes.

PubMed

Ogino, Toshio; Watanabe, Toru; Matsuura, Masato; Watanabe, Chikara; Ozaki, Hidetoshi

1998-04-17

The substituent effects on the reactions of permanganate ion with unsymmetrical alkenes are analyzed on the assumption of a concerted (3 + 2) cycloaddition model by using an equation obtained by approximation based on the FMO theory in which development and localization of the frontier molecular orbitals at the reaction sites with progress of the reaction are considered. The Hammett plots are successfully reproduced with the newly obtained rate data for the reactions of trans-chalcone and its derivatives and the data for methyl cinnamates, cinnamate ions, and alkyl vinyl ethers taken from the literature using FMO energies and orbital coefficients calculated by the PM3 method. It was indicated that a factor introduced to the basic equation in order to estimate the extent of localization of the molecular orbitals at the transition state is closely related to the position of the transition state along the reaction path.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lall-Ramnarine, Sharon I.; Zhao, Man; Rodriguez, Chanele

We used X-ray diffraction and molecular dynamics simulations to probe the structures of two families of ionic liquids containing oligoether tails on the cations. Imidazolium and pyrrolidinium bis(trifluoromethylsulfonyl)amide ILs with side chains ranging from 4 to 10 atoms in length, including both linear alkyl and oligo-ethylene oxide tails, were prepared. Furthermore, their physical properties, such as viscosity, conductivity and thermal profile, were measured and compared for systematic trends. Consistent with earlier literature, a single ether substituent substantially decreases the viscosity of pyrrolidinium and imidazolium ILs compared to their alkyl congeners. Remarkably, as the number of ether units in the pyrrolidiniummore » ILs increases there is hardly any increase in the viscosity, in contrast to alkylpyrrolidinium ILs where the viscosity increases steadily with chain length. Viscosities of imidazolium ether ILs increase with chain length but always remain well below their alkyl congeners. To complement the experimentally determined properties, molecular dynamics simulations were run on the two ILs with the longest ether chains. Our results point to specific aspects that could be useful for researchers designing ILs for specific applications.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lall-Ramnarine, Sharon I.; Zhao, Man; Rodriguez, Chanele

X-ray diffraction and molecular dynamics simulations were used to probe the structures of two families of ionic liquids containing oligoether tails on the cations. Imidazolium and pyrrolidinium bis(trifluoromethylsulfonyl)amide ILs with side chains ranging from 4 to 10 atoms in length, including both linear alkyl and oligo-ethylene oxide tails, were prepared. Their physical properties, such as viscosity, conductivity and thermal profile, were measured and compared for systematic trends. Consistent with earlier literature, a single ether substituent substantially decreases the viscosity of pyrrolidinium and imidazolium ILs compared to their alkyl congeners. Remarkably, as the number of ether units in the pyrrolidinium ILsmore » increases there is hardly any increase in the viscosity, in contrast to alkylpyrrolidinium ILs where the viscosity increases steadily with chain length. Viscosities of imidazolium ether ILs increase with chain length but always remain well below their alkyl congeners. To complement the experimentally determined properties, molecular dynamics simulations were run on the two ILs with the longest ether chains. The results point to specific aspects that could be useful for researchers designing ILs for specific applications.« less

Anti-biofilm action of nitric oxide-releasing alkyl-modified poly(amidoamine) dendrimers against Streptococcus mutans.

PubMed

Backlund, Christopher J; Worley, Brittany V; Schoenfisch, Mark H

2016-01-01

The effect of nitric oxide (NO)-releasing dendrimer hydrophobicity on Streptococcus mutans killing and biofilm disruption was examined at pH 7.4 and 6.4, the latter relevant to dental caries. Generation 1 (G1) poly(amidoamine) (PAMAM) dendrimers were modified with alkyl epoxides to generate propyl-, butyl-, hexyl-, octyl-, and dodecyl-functionalized dendrimers. The resulting secondary amines were reacted with NO to form N-diazeniumdiolate NO donor-modified dendrimer scaffolds (total NO ∼1μmol/mg). The bactericidal action of the NO-releasing dendrimers against both planktonic and biofilm-based S. mutans proved greatest with increasing alkyl chain length and at lower pH. Improved bactericidal efficacy at pH 6.4 was attributed to increased scaffold surface charge that enhanced dendrimer-bacteria association and ensuing membrane damage. For shorter alkyl chain (i.e., propyl and butyl) dendrimer modifications, increased antibacterial action at pH 6.4 was due to faster NO-release kinetics from proton-labile N-diazeniumdiolate NO donors. Octyl- and dodecyl-modified PAMAM dendrimers proved most effective for eradicating S. mutans biofilms with NO release mitigating dendrimer scaffold cytotoxicity. We report the antibacterial and anti-biofilm efficacy of dual-action nitric oxide (NO)-releasing dendrimers against S. mutans, an etiological agent in dental caries. This work was undertaken to enhance the anti-biofilm action of these scaffolds by employing various alkyl chain modifications. Furthermore, we evaluated the ability of NO to eradicate cariogenic biofilms. We found that at the lower pH associated with dental caries (pH ∼6.4), NO has a more pronounced antibacterial effect for alkyl modifications less capable of biofilm penetration and membrane disruption. Of greatest significance, we introduce dendrimers as a new macromolecular antibacterial agent against the cariogenic bacteria S. mutans. Copyright © 2015 Acta Materialia Inc. Published by Elsevier Ltd. All

Thermo-responsive triblock copolymer phase transition behaviour in imidazolium-based ionic liquids: Role of the effect of alkyl chain length of cations.

PubMed

Umapathi, Reddicherla; Venkatesu, Pannuru

2017-01-01

Different biophysical techniques such as fluorescence spectroscopy, dynamic light scattering (DLS), viscosity (η) and Fourier transform infrared (FTIR) spectroscopy have been carried out to characterize the effect of imidazolium-based ionic liquids (ILs) on the thermo-responsive triblock copolymer, poly(ethylene glycol)-block-poly(propylene glycol)-block-poly-(ethylene glycol) (PEG-PPG-PEG). In addition, to demonstrate the distinct morphological changes of various self-assembled morphologies, we further employed field emission scanning electron microscope (FESEM). To investigate the effect of alkyl chain length of the cation, concentration of the ILs and the related Hofmeister series on the phase behaviour of PEG-PPG-PEG, we used a series of ILs possessing same Cl - anion and a set of cation [C n mim] + with increasing alkyl chain length of cation such as 1-ethyl-3-methylimidazolium chloride ([Emim][Cl]), 1-butyl-3-methylimidazolium chloride ([Bmim][Cl]), 1-hexyl-3-methylimidazolium chloride ([Hmim][Cl]) and 1-decyl-3-methylimidazolium chloride ([Dmim][Cl]). The critical micellization temperature (CMT) of the copolymer in the presence of well hydrated cations is directly correlated to their hydration. The overall specific ranking of ILs in decreasing the CMT of PEG-PPG-PEG in aqueous solution was [Emim][Cl]>[Bmim][Cl]>[Hmim][Cl]>[Dmim][Cl]. The trend of these ILs followed the well-known Hofmeister series of cations of ILs. The present study provides important information about the solution properties that can be helpful to tune the IL or temperature-sensitive copolymer CMT and micelle shapes which are crucial for understanding the drug delivery mechanisms. Copyright © 2016 Elsevier Inc. All rights reserved.

Alkylarylnitrosoureas--stability in aqueous solution, partition coefficient, alkylating activity and its relationship to SCE induction in Chinese hamster V 79-E cells.

PubMed

Mendel, J; Thust, R; Schwarz, H

1982-01-01

The alkylating activity, chemical stability in aqueous solution (pH 7.0; 37 degrees C), and partition coefficient (octanol/water) of the following compounds were determined: 1-methyl-3-phenyl-1-nitrosourea (MPNU), 1-ethyl-3-phenyl-1-nitrosourea (EPNU), 1-isopropyl-3-phenyl-1-nitrosourea (i-PrPNU), 1-methyl-3-(p-fluorophenyl)-1-nitrosourea (F-MPNU), 1-methyl-3-(p-chlorophenyl)-1-nitrosourea (Cl-MPNU), 1-methyl-3-(p-bromophenyl)-1-nitrosourea (Br-MPNU), 1,3-dimethyl-3-phenyl-1-nitrosourea (DMPNU), and 1-methyl-3-naphthyl-1-nitrosocarbamate (NCA). 1-Methyl-1-nitrosourea (MNU) and 1-ethyl-1-nitrosourea (ENU) were used for the comparison. THe rate of decomposition in aqueous solution is discussed concerning the influences of the substituents at the 1- and 3-N-atom. The mono- and disubstituted N-nitrosoureas showed a coarse correlation between alkylating activity and SCE induction in Chinese hamster V 79-E cells. On the other hand, this correlation is missing in the case of NCA, which is a potent SCE inducer despite relatively low alkylating activity. DMPNU is the strongest SCE inducer, but this compound shows a high stability in aqueous solution and, consequently, we were not able to detect an alkylating activity.

40 CFR 721.9595 - Alkyl benzene sulfonic acids and alkyl sulfates, amine salts (generic).

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Alkyl benzene sulfonic acids and alkyl... Significant New Uses for Specific Chemical Substances § 721.9595 Alkyl benzene sulfonic acids and alkyl...) The chemical substances identified generically as alkyl benzene sulfonic acids and alkyl sulfates...

40 CFR 721.9595 - Alkyl benzene sulfonic acids and alkyl sulfates, amine salts (generic).

Code of Federal Regulations, 2014 CFR

2014-07-01

... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Alkyl benzene sulfonic acids and alkyl... Significant New Uses for Specific Chemical Substances § 721.9595 Alkyl benzene sulfonic acids and alkyl...) The chemical substances identified generically as alkyl benzene sulfonic acids and alkyl sulfates...

40 CFR 721.9595 - Alkyl benzene sulfonic acids and alkyl sulfates, amine salts (generic).

Code of Federal Regulations, 2012 CFR

2012-07-01

... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Alkyl benzene sulfonic acids and alkyl... Significant New Uses for Specific Chemical Substances § 721.9595 Alkyl benzene sulfonic acids and alkyl...) The chemical substances identified generically as alkyl benzene sulfonic acids and alkyl sulfates...

40 CFR 721.9595 - Alkyl benzene sulfonic acids and alkyl sulfates, amine salts (generic).

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Alkyl benzene sulfonic acids and alkyl... Significant New Uses for Specific Chemical Substances § 721.9595 Alkyl benzene sulfonic acids and alkyl...) The chemical substances identified generically as alkyl benzene sulfonic acids and alkyl sulfates...

40 CFR 721.9595 - Alkyl benzene sulfonic acids and alkyl sulfates, amine salts (generic).

Code of Federal Regulations, 2013 CFR

2013-07-01

... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Alkyl benzene sulfonic acids and alkyl... Significant New Uses for Specific Chemical Substances § 721.9595 Alkyl benzene sulfonic acids and alkyl...) The chemical substances identified generically as alkyl benzene sulfonic acids and alkyl sulfates...

40 CFR 721.1875 - Boric acid, alkyl and substituted alkyl esters (generic name).

Code of Federal Regulations, 2014 CFR

2014-07-01

... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Boric acid, alkyl and substituted... Significant New Uses for Specific Chemical Substances § 721.1875 Boric acid, alkyl and substituted alkyl... chemical substance boric acid, alkyl and substituted alkyl esters (PMN P-86-1252) is subject to reporting...

40 CFR 721.1875 - Boric acid, alkyl and substituted alkyl esters (generic name).

Code of Federal Regulations, 2012 CFR

2012-07-01

... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Boric acid, alkyl and substituted... Significant New Uses for Specific Chemical Substances § 721.1875 Boric acid, alkyl and substituted alkyl... chemical substance boric acid, alkyl and substituted alkyl esters (PMN P-86-1252) is subject to reporting...

40 CFR 721.1875 - Boric acid, alkyl and substituted alkyl esters (generic name).

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Boric acid, alkyl and substituted... Significant New Uses for Specific Chemical Substances § 721.1875 Boric acid, alkyl and substituted alkyl... chemical substance boric acid, alkyl and substituted alkyl esters (PMN P-86-1252) is subject to reporting...

40 CFR 721.1875 - Boric acid, alkyl and substituted alkyl esters (generic name).

Code of Federal Regulations, 2013 CFR

2013-07-01

... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Boric acid, alkyl and substituted... Significant New Uses for Specific Chemical Substances § 721.1875 Boric acid, alkyl and substituted alkyl... chemical substance boric acid, alkyl and substituted alkyl esters (PMN P-86-1252) is subject to reporting...

40 CFR 721.1875 - Boric acid, alkyl and substituted alkyl esters (generic name).

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Boric acid, alkyl and substituted... Significant New Uses for Specific Chemical Substances § 721.1875 Boric acid, alkyl and substituted alkyl... chemical substance boric acid, alkyl and substituted alkyl esters (PMN P-86-1252) is subject to reporting...

HeI photoelectron spectroscopic studies on the electronic structure of alkyl nitrosamines

NASA Astrophysics Data System (ADS)

Jiang, Peng; Qian, Ximei; Li, Chunhui; Qiao, Chunhua; Wang, Dianxun

1997-10-01

HeI photoelectron spectroscopic (PES) studies on the electronic structure of alkyl nitrosamines R 2N 2O (R = CH 3-, CH 3CH 2-, and CH 3CH 2CH 2-) are reported. The assignment of the PES bands for this series of compounds has been made with the aid of the band shapes, the band intensity and ab initio SCF MO calculations based on the 631 ∗ G basis sets. Both PES experiment and the ab initio SCF MO calculations show that the detoxification ability of nitrosamine with longer alkyl chain is stronger.

Synthesis, surface characterization, and biointeraction studies of low-surface energy side-chain polyetherurethanes

NASA Astrophysics Data System (ADS)

Porter, Stephen Christopher

1999-10-01

New segmented polyetherurethanes (PEUs) with low surface energy hydrocarbon and fluorocarbon side-chains attached to the polymer hard segments were synthesized. The surface chemistry of solvent cast polymer films was studied using X-ray photoelectron spectroscopy, time-of-flight secondary ion mass spectrometry, and dynamic contact angle (DCA) measurements. Increases in the overall density and length of the alkyl side-chains within the PEUs resulted in greater side-chain concentrations at the polymer surface. PEUs bearing long alkyl (> C10 ) and perfluorocarbon side-chains were found to posses surfaces with highly enriched side-chain concentrations relative to the bulk polymer. In PEUs with significant side-chain surface enrichment, the relatively polar hard segment blocks were shown to reside in high concentrations just below the side-chain enriched surface layer. Furthermore, DCA measurements demonstrated that the surface of the alkyl side-chain PEUs did not undergo significant rearrangement when placed into an aqueous environment, whereas the surface of a hard segment model polymer bearing C18 sidechains (PEU-C18-HS) did. Hydrogen bonding within the PEUs was examined using FTIR and was shown to be disrupted by the addition of side-chains; an effect dependent on the density but not on the length of the side-chains. Heteropolymer blends comprised of mixtures of high side-chain density and side-chain free PEUs were compared with homopolymers having the same overall side-chain concentration as the blends. Significantly more surface enrichment of side-chains was found in the heteropolymer blends whereas hydrogen bonding nearly the same as in the homopolymers. Adsorption of native and delipidized human serum albumin (HSA) from pure solution and blood plasma; the elutabilty of adsorbed HSA; and static platelet adhesion to plasma preadsorbed surfaces, were all examined on alkyl side-chain PEUs. Several polymers with high C18 side-chain densities displayed increased

Dimension-controlled assemblies of anion-responsive π-electronic systems bearing aryl substituents with fan-shaped geometries.

PubMed

Lakshmi, Vellanki; Haketa, Yohei; Yamakado, Ryohei; Yasuda, Nobuhiro; Maeda, Hiromitsu

2017-03-30

Pyrrole-4-aryl-substituted dipyrrolyldiketone BF 2 complexes as anion-responsive π-electronic molecules were synthesized via a 3,5-dimethylpyrrole precursor. Mesophases were observed in derivatives that possessed long alkyl chains on the pyrrole-4-aryl groups along with their anion complexes as ion-pairing assemblies in combination with appropriate cations.

Using ethane and butane as probes to the molecular structure of 1-alkyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl] imide ionic liquids.

PubMed

Costa Gomes, Margarida F; Pison, Laure; Pensado, Alfonso S; Pádua, Agilio A H

2012-01-01

In this work, we have studied the solubility and the thermodynamic properties of solvation, between 298 and 343 K and at pressures close to atmospheric, of ethane and n-butane in several ionic liquids based on the bis[(trifluoromethyl) sulfonyl]imide anion and on 1-alkyl-3-methylimidazolium cations, [CnC1Im] [NTf2], with alkyl side-chains varying from two to ten carbon atoms. The solubility of butane is circa one order of magnitude larger than that of ethane with mole fractions as high as 0.15 in [C10C1Im][NTf2] at 300 K. The solubilities of both n-butane and ethane gases are higher for ionic liquids with longer alkyl chains. The behaviour encountered is explained by the preferential solvation of the gases in the non-polar domains of the solvents, the larger solubility of n-butane being attributed to the dispersive contributions to the interaction energy. The rise in solubility with increasing size of the alkyl-side chain is explained by a more favourable entropy of solvation in the ionic liquids with larger cations. These conclusions are corroborated by molecular dynamics simulation studies.

Globular, Sponge-like to Layer-like Morphological Transition in 1-n-Alkyl-3-methylimidazolium Octylsulfate Ionic Liquid Homologous Series.

PubMed

Kapoor, Utkarsh; Shah, Jindal K

2018-01-11

Segregation of polar and nonpolar domains in ionic liquids for which either the cation or anion is responsible for inducing nonpolar domains is well understood. On the other hand, information regarding the nanoscale heterogeneities originating due to the presence of nonpolar content on both the ions is rudimentary at this point. The present contribution is aimed at addressing this question and focuses on a molecular dynamics simulation study to probe nanoscale structural and aggregation features of the 1-n-alkyl-3-methylimidazolium [C n mim] octylsulfate [C 8 SO 4 ] ionic liquid homologous series (n = 2, 4, 6, 8, 10, and 12). The objective of this work is to determine the effect of increasing alkyl chain length in the cation on nonpolar domain formation, especially when the alkyl chain lengths from both the ions participate in defining such domains. The results indicate that all the ionic liquids form nonpolar domains, morphology of which gradually changes from globular, sponge-like to layer-like structure with increase in the cationic alkyl chain length. The length of the nonpolar domains calculated from the total structure factor for [C 10 mim][C 8 SO 4 ] is considerably higher than that reported for other imidazolium-based ionic liquid containing smaller anions. The structure factor for [C 12 mim][C 8 SO 4 ] ionic liquid contains multiple intermediate peaks separating the charge alternation peak and pre-peak, which points to nonpolar domains of varying lengths, an observation that remains to be validated. Analysis of the heterogeneous order parameters and orientational correlation functions of the alkyl chains further suggests an increase in the spatial heterogeneity and long-range order along the homologous series. The origin of rich diversity of structures obtained by introducing nonpolar content on both the ions is discussed.

The Role of the Side Chain on the Performance of N-type Conjugated Polymers in Aqueous Electrolytes.

PubMed

Giovannitti, Alexander; Maria, Iuliana P; Hanifi, David; Donahue, Mary J; Bryant, Daniel; Barth, Katrina J; Makdah, Beatrice E; Savva, Achilleas; Moia, Davide; Zetek, Matyáš; Barnes, Piers R F; Reid, Obadiah G; Inal, Sahika; Rumbles, Garry; Malliaras, George G; Nelson, Jenny; Rivnay, Jonathan; McCulloch, Iain

2018-05-08

We report a design strategy that allows the preparation of solution processable n-type materials from low boiling point solvents for organic electrochemical transistors (OECTs). The polymer backbone is based on NDI-T2 copolymers where a branched alkyl side chain is gradually exchanged for a linear ethylene glycol-based side chain. A series of random copolymers was prepared with glycol side chain percentages of 0, 10, 25, 50, 75, 90, and 100 with respect to the alkyl side chains. These were characterized to study the influence of the polar side chains on interaction with aqueous electrolytes, their electrochemical redox reactions, and performance in OECTs when operated in aqueous electrolytes. We observed that glycol side chain percentages of >50% are required to achieve volumetric charging, while lower glycol chain percentages show a mixed operation with high required voltages to allow for bulk charging of the organic semiconductor. A strong dependence of the electron mobility on the fraction of glycol chains was found for copolymers based on NDI-T2, with a significant drop as alkyl side chains are replaced by glycol side chains.

Experimental and QSAR study on the surface activities of alkyl imidazoline surfactants

NASA Astrophysics Data System (ADS)

Kong, Xiangjun; Qian, Chengduo; Fan, Weiyu; Liang, Zupei

2018-03-01

15 alkyl imidazoline surfactants with different structures were synthesized and their critical micelle concentration (CMC) and surface tension under the CMC (σcmc) in aqueous solution were measured at 298 K. 54 kinds of molecular structure descriptors were selected as independent variables and the quantitative structure-activity relationship (QSAR) between surface activities of alkyl imidazoline and molecular structure were built through the genetic function approximation (GFA) method. Experimental results showed that the maximum surface excess of alkyl imidazoline molecules at the gas-liquid interface increased and the area occupied by each surfactant molecule and the free energies of micellization ΔGm decreased with increasing carbon number (NC) of the hydrophobic chain or decreasing hydrophilicity of counterions, which resulted in a CMC and σcmc decrease, while the log CMC and NC had a linear relationship and a negative correlation. The GFA-QSAR model, which was generated by a training set composed of 13 kinds of alkyl imidazoline though GFA method regression analysis, was highly correlated with predicted values and experimental values of the CMC. The correlation coefficient R was 0.9991, which means high prediction accuracy. The prediction error of 2 kinds of alkyl imidazoline CMCs in the Validation Set that quantitatively analyzed the influence of the alkyl imidazoline molecular structure on the CMC was less than 4%.

Reassessment of structure of smectic phases: Nano-segregation in smectic E phase in 4-n-alkyl-4'-isothiocyanato-1,1'-biphenyls

NASA Astrophysics Data System (ADS)

Saito, Kazuya; Miyazawa, Takahito; Fujiwara, Akio; Hishida, Mafumi; Saitoh, Hideki; Massalska-Arodź, Maria; Yamamura, Yasuhisa

2013-09-01

Based on new diffraction data from aligned samples of smectic E (SmE) phase of 4-n-alkyl-4'-isothiocyanato-1,1'-biphenyls, systematics against the alkyl chain length n is analyzed. In order to perform the analysis, the molecular form factor approximated by a box-shaped distribution is calculated while taking the rounding of the distribution at corners into account. The analysis clearly shows the nano-segregated layered structure, which does not fit to the traditional structural view of SmE phase but does fit to the model the present authors proposed recently. Some implications of this conclusion are discussed in relation to the importance of the molten state of alkyl chains in most of real mesogens revealed previously through thermodynamic analyses.

Self-Assembly, Supramolecular Organization, and Phase Behavior of L-Alanine Alkyl Esters (n = 9-18) and Characterization of Equimolar L-Alanine Lauryl Ester/Lauryl Sulfate Catanionic Complex.

PubMed

Sivaramakrishna, D; Swamy, Musti J

2015-09-08

A homologous series of l-alanine alkyl ester hydrochlorides (AEs) bearing 9-18 C atoms in the alkyl chain have been synthesized and characterized with respect to self-assembly, supramolecular structure, and phase transitions. The CMCs of AEs bearing 11-18 C atoms were found to range between 0.1 and 10 mM. Differential scanning calorimetric (DSC) studies showed that the transition temperatures (Tt), enthalpies (ΔHt) and entropies (ΔSt) of AEs in the dry state exhibit odd-even alternation, with the odd-chain-length compounds having higher Tt values, but the even-chain-length homologues showing higher values of ΔHt and ΔSt. In DSC measurements on hydrated samples, carried out at pH 5.0 and pH 10.0 (where they exist in cationic and neutral forms, respectively), compounds with 13-18 C atoms in the alkyl chain showed sharp gel-to-liquid crystalline phase transitions, and odd-even alternation was not seen in the thermodynamic parameters. The molecular structure, packing properties, and intermolecular interactions of AEs with 9 and 10 C atoms in the alkyl chain were determined by single crystal X-ray diffraction, which showed that the alkyl chains are packed in a tilted interdigitated bilayer format. d-Spacings obtained from powder X-ray diffraction studies exhibited a linear dependence on the alkyl chain length, suggesting that the other AEs also adopt an interdigitated bilayer structure. Turbidimetric, fluorescence spectroscopic, and isothermal titration calorimetric (ITC) studies established that in aqueous dispersions l-alanine lauryl ester hydrochloride (ALE·HCl) and sodium dodecyl sulfate (SDS) form an equimolar complex. Transmission electron microscopic and DSC studies indicate that the complex exists as unilamellar liposomes, which exhibit a sharp phase transition at ∼39 °C. The aggregates were disrupted at high pH, suggesting that the catanionic complex would be useful to develop a base-labile drug delivery system. ITC studies indicated that ALE·HCl forms

[Alkylating agents].

PubMed

Pourquier, Philippe

2011-11-01

With the approval of mechlorethamine by the FDA in 1949 for the treatment of hematologic malignancies, alkylating agents are the oldest class of anticancer agents. Even though their clinical use is far beyond the use of new targeted therapies, they still occupy a major place in specific indications and sometimes represent the unique option for the treatment of refractory diseases. Here, we are reviewing the major classes of alkylating agents and their mechanism of action, with a particular emphasis for the new generations of alkylating agents. As for most of the chemotherapeutic agents used in the clinic, these compounds are derived from natural sources. With a complex but original mechanism of action, they represent new interesting alternatives for the clinicians, especially for tumors that are resistant to conventional DNA damaging agents. We also briefly describe the different strategies that have been or are currently developed to potentiate the use of classical alkylating agents, especially the inhibition of pathways that are involved in the repair of DNA lesions induced by these agents. In this line, the development of PARP inhibitors is a striking example of the recent regain of interest towards the "old" alkylating agents.

Charge properties and bacterial contact-killing of hyperbranched polyurea-polyethyleneimine coatings with various degrees of alkylation

NASA Astrophysics Data System (ADS)

Roest, Steven; van der Mei, Henny C.; Loontjens, Ton J. A.; Busscher, Henk J.

2015-11-01

Coatings of immobilized-quaternary-ammonium-ions (QUAT) uniquely kill adhering bacteria upon contact. QUAT-coatings require a minimal cationic-charge surface density for effective contact-killing of adhering bacteria of around 1014 cm-2. Quaternization of nitrogen is generally achieved through alkylation. Here, we investigate the contribution of additional alkylation with methyl-iodide to the cationic-charge density of hexyl-bromide alkylated, hyperbranched polyurea-polyethyleneimine coatings measuring charge density with fluorescein staining. X-ray-photoelectron-spectroscopy was used to determine the at.% alkylated-nitrogen. Also streaming potentials, water contact-angles and bacterial contact-killing were measured. Cationic-charge density increased with methyl-iodide alkylation times up to 18 h, accompanied by an increase in the at.% alkylated-nitrogen. Zeta-potentials became more negative upon alkylation as a result of shielding of cationiccharges by hydrophobic alkyl-chains. Contact-killing of Gram-positive Staphylococci only occurred when the cationic-charge density exceeded 1016 cm-2 and was carried by alkylated-nitrogen (electron-binding energy 401.3 eV). Gram-negative Escherichia coli was not killed upon contact with the coatings. There with this study reveals that cationic-charge density is neither appropriate nor sufficient to determine the ability of QUAT-coatings to kill adhering bacteria. Alternatively, the at.% of alkylated-nitrogen at 401.3 eV is proposed, as it reflects both cationic-charge and its carrier. The at.% N401.3 eV should be above 0.45 at.% for Gram-positive bacterial contact-killing.

The Role of the Side Chain on the Performance of N-type Conjugated Polymers in Aqueous Electrolytes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Giovannitti, Alexander; Maria, Iuliana P.; Hanifi, David

Here, we report a design strategy that allows the preparation of solution processable n-type materials from low boiling point solvents for organic electrochemical transistors (OECTs). The polymer backbone is based on NDI-T2 copolymers where a branched alkyl side chain is gradually exchanged for a linear ethylene glycol-based side chain. A series of random copolymers was prepared with glycol side chain percentages of 0, 10, 25, 50, 75, 90, and 100 with respect to the alkyl side chains. These were characterized to study the influence of the polar side chains on interaction with aqueous electrolytes, their electrochemical redox reactions, and performancemore » in OECTs when operated in aqueous electrolytes. We observed that glycol side chain percentages of >50% are required to achieve volumetric charging, while lower glycol chain percentages show a mixed operation with high required voltages to allow for bulk charging of the organic semiconductor. A strong dependence of the electron mobility on the fraction of glycol chains was found for copolymers based on NDI-T2, with a significant drop as alkyl side chains are replaced by glycol side chains.« less

The Role of the Side Chain on the Performance of N-type Conjugated Polymers in Aqueous Electrolytes

DOE PAGES

Giovannitti, Alexander; Maria, Iuliana P.; Hanifi, David; ...

2018-04-24

Here, we report a design strategy that allows the preparation of solution processable n-type materials from low boiling point solvents for organic electrochemical transistors (OECTs). The polymer backbone is based on NDI-T2 copolymers where a branched alkyl side chain is gradually exchanged for a linear ethylene glycol-based side chain. A series of random copolymers was prepared with glycol side chain percentages of 0, 10, 25, 50, 75, 90, and 100 with respect to the alkyl side chains. These were characterized to study the influence of the polar side chains on interaction with aqueous electrolytes, their electrochemical redox reactions, and performancemore » in OECTs when operated in aqueous electrolytes. We observed that glycol side chain percentages of >50% are required to achieve volumetric charging, while lower glycol chain percentages show a mixed operation with high required voltages to allow for bulk charging of the organic semiconductor. A strong dependence of the electron mobility on the fraction of glycol chains was found for copolymers based on NDI-T2, with a significant drop as alkyl side chains are replaced by glycol side chains.« less

Synthesis and photopolymerization of low shrinkage methacrylate monomers containing bulky substituent groups.

PubMed

Ge, Junhao; Trujillo, Marianela; Stansbury, Jeffrey

2005-12-01

This study was conducted to determine whether novel photopolymerizable formulations based on dimethacrylate monomers with bulky substituent groups could provide low polymerization shrinkage without sacrifice to degree of conversion, and mechanical properties of the polymers. Relatively high molecular weight dimethacrylate monomers were prepared from rigid bisphenol A core groups. Photopolymerization kinetics and shrinkage as well as flexural strength and glass transition temperatures were evaluated for various comonomer compositions. Copolymerization of the bulky monomers with TEGDMA show higher conversion but similar shrinkage compared with Bis-GMA/TEGDMA controls. The resulting polymers have suitable mechanical strength properties for potential dental restorative materials applications. When copolymerized with PEGDMA, the bulky monomers show lower shrinkage, comparable conversion, and more homogeneous polymeric network structures compared with Bis-EMA/PEGDMA systems. The novel dimethacrylate monomers with reduced reactive group densities can decrease the polymerization shrinkage as anticipated, but there is no significant evidence that the bulky substituent groups have any additional effect on reducing shrinkage based on the physical interactions as polymer side chains. The bulky groups improve the double bond conversion and help maintain the mechanical properties of the resulting polymer, which would otherwise decrease rapidly due to the reduced crosslinking density. Further, it was found that bulky monomers help produce more homogeneous copolymer networks.

Substituent-induced effects on dimensionality in cadmium isophthalate coordination polymers containing 3-pyridylisonicotinamide

NASA Astrophysics Data System (ADS)

O'Donovan, Megan E.; Wudkewych, Megan J.; LaDuca, Robert L.

2015-08-01

Hydrothermal treatment of cadmium nitrate, a 5-substituted isophthalic acid, and 3-pyridylisonicotinamide (3-pina) resulted in three coordination polymers whose dimensionality depended critically on the nature of the aromatic ring substituent. These three new phases were characterized by single crystal X-ray diffraction. {[Cd(hip)(3-pina)(H2O)2]·2H2O}n (1, hip = 5-hydroxyisophthalate) and {[Cd(meoip)(3-pina)(H2O)2]·H2O}n (2, meoip = 5-methoxyisophthalate) both manifest simple 1-D chain structures with pendant 3-pina ligands. [Cd(mip)(3-pina)]n (3, mip = 5-methylisophthalate) possesses [Cd(mip)]n 1-D chains featuring {Cd2(OCO)2} dimeric units, linked by tethering 3-pina ligands into a non-interpenetrated 3-D 6-connected 41263 pcu network. Luminescent behavior in all cases is attributed to intra-ligand molecular orbital transitions.

Polyethylene composites containing a phase change material having a C14 straight chain hydrocarbon

DOEpatents

Salyer, Ival O.

1987-01-01

A composite useful in thermal energy storage, said composite being formed of a polyethylene matrix having a straight chain alkyl hydrocarbon incorporated therein, said polyethylene being crosslinked to such a degree that said polyethylene matrix is form stable and said polyethylene matrix is capable of absorbing at least 10% by weight of said straight chain alkyl hydrocarbon; the composite is useful in forming pellets or sheets having thermal energy storage characteristics.

A chiroptical switch based on supramolecular chirality transfer through alkyl chain entanglement and dynamic covalent bonding.

PubMed

Lv, Kai; Qin, Long; Wang, Xiufeng; Zhang, Li; Liu, Minghua

2013-12-14

Chirality transfer is an interesting phenomenon in Nature, which represents an important step to understand the evolution of chiral bias and the amplification of the chirality. In this paper, we report the chirality transfer via the entanglement of the alkyl chains between chiral gelator molecules and achiral amphiphilic Schiff base. We have found that although an achiral Schiff base amphiphile could not form organogels in any kind of organic solvents, it formed co-organogels when mixed with a chiral gelator molecule. Interestingly, the chirality of the gelator molecules was transferred to the Schiff base chromophore in the mixed co-gels and there was a maximum mixing ratio for the chirality transfer. Furthermore, the supramolecular chirality was also produced based on a dynamic covalent chemistry of an imine formed by the reaction between an aldehyde and an amine. Such a covalent bond of imine was formed reversibly depending on the pH variation. When the covalent bond was formed the chirality transfer occurred, when it was destroyed, the transfer stopped. Thus, a supramolecular chiroptical switch is obtained based on supramolecular chirality transfer and dynamic covalent chemistry.

Synthesis of prostaglandins by conjugate addition and alkylation of a directed enolate ion. 4,5-allenyl prostaglandins

DOE Office of Scientific and Technical Information (OSTI.GOV)

Patterson, J.W.

1990-09-28

Over the previous two decades many elegant syntheses of prostaglandins, which in more sophisticated forms, allow the stereospecific introduction of the various asymmetric carbons have been accomplished. However, among these approaches the cuprate addition/enolate alkylation of suitable cyclopentenone {sup 2} stands out because of brevity and convergence. The recent reports by Noyori{sup 3} and Corey{sup 4} and their colleagues have reduced to practice the conversion of 4-alkoxycyclopentenones to prostaglandin E{sub 2} (PGE{sub 2}) by conjugate addition of an organocopper derivative of the lower side chain followed by alkylation of the resulting carbanion with methyl 7-halohept-2-enoate. The subject of this papermore » is application of the Tardella tin enolate alkylation developed by Noyori to the synthesis of 4, 5-allenic prostaglandins, a pharmacologically important class of compounds. The authors results demonstrate that the tandem alkylation of an enone precursor with a cuprate reagent followed by alkylation of the corresponding tin enolate with bromide reagent is a viable synthetic method for 4,5-didehydro-PGE{sub 2}. Because the optically active forms of 1 and the vinyl iodide precursor of the PGE{sub 2} lower side chain have been employed to produce a single enantiomer of PGE{sub 2}, the extension of the methodology described here to the synthesis of single enantiomers of 4a awaits only the preparation of the separate enantiomers of allene 14.« less

Cyclic 3-alkyl pyridinium alkaloid monomers from a New Zealand Haliclona sp. marine sponge.

PubMed

Damodaran, Vidhiya; Ryan, Jason L; Keyzers, Robert A

2013-10-25

Bioassay and NMR approaches have been used to guide the isolation of one known and two new cyclic 3-alkyl pyridinium alkaloid (3-APA) monomers from the New Zealand marine sponge Haliclona sp. The new compounds, dehydrohaliclocyclins C (3) and F (4), are the first reported examples of cyclic 3-APA monomers with unsaturation in the alkyl chain. The known compound haliclocyclin C (2) was also isolated from a mixture with 4. The structures of compounds 2-4 were elucidated using NMR spectroscopy, mass spectrometry, and chemical degradation.

Transesterified tyrosol and hydroxytyrosol alkyl esters from cuphea oil – antioxidant behavior in Liposomes

USDA-ARS?s Scientific Manuscript database

Tyrosol and hydroxytyrosol are the antioxidant molecules abundantly found in olive oil. Transesterification of tyrosol and hydroxytyrosol with cuphea oil results in medium chain alkyl esters with antioxidant properties. Membrane partitioning, antioxidant capacity, and membrane location of these nove...

Effect of polyoxyethylene n-alkyl ethers on carrier-mediated transport of lanthanide ions through cellulose triacetate membranes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sugiura, Masaaki

1992-02-01

Fluxes of 14 kinds of lanthanides across cellulose triacetate membranes were determined by using mixtures of o-nitrophenyl n-octyl ether and a series of polyoxythylene n-alkyl ethers (POE ethers) as plasticizers, and hinokitiol as carrier. Effects of alkyl and polyoxyethylene (POE) chains of POE ether on the flux were demonstrated. The transport of the lanthanides was coupled to a flow of hydrogen ions. The POE ethers used (C{sub n}H{sub 2n+1}(OCH{sub 2}CH{sub 2}){sub x}OH, referred to as C{sub n}E{sub x}) were C{sub 10}E{sub 3}, C{sub 12}E{sub 3}, C{sub 14}E{sub 3}, C{sub 16}E{sub 3}, C{sub 12}E{sub 2}, C{sub 12}E{sub 4}, C{sub 12}E{sub 6}more » and C{sub 12}E{sub 8}, In all cases, high fluxes were observed for the lanthanides from samarium to lutetium. On the contrary, the fluxes for lanthanum to neodymium were extremely low. In experiments testing the effect of the alkyl chain, the order of the POE ethers in the lanthanide flux for samarium to lutetium was C{sub 12}E{sub 3} > C{sub 10}E{sub 3} > C{sub 14}E{sub 3} >C{sub 16}E{sub 3}. In experiments testing the effect of the POE chain, the flux decreased with an increase in the chain length.« less

Poly(alkyl methacrylate) Brush-Grafted Silica Nanoparticles as Oil Lubricant Additives: Effects of Alkyl Pendant Groups on Oil Dispersibility, Stability, and Lubrication Property

DOE PAGES

Seymour, Bryan T.; Wright, Roger A. E.; Parrott, Alexander C.; ...

2017-07-03

This paper reports on the synthesis of a series of poly(alkyl methacrylate) brush-grafted, 23 nm silica nanoparticles (hairy NPs) and the study of the effect of alkyl pendant length on their use as oil lubricant additives for friction and wear reduction. The hairy NPs were prepared by surface-initiated reversible addition–fragmentation chain transfer polymerization from trithiocarbonate chain transfer agent (CTA)-functionalized silica NPs in the presence of a free CTA. We found that hairy NPs with sufficiently long alkyl pendant groups (containing >8 carbon atoms, such as 12, 13, 16, and 18 in this study) could be readily dispersed in poly(alphaolefin) (PAO),more » forming clear, homogeneous dispersions, and exhibited excellent stability at low and high temperatures as revealed by visual inspection and dynamic light scattering studies. Whereas poly(n-hexyl methacrylate) hairy NPs cannot be dispersed in PAO under ambient conditions or at 80 °C, interestingly, poly(2-ethylhexyl methacrylate) hairy NPs can be dispersed in PAO at 80 °C but not at room temperature, with a reversible clear-to-cloudy transition observed upon cooling. High-contact-stress ball-on-flat reciprocating sliding tribological tests at 100 °C showed significant reductions in both the coefficient of friction (up to 38%) and wear volume (up to 90% for iron flat) for transparent, homogeneous dispersions of hairy NPs in PAO at a concentration of 1.0 wt % compared with neat PAO. Finally, the formation of a load-bearing tribofilm at the rubbing interface was confirmed using scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy.« less

Poly(alkyl methacrylate) Brush-Grafted Silica Nanoparticles as Oil Lubricant Additives: Effects of Alkyl Pendant Groups on Oil Dispersibility, Stability, and Lubrication Property

DOE Office of Scientific and Technical Information (OSTI.GOV)

Seymour, Bryan T.; Wright, Roger A. E.; Parrott, Alexander C.

This paper reports on the synthesis of a series of poly(alkyl methacrylate) brush-grafted, 23 nm silica nanoparticles (hairy NPs) and the study of the effect of alkyl pendant length on their use as oil lubricant additives for friction and wear reduction. The hairy NPs were prepared by surface-initiated reversible addition–fragmentation chain transfer polymerization from trithiocarbonate chain transfer agent (CTA)-functionalized silica NPs in the presence of a free CTA. We found that hairy NPs with sufficiently long alkyl pendant groups (containing >8 carbon atoms, such as 12, 13, 16, and 18 in this study) could be readily dispersed in poly(alphaolefin) (PAO),more » forming clear, homogeneous dispersions, and exhibited excellent stability at low and high temperatures as revealed by visual inspection and dynamic light scattering studies. Whereas poly(n-hexyl methacrylate) hairy NPs cannot be dispersed in PAO under ambient conditions or at 80 °C, interestingly, poly(2-ethylhexyl methacrylate) hairy NPs can be dispersed in PAO at 80 °C but not at room temperature, with a reversible clear-to-cloudy transition observed upon cooling. High-contact-stress ball-on-flat reciprocating sliding tribological tests at 100 °C showed significant reductions in both the coefficient of friction (up to 38%) and wear volume (up to 90% for iron flat) for transparent, homogeneous dispersions of hairy NPs in PAO at a concentration of 1.0 wt % compared with neat PAO. Finally, the formation of a load-bearing tribofilm at the rubbing interface was confirmed using scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy.« less

Self-Assembly of Alkylammonium Chains on Montmorillonite: Effect of Interlayer Cations, CEC, and Chain Length

NASA Astrophysics Data System (ADS)

Chen, Hua; Li, Yingjun; Zhou, Yuanlin; Wang, Shanqiang; Zheng, Jian; He, Jiacai

2017-12-01

Recently, polymeric materials have been filled with synthetic or natural inorganic compounds in order to improve their properties. Especially, polymer clay nanocomposites have attracted both academic and industrial attention. Currently, the structure and physical phenomena of organoclays at molecular level are difficultly explained by existing experimental techniques. In this work, molecular dynamics (MD) simulation was executed using the CLAYFF and CHARMM force fields to evaluate the structural properties of organoclay such as basal spacing, interlayer density, energy and the arrangement of alkyl chains in the interlayer spacing. Our results are in good agreement with available experimental or other simulation data. The effects of interlayer cations (Na+, K+, Ca2+), the cation exchange capacity, and the alkyl chain length on the basal spacing and the structural properties are estimated. These simulations are expected to presage the microstructure of organo-montmorillonite and lead relevant engineering applications.

The acute toxic effects of 1-alkyl-3-methylimidazolium nitrate ionic liquids on Chlorella vulgaris and Daphnia magna.

PubMed

Zhang, Cheng; Zhang, Shuai; Zhu, Lusheng; Wang, Jinhua; Wang, Jun; Zhou, Tongtong

2017-10-01

Given their increasingly widespread application, the toxic effects of ionic liquids (ILs) have become the subject of significant attention in recent years. Therefore, the present study assessed the acute toxic effects of 1-alkyl-3-methylimidazolium nitrate ([C n mim]NO 3 (n = 2, 4, 6, 8, 10, 12)) on Chlorella vulgaris and Daphnia magna. The sensitivity of the tested organism Daphnia magna and the investigated IL concentrations in water using high-performance liquid chromatography (HPLC) were also evaluated to demonstrate the reliability of the present study. The results illustrated that Daphnia magna is indeed sensitive to the reference toxicant and the investigated ILs were stable in the aquatic environment. The 50% effect concentration (EC 50 ) was used to represent the acute toxic effects on Chlorella vulgaris and Daphnia magna. With the increasing alkyl-chain lengths, the toxicity of the investigated ILs increased in both the test organisms. Accordingly, the alkyl-chain lengths can cause significantly toxic effects on aquatic organisms, and Daphnia magna are much more sensitive than Chlorella vulgaris to the imidazolium-based ILs used in the present study. Furthermore, the present study provides more information on the acute toxic effects of 1-alkyl-3-methylimidazolium nitrate. Copyright © 2017 Elsevier Ltd. All rights reserved.

Modification of Side Chains of Conjugated Molecules and Polymers for Charge Mobility Enhancement and Sensing Functionality.

PubMed

Liu, Zitong; Zhang, Guanxin; Zhang, Deqing

2018-06-19

Organic semiconductors have received increasing attentions in recent years because of their promising applications in various optoelectronic devices. The key performance metric for organic semiconductors is charge carrier mobility, which is governed by the electronic structures of conjugated backbones and intermolecular/interchain π-π interactions and packing in both microscopic and macroscopic levels. For this reason, more efforts have been paid to the design and synthesis of conjugated frameworks for organic semiconductors with high charge mobilities. However, recent studies manifest that appropriate modifications of side chains that are linked to conjugated frameworks can improve the intermolecular/interchain packing order and boost charge mobilities. In this Account, we discuss our research results in context of modification of side chains in organic semiconductors for charge mobility enhancement. These include the following: (i) The lengths of alkyl chains in sulfur-rich thiepin-fused heteroacences can dramatically influence the intermolecular arrangements and orbital overlaps, ushering in different hole mobilities. Inversely, the lamellar stacking modes of alkyl chains in naphthalene diimide (NDI) derivatives with tetrathiafulvalene (TTF) units are affected by the structures of conjugated cores. (ii) The steric hindrances owing to the bulky branching chains can be weakened by partial replacement of the branching alkyl chains with linear ones for diketopyrrolopyrrole (DPP)-based D (donor)-A (acceptor) conjugated polymers. Such modification of side chains makes the polymer backbones more planar and thus interchain packing order and charge mobilities are improved. The incorporation of hydrophilic tri(ethylene glycol) (TEG) chains into the polymers also leads to improved interchain packing order. In particular, the polymer in which TEG side chains are distributed uniformly exhibits relatively high charge mobility without thermal annealing. (iii) The

Asymmetric Conjugated Molecules Based on [1]Benzothieno[3,2-b][1]benzothiophene for High-Mobility Organic Thin-Film Transistors: Influence of Alkyl Chain Length.

PubMed

He, Keqiang; Li, Weili; Tian, Hongkun; Zhang, Jidong; Yan, Donghang; Geng, Yanhou; Wang, Fosong

2017-10-11

Herein, we report the synthesis and characterization of a series of [1]benzothieno[3,2-b][1]benzothiophene (BTBT)-based asymmetric conjugated molecules, that is, 2-(5-alkylthiophen-2-yl)[1]benzothieno[3,2-b][1]benzothiophene (BTBT-Tn, in which T and n represent thiophene and the number of carbons in the alkyl group, respectively). All of the molecules with n ≥ 4 show mesomorphism and display smectic A, smectic B (n = 4), or smectic E (n > 4) phases and then crystalline phases in succession upon cooling from the isotropic state. Alkyl chain length has a noticeable influence on the microstructures of vacuum-deposited films and therefore on the performance of the organic thin-film transistors (OTFTs). All molecules except for 2-(thiophen-2-yl)[1]benzothieno[3,2-b][1]benzothiophene and 2-(5-ethylthiophen-2-yl)[1]benzothieno[3,2-b][1]benzothiophene showed OTFT mobilities above 5 cm 2 V -1 s -1 . 2-(5-Hexylthiophen-2-yl)[1]benzothieno[3,2-b][1]benzothiophene and 2-(5-heptylthiophen-2-yl)[1]benzothieno[3,2-b][1]benzothiophene showed the greatest OTFT performance with reliable hole mobilities (μ) up to 10.5 cm 2 V -1 s -1 because they formed highly ordered and homogeneous films with diminished grain boundaries.

Small nickel nanoparticle arrays from long chain imidazolium ionic liquids

DOE PAGES

Yang, Mei; Campbell, Paul S.; Santini, Catherine C.; ...

2013-11-08

A series of six long chain alkyl mono- and bi-cationic imidazolium based salts with bis(trifluoromethylsulfonyl)imide (NTf 2–) as the anion were synthesized and characterized. Single crystal structure of 1-methyl-3-octadecylimidazolium bis(trifluoromethylsulfonyl)imide could be obtained by X-ray analysis. All these long chain alkyl imidazolium based ILs were applied in the synthesis of nickel nanoparticles via chemical decomposition of an organometallic precursor of nickel. In these media, spontaneous decomposition of Ni(COD) 2 (COD = 1,5-cyclooctadiene) in the absence of H 2 occurred giving small NPs (≤4 nm) with narrow size distributions. Interestingly, formation of regularly interspaced NP arrays was also observed in longmore » chain ILs. Lastly, such array formation could be interesting for potential applications such as carbon nanotube growth.« less

Prediction and interpretation of infrared intensities of polymethylene chain molecules

NASA Astrophysics Data System (ADS)

Jona, P.; Gussoni, M.; Zerbi, G.

1986-03-01

We have calculated the IR intensities of some polymethylene chain molecules containing conformational defects or polar heads. Calculations provide spectroscopic markers of end-TG, GTG', GTG, GG and GGTGG defects. Further, a spectroscopical study of interactions between polar heads and alkyl chain is allowed.

Effects of Moisture and Other Contaminants in Friction Composites

DTIC Science & Technology

1993-01-30

NC 126, (Cardolite Corporation, Newark, NJ), a cashew nut shell liquid modified phenolic resin. NC126 is different from a straight phenolic resin in...that there is an alkyl chain substituent in the meta position of the phenol. The resin is derived from cashew nut shell liquid and is a solid...crosslinked cashew resin and is often referred to as cashew particles. The friction materials were processed by compression molding at 160 °C and 1000 psi

Enhancement of polyisoprene latex production

NASA Technical Reports Server (NTRS)

Bauman, Albert J. (Inventor)

1979-01-01

Production of high molecular weight polyisoprene latex is enhanced by administering to plants, particularly Guayule Plants, an amine containing at least one two-carbon chain substituent and preferably substituted trialkylamine of the general structure: ##STR1## where R.sub.4, R.sub.5 and R.sub.6 are alkyl, preferably ethyl and at least one of R.sub.4, R.sub.5 and R.sub.6 is preferably an electron withdrawing group substituted aryloxy or arylthio ethyl group.

Effect of alkyl side chain location and cyclicity on the aerobic biotransformation of naphthenic acids.

PubMed

Misiti, Teresa M; Tezel, Ulas; Pavlostathis, Spyros G

2014-07-15

Aerobic biodegradation of naphthenic acids is of importance to the oil industry for the long-term management and environmental impact of process water and wastewater. The effect of structure, particularly the location of the alkyl side chain as well as cyclicity, on the aerobic biotransformation of 10 model naphthenic acids (NAs) was investigated. Using an aerobic, mixed culture, enriched with a commercial NA mixture (NA sodium salt; TCI Chemicals), batch biotransformation assays were conducted with individual model NAs, including eight 8-carbon isomers. It was shown that NAs with a quaternary carbon at the α- or β-position or a tertiary carbon at the β- and/or β'-position are recalcitrant or have limited biodegradability. In addition, branched NAs exhibited lag periods and lower degradation rates than nonbranched or simple cyclic NAs. Two NA isomers used in a closed bottle, aerobic biodegradation assay were mineralized, while 21 and 35% of the parent compound carbon was incorporated into the biomass. The NA biodegradation probability estimated by two widely used models (BIOWIN 2 and 6) and a recently developed model (OCHEM) was compared to the biodegradability of the 10 model NAs tested in this study as well as other related NAs. The biodegradation probability estimated by the OCHEM model agreed best with the experimental data and was best correlated with the measured NA biodegradation rate.

Enhanced production of short-chain fatty acid from food waste stimulated by alkyl polyglycosides and its mechanism.

PubMed

Zhao, Jianwei; Yang, Qi; Li, Xiaoming; Wang, Dongbo; Luo, Kun; Zhong, Yu; Xu, Qiuxiang; Zeng, Guangming

2015-12-01

Short-chain fatty acids (SCFAs) are the valuable products derived from the anaerobic fermentation of organic solid waste. However, SCFAs yield was limited by the worse solubilization and hydrolysis of particulate organic matter, and rapid consumption of organic acid by methanogens. In this study, an efficient and green strategy, i.e. adding biosurfactant alkyl polyglycosides (APG) into anaerobic fermentation system, was applied to enhance SCFAs production from food waste. Experimental results showed that APG not only greatly improved SCFAs production but also shortened the fermentation time for the maximum SCFAs accumulation. The SCFAs yield at optimal APG dosage 0.2g/g TS (total solid) reached 37.2g/L, which was 3.1-fold of that in blank. Meanwhile, the time to accumulate the maximum SCFAs in the presence of APG was shortened from day 14 to day 6. The activities of key enzymes such as hydrolytic and acid-forming enzymes were greatly promoted due to the presence of APG. These results demonstrated that the enhanced mechanism of SCFAs production should be attributed to the acceleration of solubilization and hydrolysis, enhancement of acidification and inhibition of methanogenesis by APG. Copyright © 2015 Elsevier Ltd. All rights reserved.

Accurate prediction of cation-π interaction energy using substituent effects.

PubMed

Sayyed, Fareed Bhasha; Suresh, Cherumuttathu H

2012-06-14

Substituent effects on cation-π interactions have been quantified using a variety of Φ-X···M(+) complexes where Φ, X, and M(+) are the π-system, substituent, and cation, respectively. The cation-π interaction energy, E(M(+)), showed a strong linear correlation with the molecular electrostatic potential (MESP) based measure of the substituent effect, ΔV(min) (the difference between the MESP minimum (V(min)) on the π-region of a substituted system and the corresponding unsubstituted system). This linear relationship is E(M(+)) = C(M(+))(ΔV(min)) + E(M(+))' where C(M(+)) is the reaction constant and E(M(+))' is the cation-π interaction energy of the unsubstituted complex. This relationship is similar to the Hammett equation and its first term yields the substituent contribution of the cation-π interaction energy. Further, a linear correlation between C(M(+))() and E(M(+))()' has been established, which facilitates the prediction of C(M(+)) for unknown cations. Thus, a prediction of E(M(+)) for any Φ-X···M(+) complex is achieved by knowing the values of E(M(+))' and ΔV(min). The generality of the equation is tested for a variety of cations (Li(+), Na(+), K(+), Mg(+), BeCl(+), MgCl(+), CaCl(+), TiCl(3)(+), CrCl(2)(+), NiCl(+), Cu(+), ZnCl(+), NH(4)(+), CH(3)NH(3)(+), N(CH(3))(4)(+), C(NH(2))(3)(+)), substituents (N(CH(3))(2), NH(2), OCH(3), CH(3), OH, H, SCH(3), SH, CCH, F, Cl, COOH, CHO, CF(3), CN, NO(2)), and a large number of π-systems. The tested systems also include multiple substituted π-systems, viz. ethylene, acetylene, hexa-1,3,5-triene, benzene, naphthalene, indole, pyrrole, phenylalanine, tryptophan, tyrosine, azulene, pyrene, [6]-cyclacene, and corannulene and found that E(M)(+) follows the additivity of substituent effects. Further, the substituent effects on cationic sandwich complexes of the type C(6)H(6)···M(+)···C(6)H(5)X have been assessed and found that E(M(+)) can be predicted with 97.7% accuracy using the values of E

Synthesis and evaluation of changes induced by solvent and substituent in electronic absorption spectra of some azo disperse dyes

NASA Astrophysics Data System (ADS)

Mohammadi, Asadollah; Yazdanbakhsh, Mohammad Reza; Farahnak, Lahya

2012-04-01

Five azo disperse dyes were prepared by diazotizing 4'-aminoacetophenone and p-anisidine and coupling with varies N-alkylated aromatic amines. Characterization of the dyes was carried out by using UV-vis, FTIR and 1H NMR spectroscopic techniques. The electronic absorption spectra of dyes are determined at room temperature in fifteen solvents with different polarities. The solvent dependent maximum absorption band shifts, were investigated using dielectric constant (ɛ), refractive index (n) and Kamlet-Taft polarity parameters (hydrogen bond donating ability (α), hydrogen bond accepting ability (β) and dipolarity/polarizability polarity scale (π*)). Acceptable agreement was found between the maximum absorption band of dyes and solvent polarity parameters especially with π*. The effect of substituents of coupler and/or diazo component on the color of dyes was investigated. The effects of acid and base on the visible absorption maxima of the dyes are also reported.

The characterization of hydroxypropyl methylcellulose through the analysis of its substituents

USDA-ARS?s Scientific Manuscript database

The methyl and hydroxypropyl substituents in hydroxypropyl methylcellulose (HPMC) affect the resulting gel properties. These substituents in five HPMC gels were characterized using Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy, small-amplitude oscillatory shear measurements, a...

Engineering acyclic stereocontrol in the alkylation of vinylglycine-derived dianions: asymmetric synthesis of higher alpha-vinyl amino acids.

PubMed

Berkowitz, D B; McFadden, J M; Sloss, M K

2000-05-19

A generalizable synthesis of higher L-alpha-vinyl amino acids is presented. The strategy pursued here involves the introduction of the amino acid side chain via the alkylation of a chiral, vinylglycine-derived dianionic dienolate, bearing the (-)-8-(beta-naphthyl)menthyl (d'Angelo) auxiliary. A model is presented that postulates a favored "exo-entended" conformation for this dienolate, leading to C(alpha)-alkylation at the si face. The model invokes internal amidate chelation to control ester enolate geometry and soft-soft interactions between the polarizable beta-naphthyl ring of the auxiliary and the extended pi-system of the dienolate to shield the re face. Heats of formation for four conformers of this dianion were calculated for their semiempirical optimized geometries (PM3). The results support the notion that in these vinylglycine-derived dianionic dienolates, "exo" conformations are considerable lower in energy than their "endo" counterparts, with the "exo-entended" conformation being most favorable. In fact, the d'Angelo auxiliary gives a greater degree of acyclic stereocontrol in this system when compared with the (-)-8-phenylmenthyl (Corey) and trans-2-(beta-naphthyl)cyclohexyl auxiliaries, using isobutyl iodide and benzyl bromide as model electrophiles. These dianions are generated from the corresponding dehydrobutyrine esters via sequential deprotonation with LDA and n-BuLi (2 equiv). When alkylations are carried out at -78 degrees C in THF-HMPA, they proceed in 65-81% yields, with both regiocontrol (deconjugative alpha-alkylation is preferred over gamma-alkylation) and a great degree of acyclic stereocontrol [91:9 to >/=98:2 diastereomeric ratios (10 examples)]. The auxiliary may be recovered in high yield (generally 90%) using a modification of Gassman's "anhydrous hydroxide" conditions, in which considerably higher temperatures are employed. Among the side chains introduced directly are those of butyrine, leucine, ornithine, phenylalanine, aspartate

The Scarlet Letter of Alkylation: A Mini Review of Selective Alkylating Agents

PubMed Central

Oronsky, Bryan T; Reid, Tony; Knox, Susan J; Scicinski, Jan J

2012-01-01

If there were a stigma scale for chemotherapy, alkylating agents would be ranked at the top of the list. The chemical term alkylation is associated with nonselective toxicity, an association that dates back to the use of nitrogen mustards during World War I as chemical warfare agents. That this stigma persists and extends to compounds that, through selectivity, attempt to “tame” the indiscriminate destructive potential of alkylation is the subject of this review. Selective alkylation, as it is referred to herein, constitutes an extremely nascent and dynamic field in oncology. The pharmacodynamic response to this selective strategy depends on a delicate kinetic balance between specificity and the rate and extent of binding. Three representative compounds are presented: RRx-001, 3-bromopyruvate, and TH-302. The main impetus for the development of these compounds has been the avoidance of the serious complications of traditional alkylating agents; therefore, it is the thesis of this review that they should not experience stigma by association. PMID:22937173

Tunable fictitious substituent effects on the π-π interactions of substituted sandwich benzene dimers.

PubMed

Garcia, Amee M; Determan, John J; Janesko, Benjamin G

2014-05-08

Substituent effects on the π-π interactions of aromatic rings are a topic of much recent debate. Real substituents give a complicated combination of inductive, resonant, dispersion, and other effects. To help partition these effects, we present calculations on fictitious "pure" σ donor/acceptor substituents, hydrogen atoms with nuclear charges other than 1. "Pure" σ donors with nuclear charge <1 weaken π-π stacking in the sandwich benzene dimer. This result is consistent with the electrostatic model of Hunter and Sanders, and different from real substituents. Calculated inductive effects are largely additive and transferable, consistent with a local direct interaction model. A second series of fictitious substituents, neutral hydrogen atoms with an artificially broadened nuclear charge distribution, give similar trends though with reduced additivity. These results provide an alternative perspective on substituent effects in noncovalent interactions.

Alkyl Chain Length Dependent Structural and Orientational Transformations of Water at Alcohol-Water Interfaces and Its Relevance to Atmospheric Aerosols.

PubMed

Mondal, Jahur A; Namboodiri, V; Mathi, P; Singh, Ajay K

2017-04-06

Although the hydrophobic size of an amphiphile plays a key role in various chemical, biological, and atmospheric processes, its effect at macroscopic aqueous interfaces (e.g., air-water, oil-water, cell membrane-water, etc.), which are ubiquitous in nature, is not well understood. Here we report the hydrophobic alkyl chain length dependent structural and orientational transformations of water at alcohol (C n H 2n+1 OH, n = 1-12)-water interfaces using interface-selective heterodyne-detected vibrational sum frequency generation (HD-VSFG) and Raman multivariate curve resolution (Raman-MCR) spectroscopic techniques. The HD-VSFG results reveal that short-chain alcohols (C n H 2n+1 OH, n < 4, i.e., up to 1-propanol) do not affect the structure (H-bonding) and orientation of water at the air-water interface; the OH stretch band maximum appears at ∼3470 cm -1 , and the water H atoms are pointed toward the bulk water, that is, "H-down" oriented. In contrast, long-chain alcohols (C n H 2n+1 OH, n > 4, i.e., beyond 1-butanol) make the interfacial water more strongly H-bonded and reversely orientated; the OH stretch band maximum appears at ∼3200 cm -1 , and the H atoms are pointed away from the bulk water, that is, "H-up" oriented. Interestingly, for the alcohol of intermediate chain length (C n H 2n+1 OH, n = 4, i.e, 1-butanol), the interface is quite unstable even after hours of its formation and the time-averaged result is qualitatively similar to that of the long-chain alcohols, indicating a structural/orientational crossover of interfacial water at the 1-butanol-water interface. pH-dependent HD-VSFG measurements (with H 2 O as well as isotopically diluted water, HOD) suggest that the structural/orientational transformation of water at the long-chain alcohol-water interface is associated with the adsorption of OH - anion at the interface. Vibrational mapping of the water structure in the hydration shell of OH - anion (obtained by Raman-MCR spectroscopy of NaOH in HOD

PAMAM-Based Dendrimers with Different Alkyl Chains Self-Assemble on Silica Surfaces: Controllable Layer Structure and Molecular Aggregation.

PubMed

Zhang, Minghui; Yang, Hui; Wang, Shujuan; Zhang, Wei; Hou, Qingfeng; Guo, Donghong; Liu, Fanghui; Chen, Ting; Wu, Xu; Wang, Jinben

2018-06-20

Amphiphilic poly(amidoamine) (PAMAM) dendrimers are a well-known dendritic family due to their remarkable ability to self-assemble on solid surface. However, the relationship between molecular conformation (or adsorption kinetics) of a self-assembled layer and molecular amphiphilicity of such kind of dendrimer is still lacking, which limits the development of modulating self-assembling structures and surface functionality. With this in mind, we synthesized a series of amphiphilic PAMAM-based dendrimers, denoted as G 1 C n , with different alkyl chains ( n = 8, 12, and 16), and investigated the molecular aggregation on silica surfaces by means of quartz crystal microbalance with dissipation, atomic force microscopy, and contact angle. After rinsing, remaining adsorption amounts of G 1 C 12 were higher than those of G 1 C 8 at high concentrations, suggesting that G 1 C 12 adlayers were more stable due to the stronger intermolecular hydrophobic interactions, whereas it preferred to adopt the intramolecular hydrophobic interactions for G 1 C 16 , with low adsorption amounts and unstable adlayers. Bilayer-like structures were inferred in G 1 C 8 and G 1 C 12 adlayers with loose conformation, whereas monolayer structures were likely to exist in the sparse adsorption film of G 1 C 16 . Our results provided more detailed understanding of the effect of molecular structure on the self-assembled structures of amphiphilic dendrimers on solid surfaces, shedding light on the controlled microstructure and wettability of functional surface by modulating the length of hydrophobic chains of dendrimers and a potential application of dendrimer-substrate combinations.

Molecular dynamics simulation of amino acid ionic liquids near a graphene electrode: effects of alkyl side-chain length.

PubMed

Sadeghi Moghadam, Behnoosh; Razmkhah, Mohammad; Hamed Mosavian, Mohammad Taghi; Moosavi, Fatemeh

2016-12-07

Electric double layer (EDL) supercapacitors, using ionic liquid electrolytes, have been receiving a great deal of attention in response to the growing demand for energy storage systems. In the present study, the nanoscopic structure of amino acid ionic liquids (AAILs) as biodegradable electrolytes near a neutral graphene surface was studied by molecular dynamics (MD) simulation. In order to explore the influence of the anion type and structure, the effect of the alkyl side-chain length of amino acids on the EDL was investigated. The results for the AAILs, composed of 1-ethyl-3-methylimidazolium ([EMIM]) cations near alanine ([ALA]) and isoleucine ([ILE]) anions, were compared to a conventional electrolyte, [EMIM][PF 6 ]. A lower mobility of AAIL compared to [EMIM][PF 6 ], with diffusions as low as 10 -11 m 2 s -1 , was observed. The structural results demonstrated a layered structure near the surface and most of the adsorbed imidazolium cation rings lay flat on the graphene surface. Both MD and quantum computations were performed to shed light on the charge behavior of AAIL electrolytes. As the current results demonstrate, an increase in the anion side-chain length leads to a decrease in both the number of adsorbed ions on the surface and the thickness of the first adsorbed layer. More impressively, it was observed that a low charge concentration in the EDL of AAILs is due to more side-side interactions. This remarkable feature could introduce AAILs as more efficient electrolyte materials than conventional [EMIM][PF 6 ].

Selective Hydrodeoxygenation of Alkyl Lactates to Alkyl Propionates with Fe-based Bimetallic Supported Catalysts.

PubMed

Khokarale, Santosh Govind; He, Jian; Schill, Leonhard; Yang, Song; Riisager, Anders; Saravanamurugan, Shunmugavel

2018-02-22

Hydrodeoxygenation (HDO) of methyl lactate (ML) to methyl propionate (MP) was performed with various base-metal supported catalysts. A high yield of 77 % MP was obtained with bimetallic Fe-Ni/ZrO 2 in methanol at 220 °C and 50 bar H 2 . A synergistic effect of Ni increased the yield of MP significantly when using Fe-Ni/ZrO 2 instead of Fe/ZrO 2 alone. Moreover, the ZrO 2 support contributed to improve the yield as a phase transition of ZrO 2 from tetragonal to monoclinic occurred after metal doping giving rise to fine dispersion of the Fe and Ni on the ZrO 2 , resulting in a higher catalytic activity of the material. Interestingly, it was observed that Fe-Ni/ZrO 2 also effectively catalyzed methanol reforming to produce H 2 in situ, followed by HDO of ML, yielding 60 % MP at 220 °C with 50 bar N 2 instead of H 2 . Fe-Ni/ZrO 2 also catalyzed HDO of other short-chain alkyl lactates to the corresponding alkyl propionates in high yields around 70 %. No loss of activity of Fe-Ni/ZrO 2 occurred in five consecutive reaction runs demonstrating the high durability of the catalyst system. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Side chain variations radically alter the diffusion of poly(2-alkyl-2-oxazoline) functionalised nanoparticles through a mucosal barrier.

PubMed

Mansfield, Edward D H; de la Rosa, Victor R; Kowalczyk, Radoslaw M; Grillo, Isabelle; Hoogenboom, Richard; Sillence, Katy; Hole, Patrick; Williams, Adrian C; Khutoryanskiy, Vitaliy V

2016-08-16

Functionalised nanomaterials are gaining popularity for use as drug delivery vehicles and, in particular, mucus penetrating nanoparticles may improve drug bioavailability via the oral route. To date, few polymers have been investigated for their muco-penetration, and the effects of systematic structural changes to polymer architectures on the penetration and diffusion of functionalised nanomaterials through mucosal tissue have not been reported. We investigated the influence of poly(2-oxazoline) alkyl side chain length on nanoparticle diffusion; poly(2-methyl-2-oxazoline), poly(2-ethyl-2-oxazoline), and poly(2-n-propyl-2-oxazoline) were grafted onto the surface of thiolated silica nanoparticles and characterised by FT-IR, Raman and NMR spectroscopy, thermogravimetric analysis, and small angle neutron scattering. Diffusion coefficients were determined in water and in a mucin dispersion (using Nanoparticle Tracking Analysis), and penetration through a mucosal barrier was assessed using an ex vivo fluorescence technique. The addition of a single methylene group in the side chain significantly altered the penetration and diffusion of the materials in both mucin dispersions and mucosal tissue. Nanoparticles functionalised with poly(2-methyl-2-oxazoline) were significantly more diffusive than particles with poly(2-ethyl-2-oxazoline) while particles with poly(2-n-propyl-2-oxazoline) showed no significant increase compared to the unfunctionalised particles. These data show that variations in the polymer structure can radically alter their diffusive properties with clear implications for the future design of mucus penetrating systems.

Structural effect of quaternary ammonium chitin derivatives on their bactericidal activity and specificity.

PubMed

Morkaew, Tirut; Pinyakong, Onruthai; Tachaboonyakiat, Wanpen

2017-08-01

The effect of the quaternary ammonium chitin structure on the bactericidal activity and specificity against Escherichia coli and Staphylococcus aureus was investigated. Quaternary ammonium chitins were synthesized by the separate acylation of chitin (CT) with carboxymethyl trimethylammonium chloride (CMA), 3-carboxypropyl trimethylammonium chloride (CPA) and N-dodecyl-N,N-(dimethylammonio)butyrate (DDMAB). The successful acylation was confirmed by newly formed ester linkage. All three derivatives had a higher surface charge than chitin due to the additional positively charged quaternary ammonium groups. The N-short alkyl substituent (methyl) of CTCMA and CTCPA increased the hydrophilicity whilst the N-long alkyl substituent (dodecyl) of CTDDMAB increased the hydrophobicity compared to chitin. Chitin did not exhibit any bactericidal activity, while CTCMA and CTCPA completely killed E. coli and S. aureus in 30 and 60min, respectively, and CTDDMAB completely killed S. aureus in 10min but did not kill E. coli after a 2-h exposure. Therefore, the N-short alkyl substituent was more effective for killing E. coli and the N-long alkyl substituent conferred specific bactericidal activity against S. aureus. Copyright © 2017 Elsevier B.V. All rights reserved.

Novel polymer electrolytes based on cationic polyurethane with different alkyl chain length

NASA Astrophysics Data System (ADS)

Liu, Libin; Wu, Xiwen; Li, Tianduo

2014-03-01

A series of comb-like cationic polyurethanes (PUs) were synthesized by quaternizing different bromoalkane (C2H5Br, C8H17Br, and C14H29Br) with polyurethane. Solid polymer electrolytes were prepared by complexes cationic PUs with different content of LiClO4. All the solid polymer electrolytes had sufficient thermal stability as confirmed by TGA and exhibited a single-phase behavior evidenced by DSC results. For these electrolytes, FT-IR spectra indicated the formation of polymer-ion complexes. The ac impedance spectra show that the conductivity of the electrolytes follow the Arrhenius behavior, and ionic conductivity is associated with both the charge migration of ions between coordination sites and transmission between aggregates, as confirmed by FT-IR and SEM. Alkyl quaternary ammonium salts in the polymer backbone are recognized as inherent plasticizers, which make the electrolytes exhibit liquid-like behavior. The plasticizing effect of PU-C8 and PU-C14 electrolytes are more effective than that of PU-C2 electrolyte. Maximum ionic conductivity at room temperature for PU-C8 electrolytes containing 50 wt% LiClO4 reached 1.1 × 10-4 S cm-1. This work provides a new research clue that alkyl quaternary ammonium salts could be used as inherent plasticizers and hence make the system behave like a liquid with high ionic conductivity, while preserving the dimensional stability of the solids.

Asymmetric Direct 1,2-Addition of Aryl Grignard Reagents to Aryl Alkyl Ketones.

PubMed

Osakama, Kazuki; Nakajima, Makoto

2016-01-15

The enantioselective addition of Grignard reagents to ketones was promoted by a BINOL derivative bearing alkyl chains at the 3,3'-positions. This is the first asymmetric direct aryl Grignard addition to ketones reported to date. A variety of tertiary diaryl alcohols could be obtained in high yields and enantioselectivities without using any other metal source.

Method of making alkyl esters

DOEpatents

Elliott, Brian

2010-09-14

Methods of making alkyl esters are described herein. The methods are capable of using raw, unprocessed, low-cost feedstocks and waste grease. Generally, the method involves converting a glyceride source to a fatty acid composition and esterifying the fatty acid composition to make alkyl esters. In an embodiment, a method of making alkyl esters comprises providing a glyceride source. The method further comprises converting the glyceride source to a fatty acid composition comprising free fatty acids and less than about 1% glyceride by mass. Moreover, the method comprises esterifying the fatty acid composition in the presence of a solid acid catalyst at a temperature ranging firm about 70.degree. C. to about 120.degree. C. to produce alkyl esters, such that at least 85% of the free fatty acids are converted to alkyl esters. The method also incorporates the use of packed bed reactors for glyceride conversion and/or fatty acid esterification to make alkyl esters.

Effects of 1-Alkyl-3-Methylimidazolium Nitrate on Soil Physical and Chemical Properties and Microbial Biomass.

PubMed

Zhou, Tongtong; Wang, Jun; Ma, Zhiqiang; Du, Zhongkun; Zhang, Cheng; Zhu, Lusheng; Wang, Jinhua

2018-05-01

Ionic liquids (ILs), also called room temperature ILs, are widely applied in many fields on the basis of their unique physical and chemical properties. However, numerous ILs may be released into and gradually accumulate in the environment due to their extensive use and absolute solubility. The effects of 1-alkyl-3-methylimidazolium nitrate ([C n mim]NO 3 , n = 4, 6, 8) on soil pH, conductivity, cation exchange capacity, microbial biomass carbon, and microbial biomass nitrogen were examined at the doses of 1, 10, and 100 mg/kg on days 10, 20, 30, and 40. The results demonstrated that the soil pH decreased and the conductivity increased with increasing IL doses. No significant differences were observed in the soil cation-exchange capacity. All three of the tested ILs decreased the soil microbial biomass carbon and nitrogen. Additionally, there were few differences among the ILs with different alkyl chain lengths on the tested indicators except for the microbial biomass nitrogen. The present study addressed a gap in the literature regarding the effects of the aforementioned ILs with different alkyl side chains on the physicochemical properties of soil, and the results could provide the basic data for future studies on their toxicity to soil organisms, such as earthworms and soil microbes.

Stereoconvergent Amine-Directed Alkyl–Alkyl Suzuki Reactions of Unactivated Secondary Alkyl Chlorides

PubMed Central

Lu, Zhe; Wilsily, Ashraf; Fu, Gregory C.

2011-01-01

A new family of stereoconvergent cross-couplings of unactivated secondary alkyl electrophiles has been developed, specifically, arylamine-directed alkyl–alkyl Suzuki reactions. This represents the first such investigation to be focused on the use of alkyl chlorides as substrates. Structure-enantioselectivity studies are consistent with the nitrogen, not the aromatic ring, serving as the primary site of coordination of the arylamine to the catalyst. The rate law for this asymmetric cross-coupling is compatible with transmetalation being the turnover-limiting step of the catalytic cycle. PMID:21553917

Synthesis and antiviral activity of certain second generation methylenecyclopropane nucleosides

PubMed Central

Williams, John D.; Khan, Atiyya R.; Harden, Emma A.; Hartline, Caroll B.; Jefferson, Geraldine M.; Keith, Kathy A.; Prichard, Mark N.; Zemlicka, Jiri; Peet, Norton P.; Bowlin, Terry L.

2012-01-01

A second-generation series of substituted methylenecyclopropane nucleosides (MCPNs) has been synthesized and evaluated for antiviral activity against a panel of human herpesviruses, and for cytotoxicity. Although alkylated 2,6-diaminopurine analogs showed little antiviral activity, the compounds containing ether and thioether substituents at the 6-position of the purine did demonstrate potent and selective antiviral activity against several different human herpesviruses. In the 6-alkoxy series, antiviral activity depended on the length of the ether carbon chain, with the optimum chain length being about four carbon units long. For the corresponding thioethers, compounds containing secondary thioethers were more potent than those with primary thioethers. PMID:22607883

Scope and mechanism in palladium-catalyzed isomerizations of highly substituted allylic, homoallylic, and alkenyl alcohols.

PubMed

Larionov, Evgeny; Lin, Luqing; Guénée, Laure; Mazet, Clément

2014-12-03

Herein we report the palladium-catalyzed isomerization of highly substituted allylic alcohols and alkenyl alcohols by means of a single catalytic system. The operationally simple reaction protocol is applicable to a broad range of substrates and displays a wide functional group tolerance, and the products are usually isolated in high chemical yield. Experimental and computational mechanistic investigations provide complementary and converging evidence for a chain-walking process consisting of repeated migratory insertion/β-H elimination sequences. Interestingly, the catalyst does not dissociate from the substrate in the isomerization of allylic alcohols, whereas it disengages during the isomerization of alkenyl alcohols when additional substituents are present on the alkyl chain.

Polymerization of ethylene through reversible addition-fragmentation chain transfer (RAFT).

PubMed

Dommanget, Cédric; D'Agosto, Franck; Monteil, Vincent

2014-06-23

The present paper reports the first example of a controlled radical polymerization of ethylene using reversible addition-fragmentation chain transfer (RAFT) in the presence of xanthates (Alkyl-OC(=S)S-R) as controlling agents under relative mild conditions (70 °C, <200 bars). The specific reactivity of the produced alkyl-type propagating radicals induces a side fragmentation reaction of the stabilizing O-alkyl Z group of the controlling agents. This fragmentation, rarely observed in RAFT, was proven by NMR analyses. In addition, semicrystalline copolymers of ethylene and vinyl acetate were also prepared with a similar level of control. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Tuning the probe location on zwitterionic micellar system with variation of pH and addition of surfactants with different alkyl chains: solvent and rotational relaxation studies.

PubMed

Banerjee, Chiranjib; Mandal, Sarthak; Ghosh, Surajit; Rao, Vishal Govind; Sarkar, Nilmoni

2012-09-13

In this manuscript, we have modulated the location of an anionic probe, Coumarin-343 (C-343) in a zwitterionic (N-hexadecyl-N,N-dimethylammonio-1-propanesulfonate (SB-16)) micellar system by three different approaches. The effect of addition of the surfactant sodium dodecyl sulfate (SDS) and the room temperature ionic liquid (RTIL), 1-ethyl-3-methylimidazolium octylsulfate (EmimOs) and N,N-dimethylethanol hexanoate (DAH), to the micellar solution has been studied. The effect of pH variation has been studied as well using solvent and rotational measurements. Migration of the anionic probe, C-343, from the palisade layer of SB-16 micelle to the bulk water has been observed to varying extents with the addition of SDS and EmimOs. The effect is much more pronounced in the presence of SDS and can be ascribed to the presence of the long alkyl (dodecyl) chain on SDS which can easily orient itself and fuse inside the SB-16 micelle and facilitate the observed migration of the probe molecule. This phenomenon is confirmed by faster solvation and rotational relaxation of the investigated probe molecule. The analogous fusion process is difficult in case of EmimOs and DAH because of their comparatively smaller alkyl (octyl and hexanoate) chain. However, the direction of C-343 migration is reversed with the decrease of pH of the SB-16 micellar medium. An increase in the average solvation and rotational relaxation time of the probe in acidic medium has been observed. Since experimental conditions are maintained such that the probe molecules and the zwitterionic SB-16 micelles remain oppositely charged, the observed results can be attributed to the increased electrostatic interaction (attractive) between them. Temperature dependent study also supports this finding.

Product ion tandem mass spectrometric differentiation of regioisomeric side-chain groups in cathinone derivatives.

PubMed

Abiedalla, Younis; DeRuiter, Jack; Clark, C Randall

2016-07-30

Precursor materials are available to prepare aminoketone drugs containing regioisomeric propyl and isopropyl side-chain groups related to the drug alpha-pyrrovalerone (Flakka) and MDPV (3,4-methylenedioxypyrrovalerone). These compounds yield equivalent regioisomeric iminium cation base peaks in electron ionization mass spectrometry (EI-MS). The propyl and isopropyl side-chain groups related to alpha-pyrrovalerone and MDPV were prepared and evaluated in EI-MS and tandem mass spectrometry (MS/MS) product ion experiments. Deuterium labeling in both the pyrrolidine and alkyl side-chain groups allowed for the confirmation of the structures for the major product ions formed from the regioisomeric EI-MS iminium cation base peaks. These iminium cation base peaks show characteristic product ion spectra which allow differentiation of the side-chain propyl and isopropyl groups in the structure. The n-propyl side chain containing iminium cation base peak (m/z 126) in the EI-MS spectrum yields a major product ion at m/z 84 while the regioisomeric m/z 126 base peak for the isopropyl side chain yields a characteristic product ion at m/z 70. Deuterium labeling in both the pyrrolidine ring and the alkyl side chain confirmed the process for the formation of these major product ions. Product ion fragmentation provides useful data for differentiation of n-propyl and isopropyl side-chain iminium cations from cathinone derivative drugs of abuse. Regioisomeric n-propyl and isopropyl iminium cations of equal mass yield characteristic product ions identifying the alkyl side-chain regioisomers in the pyrrolidine cathinone derivatives. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

Singlet Fission and Excimer Formation in Disordered Solids of Alkyl-Substituted 1,3-Diphenylisobenzofurans.

PubMed

Dron, Paul I; Michl, Josef; Johnson, Justin C

2017-11-16

We describe the preparation and excited state dynamics of three alkyl derivatives of 1,3-diphenylisobenzofuran (1) in both solutions and thin films. The substitutions are intended to disrupt the slip-stacked packing observed in crystals of 1 while maintaining the favorable energies of singlet and triplet for singlet fission (SF). All substitutions result in films that are largely amorphous as judged by the absence of strong X-ray diffraction peaks. The films of 1 carrying a methyl in the para position of one phenyl ring undergo SF relatively efficiently (≥75% triplet yield, Φ T ) but more slowly than thin films of 1. When the methyl is replaced with a t-butyl, kinetic competition in the excited state favors excimer formation rather than SF (Φ T = 55%). When t-Bu groups are placed in both meta positions of the phenyl substituent, SF is slowed further and Φ T = 35%.

Alkylation of enolates: An electrophilicity perspective

NASA Astrophysics Data System (ADS)

Elango, M.; Parthasarathi, R.; Subramanian, V.; Chattaraj, P. K.

Enolates are ambient nucleophiles, and alkylation can occur either at a carbon or at an oxygen site. It is known that the ratio of C/O alkylation depends significantly on various factors, including the type of enolate, alkylating agent, site of alkylation, and solvent environment. Analysis of regioselectivity and solvent effects on alkylation of lithium enolates is investigated using various reactivity descriptors, including generalized philicity. These results point out the reliability of both global and local reactivity descriptors in providing significant information about site selectivity and chemical reactivity of lithium enolates.

Do the substituent effects affect conformational freedom of squalene in hopene biosynthesis?

PubMed

Nowosielski, Marcin; Hoffmann, Marcin

2011-09-01

The analysis of biochemical processes is one of the main challenges for modern computational chemistry. Probably the biggest issue facing scientists in this case is the number of factors that have to be taken into account, as even those factors that do not seem to be meaningful may eventually be crucial. Such a belief led to the investigation on the substituent effects during squalene cyclization process. We focused on the formation of lanosterol ring A through squalene epoxide and an analogue process observed in bacteria, leading to the hopene formation without an intermediate oxide. Interestingly, our results indicate that, opposite of chemical intuition, a more substituted chain is more likely to adopt a conformation suitable for the cyclization process. Presumably the rational for this behavior is the presence of intermolecular CH ... π interactions between the hydrogen atoms from methyl groups and the squalene π bonds in the open-chain structure. The effect seems to have a firm impact on the hopene formation process. Calculations were performed using two different methods: MP2 and M06-2X, combined with the cc-pVDZ basis set.

Thioimidazolium Ionic Liquids as Tunable Alkylating Agents.

PubMed

Guterman, Ryan; Miao, Han; Antonietti, Markus

2018-01-19

Alkylating ionic liquids based on the thioimidazolium structure combine the conventional properties of ionic liquids, including low melting point and nonvolatility, with the alkylating function. Alkyl transfer occurs exclusively from the S-alkyl position, thus allowing for easy derivatization of the structure without compromising specificity. We apply this feature to tune the electrophilicty of the cation to profoundly affect the reactivity of these alkylating ionic liquids, with a caffeine-derived compound possessing the highest reactivity. Anion choice was found to affect reaction rates, with iodide anions assisting in the alkylation reaction through a "shuttling" process. The ability to tune the properties of the alkylating agent using the toolbox of ionic liquid chemistry highlights the modular nature of these compounds as a platform for alkylating agent design and integration in to future systems.

Anti-Caries Effects of Dental Adhesives Containing Quaternary Ammonium Methacrylates with Different Chain Lengths

PubMed Central

Han, Qi; Li, Bolei; Zhou, Xuedong; Ge, Yang; Wang, Suping; Li, Mingyun; Ren, Biao; Wang, Haohao; Zhang, Keke; Xu, Hockin H. K.; Peng, Xian; Feng, Mingye; Weir, Michael D.; Chen, Yu; Cheng, Lei

2017-01-01

The objectives of this study were to investigate the effects of dental adhesives containing quaternary ammonium methacrylates (QAMs) with different alkyl chain lengths (CL) on ecological caries prevention in vitro. Five QAMs were synthesized with a CL = 3, 6, 9, 12, and 16 and incorporated into adhesives. Micro-tensile bond strength and surface charge density were used to measure the physical properties of the adhesives. The proportion change in three-species biofilms consisting of Streptococcus mutans, Streptococcus sanguinis, and Streptococcus gordonii was tested using the TaqMan real-time polymerase chain reaction. Lactic acid assay, MTT [3-(4,5-dimethyl-thiazol-2-yl)-2,5-diphenyltetrazolium bromide] assay, exopolysaccharide staining, live/dead staining, scanning electron microscopy (SEM), and transverse microradiography (TMR) were performed to study the anti-biofilm and anti-demineralization effects of the dental adhesives. The results showed that incorporating QAMs with different alkyl chain lengths into the adhesives had no obvious effect on the dentin bond strength. The adhesives containing QAMs with a longer alkyl chain developed healthier biofilms. The surface charge density, anti-biofilm, and anti-demineralization effects of the adhesives increased with a CL of the QAMs from 3 to 12, but decreased slightly with a CL from 12 to 16. In conclusion, adhesives containing QAMs with a tailored chain length are promising for preventing secondary caries in an “ecological way”. PMID:28773004

Comparative study of the antioxidant activities of some lipase-catalyzed alkyl dihydrocaffeates synthesized in ionic liquid.

PubMed

Gholivand, Somayeh; Lasekan, Ola; Tan, Chin Ping; Abas, Faridah; Wei, Leong Sze

2017-06-01

The solubility limitations of phenolic acids in many lipidic environments are now greatly improved by their enzymatic esterification in ionic liquids (ILs). Herein, four different ILs were tested for the esterification of dihydrocaffeic acid with hexanol and the best IL was selected for the synthesis of four other n-alkyl esters with different chain-lengths. The effect of alkyl chain length on the anti-oxidative properties of the resulted purified esters was investigated using β-carotene bleaching (BCB) and free radical scavenging method DPPH and compared with butylated hydroxytoluene (BHT) as reference compound. All four esters (methyl, hexyl, dodecyl and octadecyl dihydrocaffeates) exhibited relatively strong radical scavenging abilities. The scavenging activity of the test compounds was in the following order: methyl ester>hexyl ester⩾dodecyl ester>octadecyl ester>BHT while the order for the BCB anti-oxidative activity was; BHT>octadecyl ester>dodecyl ester>hexyl ester>methyl ester. Copyright © 2016 Elsevier Ltd. All rights reserved.

Self-assembly properties of semiconducting donor-acceptor-donor bithienyl derivatives of tetrazine and thiadiazole-effect of the electron accepting central ring.

PubMed

Zapala, Joanna; Knor, Marek; Jaroch, Tomasz; Maranda-Niedbala, Agnieszka; Kurach, Ewa; Kotwica, Kamil; Nowakowski, Robert; Djurado, David; Pecaut, Jacques; Zagorska, Malgorzata; Pron, Adam

2013-11-26

Scanning tunneling microscopy was used to study the effect of the electron-accepting unit and the alkyl substituent's position on the type and extent of 2D supramolecular organization of penta-ring donor-acceptor-donor (DAD) semiconductors, consisting of either tetrazine or thiadiazole central acceptor ring symmetrically attached to two bithienyl groups. Microscopic observations of monomolecular layers on HOPG of four alkyl derivatives of the studied adsorbates indicate significant differences in their 2D organizations. Ordered monolayers of thiadiazole derivatives are relatively loose and, independent of the position of alkyl substituents, characterized by large intermolecular separation of acceptor units in the adjacent molecules located in the face-to-face configuration. The 2D supramolecular architecture in both derivatives of thiadiazole is very sensitive to the alkyl substituent's position. Significantly different behavior is observed for derivatives of tetrazine (which is a stronger electron acceptor). Stronger intermolecular DA interactions in these adsorbates generate an intermolecular shift in the monolayer, which is a dominant factor determining the 2D structural organization. As a consequence of this molecular arrangement, tetrazine groups (A segments) face thiophene rings (D segments) of the neighboring molecules. Monolayers of tetrazine derivatives are therefore much more densely packed and characterized by similar π-stacking of molecules independently of the position of alkyl substituents. Moreover, a comparative study of 3D supramolecular organization, deduced from the X-ray diffraction patterns, is also presented clearly confirming the polymorphism of the studied adsorbates.

Electronic structure of some adenosine receptor antagonists. III. Quantitative investigation of the electronic absorption spectra of alkyl xanthines

NASA Astrophysics Data System (ADS)

Moustafa, H.; Shalaby, Samia H.; El-sawy, K. M.; Hilal, Rifaat

2002-07-01

Quantitative and comparative investigation of the electronic absorption spectra of theophylline, caffeine and their derivatives is reported. The spectra of theophylline, caffeine and theobromine were compared to establish the predominant tautomeric species in solution. This comparison, analysis of solvent effects and assignments of the observed transitions via MO computations indicate the exits of only one tautomeric species in solution that is the N7 form. A low-lying triplet state was identified which corresponds to a HOMO-LUMO transition. This relatively long-lived T 1 state is always less polar than the ground state and may very well underlie the photochemical reactivity of alkyl xanthines. Substituents of different electron donating or withdrawing strengths and solvent effects are investigated and analyzed. The present analysis is facilitated via computer deconvolution of the observed spectra and MO computation.

Mechanism for stabilization of the molten globule state of papain by sodium n-alkyl sulfates: spectroscopic and calorimetric approaches.

PubMed

Chamani, J; Heshmati, M

2008-06-01

Papain exists in a molten globule (MG) state at pH 2 and in this state protein tends to aggregate in the presence of lower concentrations of guanidine hydrochloride (GuHCl). Such aggregation is prevented if low concentrations of sodium n-alkyl sulfates are also present in the buffer; in addition, stabilization of the protein is also induced. The guanidine hydrochloride and temperature-induced unfolding of papain, in the presence of n-alkyl sulfates, indicate stabilization of the protein as seen from the higher transition midpoints when monitored by fluorescence, circular dichroism, and differential scanning calorimetry. However, a similar phenomenon is not seen under neutral conditions in the presence of n-alkyl sulfate concentrations. The effect of n-alkyl sulfates on the structure of the MG state of papain was utilized to investigate the contribution of hydrophobic interaction to the stability of the MG state. The Td values of the MG states of papain in the presence of n-alkyl sulfates at different concentrations showed substantial variation. The enhancement of Td values at the stability criterion of MG states corresponded with increasing chain length of the cited n-alkyl sulfates. The present results suggest that the hydrophobic interactions play important roles in stabilizing and preventing the aggregation of the MG state of papain.

Transition-Metal-Catalyzed C-H Alkylation Using Alkenes.

PubMed

Dong, Zhe; Ren, Zhi; Thompson, Samuel J; Xu, Yan; Dong, Guangbin

2017-07-12

Alkylation reactions represent an important organic transformation to form C-C bonds. In addition to conventional approaches with alkyl halides or sulfonates as alkylating agents, the use of unactivated olefins for alkylations has become attractive from both cost and sustainability viewpoints. This Review summarizes transition-metal-catalyzed alkylations of various carbon-hydrogen bonds (addition of C-H bonds across olefins) using regular olefins or 1,3-dienes up to May 2016. According to the mode of activation, the Review is divided into two sections: alkylation via C-H activation and alkylation via olefin activation.

Photoinduced, copper-catalyzed alkylation of amides with unactivated secondary alkyl halides at room temperature.

PubMed

Do, Hien-Quang; Bachman, Shoshana; Bissember, Alex C; Peters, Jonas C; Fu, Gregory C

2014-02-05

The development of a mild and general method for the alkylation of amides with relatively unreactive alkyl halides (i.e., poor substrates for SN2 reactions) is an ongoing challenge in organic synthesis. We describe herein a versatile transition-metal-catalyzed approach: in particular, a photoinduced, copper-catalyzed monoalkylation of primary amides. A broad array of alkyl and aryl amides (as well as a lactam and a 2-oxazolidinone) couple with unactivated secondary (and hindered primary) alkyl bromides and iodides using a single set of comparatively simple and mild conditions: inexpensive CuI as the catalyst, no separate added ligand, and C-N bond formation at room temperature. The method is compatible with a variety of functional groups, such as an olefin, a carbamate, a thiophene, and a pyridine, and it has been applied to the synthesis of an opioid receptor antagonist. A range of mechanistic observations, including reactivity and stereochemical studies, are consistent with a coupling pathway that includes photoexcitation of a copper-amidate complex, followed by electron transfer to form an alkyl radical.

Polyimides with pendant alkyl groups

NASA Technical Reports Server (NTRS)

Jensen, B. J.; Young, P. R.

1982-01-01

The effect on selected polyimide properties when pendant alkyl groups were attached to the polymer backbone was investigated. A series of polymers were prepared using benzophenone tetracarboxylic acid dianhydride (BTDA) and seven different p-alkyl-m,p'-diaminobenzophenone monomers. The alkyl groups varied in length from C(1) (methyl) to C(9) (nonyl). The polyimide prepared from BTDA and m,p'-diaminobenzophenone was included as a control. All polymers were characterized by various chromatographic, spectroscopic, thermal, and mechanical techniques. Increasing the length of the pendant alkyl group resulted in a systematic decrease in glass transition temperature (Tg) for vacuum cured films. A 70 C decrease in Tg to 193 C was observed for the nonyl polymer compared to the Tg for the control. A corresponding systematic increase in Tg indicative of crosslinking, was observed for air cured films. Thermogravimetric analysis revealed a slight sacrifice in thermal stability with increasing alkyl length. No improvement in film toughness was observed.

Carbon dioxide-in-oil emulsions stabilized with silicone-alkyl surfactants for waterless hydraulic fracturing.

PubMed

Alzobaidi, Shehab; Lee, Jason; Jiries, Summer; Da, Chang; Harris, Justin; Keene, Kaitlin; Rodriguez, Gianfranco; Beckman, Eric; Perry, Robert; Johnston, Keith P; Enick, Robert

2018-09-15

The design of surfactants for CO 2 /oil emulsions has been elusive given the low CO 2 -oil interfacial tension, and consequently, low driving force for surfactant adsorption. Our hypothesis is that waterless, high pressure CO 2 /oil emulsions can be stabilized by hydrophobic comb polymer surfactants that adsorb at the interface and sterically stabilize the CO 2 droplets. The emulsions were formed by mixing with an impeller or by co-injecting CO 2 and oil through a beadpack (CO 2 volume fractions (ϕ) of 0.50-0.90). Emulsions were generated with comb polymer surfactants with a polydimethylsiloxane (PDMS) backbone and pendant linear alkyl chains. The C 30 alkyl chains are CO 2 -insoluble but oil soluble (oleophilic), whereas PDMS with more than 50 repeat units is CO 2 -philic but only partially oleophilic. The adsorbed surfactants sterically stabilized CO 2 droplets against Ostwald ripening and coalescence. The optimum surfactant adsorption was obtained with a PDMS degree of polymerization of ∼88 and seven C 30 side chains. The emulsion apparent viscosity reached 18 cP at a ϕ of 0.70, several orders of magnitude higher than the viscosity of pure CO 2 , with CO 2 droplets in the 10-150 µm range. These environmentally benign waterless emulsions are of interest for hydraulic fracturing, especially in water-sensitive formations. Copyright © 2018 Elsevier Inc. All rights reserved.

Computational analysis of molecular properties and spectral characteristics of cyano-containing liquid crystals: role of alkyl chains.

PubMed

Praveen, P Lakshmi; Ojha, Durga P

2011-05-01

The electronic transitions in the uv-visible range of 4'-n-alkyl-4-cyanobiphenyl (nCB) with propyl, pentyl, and heptyl groups, which are of commercial and application interests, have been studied. The uv-visible and circular dichroism spectra of nCB (n = 3,5,7) molecules have been simulated using the time dependent density functional theory Becke3-Lee-Yang-Parr hybrid functional-6-31 + G (d) method. Mulliken atomic charges for each molecule have been compared with Loewdin atomic charges to analyze the molecular charge distribution and phase stability. The highest occupied molecular orbital and lowest unoccupied molecular orbital energies corresponding to the electronic transitions in the uv-visible range have been reported. Excited states have been calculated via the configuration interaction single level with a semiempirical Hamiltonian (intermediate neglect of differential overlap method, as parametrized by Zerner and co-workers). Further, two types of calculations have been performed for model systems containing single and double molecules of nCB. Furthermore, the dimer complexes during the different modes of molecular interactions have also been studied. The interaction energies of dimer complexes have been taken into consideration in order to investigate the most energetically stable configuration. These studies are helpful for understanding the role and flexibility of end chains, in particular, phase behavior and stability.

Influence of the anion nature and alkyl substituents in the behavior of ionic liquids derived from phenylpyridines

NASA Astrophysics Data System (ADS)

Dreyse, Paulina; Alarcón, Antonia; Galdámez, Antonio; González, Iván; Cortés-Arriagada, Diego; Castillo, Francisco; Mella, Andy

2018-02-01

Quaternary alkyl 2-phenylpyridinium and 2-(2,4-difluorophenyl)pyridinium amines with iodide, hexafluorophosphate and bis(trifluoromethylsulfonyl)imide anions have been fully characterized by 1H NMR, FT-IR and MALDI mass spectroscopic methods and studied by quantum chemistry calculations. The compounds with bis(trifluoromethylsulfonyl)imide anion can be classified as ionic liquids, because they melt at room temperature. The quaternary amines with iodide and hexafluorophosphate anions are solid at 25 °C. The X-ray diffraction characterization of the 2-(2,4-difluorophenyl)-1-methylphenylpyridinium hexafluorophosphate and 1-ethyl-2-(2,4-difluorophenyl)phenylpyridinium hexafluorophosphate show an extensive series of Csbnd H⋯F, Csbnd F⋯π and Psbnd F⋯π intermolecular interactions, which give rise to a supramolecular network. The relationship between the solid-state structures and the melting points is discussed by the evaluation of the thermal behavior based on experimental data from Differential Scanning Calorimetry (DSC) studies, and also using the analysis of the ion pairs binding energies. These new compounds based on phenylpyridine allow us to grow the diversity of ionic liquids and their crystalline salts, increasing the knowledge about the chemical and physical properties of these ionic species.

Alkyl(C16, C18, C22)trimethylammonium-Based Herbicidal Ionic Liquids.

PubMed

Pernak, Juliusz; Giszter, Rafał; Biedziak, Agnieszka; Niemczak, Michał; Olszewski, Radosław; Marcinkowska, Katarzyna; Praczyk, Tadeusz

2017-01-18

In the framework of this study a synthesis methodology and characterization of long alkyl herbicidal ionic liquids (HILs) based on four commonly used herbicides (2,4-D, MCPA, MCPP, and dicamba) are presented. New HILs were obtained with high efficiency (>95%) using an acid-base reaction between herbicidal acids and hexadecyltrimethylammonium, octadecyltrimethylammonium, and behenyltrimethylammonium hydroxides in alcoholic medium. Among all synthesized salts, only three compounds comprising the MCPP anion were liquids at room temperature. Subsequently, the influence of both the alkyl chain length and the anion structure on their physicochemical properties (thermal decomposition profiles, solubility in 10 representative solvents, surface activity, density, viscosity, and refractive index) was determined. All HILs exhibited high thermal stability as well as surface activity; however, their solubility notably depended on both the length of the carbon chain and the structure of the anion. The herbicidal efficacy of the obtained salts was tested in greenhouse and field experiments. Greenhouse testing performed on common lambsquarters (Chenopodium album L.) and flixweed (Descurainia sophia L.) as test plants indicated that HILs were characterized by similar or higher efficacy compared to commercial herbicides. The results of field trials confirmed the high activity of HILs, particularly those containing phenoxyacids as anions (MCPA, 2,4-D, and MCPP).

Diamine-Functionalization of a Metal-Organic Framework Adsorbent for Superb Carbon Dioxide Adsorption and Desorption Properties.

PubMed

Lee, Woo Ram; Kim, Jeong Eun; Lee, Sung Jin; Kang, Minjung; Kang, Dong Won; Lee, Hwa Young; Hiremath, Vishwanath; Seo, Jeong Gil; Jin, Hailian; Moon, Dohyun; Cho, Moses; Jung, Yousung; Hong, Chang Seop

2018-05-25

For real-world postcombustion applications in the mitigation of CO 2 emissions using dry sorbents, adsorption and desorption behaviors should be controlled to design and fabricate prospective materials with optimal CO 2 performances. Herein, we prepared diamine-functionalized Mg 2 (dobpdc) (H 4 dobpdc=4,4'-dihydroxy-(1,1'-biphenyl)-3,3'-dicarboxylic acid). (1-diamine) with ethylenediamine (en), primary-secondary (N-ethylethylenediamine-een and N-isopropylethylenediamine-ipen), primary-tertiary, and secondary-secondary diamines. A slight alteration of the number of alkyl substituents on the diamines and their alkyl chain length dictates the desorption temperature (T des ) at 100 % CO 2 , desorption characteristics, and ΔT systematically to result in the tuning of the working capacity. The existence of bulky substituents on the diamines improves the framework stability upon exposure to O 2 , SO 2 , and water vapor, relevant to real flue-gas conditions. Bulky substituents are also responsible for an interesting two-step behavior observed for the ipen case, as revealed by DFT calculations. Among the diamine-appended metal-organic frameworks, 1-een, which has the required adsorption and desorption properties, is a promising material for sorbent-based CO 2 capture processes. Hence, CO 2 performance and framework durability can be tailored by the judicial selection of the diamine structure, which enables property design at will and facilitates the development of desirable CO 2 -capture materials. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Is there substituent cross-interaction effect in all the conjugated systems containing Cdbnd N polar bond? The substituent effects on the NMR chemical shifts of 2,5-disubstituted pyrimidines

NASA Astrophysics Data System (ADS)

Yuan, Hua; Zhang, Yan; Chen, Chun-Ni; Li, Meng-Yang

2018-03-01

The substituent cross-interaction effect in the substituted benzylidene anilines (p-Xsbnd C6H4sbnd CHdbnd Nsbnd C6H4sbnd Y-p) has been observed and widely investigated. In order to investigate whether the substituent cross-interaction effect exist in all the conjugated systems containing Cdbnd N polar bond, this paper employed 2-X-5-Y pyrimidines as the model compounds for study. The influences of substituents X and Y on the 1H NMR and 13C NMR chemical shifts of 2, 5-disubsitituted pyrimidines have been systematically investigated. Quantitative structure-chemical shifts relationship models have been built for δ(H4,6), δ(C2), δ(C4,6) and δ(C5) with four to six molecular descriptors. These models were confirmed of good stability and predictive performances by leave-one-out cross validation. This study indicates that the substituent effects of 2,5-disubstituted pyrimidines are much more complex than that of the substituted benzylidene anilines. More structural factors besides of Hammett parameter should be taken into consideration. Different from the substituted benzylidene anilines, the cross-interaction effect (Δσ2) of substituents X and Y has little contribution to δ(H4,6), δ(C2), δ(C5) and δ(C4,6) of 2,5-disubstituted pyrimidines.

Asymmetric homologation of boronic esters bearing azido and silyloxy substituents.

PubMed

Singh, R P; Matteson, D S

2000-10-06

In the asymmetric homologation of boronic esters with a (dihalomethyl)lithium, substituents that can bind metal cations tend to interfere. Accordingly, we undertook the introduction of weakly basic oxygen and nitrogen substituents into boronic esters in order to maximize the efficiency of multistep syntheses utilizing this chemistry. Silyloxy boronic esters cannot be made efficiently by direct substitution, but a (hydroxymethyl)boronic ester has been silylated in the usual manner. Conversion of alpha-halo boronic esters to alpha-azido boronic esters has been carried out with sodium azide and a tetrabutylammonium salt as phase-transfer catalyst in a two-phase system with water and either nitromethane or ethyl acetate. These are safer solvents than the previously used dichloromethane, which can form an explosive byproduct with azide ion. Boronic esters containing silyloxy or alkoxy and azido substituents have been shown to react efficiently with (dihalomethyl)lithiums, resulting in efficient asymmetric insertion of the halomethyl group into the carbon-boron bond.

Molecular design of sequence specific DNA alkylating agents.

PubMed

Minoshima, Masafumi; Bando, Toshikazu; Shinohara, Ken-ichi; Sugiyama, Hiroshi

2009-01-01

Sequence-specific DNA alkylating agents have great interest for novel approach to cancer chemotherapy. We designed the conjugates between pyrrole (Py)-imidazole (Im) polyamides and DNA alkylating chlorambucil moiety possessing at different positions. The sequence-specific DNA alkylation by conjugates was investigated by using high-resolution denaturing polyacrylamide gel electrophoresis (PAGE). The results showed that polyamide chlorambucil conjugates alkylate DNA at flanking adenines in recognition sequences of Py-Im polyamides, however, the reactivities and alkylation sites were influenced by the positions of conjugation. In addition, we synthesized conjugate between Py-Im polyamide and another alkylating agent, 1-(chloromethyl)-5-hydroxy-1,2-dihydro-3H-benz[e]indole (seco-CBI). DNA alkylation reactivies by both alkylating polyamides were almost comparable. In contrast, cytotoxicities against cell lines differed greatly. These comparative studies would promote development of appropriate sequence-specific DNA alkylating polyamides against specific cancer cells.

Ab initio study of chain branching reactions involving second generation products in hydrocarbon combustion mechanisms.

PubMed

Davis, Alexander C; Francisco, Joseph S

2012-01-28

sec-Alkyl radicals are key reactive intermediates in the hydrocarbon combustion and atmospheric decomposition mechanisms that are formed by the abstraction of hydrogen from an alkane, or as a second generation product of n-alkyl H-migrations, C-C bond scissions in branched alkyl radicals, or the bimolecular reaction between olefins and n-alkyl radicals. Since alkanes and branched alkanes, which the sec-alkyl radicals are derived from, make up roughly 40-50% of traditional fuels an understanding of their chemistry is essential to improving combustion systems. The present work investigates all H-migration reactions initiated from an sec-alkyl radical that involve the movement of a secondary hydrogen, for the 2-butyl through 4-octyl radicals, using the CBS-Q, G2, and G4 composite methods. The resulting thermodynamic and kinetic parameters are compared to similar reactions in n-alkyl radicals in order to determine underlying trends. Particular attention is paid to the effect of cis/trans and 1,3-diaxial interactions on activation energies and rate coefficients. When combined with our previous work on n-alkyl radical H-migrations, a complete picture of H-migrations in unbranched alkyl radicals is obtained. This full data set suggests that the directionality of the remaining branched chains has a minimal effect on the rate coefficients for all but the largest viable transition states, which is in stark contrast to the differences predicted by the structurally similar dimethylcycloalkanes. In fact the initial location of the secondary radical site has a greater effect on the rate than does the directionality of the remaining alkyl chains. The activation energies for secondary to secondary reactions are much closer to those of the secondary to primary H-migrations. However, the rate coefficients are found to be closer to the corresponding primary to primary reaction values. A significant ramification of these results is that there will be multiple viable reaction pathways

The cmc-value of a bolalipid with two phosphocholine headgroups and a C24 alkyl chain: Unusual binding properties of fluorescence probes to bolalipid aggregates.

PubMed

Kordts, Martin; Kerth, Andreas; Drescher, Simon; Ott, Maria; Blume, Alfred

2017-09-01

Bolalipids with a long alkyl chain and two phosphocholine polar groups self-assemble in water into two different types of aggregate structures, namely helical nanofibers at low temperature and two types of micellar aggregates at higher temperature. We tried to determine the critical aggregation concentration (cac) or critical micellar concentration (cmc) of the bolalipid tetracosane-1,24-bis(phosphocholine) (PC-C24-PC) by using different fluorescent probes. The use of pyrene or pyrene derivatives as fluorophores failed, whereas the probes 1,8-ANS and particularly bis-ANS gave consistent results. The structure of the bolalipid aggregates obviously hinders partitioning or binding of pyrene derivatives into the micellar interior, whereas 1,8-ANS and bis-ANS can bind to the surface of the aggregate structures. The observed large increase in fluorescence intensity of bis-ANS indicates that binding to the hydrophobic surface of the aggregates leads to a reduction of the dye mobility. However, binding of bis-ANS is relatively weak, so that the determination of a cac/cmc-value is difficult. Simulations of the intensity curves for PC-C24-PC lead to estimates of the cac/cmc-value of 0.3-1.0×10 -6 M, depending on the structure of the aggregates. Single molecule fluorescence correlation spectroscopy was used to determine the mobility of bis-ANS as a function of concentration of PC-C24-PC. The dye diffusion time and the molecular brightness are lower at low bolalipid concentration, when only free dye is present, and increase at higher concentration when bis-ANS is bound to the aggregates. The experimental cac/cmc-values are higher than those estimated, using an incremental method for the change in Gibbs free energy for micellization with n-alkyl-phosphocholines with only one polar group as a comparison. Apparently, for PC-C24-PC in micellar or fibrous aggregates, more CH 2 groups are exposed to water than in a conventional micelle of an n-alkyl-phosphocholine. Copyright �

Enzymic aromatization of 6-alkyl-substituted androgens, potent competitive and mechanism-based inhibitors of aromatase.

PubMed Central

Numazawa, M; Yoshimura, A; Oshibe, M

1998-01-01

To gain insight into the relationships between the aromatase inhibitory activity of 6-alkyl-substituted androgens, potent competitive inhibitors, and their ability to serve as a substrate of aromatase, we studied the aromatization of a series of 6alpha- and 6beta-alkyl (methyl, ethyl, n-propyl, n-pentyl and n-heptyl)-substituted androst-4-ene-3,17-diones (ADs) and their androsta-1,4-diene-3,17-dione (ADD) derivatives with human placental aromatase, by gas chromatography-mass spectrometry. Among the inhibitors examined, ADD and its 6alpha-alkyl derivatives with alkyl functions less than three carbons long, together with 6beta-methyl ADD, are suicide substrates of aromatase. All of the steroids, except for 6beta-n-pentyl ADD and its n-heptyl analogue as well as 6beta-n-heptyl AD, were found to be converted into the corresponding 6-alkyl oestrogens. The 6-methyl steroids were aromatized most efficiently in each series, and the aromatization rate essentially decreased in proportion to the length of the 6-alkyl chains in each series, where the 6alpha-alkyl androgens were more efficient substrates than the corresponding 6beta isomers. The Vmax of 6alpha-methyl ADD was approx. 2.5-fold that of the natural substrate AD and approx. 3-fold that of the parent ADD. On the basis of this, along with the facts that the rates of a mechanism-based inactivation of aromatase by ADD and its 6alpha-methyl derivative are similar, it is implied that alignment of 6alpha-methyl ADD in the active site could favour the pathway leading to oestrogen over the inactivation pathway, compared with that of ADD. The relative apparent Km values for the androgens obtained in this study are different from the relative Ki values obtained previously, indicating that there is a difference between the ability to serve as an inhibitor and the ability to serve as a substrate in the 6-alkyl androgen series. PMID:9405288

40 CFR 721.9892 - Alkylated urea.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Alkylated urea. 721.9892 Section 721... Alkylated urea. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as an alkylated urea (PMN P-93-1649) is subject to reporting under this...

Isomer effects on polyimide properties

NASA Technical Reports Server (NTRS)

Stump, B. L.

1975-01-01

The effect of structure variation on the solubility and glass-transition temperature of polyimide polymers is investigated. The addition of alkyl substituents to an aromatic ring in the polymer molecule, the reduction in the number of imide rings per average polymer chain-length, and a variation in the symmetry of the polymer molecule are studied. The synthesis of key intermediates for the preparation of the monomers required in this investigation is reported along with progress made in the synthesis of polyimide-precursor amines that contain functional groups to allow for post-cure cross-linking.

Synthesis and evaluation of 7-substituted 4-aminoquinoline analogues for antimalarial activity.

PubMed

Hwang, Jong Yeon; Kawasuji, Takashi; Lowes, David J; Clark, Julie A; Connelly, Michele C; Zhu, Fangyi; Guiguemde, W Armand; Sigal, Martina S; Wilson, Emily B; Derisi, Joseph L; Guy, R Kiplin

2011-10-27

We previously reported that substituted 4-aminoquinolines with a phenyl ether substituent at the 7-position of the quinoline ring and the capability of intramolecular hydrogen bonding between the protonated amine on the side chain and a hydrogen bond acceptor on the amine's alkyl substituents exhibited potent antimalarial activity against the multidrug resistant strain P. falciparum W2. We employed a parallel synthetic method to generate diaryl ether, biaryl, and alkylaryl 4-aminoquinoline analogues in the background of a limited number of side chain variations that had previously afforded potent 4-aminoquinolines. All subsets were evaluated for their antimalarial activity against the chloroquine-sensitive strain 3D7 and the chloroquine-resistant K1 strain as well as for cytotoxicity against mammalian cell lines. While all three arrays showed good antimalarial activity, only the biaryl-containing subset showed consistently good potency against the drug-resistant K1 strain and good selectivity with regard to mammalian cytotoxicity. Overall, our data indicate that the biaryl-containing series contains promising candidates for further study.

Thio-arylglycosides with Various Aglycon Para-Substituents, a Probe for Studying Chemical Glycosylation Reactions

PubMed Central

Li, Xiaoning; Huang, Lijun; Hu, Xiche; Huang, Xuefei

2009-01-01

Summary Three series of thioglycosyl donors differing only in their respective aglycon substituents within each series have been prepared as representatives of typical glycosyl donors. The relative anomeric reactivities of these donors were quantified under competitive glycosylation conditions with various reaction time, promoters, solvents and acceptors. Over three orders of magnitude reactivity difference were generated by simple transformation of the para-substituent on the aglycon with methanol as the acceptor, while chemoselectivities became lower with carbohydrate acceptors. Excellent linear correlations were attained between relative reactivity values of donors and σp values of the substituents in the Hammett plots. This indicates that the glycosylation mechanism remains the same over a wide range of reactivities and glycosylation conditions. The negative slopes of the Hammett plots suggested that electron donating substituents expedite the reactions and the magnitudes of slopes can be rationalized by neighboring group participation as well as electronic properties of the glycon protective groups. Within the same series of donors, less nucleophilic acceptors gave smaller slopes in their Hammett plots. This is consistent with the notion that acceptor nucleophilic attack onto the reactive intermediate is part of the rate limiting step of the glycosylation reaction. Excellent linear Hammett correlations were obtained between relative reactivity values of three series of donors differing only in their aglycon substituents and σp values of the substituents. PMID:19081954

Interaction and dynamics of (alkylamide + electrolyte) deep eutectics: Dependence on alkyl chain-length, temperature, and anion identity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Guchhait, Biswajit; Das, Suman; Daschakraborty, Snehasis

Here we investigate the solute-medium interaction and solute-centered dynamics in (RCONH{sub 2} + LiX) deep eutectics (DEs) via carrying out time-resolved fluorescence measurements and all-atom molecular dynamics simulations at various temperatures. Alkylamides (RCONH{sub 2}) considered are acetamide (CH{sub 3}CONH{sub 2}), propionamide (CH{sub 3}CH{sub 2}CONH{sub 2}), and butyramide (CH{sub 3}CH{sub 2}CH{sub 2}CONH{sub 2}); the electrolytes (LiX) are lithium perchlorate (LiClO{sub 4}), lithium bromide (LiBr), and lithium nitrate (LiNO{sub 3}). Differential scanning calorimetric measurements reveal glass transition temperatures (T{sub g}) of these DEs are ∼195 K and show a very weak dependence on alkyl chain-length and electrolyte identity. Time-resolved and steady statemore » fluorescence measurements with these DEs have been carried out at six-to-nine different temperatures that are ∼100–150 K above their individual T{sub g}s. Four different solute probes providing a good spread of fluorescence lifetimes have been employed in steady state measurements, revealing strong excitation wavelength dependence of probe fluorescence emission peak frequencies. Extent of this dependence, which shows sensitivity to anion identity, has been found to increase with increase of amide chain-length and decrease of probe lifetime. Time-resolved measurements reveal strong fractional power dependence of average rates for solute solvation and rotation with fraction power being relatively smaller (stronger viscosity decoupling) for DEs containing longer amide and larger (weaker decoupling) for DEs containing perchlorate anion. Representative all-atom molecular dynamics simulations of (CH{sub 3}CONH{sub 2} + LiX) DEs at different temperatures reveal strongly stretched exponential relaxation of wavevector dependent acetamide self dynamic structure factor with time constants dependent both on ion identity and temperature, providing justification for explaining the fluorescence

Catalyst-Directed Diastereoselective Isomerization of Allylic Alcohols for the Stereoselective Construction of C(20) in Steroid Side Chains: Scope and Topological Diversification.

PubMed

Li, Houhua; Mazet, Clément

2015-08-26

The stereoselective construction of C20 in steroidal derivatives by a highly diastereoselective Ir-catalyzed isomerization of primary allylic alcohols is reported. A key aspect of this strategy is a straightforward access to geometrically pure steroidal enol tosylate and enol triflate intermediates for subsequent high yielding stereoretentive Negishi cross-coupling reactions to allow structural diversity to be introduced. A range of allylic alcohols participates in the diastereoselective isomerization under the optimized reaction conditions. Electron-rich and electron-poor aryl or heteroaryl substituents are particularly well-tolerated, and the stereospecific nature of the reaction provides indifferently access to the natural C20-(R) and unnatural C20-(S) configurations. Alkyl containing substrates are more challenging as they affect regioselectivity of iridium-hydride insertion. A rationale for the high diastereoselectivities observed is proposed for aryl containing precursors. The scope of our method is further highlighted through topological diversification in the side chain and within the polycyclic domain of advanced and complex steroidal architectures. These findings have the potential to greatly simplify access to epimeric structural analogues of important steroid scaffolds for applications in biological, pharmaceutical, and medical sciences.

Highly efficient preparation of selectively isotope cluster-labeled long chain fatty acids via two consecutive C(sp3)-C(sp3) cross-coupling reactions.

PubMed

Lethu, Sébastien; Matsuoka, Shigeru; Murata, Michio

2014-02-07

An efficient synthesis involving two copper-catalyzed alkyl-alkyl coupling reactions has been designed to easily access doubly isotope-labeled fatty acids. Such NMR- and IR-active compounds were obtained in excellent overall yields and will be further used for determining the conformation of an alkyl chain of lipidic biomolecules upon interaction with proteins.

Crystal Structures of Xanthomonas campestris OleA Reveal Features That Promote Head-to-Head Condensation of Two Long-Chain Fatty Acids

DOE Office of Scientific and Technical Information (OSTI.GOV)

Goblirsch, BR; Frias, JA; Wackett, LP

2012-05-22

OleA is a thiolase superfamily enzyme that has been shown to catalyze the condensation of two long-chain fatty acylcoenzyme A (CoA) substrates. The enzyme is part of a larger gene cluster responsible for generating long-chain olefin products, a potential biofuel precursor. In thiolase superfamily enzymes, catalysis is achieved via a ping-pong mechanism. The first substrate forms a covalent intermediate with an active site cysteine that is followed by reaction with the second substrate. For OleA, this conjugation proceeds by a nondecarboxylative Claisen condensation. The OleA from Xanthomonas campestris has been crystallized and its structure determined, along with inhibitor-bound and xenon-derivatizedmore » structures, to improve our understanding of substrate positioning in the context of enzyme turnover. OleA is the first characterized thiolase superfamily member that has two long-chain alkyl substrates that need to be bound simultaneously and therefore uniquely requires an additional alkyl binding channel. The location of the fatty acid biosynthesis inhibitor, cerulenin, that possesses an alkyl chain length in the range of known OleA substrates, in conjunction with a single xenon binding site, leads to the putative assignment of this novel alkyl binding channel. Structural overlays between the OleA homologues, 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) synthase and the fatty acid biosynthesis enzyme FabH, allow assignment of the two remaining channels: one for the thioester-containing pantetheinate arm and the second for the alkyl group of one substrate. A short beta-hairpin region is ordered in only one of the crystal forms, and that may suggest open and closed states relevant for substrate binding. Cys143 is the conserved catalytic cysteine within the superfamily, and the site of alkylation by cerulenin. The alkylated structure suggests that a glutamic acid residue (Glu117 beta) likely promotes Claisen condensation by acting as the catalytic base. Unexpectedly

Crystal Structures of Xanthomonas campestris OleA Reveal Features That Promote Head-to-Head Condensation of Two Long-Chain Fatty Acids

DOE Office of Scientific and Technical Information (OSTI.GOV)

Goblirsch, Brandon R.; Frias, Janice A.; Wackett, Lawrence P.

2012-10-25

OleA is a thiolase superfamily enzyme that has been shown to catalyze the condensation of two long-chain fatty acyl-coenzyme A (CoA) substrates. The enzyme is part of a larger gene cluster responsible for generating long-chain olefin products, a potential biofuel precursor. In thiolase superfamily enzymes, catalysis is achieved via a ping-pong mechanism. The first substrate forms a covalent intermediate with an active site cysteine that is followed by reaction with the second substrate. For OleA, this conjugation proceeds by a nondecarboxylative Claisen condensation. The OleA from Xanthomonas campestris has been crystallized and its structure determined, along with inhibitor-bound and xenon-derivatizedmore » structures, to improve our understanding of substrate positioning in the context of enzyme turnover. OleA is the first characterized thiolase superfamily member that has two long-chain alkyl substrates that need to be bound simultaneously and therefore uniquely requires an additional alkyl binding channel. The location of the fatty acid biosynthesis inhibitor, cerulenin, that possesses an alkyl chain length in the range of known OleA substrates, in conjunction with a single xenon binding site, leads to the putative assignment of this novel alkyl binding channel. Structural overlays between the OleA homologues, 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) synthase and the fatty acid biosynthesis enzyme FabH, allow assignment of the two remaining channels: one for the thioester-containing pantetheinate arm and the second for the alkyl group of one substrate. A short {beta}-hairpin region is ordered in only one of the crystal forms, and that may suggest open and closed states relevant for substrate binding. Cys143 is the conserved catalytic cysteine within the superfamily, and the site of alkylation by cerulenin. The alkylated structure suggests that a glutamic acid residue (Glu117{beta}) likely promotes Claisen condensation by acting as the catalytic base

Odd-even effect on the formation of aqueous biphasic systems formed by 1-alkyl-3-methylimidazolium chloride ionic liquids and salts

NASA Astrophysics Data System (ADS)

Belchior, Diana C. V.; Sintra, Tânia E.; Carvalho, Pedro J.; Soromenho, Mário R. C.; Esperança, José M. S. S.; Ventura, Sónia P. M.; Rogers, Robin D.; Coutinho, João A. P.; Freire, Mara G.

2018-05-01

This work provides a comprehensive evaluation of the effect of the cation alkyl side chain length of the 1-alkyl-3-methylimidazolium chloride series ([CnC1im]Cl, n = 2-14) of ionic liquids (ILs) on their capability to form aqueous biphasic systems (ABSs) with salts and self-aggregation derived properties. The liquid-liquid phase behavior of ternary systems composed of [CnC1im]Cl, water, and K3PO4 or K2CO3 and the respective Setschenow salting-out coefficients (ks), a quantitative measure of the two-phase formation ability, were determined. An odd-even effect in the ks values along the number of methylene groups of the longest IL cation alkyl side chain was identified for the ABS formed by K2CO3, a weaker salting-out agent where the phenomenon is clearly identified. In general, cations with even alkyl side chains, being likely to display higher molar volumes, are more easily salted-out and thus more prone to undergo phase separation. The odd-even effect in the ks values is, however, more significant in ILs up to n = 6, where the nanostructuration/nanosegregation of ILs plays a less relevant role. Still, with the [CnC1im]Cl (n = 7-14) series of ILs, an odd-even effect was also identified in the ILs' ionization degree, molar conductivity, and conductivity at infinite dilution. In summary, it is shown here that the ILs' odd-even effect occurs in IL aqueous solutions and not just in neat ILs, an already well-established phenomenon occurring in a series of ILs' properties described as a result of the orientation of the terminal methyl groups to the imidazolium ring cation and consequent effect in the ILs' cohesive energy.

Solid-phase extraction-gas chromatography and solid-phase extraction-gas chromatography-mass spectrometry determination of corrosion inhibiting long-chain primary alkyl amines in chemical treatment of boiler water in water-steam systems of power plants.

PubMed

Kusch, Peter; Knupp, Gerd; Hergarten, Marcus; Kozupa, Marian; Majchrzak, Maria

2006-04-28

Gas chromatography with simultaneous flame-ionization detection (FID) and a nitrogen-phosphorus detection (NPD) as well as gas chromatography-mass spectrometry (GC/MS) has been used to characterize long-chain primary alkyl amines after derivatization with trifluoroacetic anhydride (TFAA). Electron impact ionization- (EI) and negative chemical ionization (NCI) mass spectra of trifluoroacetylated derivatives of the identified tert-octadecylamines are presented for the first time. The corrosion inhibiting alkyl amines were applied in a water-steam circuit of energy systems in the power industry. Solid-phase extraction (SPE) with octadecyl bonded silica (C18) sorbents followed by gas chromatography were used for quantification of the investigated tert-octadecylamines in boiler water, superheated steam and condensate samples from the power plant. The estimated values were: 89 microg l(-1)(n = 5, RSD = 7.8%), 45 microg l(-1) (n = 5, RSD = 5.4%) and 37 microg l(-1)(n = 5, RSD = 2.3%), respectively.

Biodiesel production from triolein and short chain alcohols through biocatalysis.

PubMed

Salis, Andrea; Pinna, Marcella; Monduzzi, Maura; Solinas, Vincenzo

2005-09-29

Oleic acid alkyl esters (biodiesel) were synthesised by biocatalysis in solvent-free conditions. Different commercial immobilised lipases, namely Candida antarctica B, Rizhomucor miehei, and Pseudomonas cepacia, were tested towards the reaction between triolein and butanol to produce butyl oleate. Pseudomonas cepacia lipase resulted to be the most active enzyme reaching 100% of conversion after 6h. Different operative conditions such as reaction temperature, water activity, and reagent stoichiometric ratio were investigated and optimised. These conditions were then used to investigate the effect of linear and branched short chain alcohols. Methanol and 2-butanol were the worst alcohols: the former, probably, due to its low miscibility with the oil and the latter because secondary alcohols usually are less reactive than primary alcohols. Conversely, linear and branched primary alcohols with short alkyl chains (C(2)--C(4)) showed high reaction rate and conversion. A mixture of linear and branched short chain alcohols that mimics the residual of ethanol distillation (fusel oil) was successfully used for oleic acid ester synthesis. These compounds are important in biodiesel mixtures since they improve low temperature properties.

Photostability enhancement of the pentacene derivative having two nitronyl nitroxide radical substituents.

PubMed

Shimizu, Akihiro; Ito, Akitaka; Teki, Yoshio

2016-02-18

Pentacene derivatives possessing nitronyl nitroxide radical substituents (1a and 1b) were synthesized, and their photochemical properties were evaluated. 1a with two radical substituents showed a remarkable enhancement of photostability compared with pentacene, 6,13-bis(triisopropylsilylethynyl)pentacene and the monoradical, 1b. This is understood due to the presence of the multiple deactivation pathways in the photoexcited states.

CC-1065 functional analogues possessing different electron-withdrawing substituents and leaving groups: synthesis, kinetics, and sequence specificity of reaction with DNA and biological evaluation.

PubMed

Wang, Y; Gupta, R; Huang, L; Lown, J W

1993-12-24

Antitumor agent CC-1065 functional analogues possessing different electron-withdrawing substituents and leaving groups have been synthesized. The extent and the relative rates of DNA cleavage following alkylation by these CPI structures and thermal treatment were determined independently by an ethidium binding assay and by agarose gel electrophoresis experiments. The anticipated preferential covalent binding to adenine sites within the minor groove was confirmed by sequencing determination of selected agents on high-resolution gels. Certain of the synthetic agents, unlike CC-1065, also bind covalently to G sites with weaker intensity. The cytotoxicities of these compounds were also determined against KB cells in vitro. Compounds bearing a bromo or nitro group in the benzene ring and a methylsulfonyl as a leaving group are 10 and 5 times more potent than their unsubstituted counterparts, respectively. Compounds bearing a methylsulfonyl as a leaving group are more potent than those bearing a chlorine.

Preparation, physicochemical characterisation and magnetic properties of Cu-Al layered double hydroxides with CO 32- and anionic surfactants with different alkyl chains in the interlayer

NASA Astrophysics Data System (ADS)

Trujillano, Raquel; Holgado, María Jesús; Pigazo, Fernando; Rives, Vicente

2006-03-01

Layered double hydroxides with the hydrotalcite-like structure, containing Cu(II) and Al(III) in the layers, and different alkyl sulphonates in the interlayer, have been prepared and characterised by powder X-ray diffraction, FT-IR spectroscopy, differential thermal analysis and thermogravimetric analysis. Their magnetic properties have been also studied. Except for the sample containing octadecanesulphonate in the interlayer, for which an excess of sulphonate exists, pure crystalline phases have been obtained in the other cases. Upon heating, combustion of the organic chain takes place at lower temperature than for the corresponding sodium salts. A two-dimensional antiferromagnetic behaviour is observed at 200 K in all samples containing intercalated sulphonate. The χT value is lower for the samples containing interlayer sulphonates (with layer-layer distances in the 21-31 Å range), than for a carbonate-containing analogue (basal spacing 7.51 Å).

Photoinduced, Copper-Catalyzed Carbon-Carbon Bond Formation with Alkyl Electrophiles: Cyanation of Unactivated Secondary Alkyl Chlorides at Room Temperature.

PubMed

Ratani, Tanvi S; Bachman, Shoshana; Fu, Gregory C; Peters, Jonas C

2015-11-04

We have recently reported that, in the presence of light and a copper catalyst, nitrogen nucleophiles such as carbazoles and primary amides undergo C-N coupling with alkyl halides under mild conditions. In the present study, we establish that photoinduced, copper-catalyzed alkylation can also be applied to C-C bond formation, specifically, that the cyanation of unactivated secondary alkyl chlorides can be achieved at room temperature to afford nitriles, an important class of target molecules. Thus, in the presence of an inexpensive copper catalyst (CuI; no ligand coadditive) and a readily available light source (UVC compact fluorescent light bulb), a wide array of alkyl halides undergo cyanation in good yield. Our initial mechanistic studies are consistent with the hypothesis that an excited state of [Cu(CN)2](-) may play a role, via single electron transfer, in this process. This investigation provides a rare example of a transition metal-catalyzed cyanation of an alkyl halide, as well as the first illustrations of photoinduced, copper-catalyzed alkylation with either a carbon nucleophile or a secondary alkyl chloride.

Impact of Linear Alkyl Length on the Assembly of Twisted Perylene Bisimides: From Molecular Arrangement to Nanostructures.

PubMed

Guo, Zongxia; Wang, Kun; Yu, Ping; Wang, Xiangnan; Lan, Shusha; Sun, Kai; Yi, Yuanping; Li, Zhibo

2017-11-02

The effect of the length of linear alkyl chains substituted at imine positions on the assembly of tetrachlorinated perylene bisimides (1: PBI with -C 6 H 13 ; 2: PBI with -C 12 H 25 ) has been investigated. Solvent-induced assembly was performed in solutions of THF and methanol with varying volume ratios. Morphological (SEM, AFM, and TEM) and spectral (UV/Vis, fluorescence, FTIR, and XRD) methods were used to characterize the assembled nanostructures and the molecular arrangement in the aggregates. It was found that uniform structures could be obtained for both molecules in solutions with a high ratio of methanol. PBI 1 formed rigid nanosheets, whereas 2 assembled into longer nanostripes with a high ratio of length to width. On combining the morphological data with the spectral data, it was suggested that π-π stacking predominated in assemblies of 1, and the synergetic effect of van der Waals interactions from the long alkyl chains and π-π stacking between neighboring building blocks facilitated the growth of the long-range-ordered nanostructures of 2. By changing the linear chain length, the hierarchical assembly of PBIs modified on bay positions could be manipulated effectively. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Effects of Bulky Substituents of Push-Pull Porphyrins on Photovoltaic Properties of Dye-Sensitized Solar Cells.

PubMed

Higashino, Tomohiro; Kawamoto, Kyosuke; Sugiura, Kenichi; Fujimori, Yamato; Tsuji, Yukihiro; Kurotobi, Kei; Ito, Seigo; Imahori, Hiroshi

2016-06-22

To evaluate the effects of substituent bulkiness around a porphyrin core on the photovoltaic properties of porphyrin-sensitized solar cells, long alkoxy groups were introduced at the meso-phenyl group (ZnPBAT-o-C8) and the anchoring group (ZnPBAT-o-C8Cn, n = 4, 8) of an asymmetrically substituted push-pull porphyrin with double electron-donating diarylamino groups and a single electron-withdrawing carboxyphenylethynyl anchoring group. The spectroscopic and electrochemical properties of ZnPBAT-o-C8 and ZnPBAT-o-C8Cn were found to be superior to those of a push-pull porphyrin reference (YD2-o-C8), demonstrating their excellent light-harvesting and redox properties for dye-sensitized solar cells. A power conversion efficiency (η) of the ZnPBAT-o-C8-sensitized solar cell (η = 9.1%) is higher than that of the YD2-o-C8-sensitized solar cell (η = 8.6%) using iodine-based electrolyte due to the enhanced light-harvesting ability of ZnPBAT-o-C8. In contrast, the solar cells based on ZnPBAT-o-C8Cn, possessing the additional alkoxy chains in the anchoring group, revealed the lower η values of 7.3% (n = 4) and 7.0% (n = 8). Although ZnPBAT-o-C8Cn exhibited higher resistance at the TiO2-dye-electrolyte interface by virtue of the extra alkoxy chains, the reduced amount of the porphyrins on TiO2 by excessive addition of coadsorbent chenodeoxycholic acid (CDCA) for mitigating the aggregation on TiO2 resulted in the low η values. Meanwhile, the ZnPBAT-o-C8-sensitized solar cell showed the lower η value of 8.1% than the YD2-o-C8-sensitized solar cell (η = 9.8%) using cobalt-based electrolyte. The smaller η value of the ZnPBAT-o-C8-sensitized solar cell may be attributed to the insufficient blocking effect of the bulky substituents of ZnPBAT-o-C8 under the cobalt-based electrolyte conditions. Overall, the alkoxy chain length and substitution position around the porphyrin core are important factors to affect the cell performance.

Substituent effects in infrared spectroscopy—VII. Meta and para substituted methanesulphonanilides

NASA Astrophysics Data System (ADS)

Laurence, C.; Berthelot, M.; Lucon, M.; Tsuno, Y.

Substituent effects on the NH frequencies of the conformers of methanesulphonanilides, their cyclic dimers and their hydrogen bonded complexes with acetonitrile have been analysed by means of the Hammet equation. An electron-withdrawing substituent may either increase or decrease ν(NH) in the XC 6H 4NHY series according to the electronic nature of the Y group. This can be explained by the non-monotonic dependence of the NH stretching frequency on the ionic character of the NH bond.

Light-activated phenalen-1-one bactericides: efficacy, toxicity and mechanism compared with benzalkonium chloride.

PubMed

Muehler, Denise; Sommer, Kerstin; Wennige, Sara; Hiller, Karl-Anton; Cieplik, Fabian; Maisch, Tim; Späth, Andreas

2017-11-01

Five photoactive compounds with variable elongated alkyl-substituents in a phenalen-1-one structure were examined in view of structural similarity to the antimicrobial agent benzalkonium chloride (BAC). All phenalen-1-ones and BAC were evaluated for their antimicrobial properties against Staphylococcus aureus, methicillin-resistant S. aureus, Escherichia coli, Pseudomonas aeruginosa and for their eukaryotic toxicity against normal human epidermal keratinocyte (NHEK) cells to narrow down the BAC-like effect and the photodynamic effect depending on the chemical structure. All compounds were investigated for effective concentration ranges, where a bacterial reduction of 5 log 10 is achieved, while an NHEK survival of 80% is ensured. Effective concentration ranges were found for four out of five photoactive compounds, but not for BAC and the compound with BAC-like alkyl chain length. Chain length size and polar area of the respective head-groups of phenalen-1-one compounds or BAC showed an influence on the incorporation inside lipid membranes and thus, head-groups may have an impact on the toxicity of antimicrobials.

Three-Component Aminoalkylations Yielding Dihydronaphthoxazine-Based Sirtuin Inhibitors: Scaffold Modification and Exploration of Space for Polar Side-Chains.

PubMed

Vojacek, Steffen; Beese, Katja; Alhalabi, Zayan; Swyter, Sören; Bodtke, Anja; Schulzke, Carola; Jung, Manfred; Sippl, Wolfgang; Link, Andreas

2017-07-01

Nonpolar derivatives of heterocyclic aromatic screening hits like the non-selective sirtuin inhibitor splitomicin tend to be poorly soluble in biological fluids. Unlike sp 3 -rich natural products, flat aromatic compounds are prone to stacking and often difficult to optimize into leads with activity in cellular systems. The aim of this work was to identify anchor points for the introduction of sp 3 -rich fragments with polar functional groups into the newly discovered active (IC 50  = 5 μM) but nonpolar scaffold 1,2-dihydro-3H-naphth[1,2-e][1,3]oxazine-3-thione by a molecular modeling approach. Docking studies were conducted with structural data from crystallized human SIRT2 enzyme. Subsequent evaluation of the in silico hypotheses through synthesis and biological evaluation of the designed structures was accomplished with the aim to discover new SIRT2 inhibitors with improved aqueous solubility. Derivatives of 8-bromo-1,2-dihydro-3H-naphth[1,2-e][1,3]oxazine-3-thione N-alkylated with a hydrophilic morpholino-alkyl chain at the thiocarbamate group intended for binding in the acetyl-lysine pocket of the enzyme appeared to be promising. Both the sulfur of the thiocarbamate and the bromo substituent were assumed to result in favorable hydrophobic interactions and the basic morpholino-nitrogen was predicted to build a hydrogen bond with the backbone Ile196. While the brominated scaffold showed moderately improved activity (IC 50  = 1.8 μM), none of the new compounds displayed submicromolar activity. Synthesis and characterization of the new compounds are reported and the possible reasons for the outcome are discussed. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Effects of the Substituents of Boron Atoms on Conjugated Polymers Containing B←N Units.

PubMed

Liu, Jun; Wang, Tao; Dou, Chuandong; Wang, Lixiang

2018-06-15

Organoboron chemistry is a new tool to tune the electronic structures and properties of conjugated polymers, which are important for applications in organic opto-electronic devices. To investigate the effects of substituents of boron atoms on conjugated polymers, we synthesized three conjugated polymers based on double B←N bridged bipyridine (BNBP) with various substituents on the boron atoms. By changing the substituents from four phenyl groups and two phenyl groups/two fluorine atoms to four fluorine atoms, the BNBP-based polymers show the blue-shifted absorption spectra, decreased LUMO/HOMO energy levels and enhanced electron affinities, as well as the increased electron mobilities. Moreover, these BNBP-based polymers can be used as electron acceptors for all-polymer solar cells. These results demonstrate that the substituents of boron atoms can effectively modulate the electronic properties and applications of conjugated polymers. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Asymmetric synthesis of propargylamines as amino acid surrogates in peptidomimetics

PubMed Central

Wünsch, Matthias; Schröder, David; Fröhr, Tanja; Teichmann, Lisa; Hedwig, Sebastian; Janson, Nils; Belu, Clara; Simon, Jasmin; Heidemeyer, Shari; Holtkamp, Philipp; Rudlof, Jens; Klemme, Lennard; Hinzmann, Alessa; Neumann, Beate; Stammler, Hans-Georg

2017-01-01

The amide moiety of peptides can be replaced for example by a triazole moiety, which is considered to be bioisosteric. Therefore, the carbonyl moiety of an amino acid has to be replaced by an alkyne in order to provide a precursor of such peptidomimetics. As most amino acids have a chiral center at Cα, such amide bond surrogates need a chiral moiety. Here the asymmetric synthesis of a set of 24 N-sulfinyl propargylamines is presented. The condensation of various aldehydes with Ellman’s chiral sulfinamide provides chiral N-sulfinylimines, which were reacted with (trimethylsilyl)ethynyllithium to afford diastereomerically pure N-sulfinyl propargylamines. Diverse functional groups present in the propargylic position resemble the side chain present at the Cα of amino acids. Whereas propargylamines with (cyclo)alkyl substituents can be prepared in a direct manner, residues with polar functional groups require suitable protective groups. The presence of particular functional groups in the side chain in some cases leads to remarkable side reactions of the alkyne moiety. Thus, electron-withdrawing substituents in the Cα-position facilitate a base induced rearrangement to α,β-unsaturated imines, while azide-substituted propargylamines form triazoles under surprisingly mild conditions. A panel of propargylamines bearing fluoro or chloro substituents, polar functional groups, or basic and acidic functional groups is accessible for the use as precursors of peptidomimetics. PMID:29234470

Palladium-Catalyzed Borylation of Primary Alkyl Bromides

PubMed Central

Joshi-Pangu, Amruta; Ma, Xinghua; Diane, Mohamed; Iqbal, Sidra; Kribs, Robert J.; Huang, Richard; Wang, Chao-Yuan

2012-01-01

A mild Pd-catalyzed process for the borylation of alkyl bromides has been developed using bis(pinacolato)diboron as a boron source. This process accommodates the use of a wide range of functional groups on the alkyl bromide substrate. Primary bromides react with complete selectivity in the presence of a secondary bromide. The generality of this approach is demonstrated by its extension to the use of alkyl iodides and alkyl tosylates, as well as borylation reactions employing bis(neopentyl glycolato)diboron as the boron source. PMID:22774861

Tribology of monolayer films: comparison between n-alkanethiols on gold and n-alkyl trichlorosilanes on silicon.

PubMed

Booth, Brandon D; Vilt, Steven G; McCabe, Clare; Jennings, G Kane

2009-09-01

This Article presents a quantitative comparison of the frictional performance for monolayers derived from n-alkanethiolates on gold and n-alkyl trichlorosilanes on silicon. Monolayers were characterized by pin-on-disk tribometry, contact angle analysis, ellipsometry, and electrochemical impedance spectroscopy (EIS). Pin-on-disk microtribometry provided frictional analysis at applied normal loads from 10 to 1000 mN at a speed of 0.1 mm/s. At low loads (10 mN), methyl-terminated n-alkanethiolate self-assembled monolayers (SAMs) exhibited a 3-fold improvement in coefficient of friction over SAMs with hydroxyl- or carboxylic-acid-terminated surfaces. For monolayers prepared from both n-alkanethiols on gold and n-alkyl trichlorosilanes on silicon, a critical chain length of at least eight carbons is required for beneficial tribological performance at an applied load of 9.8 mN. Evidence for disruption of chemisorbed alkanethiolate SAMs with chain lengths n chain interactions (van der Waals) and the adsorbate-substrate bond.

New cationic vesicles prepared with double chain surfactants from arginine: Role of the hydrophobic group on the antimicrobial activity and cytotoxicity.

PubMed

Pinazo, A; Petrizelli, V; Bustelo, M; Pons, R; Vinardell, M P; Mitjans, M; Manresa, A; Perez, L

2016-05-01

Cationic double chain surfactants have attracted much interest because they can give rise to cationic vesicles that can be used in biomedical applications. Using a simple and economical synthetic approach, we have synthesized four double-chain surfactants with different alkyl chain lengths (LANHCx). The critical aggregation concentration of the double chain surfactants is at least one order of magnitude lower than the CMC of their corresponding single-chain LAM and the solutions prepared with the LANHCx contain stable cationic vesicles. Encouragingly, these new arginine derivatives show very low haemolytic activity and weaker cytotoxic effects than conventional dialkyl dimethyl ammonium surfactants. In addition, the surfactant with the shortest alkyl chain exhibits good antimicrobial activity against Gram-positive bacteria. The results show that a rational design applied to cationic double chain surfactants might serve as a promising strategy for the development of safe cationic vesicular systems. Copyright © 2016 Elsevier B.V. All rights reserved.

Substituent effect on photophysical properties of bi-1,3,4-oxadiazole derivatives in solution

NASA Astrophysics Data System (ADS)

Chen, Fangyi; Tian, Taiji; Zhao, Chengxiao; Bai, Binglian; Li, Min; Wang, Haitao

2016-04-01

A series of phenyl substituted bi-1,3,4-oxadiazole derivatives were designed and synthesized; the effect of substituent on the photophysical properties and molecular electronic structures was fully studied by the combination of experimental techniques and theoretical calculations. Compared to parent compound without any substituent (BOXD), fluoro-substituent shows little effect on the absorption and emission spectra, whilst a little larger spectral red-shift could be observed for methoxy-, nitro-substituted derivatives and thienyl-substituted bi-1,3,4-oxadiazole (TBOXD). These spectral changes can be well explained by theoretically calculated HOMO and LUMO energy level changes. All these molecules show high fluorescence quantum yield except for nitro-substituted derivative in dilute solutions. The quantum yield of BOXD changes with the concentration and exhibits a high value at the concentrated solution. This work revealed the influence of substituent on the photophysical properties of bi-1,3,4-oxadizaole derivatives in dilute solutions and provided guidance for designing molecules with potential application.

Synthesis of alkyl-substituted six-membered lactones through ring-closing metathesis of homoallyl acrylates. An easy route to pyran-2-ones, constituents of tobacco flavor.

PubMed

D'Annibale, Andrea; Ciaralli, Laura; Bassetti, Mauro; Pasquini, Chiara

2007-08-03

The ring-closing metathesis (RCM) reactions of homoallylic acrylates bearing alkyl substituents on various positions of their skeleton afford the corresponding pentenolides in the presence of carbene ruthenium catalysts. For R3 = R4 = H, or R3 = Me, R4 = H, the reactions are catalyzed by complex [RuCl2(PCy3)2(=CHPh)], while a second-generation Grubbs catalyst is required when R3 = H and R4 = Me, R3 = R4 = Me, or R3 = i-Pr and R4 = H. Alkyl substitution at the homoallylic carbon (R1, R2) increases the yield of the reaction when both the acrylic and/or homoallylic double bonds are methyl-substituted. The interaction of the catalyst with the substrate in the initiation stage involves the homoallylic double bond rather than the acrylic moiety, and the resulting alkylidene species from the first-generation Grubbs catalyst can be observed by 1H and 31P NMR. The racemic tobacco constituents 4-isopropyl-5,6-dihydropyran-2-one and 4-isopropyltetrahydropyran-2-one are prepared via a short reaction sequence, involving the RCM reaction as the key transformation.

Enhancement of alkylation catalysts for improved supercritical fluid regeneration

DOEpatents

Ginosar, Daniel M [Idaho Falls, ID; Petkovic, Lucia [Idaho Falls, ID

2009-09-22

A method of modifying an alkylation catalyst to reduce the formation of condensed hydrocarbon species thereon. The method comprises providing an alkylation catalyst comprising a plurality of active sites. The plurality of active sites on the alkylation catalyst may include a plurality of weakly acidic active sites, intermediate acidity active sites, and strongly acidic active sites. A base is adsorbed to a portion of the plurality of active sites, such as the strongly acidic active sites, selectively poisoning the strongly acidic active sites. A method of modifying the alkylation catalyst by providing an alkylation catalyst comprising a pore size distribution that sterically constrains formation of the condensed hydrocarbon species on the alkylation catalyst or by synthesizing the alkylation catalyst to comprise a decreased number of strongly acidic active sites is also disclosed, as is a method of improving a regeneration efficiency of the alkylation catalyst.

Enhancement of alkylation catalysts for improved supercritical fluid regeneration

DOEpatents

Ginosar, Daniel M.; Petkovic, Lucia M.

2010-12-28

A method of modifying an alkylation catalyst to reduce the formation of condensed hydrocarbon species thereon. The method comprises providing an alkylation catalyst comprising a plurality of active sites. The plurality of active sites on the alkylation catalyst may include a plurality of weakly acidic active sites, intermediate acidity active sites, and strongly acidic active sites. A base is adsorbed to a portion of the plurality of active sites, such as the strongly acidic active sites, selectively poisoning the strongly acidic active sites. A method of modifying the alkylation catalyst by providing an alkylation catalyst comprising a pore size distribution that sterically constrains formation of the condensed hydrocarbon species on the alkylation catalyst or by synthesizing the alkylation catalyst to comprise a decreased number of strongly acidic active sites is also disclosed, as is a method of improving a regeneration efficiency of the alkylation catalyst.

The investigation of substituent effects on the fragmentation pathways of pentacoordinated phenoxyspirophosphoranes by ESI-MSn.

PubMed

Cui, Xiaoyan; Sun, Can; Zhao, Pei; Wang, Yanyan; Guo, Yanchun; Zhao, Yufen; Cao, Shuxia

2018-04-01

The fragmentation pathways of pentacoordinated phenoxyspirophosphoranes were investigated in the positive mode by electrospray ionization multistage mass spectrometry. The results demonstrate that the sodium adducts of the title compounds undergo two competitive fragmentation pathways, and the fragmentation patterns are heavily dependent on the various substituent patterns at the phenolic group. An electron-withdrawing substituent at the ortho-position always results in the removal of a corresponding phenol analogue, while cleavage by spiroring opening becomes the predominant fragmentation pathway if an electron-donating substituent is at the phenolic group. The substituent effects on the competitive fragmentation pathways were further elucidated by theoretical calculations, single crystal structure analysis, and high-resolution mass spectrometry. The results contribute to the understanding of the gas-phase fragmentation reactions and the structure identification of spirophosphorane analogues by electrospray ionization multistage mass spectrometry. Copyright © 2018 John Wiley & Sons, Ltd.

Effects of neutral and anionic substituents on the carbonyl stretching bands of substituted methylbenzoates

NASA Astrophysics Data System (ADS)

Vassileva, P. J.; Binev, I. G.; Juchnovski, I. N.

Effects of neutral and anionic substitutents on frequencies (ν CO) and integrated intensities ( ACO) of the carbonyl stretching bands of substituted methylbenzoates (solvent dimethyl sulphoxide) have been studied in relation to Hammett's equation: satisfactory correlations have been found between ν CO and σ + constants, as well as by using the dual-parameter equations to Yukawa, Tsuno and Taft; ACO have been found to increase in cases of strong electron-releasing substituents. It has been found that constants of anionic substituents, determined on the basis of nitrile i.r. frequencies and intensities, reflect satisfactorily the effects of these substituents on ν CO and ACO of methylbenzoates.

Effects of derivatization reagents consisting of n-alkyl chloroformate/n-alcohol combinations in LC-ESI-MS/MS analysis of zwitterionic antiepileptic drugs.

PubMed

Kostić, Nađa; Dotsikas, Yannis; Malenović, Anđelija; Medenica, Mirjana

2013-11-15

In the current study, three antiepileptic drugs with zwitterionic properties, namely vigabatrin, pregabalin and gabapentin, were chosen as model analytes to undergo derivatization by applying various n-alkyl chloroformate/n-alcohol combinations, followed by LC-ESI-MS/MS analysis. The employment of 16 combinations per drug using methyl, ethyl, propyl or butyl chloroformate coupled with methanol, ethanol, propanol or butanol, greatly affected a series of parameters of the derivatives, such as retention time on C8 column, signal expressed via areas, limit of detection values, as well as the yields of the main and side reactions. Practically, even slight modification of n-alkyl group of either chloroformate or alcohol resulted in significant changes in the chromatographic and mass spectrometric behavior of the novel derivative. It was clearly demonstrated that all the estimated parameters were highly correlated with the length of n-alkyl groups of the involved chloroformate and alcohol. The most significant influence was monitored in peak area values, indicating that the length of the n-alkyl chain plays an important role in electrospray ionization efficiency. For this parameter, increasing the n-alkyl chain from methyl to butyl led to increment up to 2089%, 508.7% and 1075% for area values of derivatized vigabatrin, pregabalin and gabapentin, respectively. These changes affected also the corresponding values of limits of detection, with the estimated improvements up to 1553%, 397.7% and 875.0% for the aforementioned derivatized drugs, respectively. Besides the obvious utilization of these conclusions in the development of bioanalytical methods for these analytes with the current protocol, this study offers valuable data which can be useful in more general approaches, giving insights into the effects of this derivatization reaction and its performances. Copyright © 2013 Elsevier B.V. All rights reserved.

Design of Far-Red Sensitizing Squaraine Dyes Aiming Towards the Fine Tuning of Dye Molecular Structure.

PubMed

Morimoto, Takuya; Fujikawa, Naotaka; Ogomi, Yuhei; Pandey, Shyam S; Ma, Tingli; Hayase, Shuzi

2016-04-01

Model squaraine dyes having sharp and narrow absorptions mainly in the far-red wavelength region has been logically designed, synthesized and used for their application as sensitizer in the dyesensitized solar cells (DSSC). In order to have fine control on energetics, dyes having same mother core and alkyl chain length varying only in molecular symmetry and position of substituent were designed. It has been found that even keeping all other structural factor constant, only positional variation of substituent leads to not only in the variation of energetics by 0.1 eV but affects the photovoltaic characteristics also. Optimum concentration of dye de-aggregating agent was found to be 100 times with respect to the sensitizing dye concentration. Amongst dyes utilized in this work best performance was obtained for unsymmetrical dye SQ-40 giving a photoconversion efficiency of 4.01% under simulated solar irradiation at global AM 1.5.

The Inhibition of Aluminum Corrosion in Sulfuric Acid by Poly(1-vinyl-3-alkyl-imidazolium Hexafluorophosphate).

PubMed

Arellanes-Lozada, Paulina; Olivares-Xometl, Octavio; Guzmán-Lucero, Diego; Likhanova, Natalya V; Domínguez-Aguilar, Marco A; Lijanova, Irina V; Arce-Estrada, Elsa

2014-08-07

Compounds of poly(ionic liquid)s (PILs), derived from imidazole with different alkylic chain lengths located in the third position of the imidazolium ring (poly(1-vinyl-3-dodecyl-imidazolium) (PImC 12 ), poly(1-vinyl-3-octylimidazolium) (PImC₈) and poly(1-vinyl-3-butylimidazolium) (PImC₄) hexafluorophosphate) were synthesized. These compounds were tested as corrosion inhibitors on aluminum alloy AA6061 in diluted sulfuric acid (0.1-1 M H₂SO₄) by weight loss tests, polarization resistance measurements and inductively coupled plasma optical emission spectroscopy. Langmuir's isotherms suggested film formation on bare alloy while standard free energy indicated inhibition by a physisorption process. However, compound efficiencies as inhibitors ranked low (PImC 12 > PImC₈ > PImC₄) to reach 61% for PImC 12 in highly diluted acidic solution. Apparently, the high mobility of sulfates favored their adsorption in comparison to PILs. The surface film displayed general corrosion, and pitting occurred as a consequence of PILs' partial inhibition along with a continuous dissolution of defective patchy film on formation. A slight improvement in efficiency was displayed by compounds having high molecular weight and a long alkyl chain, as a consequence of steric hindrance and PIL interactions.

Substituent and solvent effects on electronic spectra of some substituted phenoxyacetic acids.

PubMed

Shanthi, M; Kabilan, S

2007-06-01

The effects of substituents and solvents have been studied through the absorption spectra of nearly 19 para- and ortho-substituted phenoxyacetic acids in the range of 200-400 nm. The effects of substituent on the absorption spectra of compounds under present investigation are interpreted by correlation of absorption frequencies with simple and extended Hammett equations. Effect of solvent polarity and hydrogen bonding on the absorption spectra are interpreted by means of Kamlet equation and the results are discussed.

Substituent and solvent effects on electronic spectra of some substituted phenoxyacetic acids

NASA Astrophysics Data System (ADS)

Shanthi, M.; Kabilan, S.

2007-06-01

The effects of substituents and solvents have been studied through the absorption spectra of nearly 19 para- and ortho-substituted phenoxyacetic acids in the range of 200-400 nm. The effects of substituent on the absorption spectra of compounds under present investigation are interpreted by correlation of absorption frequencies with simple and extended Hammett equations. Effect of solvent polarity and hydrogen bonding on the absorption spectra are interpreted by means of Kamlet equation and the results are discussed.

Effect of substituents on polarizability and hyperpolarizability values of benzimidazole metal complexes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Praveen, P. A.; Babu, R. Ramesh, E-mail: rampap2k@yahoo.co.in

2016-05-23

In this report, the polarizability and first and second order hyperpolarizability values of bis benzimidazole Zn(II)-2R and bis benzimidazole Cd(II)-2R complexes, with different electron donating moieties R (R= Cl, Br, I, Acetate) were calculated using time dependent Hartree-Fock (TDHF) formalism embedded in MOPAC2012 package. Further the role of substituents on polarizability and hyperpolarizability values is investigated for the first time by analyzing the frontier molecular orbitals of the complexes with respect to the electronegativity of the substituents. It is found that the increase in electronegativity of the substituents correspondingly increases the energy gap of the molecules, which in turn reducesmore » the polarizability values of both Zn and Cd benzimidazole complexes. Similarly, increase in electronegativity reduces the electric quadrupole moments of both the metal complexes, which in turn reduces the hyperpolarizability values.« less

[Adenylate cyclase from rabbit heart: substrate binding site].

PubMed

Perfil'eva, E A; Khropov, Iu V; Khachatrian, L; Bulargina, T V; Baranova, L A

1981-08-01

The effects of 17 ATP analogs on the solubilized rabbit heart adenylate cyclase were studied. The triphosphate chain, position 8 of the adenine base and the ribose residue of the ATP molecule were modified. Despite the presence of the alkylating groups in two former types of the analogs tested, no covalent blocking of the active site of the enzyme was observed. Most of the compounds appeared to be competitive reversible inhibitors. The kinetic data confirmed the importance of the triphosphate chain for substrate binding in the active site of adenylate cyclase. (Formula: See Text) The inhibitors with different substituents in position 8 of the adenine base had a low affinity for the enzyme. The possible orientation of the triphosphate chain and the advantages of anti-conformation of the ATP molecule for their binding in the active site of adenylate cyclase are discussed.

Impact of Alkyl Spacer Length on Aggregation Pathways in Kinetically Controlled Supramolecular Polymerization.

PubMed

Ogi, Soichiro; Stepanenko, Vladimir; Thein, Johannes; Würthner, Frank

2016-01-20

We have investigated the kinetic and thermodynamic supramolecular polymerizations of a series of amide-functionalized perylene bisimide (PBI) organogelator molecules bearing alkyl spacers of varied lengths (ethylene to pentylene chains, PBI-1-C2 to PBI-1-C5) between the amide and PBI imide groups. These amide-functionalized PBIs form one-dimensional fibrous nanostructures as the thermodynamically favored states in solvents of low polarity. Our in-depth studies revealed, however, that the kinetic behavior of their supramolecular polymerization is dependent on the spacer length. Propylene- and pentylene-tethered PBIs follow a similar polymerization process as previously observed for the ethylene-tethered PBI. Thus, the monomers of these PBIs are kinetically trapped in conformationally restricted states through intramolecular hydrogen bonding between the amide and imide groups. In contrast, the intramolecularly hydrogen-bonded monomers of butylene-tethered PBI spontaneously self-assemble into nanoparticles, which constitute an off-pathway aggregate state with regard to the thermodynamically stable fibrous supramolecular polymers obtained. Thus, for this class of π-conjugated system, an unprecedented off-pathway aggregate with high kinetic stability could be realized for the first time by introducing an alkyl linker of optimum length (C4 chain) between the amide and imide groups. Our current system with an energy landscape of two competing nucleated aggregation pathways is applicable to the kinetic control over the supramolecular polymerization by the seeding approach.

Synergistic effects of Lewis bases and substituents on the electronic structure and reactivity of boryl radicals.

PubMed

Lu, Dongmei; Wu, Chao; Li, Pengfei

2014-02-03

Boryl radicals have the potential for the development of new molecular entities and for application in new radical reactions. However, the effects of the substituents and coordinating Lewis bases on the reactivity of boryl radicals are not fully understood. By using first-principles methods, we investigated the spin-density distribution and reactivity of a series of boryl radicals with various substituents and Lewis bases. The substituents, along with the Lewis bases, only affect the radical reactivity when an unpaired electron is in the boron pz orbital, that is, for three-coordinate radicals. We found evidence of synergistic effects between the substituents and the Lewis bases that can substantially broaden the tunability of the reactivity of the boryl radicals. Among Lewis bases, pyridine and imidazol-2-ylidene show a similar capacity for stabilization by delocalizing the spin density. Electron-donating substituents, such as nitrogen, more efficiently stabilize boryl radicals than oxygen and carbon atoms. The reactivity of a boryl radical is always boron based, irrespective of the spin density on boron. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Molecular structures and antiproliferative activity of side-chain saturated and homologated analogs of 2-chloro-3-(n-alkylamino)-1,4-napthoquinone

NASA Astrophysics Data System (ADS)

Pal, Sanjima; Jadhav, Mahesh; Weyhermüller, Thomas; Patil, Yogesh; Nethaji, M.; Kasabe, Umesh; Kathawate, Laxmi; Konkimalla, V. Badireenath; Salunke-Gawali, Sunita

2013-10-01

Side chain homologated derivatives of 2-chloro-3-(n-alkylamino)-1,4-naphthoquinone {n-alkyl: pentyl; L-5, hexyl; L-6, heptyl; L-7 and octyl; L-8} have been synthesized and characterized by elemental analysis, FT-IR, 1H NMR, UV-visible spectroscopy and LC-MS. Compounds, L-4, {n-alkyl: butyl; L-4}, L-6 and L-8 have been characterized by single crystal X-ray diffraction studies. The single crystal X-ray structures reveal that L-4 and L-8 crystallizes in P21 space group, while L-6 in P21/c space group. Molecules of L-4 and L-8 from polymeric chains through Csbnd H⋯O and Nsbnd H⋯O close contacts. L-6 is a dimer formed by Nsbnd H⋯O interaction. Slipped π-π stacking interactions are observed between quinonoid and benzenoid rings of L-4 and L-8. Orientations of alkyl group in L-4 and L-8 is on same side of the chain and polymeric chains run opposite to one another to form zip like structure to the alkyl groups. Antiproliferative activities of L-1 to L-8{n-alkyl: methyl; L-1, ethyl; L-2, propyl; L-3 and butyl; L-4} were studied in cancer cells of colon (COLO205), brain (U87MG) and pancreas (MIAPaCa2) where L-1, L-2 and L-3 were active in MIAPaCa2 (L-1 = L-2 > L-3) and COLO205 (L-2 = L-3 > L-1) and inactive in U87MG. From antiproliferative studies with compounds L-1 to L-8 it can be concluded that homologation of 2-chloro-3-(n-alkylamino)-1,4-napthoquinone with saturated methyl groups yielded tissue specific compounds such as L-2 (for MIAPaCa2) and L-3 (for COLO205) with optimal activity.

Influence of chain length and double bond on the aqueous behavior of choline carboxylate soaps.

PubMed

Rengstl, Doris; Diat, Olivier; Klein, Regina; Kunz, Werner

2013-02-26

In preceding studies, we demonstrated that choline carboxylates ChC(m) with alkyl chain lengths of m = 12 - 18 are highly water-soluble (for m = 12, soluble up to 93 wt % soap and 0 °C). In addition, choline soaps are featured by an extraordinary lyotropic phase behavior. With decreasing water concentration, the following phases were found: micellar phase (L(1)), discontinuous cubic phase (I(1)' and I(1)"), hexagonal phase (H(1)), bicontinuous cubic phase (V(1)), and lamellar phase (L(α)). The present work is also focused on the lyotropic phase behavior of choline soaps but with shorter alkyl chains or different alkyl chain properties. We have investigated the aqueous phase behavior of choline soaps with C(8) and C(10) chain-lengths (choline octanoate and choline decanoate) and with a C(18) chain-length with a cis-double bond (choline oleate). We found that choline decanoate follows the lyotropic phase behavior of the longer-chain homologues mentioned above. Choline octanoate in water shows no discontinuous cubic phases, but an extended, isotropic micellar solution phase. In addition, choline octanoate is at the limit between a surfactant and a hydrotrope. The double bond in choline oleate leads also to a better solubility in water and a decrease of the solubilization temperature. It also influences the Gaussian curvature of the aggregates which results in a loss of discontinuous cubic phases in the binary phase diagram. The different lyotropic mesophases were identified by the penetration scan technique with polarizing light microscope and visual observations. To clarify the structural behavior small (SAXS) and wide (WAXS) angle X-ray scattering were performed. To further characterize the extended, isotropic micellar solution phase in the binary phase diagram of choline octanoate viscosity and conductivity measurements were also carried out.

Inhibitors of glycogen synthase 3 kinase

DOEpatents

Schultz, Peter; Ring, David B.; Harrison, Stephen D.; Bray, Andrew M.

2000-01-01

Compounds of formula 1: ##STR1## wherein R.sub.1 is alkyl, cycloalkyl, aryl, aralkyl, heteroaryl, or heteroaralkyl, substituted with 0-3 substituents selected from lower alkyl, halo, hydroxy, lower alkoxy, amino, lower alkyl-amino, and nitro; R.sub.2 is hydroxy, amino, or lower alkoxy; R.sub.3 is H, lower alkyl, lower acyl, lower alkoxy-acyl, or amnino-acyl; R.sub.4 is H or lower alkyl; and pharmaceutically acceptable salts and esters thereof; are effective inhibitors of GSK3.

Inhibitors of glycogen synthase 3 kinase

DOEpatents

Schultz, Peter; Ring, David B.; Harrison, Stephen D.; Bray, Andrew M.

2006-05-30

Compounds of formula 1: ##STR00001## wherein R.sub.1 is alkyl, cycloalkyl, aryl, aralkyl, heteroaryl, or heteroaralkyl, substituted with 0 3 substituents selected from lower alkyl, halo, hydroxy, lower alkoxy, amino, lower alkyl-amino, and nitro; R.sub.2 is hydroxy, amino, or lower alkoxy; R.sub.3 is H, lower alkyl, lower acyl, lower alkoxy-acyl, or amino-acyl; R.sub.4 is H or lower alkyl; and pharmaceutically acceptable salts and esters thereof; are effective inhibitors of GSK3.

Diketopyrrolopyrrole-Based Conjugated Polymer Entailing Triethylene Glycols as Side Chains with High Thin-Film Charge Mobility without Post-Treatments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, Si-Fen; Liu, Zi-Tong; Cai, Zheng-Xu

Side chain engineering of conjugated donor-acceptor polymers is a new way to manipulate their optoelectronic properties. Two new diketopyrrolopyrrole (DPP)-terthiophene-based conjugated polymers PDPP3T-1 and PDPP3T-2, with both hydrophilic triethylene glycol (TEG) and hydrophobic alkyl chains, are reported. It is demonstrated that the incorporation of TEG chains has a significant effect on the interchain packing and thin-film morphology with noticeable effect on charge transport. Polymer chains of PDPP3T-1 in which TEG chains are uniformly distributed can self-assemble spontaneously into a more ordered thin film. As a result, the thin film of PDPP3T-1 exhibits high saturated hole mobility up to 2.6 cm(2)more » V-1 s(-1) without any post-treatment. This is superior to those of PDPP3T with just alkyl chains and PDPP3T-2. Moreover, the respective field effect transistors made of PDPP3T-1 can be utilized for sensing ethanol vapor with high sensitivity (down to 100 ppb) and good selectivity.« less

Biophysical Characterization of the Strong Stabilization of the RNA Triplex poly(U)•poly(A)*poly(U) by 9-O-(ω-amino) Alkyl Ether Berberine Analogs

PubMed Central

Hossain, Maidul; Haq, Lucy; Suresh Kumar, Gopinatha

2012-01-01

Background Binding of two 9-O-(ω-amino) alkyl ether berberine analogs BC1 and BC2 to the RNA triplex poly(U)•poly(A)*poly(U) was studied by various biophysical techniques. Methodology/Principal Findings Berberine analogs bind to the RNA triplex non-cooperatively. The affinity of binding was remarkably high by about 5 and 15 times, respectively, for BC1 and BC2 compared to berberine. The site size for the binding was around 4.3 for all. Based on ferrocyanide quenching, fluorescence polarization, quantum yield values and viscosity results a strong intercalative binding of BC1 and BC2 to the RNA triplex has been demonstrated. BC1 and BC2 stabilized the Hoogsteen base paired third strand by about 18.1 and 20.5°C compared to a 17.5°C stabilization by berberine. The binding was entropy driven compared to the enthalpy driven binding of berbeine, most likely due to additional contacts within the grooves of the triplex and disruption of the water structure by the alkyl side chain. Conclusions/Significance Remarkably higher binding affinity and stabilization effect of the RNA triplex by the amino alkyl berberine analogs was achieved compared to berberine. The length of the alkyl side chain influence in the triplex stabilization phenomena. PMID:22666416

(13)C NMR substituent-induced chemical shifts in 4-(substituted phenyl)-3-phenyl-1,2,4-oxadiazol-5(4H)-ones (thiones).

PubMed

Kara, Yesim Saniye

2015-01-01

In the present, study mostly novel ten 4-(substituted phenyl)-3-phenyl-1,2,4-oxadiazol-5(4H)-ones and ten 4-(substituted phenyl)-3-phenyl-1,2,4-oxadiazol-5(4H)-thiones were synthesized. These oxadiazole derivatives were characterized by IR, (1)H NMR, (13)C NMR and elemental analyses. Their (13)C NMR spectra were measured in Deuterochloroform (CDCl3). The correlation analysis for the substituent-induced chemical shift (SCS) with Hammett substituent constants (σ), Brown Okamoto substituent constants (σ(+), σ(-)), inductive substituent constants (σI) and different of resonance substituent constants (σR, σR(o)) were performed using SSP (single substituent parameter), DSP (dual substituent parameter) and DSP-NLR (dual substituent parameter-non-linear resonance) methods, as well as single and multiple regression analysis. Negative ρ values were found for all correlations (reverse substituent effect). The results of all statistical analyses, (13)C NMR chemical shift of CN, CO and CS carbon of oxadiazole rings have shown satisfactory correlation. Copyright © 2015 Elsevier B.V. All rights reserved.

The formation of [M-H]+ ions in N-alkyl-substituted thieno[3,4-c]-pyrrole-4,6-dione derivatives during atmospheric pressure photoionization mass spectrometry.

PubMed

Sioud, Salim; Kharbatia, Najeh; Amad, Maan H; Zhu, Zhiyong; Cabanetos, Clement; Lesimple, Alain; Beaujuge, Pierre

2014-11-30

The formation of ions during atmospheric pressure photoionization (APPI) mass spectrometry in the positive mode usually provides radical cations and/or protonated species. Intriguingly, during the analysis of some N-alkyl-substituted thieno[3,4-c]pyrrole-4,6-dione (TPD) derivatives synthesized in our laboratory, unusual [M-H](+) ion peaks were observed. In this work we investigate the formation of [M-H](+) ions observed under APPI conditions. Multiple experimental parameters, including the type of ionization source, the composition of the solvent, the type of dopant, the infusion flow rate, and the length of the alkyl side chain were investigated to determine their effects on the formation of [M-H](+) ions. In addition, a comparison study of the gas-phase tandem mass spectrometric (MS/MS) fragmentation of [M + H](+) vs [M-H](+) ions and computational approaches were used. [M-H](+) ions were observed under APPI conditions. The type of dopant and the length of the alkyl chain affected the formation of these ions. MS/MS fragmentation of [M-H](+) and [M + H](+) ions exhibited completely different patterns. Theoretical calculations revealed that the loss of hydrogen molecules from the [M + H](+) ions is the most favourable condition under which to form [M-H](+) ions. [M-H](+) ions were detected in all the TPD derivatives studied here under the special experimental conditions during APPI, using a halogenated benzene dopant, and TPD containing substituted N-alkyl side chains with a minimum of four carbon atoms. Density functional theory calculations showed that for [M-H](+) ions to be formed under these conditions, the loss of hydrogen molecules from the [M + H](+)  ions is proposed to be necessary. Copyright © 2014 John Wiley & Sons, Ltd.

Sorbate-nitrite interactions: acetonitrile oxide as an alkylating agent.

PubMed

Pérez-Prior, M Teresa; Gómez-Bombarelli, Rafael; González-Pérez, Marina; Manso, José A; García-Santos, M Pilar; Calle, Emilio; Casado, Julio

2009-07-01

Because chemical species with DNA-damaging and mutagenic activity are formed in sorbate-nitrite mixtures and because sorbic acid sometimes coexists with nitrite occurring naturally or incorporated as a food additive, the study of sorbate-nitrite interactions is important. Here, the alkylating potential of the products resulting from such interactions was investigated. Drawn were the following conclusions: (i) Acetonitrile oxide (ACNO) is the compound responsible for the alkylating capacity of sorbate-nitrite mixtures; (ii) ACNO alkylates 4-(p-nitrobenzyl)pyridine (NBP), a trap for alkylating agents with nucleophilic characteristics similar to those of DNA bases, forming an adduct (AD; epsilon = 1.4 x 10(4) M(-1) cm(-1); lambda = 519 nm); (iii) the NBP alkylation reaction complies with the rate equation, r = d[AD]/dt = k(alk)(ACNO)[ACNO][NBP]-k(hyd)(AD)[AD], k(alk)(ACNO) being the NBP alkylation rate constant for ACNO and k(hyd)(AD) the rate constant for the adduct hydrolysis reaction; (iv) the small fraction of ACNO forming the adduct with NBP, as well as the small magnitude of the quotient (k(alk) (ACNO)/k(hyd)(ACNO)) as compared with those reported for other alkylating agents, such as some lactones and N-alkyl-N-nitrosoureas, reveals the ACNO effective alkylating capacity to be less significant; (v) the low value of the NBP-ACNO adduct life (defined as the total amount of adduct present along the progression of the NBP alkylation per unit of alkylating agent concentration) points to the high instability of this adduct; and (vi) the obtained results are in accordance with the low carcinogenicity of ACNO.

Cooperative alpha-helix formation of beta-lactoglobulin induced by sodium n-alkyl sulfates.

PubMed

Chamani, J; Moosavi-Movahedi, A A; Rajabi, O; Gharanfoli, M; Momen-Heravi, M; Hakimelahi, G H; Neamati-Baghsiah, A; Varasteh, A R

2006-01-01

It is generally assumed that folding intermediates contain partially formed native-like secondary structures. However, if we consider the fact that the conformational stability of the intermediate state is simpler than that of the native state, it would be expected that the secondary structures in a folding intermediate would not necessarily be similar to those of the native state. beta-Lactoglobulin is a predominantly beta-sheet protein, although it has a markedly high intrinsic preference for alpha-helical structure. The formation of non-native alpha-helical intermediate of beta-lactoglobulin was induced by n-alkyl sulfates including sodium octyl sulfate, SOS; sodium decyl sulfate, SDeS; sodium dodecyl sulfate, SDS; and sodium tetradecyl sulfate, STS at special condition. The effect of n-alkyl sulfates on the structure of native beta-lactoglobulin at pH 2 was utilized to investigate the contribution of hydrophobic interactions to the stability of non-native alpha-helical intermediate. The addition of various concentrations of n-alkyl sulfates to the native state of beta-lactoglobulin (pH 2) appears to support the stabilized form of non-native alpha-helical intermediate at pH 2. The m values of the intermediate state of beta-lactoglobulin by SOS, SDeS, SDS and STS showed substantial variation. The enhancement of m values as the stability criterion of non-native alpha-helical intermediate state corresponded with increasing chain length of the cited n-alkyl sulfates. The present results suggest that the folding reaction of beta-lactoglobulin follows a non-hierarchical mechanism and hydrophobic interactions play important roles in stabilizing the non-native alpha-helical intermediate state.

Sterol Alkyl Ethers in Immature Callovian (Middle Jurassic) Sediments of Pas de Calais and Normandy (France): Environmental Constraints on their Potential Origins.

NASA Astrophysics Data System (ADS)

Kenig, F. P. H.

2017-12-01

Steryl alkyl ethers (SAEs), steroids with C8-C12 alkyl ether substituent at C3have only been reported in a limited number of studies since their first identification in modern diatomaceous ooze (Boon and de Leeuw, 1979 Mar. Chem. 7, 117-132). These compounds were identified in Holocene to Eocene sediments, but only once in the Cretaceous, in the Valanginian sediments of Shasky Rise (Brassell, 2009; Palaeo Palaeo Palaeo 282, 45-57). The origin of these compounds remains unclear, though they have been proposed to be associated with diatoms and biologically productive environments and cold water. Here we report the occurrence of SAEs in Callovian (Middle Jurassic), thermally immature sediments of the Marnes d'Argences near Caen (Normandy, France) and near Le Wast (Pas de Calais, France), extanding their geological occurrence by 28 million years. These marls contain C36 to C41 SAEs with C9 or C10 alkyl moieties. The steroid moieties (C27 to C31) are saturated, unsaturated (at C5 or C22), or di-unsaturated (at C5 and C22). Some of the samples collected near Le Wast contain only 4-methyl substituted C27, C28 and C29 steroid moieties as well as steroid moieties typical of dinoflagellates such 4,23,24-trimethylsteroids saturated and unsaturated at C22, and diatoms such as 4-desmethyl-23,24-dimethyl-steroid. The origin of SAEs will be discussed in view of their novel identification in Jurassic sediments and considering the environment of deposition of the Marnes d'Argences and comparison with their stratigraphic equivalent in England (Oxford Clay) and Eastern France where none of these compounds were observed.

Alkylsilyl Peroxides as Alkylating Agents in the Copper-Catalyzed Selective Mono-N-Alkylation of Primary Amides and Arylamines.

PubMed

Sakamoto, Ryu; Sakurai, Shunya; Maruoka, Keiji

2017-07-06

The copper-catalyzed selective mono-N-alkylation of primary amides or arylamines using alkylsilyl peroxides as alkylating agents is reported. The reaction proceeds under mild reaction conditions and exhibits a broad substrate scope with respect to the alkylsilyl peroxides, as well as to the primary amides and arylamines. Mechanistic studies suggest that the present reaction should proceed through a free-radical process that includes alkyl radicals generated from the alkylsilyl peroxides. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Reactions of Tributylstannyl Anioniods with Alkyl Bromides.

DTIC Science & Technology

1981-09-28

g (12 mmol) of cesium tert-butoxide was added to the reaction vessel before the addition of n-butyllithium. Alkylation of Tributylstannyl Anionoids...Dry reaction vessels were purged with argon. The desired alkyl halide (1.0 mmol unless noted) and any desired additive were added to the reaction ...OFFICE OF NAVAL RESEARCH Contract N00014-79-C-0584 Task No. NR 053-714 TECHNICAL REPORT No. 2 Reactions of Tributylstannyl Anionoids with Alkyl

Experimental and theoretical study of substituent effect on 13C NMR chemical shifts of 5-arylidene-2,4-thiazolidinediones

NASA Astrophysics Data System (ADS)

Rančić, Milica P.; Trišović, Nemanja P.; Milčić, Miloš K.; Ajaj, Ismail A.; Marinković, Aleksandar D.

2013-10-01

The electronic structure of 5-arylidene-2,4-thiazolidinediones has been studied by using experimental and theoretical methodology. The theoretical calculations of the investigated 5-arylidene-2,4-thiazolidinediones have been performed by the use of quantum chemical methods. The calculated 13C NMR chemical shifts and NBO atomic charges provide an insight into the influence of such a structure on the transmission of electronic substituent effects. Linear free energy relationships (LFERs) have been further applied to their 13C NMR chemical shifts. The correlation analyses for the substituent-induced chemical shifts (SCS) have been performed with σ using SSP (single substituent parameter), field (σF) and resonance (σR) parameters using DSP (dual substituent parameter), as well as the Yukawa-Tsuno model. The presented correlations account satisfactorily for the polar and resonance substituent effects operative at Cβ, and C7 carbons, while reverse substituent effect was found for Cα. The comparison of correlation results for the investigated molecules with those obtained for seven structurally related styrene series has indicated that specific cross-interaction of phenyl substituent and groups attached at Cβ carbon causes increased sensitivity of SCS Cβ to the resonance effect with increasing of electron-accepting capabilities of the group present at Cβ.

Theoretical study of chain transfer to solvent reactions of alkyl acrylates.

PubMed

Moghadam, Nazanin; Srinivasan, Sriraj; Grady, Michael C; Rappe, Andrew M; Soroush, Masoud

2014-07-24

This computational and theoretical study deals with chain transfer to solvent (CTS) reactions of methyl acrylate (MA), ethyl acrylate (EA), and n-butyl acrylate (n-BA) self-initiated homopolymerization in solvents such as butanol (polar, protic), methyl ethyl ketone (MEK) (polar, aprotic), and p-xylene (nonpolar). The results indicate that abstraction of a hydrogen atom from the methylene group next to the oxygen atom in n-butanol, from the methylene group in MEK, and from a methyl group in p-xylene by a live polymer chain are the most likely mechanisms of CTS reactions in MA, EA, and n-BA. Energy barriers and molecular geometries of reactants, products, and transition states are predicted. The sensitivity of the predictions to three hybrid functionals (B3LYP, X3LYP, and M06-2X) and three different basis sets (6-31G(d,p), 6-311G(d), and 6-311G(d,p)) is investigated. Among n-butanol, sec-butanol, and tert-butanol, tert-butanol has the highest CTS energy barrier and the lowest rate constant. Although the application of the conductor-like screening model (COSMO) does not affect the predicted CTS kinetic parameter values, the application of the polarizable continuum model (PCM) results in higher CTS energy barriers. This increase in the predicted CTS energy barriers is larger for butanol and MEK than for p-xylene. The higher rate constants of chain transfer to n-butanol reactions compared to those of chain transfer to MEK and p-xylene reactions suggest the higher CTS reactivity of n-butanol.

Alkylation Damage by Lipid Electrophiles Targets Functional Protein Systems*

PubMed Central

Codreanu, Simona G.; Ullery, Jody C.; Zhu, Jing; Tallman, Keri A.; Beavers, William N.; Porter, Ned A.; Marnett, Lawrence J.; Zhang, Bing; Liebler, Daniel C.

2014-01-01

Protein alkylation by reactive electrophiles contributes to chemical toxicities and oxidative stress, but the functional impact of alkylation damage across proteomes is poorly understood. We used Click chemistry and shotgun proteomics to profile the accumulation of proteome damage in human cells treated with lipid electrophile probes. Protein target profiles revealed three damage susceptibility classes, as well as proteins that were highly resistant to alkylation. Damage occurred selectively across functional protein interaction networks, with the most highly alkylation-susceptible proteins mapping to networks involved in cytoskeletal regulation. Proteins with lower damage susceptibility mapped to networks involved in protein synthesis and turnover and were alkylated only at electrophile concentrations that caused significant toxicity. Hierarchical susceptibility of proteome systems to alkylation may allow cells to survive sublethal damage while protecting critical cell functions. PMID:24429493

Effects analysis of substituent characteristics and solvents on the photodegradation of polybrominated diphenyl ethers.

PubMed

Jiang, Long; Qiu, Youli; Li, Yu

2017-10-01

The ultraviolet spectra and electron transition information of 209 polybrominated diphenyl ethers (PBDEs) in gas were first calculated via time-dependent density functional theory using Gaussian 09 software. The main and second-order interactional effects of substituent characteristics on the photodegradation of PBDEs were then analysed using a full factorial experimental design. Solvent effects were considered to research the effect and promotion mechanism of solvent molecules on the photodegradation of PBDEs compared with that in gas. The results showed that the introduction of substituents at each position promoted excitation of PBDEs from their ground states to excited states to induce photodegradation. The different positions affected the photodegradation of PBDEs with magnitudes of para > meta > ortho. The congeners with a concentrated distribution of substituents can always be photodegraded more easily than those with separated substituents. From the viewpoint of light-induced reactions, the electron transfer reactions between molecules of PBDE* T1 and Solvent* T1 are the main driving force for the enhanced photodegradation of PBDEs in solvents compared with that in gas. Copyright © 2017 Elsevier Ltd. All rights reserved.

Structural design, synthesis and substituent effect of hydrazone-N-acylhydrazones reveal potent immunomodulatory agents.

PubMed

Meira, Cássio S; Dos Santos Filho, José Maurício; Sousa, Caroline C; Anjos, Pâmela S; Cerqueira, Jéssica V; Dias Neto, Humberto A; da Silveira, Rafael G; Russo, Helena M; Wolfender, Jean-Luc; Queiroz, Emerson F; Moreira, Diogo R M; Soares, Milena B P

2018-05-01

4-(Nitrophenyl)hydrazone derivatives of N-acylhydrazone were synthesized and screened for suppress lymphocyte proliferation and nitrite inhibition in macrophages. Compared to an unsubstituted N-acylhydrazone, active compounds were identified within initial series when hydroxyl, chloride and nitro substituents were employed. Structure-activity relationship was further developed by varying the position of these substituents as well as attaching structurally-related substituents. Changing substituent position revealed a more promising compound series of anti-inflammatory agents. In contrast, an N-methyl group appended to the 4-(nitrophenyl)hydrazone moiety reduced activity. Anti-inflammatory activity of compounds is achieved by modulating IL-1β secretion and prostaglandin E2 synthesis in macrophages and by inhibiting calcineurin phosphatase activity in lymphocytes. Compound SintMed65 was advanced into an acute model of peritonitis in mice, where it inhibited the neutrophil infiltration after being orally administered. In summary, we demonstrated in great details the structural requirements and the underlying mechanism for anti-inflammatory activity of a new family of hydrazone-N-acylhydrazone, which may represent a valuable medicinal chemistry direction for the anti-inflammatory drug development in general. Copyright © 2018 Elsevier Ltd. All rights reserved.

Chemistry of alkali cation exchanged faujasite and mesoporous NaX using alkyl halides and phosphates

NASA Astrophysics Data System (ADS)

Lee, Min-Hong

the length of the alkyl chain. Although introduced mesopores alleviated the limited reagent diffusion to reactive sites due to the microporosity of the NaX zeolites, no marked improvement in the product yields was achieved with either the 1-chloroalkanes or the trialkyl phosphates test compounds, regardless of alkyl chain length. The disappointing results have been attributed to lack of substantial net increase in the numbers of zeolite nucleophilic sites accompanying mesopore introduction.

Alkylating agents for Waldenstrom's macroglobulinaemia.

PubMed

Yang, Kun; Tan, Jianlong; Wu, Taixiang

2009-01-21

Waldenstrom's macroglobulinaemia (WM) is an uncommon B-cell lymphoproliferative disorder characterized by bone marrow infiltration and production of monoclonal immunoglobulin. Uncertainty remains if alkylating agents, such as chlorambucil, melphalan or cyclophosphamide, are an effective form of management. To assess the effects and safety of the alkylating agents on Waldenstrom's macroglobulinaemia (WM). We searched the Cochrane Central Register of Controlled Trials (Issue 1, 2008), MEDLINE (1966 to 2008), EMBASE (1980 to 2008), the Chinese Biomedical Base (1982 to 2008) and reference lists of articles.We also handsearched relevant conference proceedings from 1990 to 2008. Randomised controlled trials (RCTs) comparing alkylating agents given concomitantly with radiotherapy, splenectomy, plasmapheresis, stem-cell transplantation in patients with a confirmed diagnosis of WM. Two authors independently assessed trial quality and extracted data. We contacted study authors for additional information. We collected adverse effects information from the trials. One trial involving 92 participants with pretreated/relapsed WM compared the effect of fludarabine versus the combination of cyclophosphamide (the alkylating agent), doxorubicin and prednisone (CAP). Compared to CAP, the Hazard ratio (HR) for deaths of treatment with fludarabine was estimated to be 1.04, with a standard error of 0.30 (95% CI 0.58 to 1.48) and it indicated that the mean difference of median survival time was -4.00 months, and 16.00 months for response duration. The relative risks (RR) of response rate was 2.80 (95% CI 1.10 to 7.12). There were no statistically difference in overall survival rate and median survival months, while on the basis of response rate and response duration, fludarabine seemed to be superior to CAP for pretreated/relapsed patients with macroglobulinaemia. Although alkylating agents have been used for decades they have never actually been tested in a proper randomised trial. This

The alkyl amines effect on the optical properties of inorganic perovskite quantum dot

NASA Astrophysics Data System (ADS)

Yang, Ya-Zhu; Chung, Shu-Ru

2017-08-01

Perovskite quantum dots (P-QDs) is a new kind of optoelectronic materials in recent years. Compared with organic perovskite QDs (MAPbX3), inorganic perovskite QDs (CsPbX3) have a better stability. Inorganic P-QDs can be prepared at low temperature. Those novel QDs can be applied in solar cells, light-emitting diodes (LEDs), display, and biolables. Typical synthesis process to prepare CsPbX3 QDs is used oleic acid (OA) and cesium carbonate (Cs2CO3) to form Cs-oleate complex first. Moreover, the oleylamine (OLA) and octadecene (ODE) are used as capping agents. Cs-oleate complex then reacts with PbX2 to form CsPbX3 QDs (reacts for 5 s). As we know that the CsPbBr3 QDs emits green light, and its emission wavelength can be tuned by adding Cland Iions to replace Brion. However, the reaction rate of CsPbX3 QDs is fast, and it is not easy to control the emission wavelength by particle size. In this study, we use the saturated alkyl amines with difference of carbon chain length such as dodecylamine (DDA), hexadecylamine (HDA), and octadecylamine (ODA) to prepare CsPbBr3 QDs. The result shows that the emission spectra for all samples range from 489 (ODA) to 514 nm (DDA), the full width at half-maximum (FWHM) is between 23 to 28 nm, the surface morphologies of all samples are nearly spherical, and the quantum yields (QYs) are higher up to 130 % (compared with R6G and the excitation wavelength is 450 nm). Based on emission spectra we can find that the emission peaks are fixed even under different excitation wavelength, imply that the particle size distribution of QDs is uniform. Moreover, the emission wavelength blue shifts with increasing carbon chain length of amines. The stability of alkyl amine-capped CsPbBr3 QDs is good, especially for DDA-capped sample. We also find that a small emission peak around 462 nm can be only observed for DDA-capped sample. Furthermore, this small peak also can be observed even prolong the reaction time to 10 min. The emission wavelengths of Cs

Thermodynamic characterization of the interaction behavior of a hydrophobically modified polyelectrolyte and oppositely charged surfactants in aqueous solution: effect of surfactant alkyl chain length.

PubMed

Bai, Guangyue; Nichifor, Marieta; Lopes, António; Bastos, Margarida

2005-01-13

We have used a precision isothermal titration microcalorimeter (ITC) to measure the enthalpy curves for the interaction of a hydrophobically modified polyelectrolyte (D40OCT30) with oppositely charged surfactants (SC(n)S) in aqueous solution. D40OCT30 is a newly synthesized polymer based on dextran having pendant N-(2-hydroxypropyl)-N,N-dimethyl-N-octylammonium chloride groups randomly distributed along the polymer backbone with degree of substitution of 28.1%. The employed anionic surfactants are sodium octyl sulfate (SC(8)S) and sodium tetradecyl sulfate (SC(14)S). Microcalorimetric results along with turbidity and kinematic viscosity measurements demonstrate systematically the thermodynamic characterization of the interaction of D40OCT30/SC(n)S. A three-dimensional diagram with the derived phase boundaries is drawn to describe the effect of the alkyl chain length of surfactant and of the ratio between surfactant and pendant groups on the interaction. A more complete picture of the interaction mechanism for D40OCT30/SC(n)S systems is proposed here.

Improving Cellulose Dissolution in Ionic Liquids by Tuning the Size of the Ions: Impact of the Length of the Alkyl Chains in Tetraalkylammonium Carboxylate.

PubMed

Meng, Xiangqian; Devemy, Julien; Verney, Vincent; Gautier, Arnaud; Husson, Pascale; Andanson, Jean-Michel

2017-04-22

Twenty ionic liquids based on tetraalkylammonium cations and carboxylate anions have been synthesized, characterized, and tested for cellulose dissolution. The amount of cellulose dissolved in these ionic liquids depends strongly on the size of the ions: from 0 to 22 wt % cellulose can be dissolved at 90 °C. The best ionic liquids are less viscous and ammonium carboxylate based ionic liquids can dissolve as much as imidazolium-based ones. The viscosity of an ionic liquid can be decreased by the addition of DMSO as a cosolvent. After the addition of cosolvent, similar amounts of cellulose per ions are reached for most ionic liquids. As observed by rheology, ionic liquids with the longest alkyl chains form a gel when a high amount of cellulose is dissolved; this drastically limits their potential. Molecular simulations and IR spectroscopy have also been used with the aim of understanding how molecular interactions differ between efficient and inefficient ionic liquids. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

The Inhibition of Aluminum Corrosion in Sulfuric Acid by Poly(1-vinyl-3-alkyl-imidazolium Hexafluorophosphate)

PubMed Central

Arellanes-Lozada, Paulina; Olivares-Xometl, Octavio; Guzmán-Lucero, Diego; Likhanova, Natalya V.; Domínguez-Aguilar, Marco A.; Lijanova, Irina V.; Arce-Estrada, Elsa

2014-01-01

Compounds of poly(ionic liquid)s (PILs), derived from imidazole with different alkylic chain lengths located in the third position of the imidazolium ring (poly(1-vinyl-3-dodecyl-imidazolium) (PImC12), poly(1-vinyl-3-octylimidazolium) (PImC8) and poly(1-vinyl-3-butylimidazolium) (PImC4) hexafluorophosphate) were synthesized. These compounds were tested as corrosion inhibitors on aluminum alloy AA6061 in diluted sulfuric acid (0.1–1 M H2SO4) by weight loss tests, polarization resistance measurements and inductively coupled plasma optical emission spectroscopy. Langmuir’s isotherms suggested film formation on bare alloy while standard free energy indicated inhibition by a physisorption process. However, compound efficiencies as inhibitors ranked low (PImC12 > PImC8 > PImC4) to reach 61% for PImC12 in highly diluted acidic solution. Apparently, the high mobility of sulfates favored their adsorption in comparison to PILs. The surface film displayed general corrosion, and pitting occurred as a consequence of PILs’ partial inhibition along with a continuous dissolution of defective patchy film on formation. A slight improvement in efficiency was displayed by compounds having high molecular weight and a long alkyl chain, as a consequence of steric hindrance and PIL interactions. PMID:28788156

Spectroscopy Identification of Benzyl-Type Radicals Generated by Corona Discharge of Precursors of Mixed Substituents

NASA Astrophysics Data System (ADS)

Yoon, Young Wook; Huh, Chang Soon; Lee, Sang Kuk

2012-06-01

We generated vibronically excited but jet-cooled benzyl-type radicals from corona discharge of precursor of mixed substituents using a technique of corona excited supersonic expansion coupled with a pinhole-type glass nozzle, from which the visible vibronic emission spectra were recorded with a long-path monochromator. The spectra exhibit the intensity variation of each species with discharging voltage, indicating the radical species generated in corona discharge is highly sensitive to excitation. From the analysis of the spectra, we found the Cl substituent is replaced in preference to the F substituent by the hydrogen atoms liberated from the dissociation of the C-H bond of the methyl group of the precursor, from which we proposed the possible mechanism for the elimination reaction of substituent in terms of the bond dissociation energy. Additionally, we obtained an accurate electronic energy in the D_1 → D_0 transition and the vibrational mode frequencies of newly detected benzyl-type radicals in the ground electronic state by comparison with those of ab initio calculations and the known spectroscopic data of precursors for the first time.

Conformational arm-wrestling: battles for stereochemical control in benzamides bearing matched and mismatched chiral 2- and 6-substituents.

PubMed

Clayden, Jonathan; Foricher, Yann J Y; Helliwell, Madeleine; Johnson, Paul; Mitjans, David; Vinader, Victoria

2006-02-07

The orientation of a tertiary amide group adjacent to an aromatic ring may be governed by the stereochemistry of an adjacent chiral substituent. With a chiral substituent in both ortho positions, matched/mismatched pairs of isomers result. Evidence for matched stereochemistry is provided by the clean NMR spectra of single conformers, while mismatching gives poor or unexpected selectivities in the formation of chiral substituents, or mixtures of amide conformers. Attempts to use the match-mismatch effect to select for racemic pairs of enantiomeric substituents, and hence develop a "racemate-sequestering" reagent, are described, along with the use of "matching" to scavenge a single enantiomer of a diamine from material of incomplete enantiomeric purity.

Alkyl phosphonic acids and sulfonic acids in the Murchison meteorite

NASA Technical Reports Server (NTRS)

Cooper, George W.; Onwo, Wilfred M.; Cronin, John R.

1992-01-01

Homologous series of alkyl phosphonic acids and alkyl sulfonic acids, along with inorganic orthophosphate and sulfate, are identified in water extracts of the Murchison meteorite after conversion to their t-butyl dimethylsilyl derivatives. The methyl, ethyl, propyl, and butyl compounds are observed in both series. Five of the eight possible alkyl phosphonic acids and seven of the eight possible alkyl sulfonic acids through C4 are identified. Abundances decrease with increasing carbon number as observed of other homologous series indigenous to Murchison. Concentrations range downward from approximately 380 nmol/gram in the alkyl sulfonic acid series, and from 9 nmol/gram in the alkyl phosphonic acid series.

Critical behaviour and vapour-liquid coexistence of 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide ionic liquids via Monte Carlo simulations.

PubMed

Rai, Neeraj; Maginn, Edward J

2012-01-01

Atomistic Monte Carlo simulations are used to compute vapour-liquid coexistence properties of a homologous series of [C(n)mim][NTf2] ionic liquids, with n = 1, 2, 4, 6. Estimates of the critical temperatures range from 1190 K to 1257 K, with longer cation alkyl chains serving to lower the critical temperature. Other quantities such as critical density, critical pressure, normal boiling point, and accentric factor are determined from the simulations. Vapour pressure curves and the temperature dependence of the enthalpy of vapourisation are computed and found to have a weak dependence on the length of the cation alkyl chain. The ions in the vapour phase are predominately in single ion pairs, although a significant number of ions are found in neutral clusters of larger sizes as temperature is increased. It is found that previous estimates of the critical point obtained from extrapolating experimental surface tension data agree reasonably well with the predictions obtained here, but group contribution methods and primitive models of ionic liquids do not capture many of the trends observed in the present study

Alkyl polyglucose enhancing propionic acid enriched short-chain fatty acids production during anaerobic treatment of waste activated sludge and mechanisms.

PubMed

Luo, Jingyang; Feng, Leiyu; Chen, Yinguang; Sun, Han; Shen, Qiuting; Li, Xiang; Chen, Hong

2015-04-15

Adding alkyl polyglucose (APG) into an anaerobic treatment system of waste activated sludge (WAS) was reported to remarkably improve the production of short-chain fatty acids (SCFAs), especially propionic acid via simultaneously accelerating solubilization and hydrolysis, enhancing acidification, inhibiting methanogenesis and balancing carbon to nitrogen (C/N) ratio of substrate. Not only the production of SCFAs, especially propionic acid, was significantly improved by APG, but also the feasible operation time was shortened. The SCFAs yield at 0.3 g APG per gram of total suspended solids (TSS) within 4 d was 2988 ± 60 mg chemical oxygen demand (COD) per liter, much higher than that those from sole WAS or sole WAS plus sole APG. The corresponding yield of propionic acid was 1312 ± 25 mg COD/L, 7.9-fold of sole WAS. Mechanism investigation showed that during anaerobic treatment of WAS in the presence of APG both the solubilization and hydrolysis were accelerated and the acidification was enhanced, while the methanogenesis was inhibited. Moreover, the activities of key enzymes involved in WAS hydrolysis and acidification were improved through the adjustment of C/N ratio of substrates with APG. The abundance of microorganisms responsible for organic compounds hydrolysis and SCFAs production was also observed to be greatly enhanced with APG via 454 high-throughput pyrosequencing analysis. Copyright © 2015 Elsevier Ltd. All rights reserved.

40 CFR 721.2420 - Alkoxylated dialkyldiethylenetriamine, alkyl sulfate salt.

Code of Federal Regulations, 2013 CFR

2013-07-01

..., alkyl sulfate salt. 721.2420 Section 721.2420 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Specific Chemical Substances § 721.2420 Alkoxylated dialkyldiethylenetriamine, alkyl sulfate salt. (a... generically as an alkoxylated dialkyldiethylenetriamine, alkyl sulfate salt (PMN P-91-288) is subject to...

40 CFR 721.2420 - Alkoxylated dialkyldiethylenetriamine, alkyl sulfate salt.

Code of Federal Regulations, 2011 CFR

2011-07-01

..., alkyl sulfate salt. 721.2420 Section 721.2420 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Specific Chemical Substances § 721.2420 Alkoxylated dialkyldiethylenetriamine, alkyl sulfate salt. (a... generically as an alkoxylated dialkyldiethylenetriamine, alkyl sulfate salt (PMN P-91-288) is subject to...

40 CFR 721.2410 - Alkoxylated alkyldiethylenetriamine, alkyl sulfate salts.

Code of Federal Regulations, 2013 CFR

2013-07-01

..., alkyl sulfate salts. 721.2410 Section 721.2410 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Specific Chemical Substances § 721.2410 Alkoxylated alkyldiethylenetriamine, alkyl sulfate salts. (a... generically as alkoxylated dialkyldiethylenetriamine, alkyl sulfate salts (PMN P-94-325, 326, and 327) are...

40 CFR 721.2410 - Alkoxylated alkyldiethylenetriamine, alkyl sulfate salts.

Code of Federal Regulations, 2012 CFR

2012-07-01

..., alkyl sulfate salts. 721.2410 Section 721.2410 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Specific Chemical Substances § 721.2410 Alkoxylated alkyldiethylenetriamine, alkyl sulfate salts. (a... generically as alkoxylated dialkyldiethylenetriamine, alkyl sulfate salts (PMN P-94-325, 326, and 327) are...

40 CFR 721.2420 - Alkoxylated dialkyldiethylenetriamine, alkyl sulfate salt.

Code of Federal Regulations, 2014 CFR

2014-07-01

..., alkyl sulfate salt. 721.2420 Section 721.2420 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Specific Chemical Substances § 721.2420 Alkoxylated dialkyldiethylenetriamine, alkyl sulfate salt. (a... generically as an alkoxylated dialkyldiethylenetriamine, alkyl sulfate salt (PMN P-91-288) is subject to...

40 CFR 721.2420 - Alkoxylated dialkyldiethylenetriamine, alkyl sulfate salt.

Code of Federal Regulations, 2012 CFR

2012-07-01

..., alkyl sulfate salt. 721.2420 Section 721.2420 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Specific Chemical Substances § 721.2420 Alkoxylated dialkyldiethylenetriamine, alkyl sulfate salt. (a... generically as an alkoxylated dialkyldiethylenetriamine, alkyl sulfate salt (PMN P-91-288) is subject to...

40 CFR 721.2410 - Alkoxylated alkyldiethylenetriamine, alkyl sulfate salts.

Code of Federal Regulations, 2011 CFR

2011-07-01

..., alkyl sulfate salts. 721.2410 Section 721.2410 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Specific Chemical Substances § 721.2410 Alkoxylated alkyldiethylenetriamine, alkyl sulfate salts. (a... generically as alkoxylated dialkyldiethylenetriamine, alkyl sulfate salts (PMN P-94-325, 326, and 327) are...

40 CFR 721.2410 - Alkoxylated alkyldiethylenetriamine, alkyl sulfate salts.

Code of Federal Regulations, 2014 CFR

2014-07-01

..., alkyl sulfate salts. 721.2410 Section 721.2410 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Specific Chemical Substances § 721.2410 Alkoxylated alkyldiethylenetriamine, alkyl sulfate salts. (a... generically as alkoxylated dialkyldiethylenetriamine, alkyl sulfate salts (PMN P-94-325, 326, and 327) are...

The impact of alkyl sulfate surfactant geometry and electrolyte on the co-adsorption of anionic surfactants with model perfumes at the air-solution interface.

PubMed

Bradbury, Robert; Penfold, Jeffrey; Thomas, Robert K; Tucker, Ian M; Petkov, Jordan T; Jones, Craig

2013-08-01

The impact of surfactant geometry and electrolyte on the co-adsorption of anionic surfactants and model perfumes at the air-solution interface has been studied by neutron reflectivity. The more hydrophobic perfume linalool, competes more favourably for the surface with sodium dodecylsulfate than was previously reported for the anionic surfactant, sodium dodecyl 6-benzenesulfonate. Due to an increase in surface activity of the sodium dodecylsulfate, the addition of electrolyte results in a reduction in the linalool adsorption. Changing the alkyl chain length affects the relative adsorption of linalool and surfactant at the interface. Similar measurements for the different alkyl sulfates and with electrolyte with the more hydrophilic perfume phenyl ethanol, reveal broadly similar trends. Although the relative adsorption of phenyl ethanol with sodium dodecylsulfate is substantially enhanced compared to sodium dodecyl-6-benzenesulfonate the effects are not as significant as was observed with linalool. The variations with alkyl chain geometry show the importance of the hydrophobic interaction between the perfume and surfactant and changes in the packing constraints on the relative adsorption. The results highlight the importance of the specific interaction between the surfactant and perfume, and the surfactant and perfume geometries on the relative adsorption at the interface. Copyright © 2013 Elsevier Inc. All rights reserved.

Self-assembled structures of N-alkylated bisbenzimidazolyl naphthalene in aqueous media for highly sensitive detection of picric acid.

PubMed

Wu, Yan-Cheng; Luo, Shi-He; Cao, Liang; Jiang, Kai; Wang, Ling-Yun; Xie, Jie-Chun; Wang, Zhao-Yang

2017-07-11

A 2,6-dibenzimidazole-appended naphthalene derivative flanking with two N-alkyl chains (sensor 4) was designed and applied for highly sensitive detection of picric acid (PA) in aqueous media. Driven by the hydrophobicity of alkyl chain and π-π stacking effect of aryl, sensor 4 can undergo self-assembly to form an orderly rod-like structure in H 2 O/THF (v/v, 90/10) solution, as shown by the dynamic light scattering (DLS) and scanning electron microscopy (SEM) studies. Sensor 4 shows high selectivity and sensitivity toward PA over other nitroaromatic explosives. DFT calculations and 1 H NMR, the time-correlated single photon counting (TCSPC) experiments confirm that the quenching mechanism is due to both electron and energy transfer from the electron-rich sensor 4 to the electron-deficient PA. Sensor 4 can detect as low as 0.57 ppb PA in aqueous media and 11.46 ag cm -2 PA by contact mode. Importantly, sensor 4 exhibits low interference against common solvents, metal ions and anions. Thus, it is practically applicable for sensing PA in real environmental samples and vapor phase. Copyright © 2017 Elsevier B.V. All rights reserved.

Polymerization of Conducting Polymers Confined to Free Surfaces: A comparison of the Langmuir-Blodgett Polymerization of 3-Alkyl Pyrroles and 2- Alkyl Anilines

DTIC Science & Technology

1992-05-19

Confined to Free Surfaces: A Comparison of the Langmuir-Blodgett Polymerization of 3- Alkyl Pyrroles and 2- Alkyl Anilines Submitted for Publication in...Surfaces: A Comparison of the Langmuir Blodgett Polymerizations of 3- alkyl pyrroles and 2- alkyl anilines R. S. Duran and H.C. Zhou Dept. of Chemistry...polymerization reactions in more detail and compare them. To do this, the polymerization reactions were run under two conditions. In the first case

21 CFR 176.120 - Alkyl ketene dimers.

Code of Federal Regulations, 2011 CFR

2011-04-01

... section. (a) The alkyl ketene dimers are manufactured by the dehydrohalogenation of the acyl halides derived from the fatty acids of animal or vegetable fats and oils. (b) The alkyl ketene dimers are used as...

A Guide to Design Functional Molecular Liquids with Tailorable Properties using Pyrene-Fluorescence as a Probe.

PubMed

Lu, Fengniu; Takaya, Tomohisa; Iwata, Koichi; Kawamura, Izuru; Saeki, Akinori; Ishii, Masashi; Nagura, Kazuhiko; Nakanishi, Takashi

2017-06-13

Solvent-free, nonvolatile, room-temperature alkylated-π functional molecular liquids (FMLs) are rapidly emerging as a new generation of fluid matter. However, precision design to tune their physicochemical properties remains a serious challenge because the properties are governed by subtle π-π interactions among functional π-units, which are very hard to control and characterize. Herein, we address the issue by probing π-π interactions with highly sensitive pyrene-fluorescence. A series of alkylated pyrene FMLs were synthesized. The photophysical properties were artfully engineered with rational modulation of the number, length, and substituent motif of alkyl chains attached to the pyrene unit. The different emission from the excimer to uncommon intermediate to the monomer scaled the pyrene-pyrene interactions in a clear trend, from stronger to weaker to negligible. Synchronously, the physical nature of these FMLs was regulated from inhomogeneous to isotropic. The inhomogeneity, unexplored before, was thoroughly investigated by ultrafast time-resolved spectroscopy techniques. The result provides a clearer image of liquid matter. Our methodology demonstrates a potential to unambiguously determine local molecular organizations of amorphous materials, which cannot be achieved by conventional structural analysis. Therefore this study provides a guide to design alkylated-π FMLs with tailorable physicochemical properties.

The effects of characteristics of substituents on toxicity of the nitroaromatics: HiT QSAR study

NASA Astrophysics Data System (ADS)

Kuz'min, Victor E.; Muratov, Eugene N.; Artemenko, Anatoly G.; Gorb, Leonid; Qasim, Mohammad; Leszczynski, Jerzy

2008-10-01

The present study applies the Hierarchical Technology for Quantitative Structure-Activity Relationships (HiT QSAR) for (i) evaluation of the influence of the characteristics of 28 nitroaromatic compounds (some of which belong to a widely known class of explosives) as to their toxicity; (ii) prediction of toxicity for new nitroaromatic derivatives; (iii) analysis of the effects of substituents in nitroaromatic compounds on their toxicity in vivo. The 50% lethal dose concentration for rats (LD50) was used to develop the QSAR models based on simplex representation of molecular structure. The preliminary 1D QSAR results show that even the information on the composition of molecules reveals the main tendencies of changes in toxicity. The statistic characteristics for partial least squares 2D QSAR models are quite satisfactory ( R 2 = 0.96-0.98; Q 2 = 0.91-0.93; R 2 test = 0.89-0.92), which allows us to carry out the prediction of activity for 41 novel compounds designed by the application of new combinations of substituents represented in the training set. The comprehensive analysis of toxicity changes as a function of substituent position and nature was carried out. Molecular fragments that promote and interfere with toxicity were defined on the basis of the obtained models. It was shown that the mutual influence of substituents in the benzene ring plays a crucial role regarding toxicity. The influence of different substituents on toxicity can be mediated via different C-H fragments of the aromatic ring.

Effect analysis of quantum chemical descriptors and substituent characteristics on Henry's law constants of polybrominated diphenyl ethers at different temperatures.

PubMed

Long, Jiang; Youli, Qiu; Yu, Li

2017-11-01

Twelve substituent descriptors, 17 quantum chemical descriptors and 1/T were selected to establish a quantitative structure-property relationship (QSPR) model of Henry's law constants for 7 polybrominated diphenyl ethers (PBDEs) at five different temperatures. Then, the lgH of 202 congeners at different temperatures were predicted. The variation rule and regulating mechanism of lgH was studied from the perspectives of both quantum chemical descriptors and substituent characteristics. The R 2 for modeling and testing sets of the final QSPR model are 0.977 and 0.979, respectively, thus indicating good fitness and predictive ability for Henry' law constants of PBDEs at different temperatures. The favorable hydrogen binding sites are the 5,5',6,6'-positions for high substituent congeners and the O atom of the ether bond for low substituent congeners, which affects the interaction between PBDEs and water molecules. lgH is negatively and linearly correlated with 1/T, and the variation trends of lgH with temperature are primarily regulated by individual substituent characteristics, wherein: the more substituents involved, the smaller the lgH. The significant sequence for the main effect of substituent positions is para>meta>ortho, where the ortho-positions are mainly involved in second-order interaction effect (64.01%). Having two substituents in the same ring also provides a significant effect, with 81.36% of second-order interaction effects, particularly where there is an adjacent distribution (55.02%). Copyright © 2017 Elsevier Inc. All rights reserved.

IONIC LIQUID-CATALYZED ALKYLATION OF ISOBUTANE WITH 2-BUTENE

EPA Science Inventory

A detailed study of the alkylation of isobutane with 2-butene in ionic liquid media has been conducted using 1-alkyl-3-methylimidazolium halides?aluminum chloride encompassing various alkyl groups (butyl-, hexyl-, and octyl-) and halides (Cl, Br, and I) on its cations and anions,...

Nucleoside conformation is determined by the electronegativity of the sugar substituent.

PubMed Central

Guschlbauer, W; Jankowski, K

1980-01-01

The proton and 13C NMR spectra of uridine, deoxyuridine and four 2' substituted uridines (dUn, dUz, dUcl and dUfl) are reported. A linear relationship between the electronegativity of the 2'-substituent and the carbon-13 chemical shift of C2' is observed. Taking into account the effect of electronegativity by using the correction proposed by Karplus or by Jankowski, the proton-proton coupling constants have been used to compute the conformational equilibria of the six uridines. It is shown that the contribution of the N form (3'-endo -2'-exo) increases with the electronegativity of the 2' substituent. Thus dUfl contains some 85% N form in solution. - Applying similar corrections to published data in the adenosine series, a similar correlation is observed. This observation, that the most polar substituent pulls the pucker to its side, holds also for 3'-substituted compounds, like cordycepin (3'dAdo) and 3'-deoxy-3'-amino-adenosine. It is suggested that the influence of the electronegativity could be the dominating effect of nucleoside conformations and would also hold for arabinosides and xylosides. This effect should therefore also be the principal force which determines the differences between DNA and RNA. PMID:7433125

A theoretical investigation of substituent effects on the stability and reactivity of N-heterocyclic olefin carboxylates.

PubMed

Dong, Liang; Wen, Jun; Li, Weiyi

2015-08-21

A theoretical study of substituent effects on the stability and reactivity of novel synthesized N-heterocyclic olefin (NHO) carboxylates has been performed using a combination of density functional theory (DFT) calculations, molecular electrostatic potential (MESP) minimum and nucleophilicity index analyses. These calculations demonstrate that the nucleophilicity of free NHO is stronger than that of the NHO-CO2 adduct and, hence, the thermally unstable NHO-CO2 adduct should be a more efficient organocatalyst for nucleophile-mediated reactions. The stability of the NHO-CO2 adduct, as well as the reactivity of free NHO, is strongly dependent on the electronic and steric effects of the C- and N-substituents on the imidazole ring. This dependency is reflected by the measured MESP minimum for the carboxylate moiety, the NHO-CO2 adduct (Vmin1), and the terminal carbon atom of free NHO (Vmin2). C-Substituents exert only electronic effects while N-substituents exert both electronic and steric effects. In general, the electron-withdrawing groups on the C- and N-positions favor decarboxylation while weakening the reactivity of NHO. These positions favor decarboxylation due to the simultaneous decrease of the electronic density on the carboxyl moiety of the NHO-CO2 and the terminal carbon atom of olefins. Additionally, the balance between the stability of the NHO-CO2 and the reactivity of free NHO can be tuned by the combined effects of the C- and N-substituents. The introduction of weak electron-withdrawing groups at the C-position and aromatic substituents or similar ring-strained entities at the N-position favors decarboxylation of the NHO-CO2 adduct and ensures the free NHO as a strong nucleophile.

40 CFR 721.1878 - Alkali metal alkyl borohydride (generic).

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Alkali metal alkyl borohydride... Specific Chemical Substances § 721.1878 Alkali metal alkyl borohydride (generic). (a) Chemical substance... alkali metal alkyl borohydride (PMN P-00-1089) is subject to reporting under this section for the...

40 CFR 721.1878 - Alkali metal alkyl borohydride (generic).

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Alkali metal alkyl borohydride... Specific Chemical Substances § 721.1878 Alkali metal alkyl borohydride (generic). (a) Chemical substance... alkali metal alkyl borohydride (PMN P-00-1089) is subject to reporting under this section for the...

Enhanced antiamyloidal activity of hydroxy cinnamic acids by enzymatic esterification with alkyl alcohols.

PubMed

Kondo, Hazuki; Sugiyama, Haruka; Katayama, Shigeru; Nakamura, Soichiro

2014-01-01

Lipophilic derivatives of hydroxyl cinnamic acids (HCAs) including caffeic acid (CA), ferulic acid, sinapic acid (SA), and chlorogenic acid were synthesized by esterification with butanol, octanol, or hexadecanol catalyzed by the lipase from Candida antarctica to investigate the effect of lipophilicity on their antiamyloidal activity assessed by the inhibitory activities toward fibrillization of amyloid β (Aβ) peptide. Among them, CA showed the highest activity at 50 μM, reducing the amyloid fibril formation of Aβ to 34.4 ± 6.8%. The antiamyloidal effects of HCAs were enhanced by esterification with alkyl alcohols, and the longer alkyl chain tended to be more effective except for SA. Aβ fibril formation was suppressed by the hexadecyl ester of CA, which was reduced to 8.8 ± 2.3%. In contrast, those of octyl and butyl esters were 19.3 ± 2.3% and 41.6 ± 6.1%, respectively. These results show that lipophilicity plays an important role in the antiamyloidal activities of esterified phenolic compounds. © 2013 International Union of Biochemistry and Molecular Biology, Inc.

Grafting C8-C16 alkyl groups altered the self-assembly and curcumin -loading properties of sodium caseinate in water.

PubMed

Zhang, Yaqiong; Yang, Puyu; Yao, Fangyi; Liu, Jie; Yu, Liangli Lucy

2018-02-01

The data presented here are related to the research article entitled "Synthesis and characterization of alkylated caseinate, and its structure-curcumin loading property relationship in water" (Zhang et al., 2018) [1]. This data article reports the detailed spectra information for 1 H NMR, 13 C NMR and UPLC-Q-TOF MS of the N-succinimidyl fatty acid esters with various alkyl chain lengths (Cn-NHSs, n = 8, 12, 14 and 16). 1 H NMR, 13 C NMR and UPLC-Q-TOF MS spectra for C16-NHS are shown as an example. Then the stacked 1 H NMR spectra of the obtained alkylated caseinates (Cn-caseinates, n = 8, 12, 14 and 16) are provided. The surface hydrophobicity index (S 0 ) of Cn-caseinates with different substitution degrees (SD) of alkyl groups is shown. Additionally, Visual appearances for the formed aqueous dispersions of curcumin-loaded native caseinate (NaCas) and Cn-caseinates self-assemblies are shown. X-ray diffraction patterns of curcumin, C16-caseinate, its physical mixture and curcumin-loaded C16-caseinate self-assemblies are examined. The re-dispersibility and short-term storage stability of the curcumin-loaded NaCas and C16-caseinate self-assemblies are also studied.

Design and synthesis of highly potent benzodiazepine gamma-secretase inhibitors: preparation of (2S,3R)-3-(3,4-difluorophenyl)-2-(4-fluorophenyl)-4- hydroxy-N-((3S)-1-methyl-2-oxo-5- phenyl-2,3-dihydro-1H-benzo[e][1,4]-diazepin-3-yl)butyramide by use of an asymmetric Ireland-Claisen rearrangement.

PubMed

Churcher, Ian; Williams, Susie; Kerrad, Sonia; Harrison, Timothy; Castro, José L; Shearman, Mark S; Lewis, Huw D; Clarke, Earl E; Wrigley, Jonathan D J; Beher, Dirk; Tang, Yui S; Liu, Wensheng

2003-06-05

Novel benzodiazepine-containing gamma-secretase inhibitors for potential use in Alzheimer's disease have been designed that incorporate a substituted hydrocinnamide C-3 side chain. A syn combination of alpha-alkyl or aryl and beta-hydroxy or hydroxymethyl substituents was shown to give highly potent compounds. In particular, (2S,3R)-3-(3,4-difluorophenyl)-2-(4-fluorophenyl)-4-hydroxy-N-((3S)-2-oxo-5-phenyl-2,3-dihydro-1H-benzo[e][1,4]diazepin-3-yl)butyramide (34) demonstrated excellent in vitro potency (IC(50) = 0.06 nM). 34 could also be selectively methylated to give [(3)H]-28, which is of use in radioligand binding assays.

Synthesis and in vitro antiplasmodial evaluation of 7-chloroquinoline-chalcone and 7-chloroquinoline-ferrocenylchalcone conjugates.

PubMed

Raj, Raghu; Saini, Anu; Gut, Jiri; Rosenthal, Philip J; Kumar, Vipan

2015-05-05

The manuscript describes the synthesis of novel amide tethered 7-chloroquinoline-chalcone and 7-chloroquinoline-ferrocenylchalcone bifunctional hybrids and their evaluation as antimalarial agents against W2 resistant strain of Plasmodium falciparum. The antiplasmodial activity of 7-chloroquinoline-ferrocenylchalcones was found to be less than their corresponding simple chalcone conjugates. The presence of a methoxy substituent at para position of ring B on chalcones and longer alkyl chain length markedly improved the antiplasmodial profiles of the synthesized scaffolds with the most potent of the test compound exhibiting an IC50 value of 17.8 nM. Copyright © 2015 Elsevier Masson SAS. All rights reserved.

Uptake of perfluorinated alkyl acids by hydroponically grown lettuce (Lactuca sativa).

PubMed

Felizeter, Sebastian; McLachlan, Michael S; de Voogt, Pim

2012-11-06

An uptake study was carried out to assess the potential human exposure to perfluorinated alkyl acids (PFAAs) through the ingestion of vegetables. Lettuce (Lactuca sativa) was grown in PFAA-spiked nutrient solutions at four different concentrations, ranging from 10 ng/L to 10 μg/L. Eleven perfluorinated carboxylic acids (PFCAs) and three perfluorinated sulfonic acids (PFSAs) were analyzed by HPLC-MS/MS. At the end of the experiment, the major part of the total mass of each of the PFAAs (except the short-chain, C4-C7, PFCAs) taken up by plants appeared to be retained in the nonedible part, viz. the roots. Root concentration factors (RCF), foliage/root concentration factors (FRCF), and transpiration stream concentration factors (TSCF) were calculated. For the long chained PFAAs, RCF values were highest, whereas FRCF were lowest. This indicates that uptake by roots is likely governed by sorption of PFAAs to lipid-rich root solids. Translocation from roots to shoots is restricted and highly depending on the hydrophobicity of the compounds. Although the TSCF show that longer-chain PFCAs (e.g., perfluorododecanoic acid) get better transferred from the nutrient solution to the foliage than shorter-chain PFCAs (e.g., perfluoroheptanoic acid), the major fraction of longer-chain PFCAs is found in roots due to additional adsorption from the spiked solution. Due to the strong electron-withdrawing effect of the fluorine atoms the role of the negative charge of the dissociated PFAAs is likely insignificant.

Polyimide characterization studies - Effect of pendant alkyl groups

NASA Technical Reports Server (NTRS)

Jensen, B. J.; Young, P. R.

1984-01-01

The effect on selected polyimide properties when pendant alkyl groups were attached to the polymer backbone was investigated. A series of polymers were prepared using benzophenone tetracarboxylic acid dianhydride (BTDA) and seven different p-alkyl-m,p'-diaminobenzophenone monomers. The alkyl groups varied in length from C(1) (methyl) to C(9) (nonyl). The polyimide prepared from BTDA and m,p'-diaminobenzophenone was included as a control. All polymers were characterized by various chromatographic, spectroscopic, thermal, and mechanical techniques. Increasing the length of the pendant alkyl group resulted in a systematic decrease in glass transition temperature (Tg) for vacuum cured films. A 70 C decrease in Tg to 193 C was observed for the nonyl polymer compared to the Tg for the control. A corresponding systematic increase in Tg indicative of crosslinking, was observed for air cured films. Thermogravimetric analysis revealed a slight sacrifice in thermal stability with increasing alkyl length. No improvement in film toughness was observed.

Metallocene catalyst containing bulky organic group

DOEpatents

Marks, T.J.; Ja, L.; Yang, X.

1996-03-26

An ionic metallocene catalyst for olefin polymerization which comprises: (1) a cyclopentadienyl-type ligand, a Group IVB transition metal, and alkyl, aryl, or hydride substituents, as a cation, and (2) a weakly coordinating anion comprising boron substituted with halogenated, such as tetrafluoro-aryl substituents preferably containing silylalkyl substitution, such as para-silyl t-butyldimethyl.

Metallocene catalyst containing bulky organic group

DOEpatents

Marks, Tobin J.; Ja, Li; Yang, Xinmin

1996-03-26

An ionic metallocene catalyst for olefin polymerization which comprises: (1) a cyclopentadienyl-type ligand, a Group IVB transition metal, and alkyl, aryl, or hydride substituents, as a cation, and (2) a weakly coordinating anion comprising boron substituted with halogenated, such as tetra fluoro, aryl substituents preferably containing silylalkyl substitution, such as para-silyl t-butyldimethyl.

Dynamic adsorption properties of n-alkyl glucopyranosides determine their ability to inhibit cytolysis mediated by acoustic cavitation.

PubMed

Sostaric, Joe Z; Miyoshi, Norio; Cheng, Jason Y; Riesz, Peter

2008-10-09

Suspensions of human leukemia (HL-60) cells readily undergo cytolysis when exposed to ultrasound above the acoustic cavitation threshold. However, n-alkyl glucopyranosides (hexyl, heptyl, and octyl) completely inhibit ultrasound-induced (1057 kHz) cytolysis (Sostaric, et al. Free Radical Biol. Med. 2005, 39, 1539-1548). The efficacy of protection from ultrasound-induced cytolysis was determined by the n-alkyl chain length of the glucopyranosides, indicating that protection efficacy depended on adsorption of n-alkyl glucopyranosides to the gas/solution interface of cavitation bubbles and/or the lipid membrane of cells. The current study tests the hypothesis that "sonoprotection" (i.e., protection of cells from ultrasound-induced cytolysis) in vitro depends on the adsorption of glucopyranosides at the gas/solution interface of cavitation bubbles. To test this hypothesis, the effect of ultrasound frequency (from 42 kHz to 1 MHz) on the ability of a homologous series of n-alkyl glucopyranosides to protect cells from ultrasound-induced cytolysis was investigated. It is expected that ultrasound frequency will affect sonoprotection ability since the nature of the cavitation bubble field will change. This will affect the relative importance of the possible mechanisms for ultrasound-induced cytolysis. Additionally, ultrasound frequency will affect the lifetime and rate of change of the surface area of cavitation bubbles, hence the dynamically controlled adsorption of glucopyranosides to their surface. The data support the hypothesis that sonoprotection efficiency depends on the ability of glucopyranosides to adsorb at the gas/solution interface of cavitation bubbles.

Substituent effects in double-helical hydrogen-bonded AAA-DDD complexes.

PubMed

Wang, Hong-Bo; Mudraboyina, Bhanu P; Wisner, James A

2012-01-27

Two series of DDD and AAA hydrogen-bond arrays were synthesized that form triply-hydrogen-bonded double-helical complexes when combined in CDCl(3) solution. Derivatization of the DDD arrays with electron-withdrawing groups increases the complex association constants by up to a factor of 30 in those arrays examined. Derivatization of the AAA arrays with electron donating substituents reveals a similar magnitude effect on the complex stabilities. The effect of substitution on both types of arrays are modeled quite satisfactorily (R(2) > 0.96 in all cases) as free energy relationships with respect to the sums of their Hammett substituent constants. In all, the complex stabilities can be manipulated over more than three orders of magnitude (>20 kJ mol(-1)) using this type of modification. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Saturated amine oxides: Part 8. Hydroacridines: Part 27. Effects of N-oxidation and of N-quaternization on the 15N NMR chemical shifts of N-methylpiperidine-derived mono-, bi-, and tricycloaliphatic tertiary amines.

PubMed

Potmischil, Francisc; Duddeck, Helmut; Nicolescu, Alina; Deleanu, Calin

2007-03-01

The (15)N chemical shifts of 13 N-methylpiperidine-derived mono-, bi- and tricycloaliphatic tertiary amines, their methiodides and their N-epimeric pairs of N-oxides were measured, and the contributions of specific structural parameters to the chemical shifts were determined by multilinear regression analysis. Within the examined compounds, the effects of N-oxidation upon the (15)N chemical shifts of the amines vary from +56 ppm to +90 ppm (deshielding), of which approx. +67.7 ppm is due to the inductive effect of the incoming N(+)--O(-) oxygen atom, whereas the rest is due to the additive shift effects of the various C-alkyl substituents of the piperidine ring. The effects of quaternization vary from -3.1 ppm to +29.3 ppm, of which approx. +8.9 ppm is due to the inductive effect of the incoming N(+)--CH(3) methyl group, and the rest is due to the additive shift effects of the various C-alkyl substituents of the piperidine ring. The shift effects of the C-alkyl substituents in the amines, the N-oxides and the methiodides are discussed. Copyright (c) 2007 John Wiley & Sons, Ltd.

Carrier transport property of truxene discotic liquid crystals with three different ring substituents

NASA Astrophysics Data System (ADS)

Monobe, Hirosato; Ni, Hai-Liang; Hu, Ping; Wang, Bi-Qin; Zhao, Ke-Qing; Shimizu, Yo

2016-03-01

In this study, the charge carrier transport property of 3,8,13-trioctyloxytruxene [Trx(OC8)3] and its analogues, to which two different ring substituents of hydroxyl [Trx(OH)3(OC8)3] and methoxy [Trx(OMe)3(OC8)3] groups are introduced, has been studied relative to mesomorphism. Three analogues exhibit a hexagonal columnar (Colh) mesophase and their thermal stability increases with the introduction of hydroxyl and methoxy groups. The drift mobility measurements of Trx(OC8)3 and Trx(OH)3(OC8)3 reveal that the drift mobility is on the order of 5 × 10-2 cm2 V-1 s-1 in the Colh phase and it increases to 10-1 cm2 V-1 s-1 at the Colh-metastable phase transition, although Trx(OMe)3(OC8)3 shows a drift mobility of 1 × 10-2 cm2 V-1 s-1 in the Colh phase with temperature dependence. These results indicate that truxene with three alkoxy chains is an interesting molecular core for mesophase semiconductors.

A Convenient Approach to Synthesizing Peptide C-Terminal N-Alkyl Amides

PubMed Central

Fang, Wei-Jie; Yakovleva, Tatyana; Aldrich, Jane V.

2014-01-01

Peptide C-terminal N-alkyl amides have gained more attention over the past decade due to their biological properties, including improved pharmacokinetic and pharmacodynamic profiles. However, the synthesis of this type of peptide on solid phase by current available methods can be challenging. Here we report a convenient method to synthesize peptide C-terminal N-alkyl amides using the well-known Fukuyama N-alkylation reaction on a standard resin commonly used for the synthesis of peptide C-terminal primary amides, the PAL-PEG-PS (Peptide Amide Linker-polyethylene glycol-polystyrene) resin. The alkylation and oNBS deprotection were conducted under basic conditions and were therefore compatible with this acid labile resin. The alkylation reaction was very efficient on this resin with a number of different alkyl iodides or bromides, and the synthesis of model enkephalin N-alkyl amide analogs using this method gave consistently high yields and purities, demonstrating the applicability of this methodology. The synthesis of N-alkyl amides was more difficult on a Rink amide resin, especially the coupling of the first amino acid to the N-alkyl amine, resulting in lower yields for loading the first amino acid onto the resin. This method can be widely applied in the synthesis of peptide N-alkyl amides. PMID:22252422

Mass spectrometry of analytical derivatives. 1. Cyanide cations in the spectra of N-alkyl-N-perfluoroacyl-α-amino acids and their methyl esters

PubMed Central

Todua, Nino G.; Tretyakov, Kirill V.; Mikaia, Anzor I.

2016-01-01

The central mission for the development of the National Institute of Standards and Technology/National Institutes of Health/Environmental Protection Agency Mass Spectral Library is the acquisition of reference gas chromatography–mass spectrometry data for important compounds and their chemical modification products. The addition of reliable reference data of various derivatives of amino acids to The Library, and the study of their behavior under electron ionization conditions may be useful for their identification, structure elucidation, and a better understanding of the data obtained when the same derivatives are subjected to other ionization methods. N-Alkyl-N-perfluoroacyl derivatives of amino acids readily produce previously unreported alkylnitrilium cations of composition [HC≡N-alkyl]+. Homologous [HC≡N-aryl]+ cations are typical for corresponding N-aryl analogs. The formation of other ions characteristic for these derivatives involves oxygen rearrangement giving rise to ions [CnF2n+1–C≡N+–CnH2n+1] and [CnF2n+1–C≡N+-aryl]. The introduction of an N-benzyl substituent in a molecule favors a process producing benzylidene iminium cations. l-Threonine and l-cysteine derivatives exhibit more fragmentation pathways not typical for other α-amino acids; additionally, the Nω-amino group in l-lysine directs the dissociation process and provides structural information on the substitution at the amino functions in the molecule. PMID:26307698

Enhancement of endotoxin neutralization by coupling of a C12-alkyl chain to a lactoferricin-derived peptide

PubMed Central

2004-01-01

Antibacterial peptide acylation, which mimics the structure of the natural lipopeptide polymyxin B, increases antimicrobial and endotoxin-neutralizing activities. The interaction of the lactoferricin-derived peptide LF11 and its N-terminally acylated analogue, lauryl-LF11, with different chemotypes of bacterial lipopolysaccharide (LPS Re, Ra and smooth S form) was investigated by biophysical means and was related to the peptides' biological activities. Both peptides exhibit high antibacterial activity against the three strains of Salmonella enterica differing in the LPS chemotype. Lauryl-LF11 has one order of magnitude higher activity against Re-type, but activity against Ra- and S-type bacteria is comparable with that of LF11. The alkyl derivative peptide lauryl-LF11 shows a much stronger inhibition of the LPS-induced cytokine induction in human mononuclear cells than LF11. Although peptide–LPS interaction is essentially of electrostatic nature, the lauryl-modified peptide displays a strong hydrophobic component. Such a feature might then explain the fact that saturation of the peptide binding takes place at a much lower peptide/LPS ratio for LF11 than for lauryl-LF11, and that an overcompensation of the negative LPS backbone charges is observed for lauryl-LF11. The influence of LF11 on the gel-to-liquid-crystalline phase-transition of LPS is negligible for LPS Re, but clearly fluidizing for LPS Ra. In contrast, lauryl-LF11 causes a cholesterol-like effect in the two chemotypes, fluidizing in the gel and rigidifying of the hydrocarbon chains in the liquid-crystalline phase. Both peptides convert the mixed unilamellar/non-lamellar aggregate structure of lipid A, the ‘endotoxic principle’ of LPS, into a multilamellar one. These data contribute to the understanding of the mechanisms of the peptide-mediated neutralization of endotoxin and effect of lipid modification of peptides. PMID:15344905

Substituent and solvent effects on electronic absorption spectra of some N-(substitutedphenyl)benzene sulphonamides

NASA Astrophysics Data System (ADS)

Suganya, Krishnasamy; Kabilan, Senthamaraikannan

2004-04-01

The effects of substituents and solvents have been studied through the absorption spectra of nearly 23 ortho- and para-N-(substitutedphenyl)benzene sulphonamides in the range of 200-400 nm. The effects of substituents on the absorption spectra of compounds under present investigation are interpreted by correlation of absorption frequencies with simple and extended Hammett equations. Effect of solvent polarity and hydrogen bonding on the absorption spectra are interpreted by means of Kamlet equation and the results are discussed.

40 CFR 721.10677 - Alkyl phosphonate (generic).

Code of Federal Regulations, 2014 CFR

2014-07-01

... CONTROL ACT SIGNIFICANT NEW USES OF CHEMICAL SUBSTANCES Significant New Uses for Specific Chemical Substances § 721.10677 Alkyl phosphonate (generic). (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as alkyl phosphonate (PMN P-12-584...

Speciation of Reactive Sulfur Species and their Reactions with Alkylating Agents: Do we have any clue about what is present inside the cell?

PubMed

Bogdándi, Virág; Ida, Tomoaki; Sutton, Thomas R; Bianco, Christopher; Ditrói, Tamás; Koster, Grielof; Henthorn, Hillary A; Minnion, Magda; Toscano, John P; van der Vliet, Albert; Pluth, Michael D; Feelisch, Martin; Fukuto, Jon M; Akaike, Takaaki; Nagy, Péter

2018-06-17

Posttranslational modifications of cysteine (Cys) residues represent a major aspect of redox biology, and their reliable detection is key in providing mechanistic insights. The metastable character of these modifications and cell lysis-induced artifactual oxidation render current state-of-the-art protocols to rely on alkylation-based stabilization of labile Cys derivatives before cell/tissue rupture. An untested assumption in these procedures is that for all Cys derivatives alkylation rates are faster than their dynamic interchange. However, when the interconversion of Cys derivatives is not rate-limiting, then electrophilic labeling is under Curtin-Hammett control and hence the final alkylated mixture may not represent the speciation that prevailed before alkylation. We here present evidence that in the majority of cases, the speciation of alkylated polysulfide/thiol derivatives indeed depends on the experimental conditions. Our results reveal that alkylation perturbs sulfur speciation in both a concentration- and time-dependent manner, and that strong alkylating agents can cleave polysulfur chains. Moreover, we show that labeling of sulfenic acids with dimedone also affects Cys speciation, suggesting that part of the endogenous pool of products previously believed to represent sulfenic acid species may in fact represent polysulfides. These observations were obtained using buffered aqueous solutions of inorganic-, organic-, cysteine-, glutathione- and GAPDH-polysulfide species. Additional experiments in human plasma and serum revealed that monobromobimane can extract sulfide from the endogenous sulfur pool by shifting speciation equilibria, suggesting caution should be exercised when interpreting experimental results using this tool. We highlight methodological caveats potentially arising from these pitfalls and conclude that current derivatization strategies often fail to adequately capture physiologic speciation of sulfur species. This article is protected by

PREPARATION OF ALKYL PYROPHOSPHATE EXTRACTANTS

DOEpatents

Levine, C.A.; Skiens, W.E.; Moore, G.R.

1960-08-01

A process for providing superior solvent extractants for metal recovery processes is given wherein the extractant comprises an alkyl pyrophosphoric acid ester dissolved in an organic solvent diluent. Finely divided solid P/sub 2/O/ sub 5/ is slurried in an organic solvent-diluent selected from organic solvents such as kerosene, benzene, chlorobenzene, toluene, etc. An alcohol selected from the higher alcohols having 4 to 17 carbon atoms. e.g.. hexanol-1. heptanol-3, octanol-1. 2.6-dimethyl-heptanol-4, and decanol-1, is rapidly added to the P/sub 2/O/sub 5/ slurry in the amount of about 2 moles of alcohol to 1 mole of P/sub 2/ O/sub 5/. The temperature is maintained below about 110 deg C during the course of the P/sub 2/O/sub 5/-alcohol reaction. An alkyl pyrophosphate extractant compound is formed as a consequence of the reaction process. The alkyl pyrophosphate solvent-diluent extractant phase is useful in solvent extraction metal recovery processes.

Substituent Effects on Keto-Enol Equilibria Using NMR Spectroscopy

ERIC Educational Resources Information Center

Manbeck, Kimberly A.; Boaz, Nicholas C.; Bair, Nathaniel C.; Sanders, Allix M. S.; Marsh, Anderson L.

2011-01-01

In this extension to a classic physical chemistry experiment, students record the proton nuclear magnetic resonance spectra of the [beta]-diketones 2,4-pentanedione, 3-methyl-2,4-pentanedione, and 3-chloro-2,4-pentanedione to investigate the effect of substituents on keto-enol tautomerization equilibria. From the integrated intensities of keto and…

Structure-activity relationships of amide-phosphonate derivatives as inhibitors of the human soluble epoxide hydrolase.

PubMed

Kim, In-Hae; Park, Yong-Kyu; Nishiwaki, Hisashi; Hammock, Bruce D; Nishi, Kosuke

2015-11-15

Structure-activity relationships of amide-phosphonate derivatives as inhibitors of the human soluble epoxide hydrolase (sEH) were investigated. First, a series of alkyl or aryl groups were substituted on the carbon alpha to the phosphonate function in amide compounds to see whether substituted phosphonates can act as a secondary pharmacophore. A tert-butyl group (16) on the alpha carbon was found to yield most potent inhibition on the target enzyme. A 4-50-fold drop in inhibition was induced by other substituents such as aryls, substituted aryls, cycloalkyls, and alkyls. Then, the modification of the O-substituents on the phosphonate function revealed that diethyl groups (16 and 23) were preferable for inhibition to other longer alkyls or substituted alkyls. In amide compounds with the optimized diethylphosphonate moiety and an alkyl substitution such as adamantane (16), tetrahydronaphthalene (31), or adamantanemethane (36), highly potent inhibitions were gained. In addition, the resulting potent amide-phosphonate compounds had reasonable water solubility, suggesting that substituted phosphonates in amide inhibitors are effective for both inhibition potency on the human sEH and water solubility as a secondary pharmacophore. Copyright © 2015 Elsevier Ltd. All rights reserved.

Mixed-Substituent Cyclophosphazenes with Calamitic and Polycatenar Mesogens.

PubMed

Jiménez, J; Callizo, L; Serrano, J L; Barberá, J; Oriol, L

2017-07-17

A synthetic strategy has been developed to prepare liquid crystalline cyclotriphosphazenes that have two different types of mesogenic units linked to the same phosphorus atom. Hexachlorocyclotriphosphazene, N 3 P 3 Cl 6 , was reacted with 3 mol of the calamitic unit 4-cyano-4'-hydroxybiphenyl to give a mixture of compounds in which the nongem-trans-trisubstituted derivative N 3 P 3 Cl 3 (OC 6 H 4 C 6 H 4 {CN}-p) 3 was the major product. The substitution of all three chlorine atoms in this nongeminal compound gave rise to the hydroxyl-functional phosphazenes, nongem-trans-N 3 P 3 (OC 6 H 4 C 6 H 4 {CN}-p) 3 (OC 6 H 4 {OH}-p) 3 or nongem-trans-N 3 P 3 (OC 6 H 4 C 6 H 4 {CH 3 }-p) 3 (OC 6 H 4 {OH}-p) 3 , from which the second mesogenic unit, a polycatenar one, was introduced. The chemical structure of the resulting materials, deduced from spectroscopic and MALDI-TOF techniques, was in accordance with monodisperse, fully functionalized cyclotriphosphazenes. Mesomorphism is highly dependent on the terminal group of the calamitic units, and liquid crystal phases were only detected on the cyano-derivatives. The calamitic or columnar nature of the mesophase depends on the number of alkyl chains of the polycatenar moieties.

Substituents on Quinone Methides Strongly Modulate Formation and Stability of Their Nucleophilic Adducts

PubMed Central

Weinert, Emily E.; Dondi, Ruggero; Colloredo-Melz, Stefano; Frankenfield, Kristen N.; Mitchell, Charles H.; Freccero, Mauro; Rokita, Steven E.

2008-01-01

Electronic perturbation of quinone methides (QM) greatly influences their stability and in turn alters the kinetics and product profile of QM reaction with deoxynucleosides. Consistent with the electron deficient nature of this reactive intermediate, electron-donating substituents are stabilizing and electron-withdrawing substituents are destabilizing. For example, a dC N3-QM adduct is made stable over the course of observation (7 days) by the presence of an electron-withdrawing ester group that inhibits QM regeneration. Conversely, a related adduct with an electron donating methyl group is very labile and regenerates its QM with a half-life of approximately 5 hr. The generality of these effects is demonstrated with a series of alternative quinone methide precursors (QMP) containing a variety of substituents attached at different positions with respect to the exocyclic methylene. The rates of nucleophilic addition to substituted QMs measured by laser flash photolysis similarly span five orders of magnitude with electron rich species reacting most slowly and electron deficient species reacting most quickly. The reversibility of QM reaction can now be predictably adjusted for any desired application. PMID:16953635

Photooxidation products of polycyclic aromatic compounds containing sulfur.

PubMed

Bobinger, Stefan; Andersson, Jan T

2009-11-01

Photooxidation of crude oil components is an important process that removes pollutants from the environment. Polycyclic aromatic compounds (PACs) are known to be toxic to many life forms, but little is known about their photooxidation products in the aqueous phase. We here identify a large number of photoproducts from 11 benzothiophenes, a polycyclic aromatic sulfur heterocycle that is a major representative of PACs in crude oil. The investigated compounds contain two to four methyl groups and an ethyl or an n-octyl group. In water, the products arise through oxidation of alkyl side chains to aldehydes and carboxylic acids or through an opening in one of the aromatic rings. The product analysis was performed using gas chromatography with mass spectrometric or atomic emission detection. The main product is always a sulfobenzoic acid, which strongly lowers the pH of the solution. With long alkyl substituents, surfactants are formed, which may possess solubilizing properties in water. The larger the number of alkyl groups, the faster is the photooxidation. Several of the identified acidic compounds were also found when whole crude oil was photooxidized, showing that simulation with individual compounds reflects the situation in whole crude.

A Computational Study of Structure and Reactivity of N-Substitued-4-Piperidones Curcumin Analogues and Their Radical Anions.

PubMed

Martínez-Cifuentes, Maximiliano; Weiss-López, Boris; Araya-Maturana, Ramiro

2016-12-02

In this work, a computational study of a series of N -substitued-4-piperidones curcumin analogues is presented. The molecular structure of the neutral molecules and their radical anions, as well as their reactivity, are investigated. N -substituents include methyl and benzyl groups, while substituents on the aromatic rings cover electron-donor and electron-acceptor groups. Substitutions at the nitrogen atom do not significantly affect the geometry and frontier molecular orbitals (FMO) energies of these molecules. On the other hand, substituents on the aromatic rings modify the distribution of FMO. In addition, they influence the capability of these molecules to attach an additional electron, which was studied through adiabatic (AEA) and vertical electron affinities (VEA), as well as vertical detachment energy (VDE). To study electrophilic properties of these structures, local reactivity indices, such as Fukui ( f ⁺) and Parr ( P ⁺) functions, were calculated, and show the influence of the aromatic rings substituents on the reactivity of α,β-unsaturated ketones towards nucleophilic attack. This study has potential implications for the design of curcumin analogues based on a 4-piperidone core with desired reactivity.

Indolylarylsulfones as HIV-1 non-nucleoside reverse transcriptase inhibitors: new cyclic substituents at indole-2-carboxamide.

PubMed

La Regina, Giuseppe; Coluccia, Antonio; Brancale, Andrea; Piscitelli, Francesco; Gatti, Valerio; Maga, Giovanni; Samuele, Alberta; Pannecouque, Christophe; Schols, Dominique; Balzarini, Jan; Novellino, Ettore; Silvestri, Romano

2011-03-24

New indolylarylsulfone derivatives bearing cyclic substituents at indole-2-carboxamide linked through a methylene/ethylene spacer were potent inhibitors of the WT HIV-1 replication in CEM and PBMC cells with inhibitory concentrations in the low nanomolar range. Against the mutant L100I and K103N RT HIV-1 strains in MT-4 cells, compounds 20, 24-26, 36, and 40 showed antiviral potency superior to that of NVP and EFV. Against these mutant strains, derivatives 20, 24-26, and 40 were equipotent to ETV. Molecular docking experiments on this novel series of IAS analogues have also suggested that the H-bond interaction between the nitrogen atom in the carboxamide chain of IAS and Glu138:B is important in the binding of these compounds. These results are in accordance with the experimental data obtained on the WT and on the mutant HIV-1 strains tested.

Substituent effect study on experimental ¹³C NMR chemical shifts of (3-(substituted phenyl)-cis-4,5-dihydroisoxazole-4,5-diyl)bis(methylene)diacetate derivatives.

PubMed

Kara, Yesim S

2015-12-05

Eleven novel (3-(substituted phenyl)-cis-4,5-dihydroisoxazole-4,5-diyl)bis(methylene) diacetate derivatives were synthesized in the present study. These dihydroisoxazole derivatives were characterized by IR, (1)H NMR, (13)C NMR and elemental analyses. Their (13)C NMR spectra were measured in Deuterochloroform (CDCl3). The correlation analysis for the substituent-induced chemical shift (SCS) with Hammett substituent constant (σ), inductive substituent constant (σI), different of resonance substituent constants (σR, σR(o)) and Swain-Lupton substituent parameters (F, R) were performed using SSP (single substituent parameter), and DSP (dual substituent parameter) methods, as well as single and multiple regression analysis. From the result of regression analysis, the effect of substituent on the (13)C NMR chemical shifts was explained. Copyright © 2015 Elsevier B.V. All rights reserved.

Direct N-alkylation of unprotected amino acids with alcohols

PubMed Central

Yan, Tao; Feringa, Ben L.; Barta, Katalin

2017-01-01

N-alkyl amino acids find widespread application as highly valuable, renewable building blocks. However, traditional synthesis methodologies to obtain these suffer from serious limitations, providing a major challenge to develop sustainable alternatives. We report the first powerful catalytic strategy for the direct N-alkylation of unprotected α-amino acids with alcohols. This method is highly selective, produces water as the only side product leading to a simple purification procedure, and a variety of α-amino acids are mono- or di-N-alkylated, in most cases with excellent retention of optical purity. The hydrophobicity of the products is tunable, and even simple peptides are selectively alkylated. An iron-catalyzed route to mono-N-alkyl amino acids using renewable fatty alcohols is also described that represents an ideal green transformation for obtaining fully bio-based surfactants. PMID:29226249

Salvage of failed protein targets by reductive alkylation.

PubMed

Tan, Kemin; Kim, Youngchang; Hatzos-Skintges, Catherine; Chang, Changsoo; Cuff, Marianne; Chhor, Gekleng; Osipiuk, Jerzy; Michalska, Karolina; Nocek, Boguslaw; An, Hao; Babnigg, Gyorgy; Bigelow, Lance; Joachimiak, Grazyna; Li, Hui; Mack, Jamey; Makowska-Grzyska, Magdalena; Maltseva, Natalia; Mulligan, Rory; Tesar, Christine; Zhou, Min; Joachimiak, Andrzej

2014-01-01

The growth of diffraction-quality single crystals is of primary importance in protein X-ray crystallography. Chemical modification of proteins can alter their surface properties and crystallization behavior. The Midwest Center for Structural Genomics (MCSG) has previously reported how reductive methylation of lysine residues in proteins can improve crystallization of unique proteins that initially failed to produce diffraction-quality crystals. Recently, this approach has been expanded to include ethylation and isopropylation in the MCSG protein crystallization pipeline. Applying standard methods, 180 unique proteins were alkylated and screened using standard crystallization procedures. Crystal structures of 12 new proteins were determined, including the first ethylated and the first isopropylated protein structures. In a few cases, the structures of native and methylated or ethylated states were obtained and the impact of reductive alkylation of lysine residues was assessed. Reductive methylation tends to be more efficient and produces the most alkylated protein structures. Structures of methylated proteins typically have higher resolution limits. A number of well-ordered alkylated lysine residues have been identified, which make both intermolecular and intramolecular contacts. The previous report is updated and complemented with the following new data; a description of a detailed alkylation protocol with results, structural features, and roles of alkylated lysine residues in protein crystals. These contribute to improved crystallization properties of some proteins.

Salvage of Failed Protein Targets by Reductive Alkylation

PubMed Central

Tan, Kemin; Kim, Youngchang; Hatzos-Skintges, Catherine; Chang, Changsoo; Cuff, Marianne; Chhor, Gekleng; Osipiuk, Jerzy; Michalska, Karolina; Nocek, Boguslaw; An, Hao; Babnigg, Gyorgy; Bigelow, Lance; Joachimiak, Grazyna; Li, Hui; Mack, Jamey; Makowska-Grzyska, Magdalena; Maltseva, Natalia; Mulligan, Rory; Tesar, Christine; Zhou, Min; Joachimiak, Andrzej

2014-01-01

The growth of diffraction-quality single crystals is of primary importance in protein X-ray crystallography. Chemical modification of proteins can alter their surface properties and crystallization behavior. The Midwest Center for Structural Genomics (MCSG) has previously reported how reductive methylation of lysine residues in proteins can improve crystallization of unique proteins that initially failed to produce diffraction-quality crystals. Recently, this approach has been expanded to include ethylation and isopropylation in the MCSG protein crystallization pipeline. Applying standard methods, 180 unique proteins were alkylated and screened using standard crystallization procedures. Crystal structures of 12 new proteins were determined, including the first ethylated and the first isopropylated protein structures. In a few cases, the structures of native and methylated or ethylated states were obtained and the impact of reductive alkylation of lysine residues was assessed. Reductive methylation tends to be more efficient and produces the most alkylated protein structures. Structures of methylated proteins typically have higher resolution limits. A number of well-ordered alkylated lysine residues have been identified, which make both intermolecular and intramolecular contacts. The previous report is updated and complemented with the following new data; a description of a detailed alkylation protocol with results, structural features, and roles of alkylated lysine residues in protein crystals. These contribute to improved crystallization properties of some proteins. PMID:24590719

Balancing repair and tolerance of DNA damage caused by alkylating agents.

PubMed

Fu, Dragony; Calvo, Jennifer A; Samson, Leona D

2012-01-12

Alkylating agents constitute a major class of frontline chemotherapeutic drugs that inflict cytotoxic DNA damage as their main mode of action, in addition to collateral mutagenic damage. Numerous cellular pathways, including direct DNA damage reversal, base excision repair (BER) and mismatch repair (MMR), respond to alkylation damage to defend against alkylation-induced cell death or mutation. However, maintaining a proper balance of activity both within and between these pathways is crucial for a favourable response of an organism to alkylating agents. Furthermore, the response of an individual to alkylating agents can vary considerably from tissue to tissue and from person to person, pointing to genetic and epigenetic mechanisms that modulate alkylating agent toxicity.

Asymmetric synthesis of α-amino acids via homologation of Ni(II) complexes of glycine Schiff bases; Part 1: alkyl halide alkylations.

PubMed

Sorochinsky, Alexander E; Aceña, José Luis; Moriwaki, Hiroki; Sato, Tatsunori; Soloshonok, Vadim A

2013-10-01

Alkylations of chiral or achiral Ni(II) complexes of glycine Schiff bases constitute a landmark in the development of practical methodology for asymmetric synthesis of α-amino acids. Straightforward, easy preparation as well as high reactivity of these Ni(II) complexes render them ready available and inexpensive glycine equivalents for preparing a wide variety of α-amino acids, in particular on a relatively large scale. In the case of Ni(II) complexes containing benzylproline moiety as a chiral auxiliary, their alkylation proceeds with high thermodynamically controlled diastereoselectivity. Similar type of Ni(II) complexes derived from alanine can also be used for alkylation providing convenient access to quaternary, α,α-disubstituted α-amino acids. Achiral type of Ni(II) complexes can be prepared from picolinic acid or via recently developed modular approach using simple secondary or primary amines. These Ni(II) complexes can be easily mono/bis-alkylated under homogeneous or phase-transfer catalysis conditions. Origin of diastereo-/enantioselectivity in the alkylations reactions, aspects of practicality, generality and limitations of this methodology is critically discussed.

Interaction of albumin with perylene-diimides with aromatic substituents

NASA Astrophysics Data System (ADS)

Farooqi, Mohammed; Penick, Mark; Burch, Jessica; Negrete, George; Brancaleon, Lorenzo

2015-03-01

Polyaromatic hydrocarbons (PAH) binding to proteins remains one of the fundamental aspects of research in biophysics. Ligand binding can regulate the function of proteins. Binding to small ligands remains a very important aspect in the study of the function of many proteins. Perylene diimide or PDI derivatives have attracted initial interest as industrial dyes and pigments. Recently, much attention has been focused on their strong π - π stacks resulting from the large PDI aromatic core. These PDI stacks have distinct optical properties, and provide informative models that mimic the light-harvesting system and initial charge separation and charge transfer in the photosynthetic system. The absorption property of PDI derivatives may be largely tuned from visible to near-infrared region by chemical modifications at the bay-positions. We are currently studying a new class of PDI derivatives with substituents made of the side chains of aromatic amino acids (Tyrosine, Tryptophan and Phenylalanine). We have looked at the fluorescence absorption and emission of these PDIs in water and other organic solvents. PDIs show evidence of dimerization and possible aggregation. We also present binding studies of these PDIs with Human Serum Albumin (HSA). The binding was studied using fluorescence emission quenching of the HSA Tryptophan residue. Stern-Volmer equation is used to derive the quenching constants. PDI binding to HSA also has an effect on the fluorescence emission of the PDIs themselves by red shifting the spectra. Funded by RCMI grant.

Substituent effects on rates and torquoselectivities of electrocyclic ring-openings of N-substituted 2-azetines.

PubMed

Lopez, Steven A; Houk, K N

2014-07-03

Transition structures for the conrotatory electrocyclic ring-opening reactions of N-substituted 2-azetines were computed with the density functional M06-2X/6-31+G(d,p). A wide range of substituents from π acceptors (e.g., CHO, CN) to π donors (NMe2, OMe) was explored. Acceptor substituents delocalize the nitrogen lone pair and stabilize the reactant state of 2-azetines, while donors destabilize the 2-azetine reactant state. The conrotatory ring-opening is torquoselective, and the transition state for the outward rotation of the N-substituent and inward rotation of the nitrogen lone pair is preferred. This transition structure is stabilized by an interaction between the nitrogen lone pair and the vacant π* orbital. The activation free energies are linearly related to the reaction free energies and the Taft σR(0) parameter.

Fragmentation of Electrospray-produced Deprotonated Ions of Oligodeoxyribonucleotides Containing an Alkylated or Oxidized Thymidine

PubMed Central

Wang, Pengcheng; Williams, Renee T.; Guerrero, Candace R.; Ji, Debin; Wang, Yinsheng

2014-01-01

Alkylation and oxidation constitute major routes of DNA damage induced by endogenous and exogenous genotoxic agents. Understanding the biological consequences of DNA lesions often necessitates the availability of oligodeoxyribonucleotide (ODN) substrates harboring these lesions, and sensitive and robust methods for validating the identities of these ODNs. Tandem mass spectrometry is well suited for meeting these latter analytical needs. In the present study, we evaluated how the incorporation of an ethyl group to different positions (i.e., O2, N3 and O4) of thymine and the oxidation of its 5-methyl carbon impact collisionally activated dissociation (CAD) pathways of electrospray-produced deprotonated ions of ODNs harboring these thymine modifications. Unlike an unmodified thymine, which often manifests poor cleavage of the C3′-O3′ bond, the incorporation of an alkyl group to the O2 position and, to a much lesser extent, the O4 position, but not the N3 position of thymine, led to facile cleavage of the C3′-O3′ bond on the 3′ side of the modified thymine. Similar efficient chain cleavage was observed when thymine was oxidized to 5-formyluracil or 5-carboxyluracil, but not 5-hydroxymethyluracil. Additionally, with the support of computational modeling, we revealed that proton affinity and acidity of the modified nucleobases govern the fragmentation of ODNs containing the alkylated and oxidized thymidine derivatives, respectively. These results provided important insights into the effects of thymine modifications on ODN fragmentation. PMID:24664806

Identification of alkyl carbazoles and alkyl benzocarbazoles in Brazilian petroleum derivatives.

PubMed

Oliveira, Eniz Conceição; Vaz de Campos, Maria Cecília; Rodrigues, Maria Regina Alves; Pérez, Valéria Flores; Melecchi, Maria Inês Soares; Vale, Maria Goreti Rodrigues; Zini, Cláudia Alcaraz; Caramão, Elina Bastos

2006-02-10

Carbozoles are important compounds in crude oils, as they may be used as geochemical tracers, being the major type of nitrogen compounds in petroleum. At the same time, they are regarded as undesirable due to the problems they may cause in the refining process, such as catalyst poisoning, corrosion, gum or color formation in final products. As separation and identification of carbazoles are challenging goals, this work presents a chromatographic method, made of a pre-fractionation on neutral alumina followed by the separation and identification of two classes of carbazoles using FeCl(3)/Chromossorb W and gas chromatograph with mass spectrometer (GC/MS) (SIM-single ion monitoring mode) analysis. For the first time, a series of alkyl carbazoles and alkyl benzocarbazoles were identified in heavy gas oil (HGO) and atmospheric residue of distillation (ARD) obtained from Brazilian petroleum.

Substituent and solvent effects on electronic absorption spectra of some N-(substitutedphenyl)benzene sulphonamides.

PubMed

Suganya, Krishnasamy; Kabilan, Senthamaraikannan

2004-04-01

The effects of substituents and solvents have been studied through the absorption spectra of nearly 23 ortho- and para-N-(substitutedphenyl)benzene sulphonamides in the range of 200-400 nm. The effects of substituents on the absorption spectra of compounds under present investigation are interpreted by correlation of absorption frequencies with simple and extended Hammett equations. Effect of solvent polarity and hydrogen bonding on the absorption spectra are interpreted by means of Kamlet equation and the results are discussed. Copyright 2003 Elsevier B.V.

40 CFR 721.10548 - Mixed alkyl phosphate esters alkoxylated (generic).

Code of Federal Regulations, 2013 CFR

2013-07-01

... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Mixed alkyl phosphate esters... Specific Chemical Substances § 721.10548 Mixed alkyl phosphate esters alkoxylated (generic). (a) Chemical... as mixed alkyl phosphate esters alkoxylated (PMN P-04-624) is subject to reporting under this section...

40 CFR 721.10548 - Mixed alkyl phosphate esters alkoxylated (generic).

Code of Federal Regulations, 2014 CFR

2014-07-01

... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Mixed alkyl phosphate esters... Specific Chemical Substances § 721.10548 Mixed alkyl phosphate esters alkoxylated (generic). (a) Chemical... as mixed alkyl phosphate esters alkoxylated (PMN P-04-624) is subject to reporting under this section...

Homogeneous synthesis of cellulose acrylate-g-poly (n-alkyl acrylate) solid-solid phase change materials via free radical polymerization.

PubMed

Qian, Yong-Qiang; Han, Na; Bo, Yi-Wen; Tan, Lin-Li; Zhang, Long-Fei; Zhang, Xing-Xiang

2018-08-01

A novel solid-solid phase change materials, namely, cellulose acrylate-g-poly (n-alkyl acrylate) (CA-g-PAn) (n = 14, 16 and 18) were successfully synthesized by free radical polymerization in N, N-dimethylacetamide (DMAc). The successful grafting was confirmed by fourier transform infrared spectra (FT-IR) and nuclear magnetic resonance (NMR). The properties of the CA-g-PAn copolymers were investigated by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA). The phase change temperatures and the melting enthalpies of CA-g-PAn copolymers are in the range of 10.1-53.2 °C and 15-95 J/g, respectively. It can be adjusted by the contents of poly (n-alkyl acrylate) and the length of alkyl side-chain. The thermal resistant temperatures of CA-g-PA14, 16 and 18 copolymers are 308 °C, 292 °C and 273 °C, respectively. It show that all of grafting materials exhibit good thermal stability and shape stability. Therefore, it is expected to be applied in the cellulose-based thermos-regulating field. Copyright © 2018 Elsevier Ltd. All rights reserved.

Anticancer activity of botanical alkyl hydroquinones attributed to topoisomerase II poisoning

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huang, C.-P.; Fang, W.-H.; Lin, L.-I.

2008-03-15

Cytotoxic alkyl hydroquinone compounds have been isolated from many plants. We previously isolated 3 structurally similar cytotoxic alkyl hydroquinone compounds from the sap of the lacquer tree Rhus succedanea L. belonging to the sumac family, which have a long history of medicinal use in Asia. Each has an unsaturated alkyl chain attached to the 2-position of a hydroquinone ring. One of these isolates, 10'(Z),13'(E),15'(E)-heptadecatrienylhydroquinone [HQ17(3)], being the most cytotoxic, was chosen for studying the anticancer mechanism of these compounds. We found that HQ17(3) was a topoisomerase (Topo) II poison. It irreversibly inhibited Topo II{alpha} activity through the accumulation of Topomore » II-DNA cleavable complexes. A cell-based assay showed that HQ17(3) inhibited the growth of leukemia HL-60 cells with an EC{sub 50} of 0.9 {mu}M, inhibited the topoisomerase-II-deficient cells HL-60/MX2 with an EC{sub 50} of 9.6 {mu}M, and exerted no effect on peripheral blood mononuclear cells at concentrations up to 50 {mu}M. These results suggest that Topo II is the cellular drug target. In HL-60 cells, HQ17(3) promptly inhibited DNA synthesis, induced chromosomal breakage, and led to cell death with an EC{sub 50} about one-tenth that of hydroquinone. Pretreatment of the cells with N-acetylcysteine could not attenuate the cytotoxicity and DNA damage induced by HQ17(3). However, N-acetylcysteine did significantly reduce the cytotoxicity of hydroquinone. In F344 rats, intraperitoneal injection of HQ17(3) for 28 days induced no clinical signs of toxicity. These results indicated that HQ17(3) is a potential anticancer agent, and its structural features could be a model for anticancer drug design.« less

40 CFR 721.5380 - Mixed alkyl phenolic novolak resin (generic).

Code of Federal Regulations, 2014 CFR

2014-07-01

... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Mixed alkyl phenolic novolak resin... Specific Chemical Substances § 721.5380 Mixed alkyl phenolic novolak resin (generic). (a) Chemical... as mixed alkyl phenolic novolak resin (PMN P-98-718) is subject to reporting under this section for...

40 CFR 721.5380 - Mixed alkyl phenolic novolak resin (generic).

Code of Federal Regulations, 2012 CFR

2012-07-01

... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Mixed alkyl phenolic novolak resin... Specific Chemical Substances § 721.5380 Mixed alkyl phenolic novolak resin (generic). (a) Chemical... as mixed alkyl phenolic novolak resin (PMN P-98-718) is subject to reporting under this section for...

40 CFR 721.5380 - Mixed alkyl phenolic novolak resin (generic).

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Mixed alkyl phenolic novolak resin... Specific Chemical Substances § 721.5380 Mixed alkyl phenolic novolak resin (generic). (a) Chemical... as mixed alkyl phenolic novolak resin (PMN P-98-718) is subject to reporting under this section for...

40 CFR 721.5380 - Mixed alkyl phenolic novolak resin (generic).

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Mixed alkyl phenolic novolak resin... Specific Chemical Substances § 721.5380 Mixed alkyl phenolic novolak resin (generic). (a) Chemical... as mixed alkyl phenolic novolak resin (PMN P-98-718) is subject to reporting under this section for...

40 CFR 721.5380 - Mixed alkyl phenolic novolak resin (generic).

Code of Federal Regulations, 2013 CFR

2013-07-01

... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Mixed alkyl phenolic novolak resin... Specific Chemical Substances § 721.5380 Mixed alkyl phenolic novolak resin (generic). (a) Chemical... as mixed alkyl phenolic novolak resin (PMN P-98-718) is subject to reporting under this section for...

40 CFR 721.10493 - Tris-alkyl-alkoxy melamine polymer (generic).

Code of Federal Regulations, 2013 CFR

2013-07-01

... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Tris-alkyl-alkoxy melamine polymer... Specific Chemical Substances § 721.10493 Tris-alkyl-alkoxy melamine polymer (generic). (a) Chemical... as tris-alkyl-alkoxy melamine polymer (PMN P-05-417) is subject to reporting under this section for...

40 CFR 721.10493 - Tris-alkyl-alkoxy melamine polymer (generic).

Code of Federal Regulations, 2014 CFR

2014-07-01

... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Tris-alkyl-alkoxy melamine polymer... Specific Chemical Substances § 721.10493 Tris-alkyl-alkoxy melamine polymer (generic). (a) Chemical... as tris-alkyl-alkoxy melamine polymer (PMN P-05-417) is subject to reporting under this section for...

Selective alkylation of T–T mismatched DNA using vinyldiaminotriazine–acridine conjugate

PubMed Central

Onizuka, Kazumitsu; Usami, Akira; Yamaoki, Yudai; Kobayashi, Tomohito; Hazemi, Madoka E; Chikuni, Tomoko; Sato, Norihiro; Sasaki, Kaname; Katahira, Masato

2018-01-01

Abstract The alkylation of the specific higher-order nucleic acid structures is of great significance in order to control its function and gene expression. In this report, we have described the T–T mismatch selective alkylation with a vinyldiaminotriazine (VDAT)–acridine conjugate. The alkylation selectively proceeded at the N3 position of thymidine on the T–T mismatch. Interestingly, the alkylated thymidine induced base flipping of the complementary base in the duplex. In a model experiment for the alkylation of the CTG repeats DNA which causes myotonic dystrophy type 1 (DM1), the observed reaction rate for one alkylation increased in proportion to the number of T–T mismatches. In addition, we showed that primer extension reactions with DNA polymerase and transcription with RNA polymerase were stopped by the alkylation. The alkylation of the repeat DNA will efficiently work for the inhibition of replication and transcription reactions. These functions of the VDAT–acridine conjugate would be useful as a new biochemical tool for the study of CTG repeats and may provide a new strategy for the molecular therapy of DM1. PMID:29309639

The effect of varying halogen substituent patterns on the cytochrome P450 catalysed dehalogenation of 4-halogenated anilines to 4-aminophenol metabolites.

PubMed

Cnubben, N H; Vervoort, J; Boersma, M G; Rietjens, I M

1995-05-11

The cytochrome P450 catalysed biotransformation of 4-halogenated anilines was studied in vitro with special emphasis on the dehalogenation to 4-aminophenol metabolites. The results demonstrated that a fluorine substituent at the C4 position was more easily eliminated from the aromatic ring than a chloro-, bromo- or iodo-substituent. HPLC analysis of in vitro biotransformation patterns revealed that the dehalogenation of the C4-position was accompanied by formation of non-halogenated 4-aminophenol, without formation of NIH-shifted metabolites. Changes in the apparent Vmax for the microsomal oxidative dehalogenation appeared to correlate with the electronegativity of the halogen substituent at C4, the fluorine substituent being the one most easily eliminated. A similar decrease in the rate of dehalogenation from a fluoro- to a chloro- to a bromo- to an iodo-substituent was observed in a system with purified reconstituted cytochrome P450 IIB1, in a tertiair butyl hydroperoxide supported microsomal cytochrome P450 system as well as in a system with microperoxidase 8. This microperoxidase 8 is a haem-based mini-enzyme without a substrate binding site, capable of catalysing cytochrome P450-like reaction chemistry. Together, these results excluded the possibility that the difference in the rate of dehalogenation with a varying C4-halogen substituent arose from a change in the contribution of cytochrome P450 enzymes involved in oxidative dehalogenation with a change in the halogen substituent. Rather, they strongly suggested that the difference was indeed due to an intrinsic electronic parameter of the various C4 halogenated anilines dependent on the type of halogen substituent. Additional in vitro experiments with polyfluorinated anilines demonstrated that elimination of the C4-fluorine substituent became more difficult upon the introduction of additional electron withdrawing fluorine substituents in the aniline-ring. 19F-NMR analysis of the metabolite patterns showed

Synthesis of pyridine-fused perylene imides with an amidine moiety for hydrogen bonding.

PubMed

Ito, Satoru; Hiroto, Satoru; Shinokubo, Hiroshi

2013-06-21

Pyridine-fused perylene tetracarboxylic acid bisimides (PBIs) were synthesized via Suzuki-Miyaura coupling and acid condensation. The fused PBIs with electron-donating substituents exhibited an intramolecular charge transfer interaction. One of the N-alkyl substituents was selectively removed with BBr3 to create an amidine guest binding site. A hydrogen bonding interaction with pentafluorobenzoic acid changed the absorption spectra and enhanced fluorescence.

Interrogating alkyl and arylalkylpolyamino (bis)urea and (bis)thiourea isosteres as potent antimalarial chemotypes against multiple lifecycle forms of Plasmodium falciparum parasites.

PubMed

Verlinden, Bianca K; de Beer, Marna; Pachaiyappan, Boobalan; Besaans, Ethan; Andayi, Warren A; Reader, Janette; Niemand, Jandeli; van Biljon, Riette; Guy, Kiplin; Egan, Timothy; Woster, Patrick M; Birkholtz, Lyn-Marie

2015-08-15

A new series of potent potent aryl/alkylated (bis)urea- and (bis)thiourea polyamine analogues were synthesized and evaluated in vitro for their antiplasmodial activity. Altering the carbon backbone and terminal substituents increased the potency of analogues in the compound library 3-fold, with the most active compounds, 15 and 16, showing half-maximal inhibitory concentrations (IC50 values) of 28 and 30 nM, respectively, against various Plasmodium falciparum parasite strains without any cross-resistance. In vitro evaluation of the cytotoxicity of these analogues revealed marked selectivity towards targeting malaria parasites compared to mammalian HepG2 cells (>5000-fold lower IC50 against the parasite). Preliminary biological evaluation of the polyamine analogue antiplasmodial phenotype revealed that (bis)urea compounds target parasite asexual proliferation, whereas (bis)thiourea compounds of the same series have the unique ability to block transmissible gametocyte forms of the parasite, indicating pluripharmacology against proliferative and non-proliferative forms of the parasite. In this manuscript, we describe these results and postulate a refined structure-activity relationship (SAR) model for antiplasmodial polyamine analogues. The terminally aryl/alkylated (bis)urea- and (bis)thiourea-polyamine analogues featuring a 3-5-3 or 3-6-3 carbon backbone represent a structurally novel and distinct class of potential antiplasmodials with activities in the low nanomolar range, and high selectivity against various lifecycle forms of P. falciparum parasites. Copyright © 2015 Elsevier Ltd. All rights reserved.

Alkyl chitosan film-high strength, functional biomaterials.

PubMed

Lu, Li; Xing, Cao; Xin, Shen; Shitao, Yu; Feng, Su; Shiwei, Liu; Fusheng, Liu; Congxia, Xie

2017-11-01

Biofilm with strong tensile strength is a topic item in the area of tissue engineering, medicine engineering, and so forth. Here we introduced an alkyl chitosan film with strong tensile strength and its possibility for an absorbable anticoagulation material in vivo was tested in the series of blood test, such as dynamic coagulation time, plasma recalcification time and hemolysis. Alkyl chitosan film was a better biomaterial than traditional chitosan film in the anticoagulation, tissue compatibility and cell compatibility. The unique trait of alkyl chitosan film may be for its greater contact angle and hydrophobicity ability to reduce the adsorption capacity for the blood component and the activity of fibrinolytic enzymes, enhance the antibacterial capacity than chitosan film. Moreover, none of chitosan film or butyl chitosan film exhibited quick inflammation or other disadvantage and degraded quickly by implanted test. Therefore, Alkyl chitosan film is of prospective properties as an implantable, absorbable agent for tissue heals, and this material need further research. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 3034-3041, 2017. © 2017 Wiley Periodicals, Inc.

Summertime C1-C5 alkyl nitrates over Beijing, northern China: Spatial distribution, regional transport, and formation mechanisms

NASA Astrophysics Data System (ADS)

Sun, Jingjing; Li, Zeyuan; Xue, Likun; Wang, Tao; Wang, Xinfeng; Gao, Jian; Nie, Wei; Simpson, Isobel J.; Gao, Rui; Blake, Donald R.; Chai, Fahe; Wang, Wenxing

2018-05-01

Alkyl nitrates (RONO2) are an important class of nitrogen oxides reservoirs in the atmosphere and play a key role in tropospheric photochemistry. Despite the increasing concern for photochemical air pollution over China, the knowledge of characteristics and formation mechanisms of alkyl nitrates in this region is limited. We analyzed C1-C5 alkyl nitrates measured in Beijing at a polluted urban site in summer 2008 and at a downwind rural site in summers of both 2005 and 2008. Although the abundances of NOx and hydrocarbons were much lower at the rural site, the mixing ratios of RONO2 were comparable between both sites, emphasizing the regional nature of alkyl nitrate pollution. Regional transport of urban plumes governed the elevated RONO2 levels at the rural site. The concentrations of C1-C2 RONO2 were significantly higher at the rural site in 2008 compared to 2005 despite a decline in NOx and anthropogenic VOCs, mainly owing to enhanced contributions from biogenic VOCs. The photochemical formation regimes of RONO2 were evaluated by both a simplified sequential reaction model and a detailed master chemical mechanism box model. The observed C4-C5 RONO2 levels can be well explained by the photochemical degradation of n-butane and n-pentane, while the sources of C1-C3 RONO2 were rather complex. In addition to the C1-C3 alkanes, biogenic VOCs and reactive aromatics were also important precursors of methyl nitrate, and alkenes and long-chain alkanes contributed to the formation of C2-C3 RONO2. This study provides insights into the spatial distribution, inter-annual variation and photochemical formation mechanisms of alkyl nitrate pollution over the Beijing area.

Discovery of a novel protein modification: alpha-glycerophosphate is a substituent of meningococcal pilin.

PubMed Central

Stimson, E; Virji, M; Barker, S; Panico, M; Blench, I; Saunders, J; Payne, G; Moxon, E R; Dell, A; Morris, H R

1996-01-01

Pili, which are filamentous protein structures on the surface of the meningitis-causing organism Neisseria meningitidis, are known to be post-translationally modified with substituents that affect their mobility in SDS/PAGE and which might play a crucial role in adherence and bloodstream invasion. Tryptic digests of pili were analysed by fast atom bombardment and electrospray MS to identify putative modifications. Serine-93 was found to carry a novel modification of alpha-glycerophosphate. This is the first time that alpha-glycerophosphate has been observed as a substituent of a prokaryotic or eukaryotic protein. PMID:8645220

IR and NMR spectral studies of 4-bromo-1-naphthyl chalcones-assessment of substituent effects

NASA Astrophysics Data System (ADS)

Thirunarayanan, G.; Gopalakrishnan, M.; Vanangamudi, G.

2007-07-01

Infrared νCO (cm -1) of s-cis and s-trans frequencies and nuclear magnetic resonance chemical shifts δ1H (ppm) of H-α and H-β, δ13C (ppm) of C-α and C-β data were assigned from their respective spectra of a series of various substituted styryl 4-bromo-1-naphthyl chalcones. These values are correlated with various Hammett substituent constants. From the results of statistical analysis, the effect of substituents can be explained.

40 CFR 721.2565 - Alkylated sulfonated diphenyl oxide, alkali and amine salts.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Alkylated sulfonated diphenyl oxide... New Uses for Specific Chemical Substances § 721.2565 Alkylated sulfonated diphenyl oxide, alkali and... substances identified as alkylated sulfonated diphenyl oxide, alkali salt (PMN P-93-352) and alkylated...

40 CFR 721.2565 - Alkylated sulfonated diphenyl oxide, alkali and amine salts.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Alkylated sulfonated diphenyl oxide... New Uses for Specific Chemical Substances § 721.2565 Alkylated sulfonated diphenyl oxide, alkali and... substances identified as alkylated sulfonated diphenyl oxide, alkali salt (PMN P-93-352) and alkylated...

Substituent Effects on Thermal Decolorization Rates of Bisbenzospiropyrans

PubMed Central

Lu, Nina T.; Nguyen, Vi N.; Kumar, Satish; McCurdy, Alison

2009-01-01

A novel application of photochromic molecules is to mimic physiological oscillatory calcium signals by reversibly binding and releasing calcium ions in response to light. Substituent changes on the largely unexplored photochromic bisbenzospiropyran scaffold led to significant changes in thermal fading rates in several organic solvents. Excellent correlations have been found between fading rates and empirical Hammett constants as well as calculated ground-state energies. These correlations can be used to improve scaffold design. PMID:16238356

Detection and identification of alkylating agents by using a bioinspired "chemical nose".

PubMed

Hertzog-Ronen, Carmit; Borzin, Elena; Gerchikov, Yulia; Tessler, Nir; Eichen, Yoav

2009-10-12

Alkylating agents are simple and reactive molecules that are commonly used in many and diverse fields such as organic synthesis, medicine, and agriculture. Some highly reactive alkylating species are also being used as blister chemical-warfare agents. The detection and identification of alkylating agents is not a trivial issue because of their high reactivity and simple structure. Herein, we report on a new multispot luminescence-based approach to the detection and identification of alkylating agents. In order to demonstrate the potential of the approach, seven pi-conjugated oligomers and polymers bearing nucleophilic pyridine groups, 1-7, were adsorbed onto a solid support and exposed to vapors of alkylators 8-15. The alkylation-induced color-shift patterns of the seven-spot array allow clear discrimination of the different alkylators. The spots are sensitive to minute concentrations of alkylators and, because the detection is based on the formation of new covalent bonds, these spots saturate at about 50 ppb.

Structure-biocompatibility and transfection activity relationships of cationic polyaspartamides with (dialkylamino)alkyl and alkyl or hydroxyalkyl side groups.

PubMed

Salakhieva, Diana; Shevchenko, Vesta; Németh, Csaba; Gyarmati, Benjámin; Szilágyi, András; Abdullin, Timur

2017-01-30

A series of 14 cationic derivatives of poly(aspartic acid) i.e. cationic polyaspartamides with different (dialkylamino)alkyl and alkyl or hydroxyalkyl side groups was synthesized by nucleophilic addition on polysuccinimide. The resulting polyaspartamides have moderate amphiphilic properties. Relationships between the structure and ratio of side groups and in vitro properties of polyaspartamides, including their cytotoxic and membrane-damaging activity towards human cell lines, primary skin fibroblasts and erythrocytes, were established and discussed. Cationic polyaspartamides vary in their DNA-binding, condensing and nuclease-protecting characteristics depending on the concentration ratio of (dialkylamino)alkyl and alkyl or hydroxyalkyl side groups. Effective cell transfection was achieved upon polyaspartamide-mediated plasmid DNA delivery in serum-free medium in the presence of chloroquine. Effect of serum proteins adsorption onto polyaspartamide based polyplexes, and the role of concentration of polyplexes in culture medium in their colloidal stability and transfection process were demonstrated. Synthesized polyaspartamides are biocompatible and long-acting gene carriers, which are applied to cells after dilution and without washing, thus providing transfection level comparable to that of commercial transfection reagent. Copyright © 2016 Elsevier B.V. All rights reserved.

Mechanisms of chemoresistance to alkylating agents in malignant glioma.

PubMed

Sarkaria, Jann N; Kitange, Gaspar J; James, C David; Plummer, Ruth; Calvert, Hilary; Weller, Michael; Wick, Wolfgang

2008-05-15

Intrinsic or acquired chemoresistance to alkylating agents is a major cause of treatment failure in patients with malignant brain tumors. Alkylating agents, the mainstay of treatment for brain tumors, damage the DNA and induce apoptosis, but the cytotoxic activity of these agents is dependent on DNA repair pathways. For example, O6-methylguanine DNA adducts can cause double-strand breaks, but this is dependent on a functional mismatch repair pathway. Thus, tumor cell lines deficient in mismatch repair are resistant to alkylating agents. Perhaps the most important mechanism of resistance to alkylating agents is the DNA repair enzyme O6-methylguanine methyltransferase, which can eliminate the cytotoxic O6-methylguanine DNA adduct before it causes harm. Another mechanism of resistance to alkylating agents is the base excision repair (BER) pathway. Consequently, efforts are ongoing to develop effective inhibitors of BER. Poly(ADP-ribose)polymerase plays a pivotal role in BER and is an important therapeutic target. Developing effective strategies to overcome chemoresistance requires the identification of reliable preclinical models that recapitulate human disease and which can be used to facilitate drug development. This article describes the diverse mechanisms of chemoresistance operating in malignant glioma and efforts to develop reliable preclinical models and novel pharmacologic approaches to overcome resistance to alkylating agents.

Alcohols as alkylating agents in heteroarene C-H functionalization

NASA Astrophysics Data System (ADS)

Jin, Jian; MacMillan, David W. C.

2015-09-01

Redox processes and radical intermediates are found in many biochemical processes, including deoxyribonucleotide synthesis and oxidative DNA damage. One of the core principles underlying DNA biosynthesis is the radical-mediated elimination of H2O to deoxygenate ribonucleotides, an example of `spin-centre shift', during which an alcohol C-O bond is cleaved, resulting in a carbon-centred radical intermediate. Although spin-centre shift is a well-understood biochemical process, it is underused by the synthetic organic chemistry community. We wondered whether it would be possible to take advantage of this naturally occurring process to accomplish mild, non-traditional alkylation reactions using alcohols as radical precursors. Because conventional radical-based alkylation methods require the use of stoichiometric oxidants, increased temperatures or peroxides, a mild protocol using simple and abundant alkylating agents would have considerable use in the synthesis of diversely functionalized pharmacophores. Here we describe the development of a dual catalytic alkylation of heteroarenes, using alcohols as mild alkylating reagents. This method represents the first, to our knowledge, broadly applicable use of unactivated alcohols as latent alkylating reagents, achieved via the successful merger of photoredox and hydrogen atom transfer catalysis. The value of this multi-catalytic protocol has been demonstrated through the late-stage functionalization of the medicinal agents, fasudil and milrinone.

Alcohols as alkylating agents in heteroarene C-H functionalization.

PubMed

Jin, Jian; MacMillan, David W C

2015-09-03

Redox processes and radical intermediates are found in many biochemical processes, including deoxyribonucleotide synthesis and oxidative DNA damage. One of the core principles underlying DNA biosynthesis is the radical-mediated elimination of H2O to deoxygenate ribonucleotides, an example of 'spin-centre shift', during which an alcohol C-O bond is cleaved, resulting in a carbon-centred radical intermediate. Although spin-centre shift is a well-understood biochemical process, it is underused by the synthetic organic chemistry community. We wondered whether it would be possible to take advantage of this naturally occurring process to accomplish mild, non-traditional alkylation reactions using alcohols as radical precursors. Because conventional radical-based alkylation methods require the use of stoichiometric oxidants, increased temperatures or peroxides, a mild protocol using simple and abundant alkylating agents would have considerable use in the synthesis of diversely functionalized pharmacophores. Here we describe the development of a dual catalytic alkylation of heteroarenes, using alcohols as mild alkylating reagents. This method represents the first, to our knowledge, broadly applicable use of unactivated alcohols as latent alkylating reagents, achieved via the successful merger of photoredox and hydrogen atom transfer catalysis. The value of this multi-catalytic protocol has been demonstrated through the late-stage functionalization of the medicinal agents, fasudil and milrinone.

40 CFR 721.10711 - Alkyl substituted catechol (generic).

Code of Federal Regulations, 2014 CFR

2014-07-01

...) TOXIC SUBSTANCES CONTROL ACT SIGNIFICANT NEW USES OF CHEMICAL SUBSTANCES Significant New Uses for Specific Chemical Substances § 721.10711 Alkyl substituted catechol (generic). (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as alkyl...

40 CFR 721.840 - Alkyl substituted diaromatic hydrocarbons.

Code of Federal Regulations, 2010 CFR

2010-07-01

... hydrocarbons. 721.840 Section 721.840 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED... Specific Chemical Substances § 721.840 Alkyl substituted diaromatic hydrocarbons. (a) Chemical substance... alkyl substituted di-aro-matic hydrocarbons (PMN P-91-710) is subject to reporting under this section...

40 CFR 721.840 - Alkyl substituted diaromatic hydrocarbons.

Code of Federal Regulations, 2011 CFR

2011-07-01

... hydrocarbons. 721.840 Section 721.840 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED... Specific Chemical Substances § 721.840 Alkyl substituted diaromatic hydrocarbons. (a) Chemical substance... alkyl substituted di-aro-matic hydrocarbons (PMN P-91-710) is subject to reporting under this section...

Copper-catalyzed radical carbooxygenation: alkylation and alkoxylation of styrenes.

PubMed

Liao, Zhixiong; Yi, Hong; Li, Zheng; Fan, Chao; Zhang, Xu; Liu, Jie; Deng, Zixin; Lei, Aiwen

2015-01-01

A simple copper-catalyzed direct radical carbooxygenation of styrenes is developed utilizing alkyl bromides as radical resources. This catalytic radical difunctionalization accomplishes both alkylation and alkoxylation of styrenes in one pot. A broad range of styrenes and alcohols are well tolerated in this transformation. The EPR experiment shows that alkyl halides could oxidize Cu(I) to Cu(II) in this transformation. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Lithium perchlorate-nitromethane-promoted alkylation of anilines with arylmethanols.

PubMed

Zhou, Jun; Mao, Hai-Feng; Wang, Lu; Zou, Jian-Ping; Zhang, Wei

2011-11-01

A new application of lithium perchlorate-nitromethane (LPNM) for the formation of aromatic C-N and C-C bonds is introduced. LPNM-promoted reactions of anilines with diarylmethanols selectively generate N-alkylated anilines or mono and double Friedel-Crafts alkylation products under different conditions by changing the reaction time, reaction temperature, and the ratio of the reactants. This method does not require the use of transition metal catalysts to prepare alkylated aniline derivatives.

Chiral Brønsted Base-Promoted Nitroalkane Alkylation: Enantioselective Synthesis of sec-Alkyl-3-Substituted Indoles

PubMed Central

Dobish, Mark C.; Johnston, Jeffrey N.

2010-01-01

A Brønsted base-catalyzed reaction of nitroalkanes with alkyl electrophiles provides indole heterocycles substituted at C3 bearing a sec-alkyl group with good enantioselectivity (up to 90% ee). Denitration by hydrogenolysis provides a product with equally high ee. An indolenine intermediate is implicated in the addition step, and surprisingly, water cosolvent was found to have a beneficial effect in this step, leading to a one-pot protocol for elimination/enantioselective addition using PBAM, a bis(amidine) chiral nonracemic base. PMID:21090654

Virucidal effects of bleach activators, sodium alkyl acyloxybenzene sulfonate and acyloxybenzoic acid, against Feline calicivirus.

PubMed

Tobe, Seiichi; Hoshi, Marika; Iizuka, Kinue; Tadenuma, Hirohiko; Takaoka, Hiromitsu; Komoriya, Tomoe; Kohno, Hideki

2012-01-01

Noroviruses (NVs) are major causative pathogens of gastroenteritis. The disinfection of contaminated clothing during common household washing is desirable. The virucidal effects of 2 bleach activators, sodium alkyl acyloxybenzene sulfonate (OBS) and alkyl acyloxybenzoic acid (OBC), were studied using Feline calicivirus (FCV) as a surrogate for NVs. FCV was added to solutions containing either OBS or OBC and sodium percarbonate at various temperatures and for varying lengths of time. OBS and OBC, which generate long carbon chain peroxy acids, enhanced the virucidal effect of sodium percarbonate (PC). In particular, sodium lauroyloxybenzene sulfonate (OBS-12) and decanoyloxybenzoic acid (OBC-10) showed superior virucidal effects. Although the virucidal effect of 38-200 mg/L OBS-12 was maintained with 2-5% (v/v) horse serum, there was less of an effect with the same concentration of available chlorine. OBS and OBC have been used as ingredients in some laundry products to increase bleaching activity. It is expected that the use of OBS and OBC is also effective for the inactivation of NVs under common household washing conditions.

Tuning Thermoresponsive Properties of Cationic Elastin-like Polypeptides by Varying Counterions and Side-Chains.

PubMed

Petitdemange, Rosine; Garanger, Elisabeth; Bataille, Laure; Bathany, Katell; Garbay, Bertrand; Deming, Timothy J; Lecommandoux, Sébastien

2017-05-17

We report the synthesis of methionine-containing recombinant elastin-like polypeptides (ELPs) of different lengths that contain periodically spaced methionine residues. These ELPs were chemoselectively alkylated at all methionine residues to give polycationic derivatives. Some of these samples were found to possess solubility transitions in water, where the temperature of these transitions varied with ELP concentration, nature of the methionine alkylating group, and nature of the sulfonium counterions. These studies show that introduction and controlled spacing of methionine sulfonium residues into ELPs can be used as a means both to tune their solubility transition temperatures in water using a variety of different parameters and to introduce new side-chain functionality.

Highly productive CNN pincer ruthenium catalysts for the asymmetric reduction of alkyl aryl ketones.

PubMed

Baratta, Walter; Chelucci, Giorgio; Magnolia, Santo; Siega, Katia; Rigo, Pierluigi

2009-01-01

Chiral pincer ruthenium complexes of formula [RuCl(CNN)(Josiphos)] (2-7; Josiphos = 1-[1-(dicyclohexylphosphano)ethyl]-2-(diarylphosphano)ferrocene) have been prepared by treating [RuCl(2)(PPh(3))(3)] with (S,R)-Josiphos diphosphanes and 1-substituted-1-(6-arylpyridin-2-yl)methanamines (HCNN; substituent = H (1 a), Me (1 b), and tBu (1 c)) with NEt(3). By using 1 b and 1 c as a racemic mixture, complexes 4-7 were obtained through a diastereoselective synthesis promoted by acetic acid. These pincer complexes, which display correctly matched chiral PP and CNN ligands, are remarkably active catalysts for the asymmetric reduction of alkyl aryl ketones in basic alcohol media by both transfer hydrogenation (TH) and hydrogenation (HY), achieving enantioselectivities of up to 99 %. In 2-propanol, the enantioselective TH of ketones was accomplished by using a catalyst loading as low as 0.002 mol % and afforded a turnover frequency (TOF) of 10(5)-10(6) h(-1) (60 and 82 degrees C). In methanol/ethanol mixtures, the CNN pincer complexes catalyzed the asymmetric HY of ketones with H(2) (5 atm) at 0.01 mol % relative to the complex with a TOF of approximately 10(4) h(-1) at 40 degrees C.

Structuring of Amide Cross-Linked Non-Bridged and Bridged Alkyl-Based Silsesquioxanes.

PubMed

Nunes, S C; de Zea Bermudez, V

2018-02-06

The development of sophisticated organized materials exhibiting enhanced properties is a challenging topic of the domain of organic/inorganic hybrid materials. This review, composed of four sections, reports the work we have carried out over the last 10 years on the synthesis of amide cross-linked alkyl/siloxane hybrids by means of sol-gel chemistry and self-directed assembly/self-organization routes relying on weak interactions (hydrophobic interactions and hydrogen bonding). The various as-produced lamellar structures displaying a myriad of morphologies, often closely resembling those found in natural materials, are discussed. The major role played by the synthetic conditions (pH, water content, co-solvent(s) nature/concentration and dopant presence/concentration), the alkyl chains (length and presence of ramification or not) and the number of the amide cross-links present in the precursor, is evidenced. Examples of highly organized hybrids structures incorporating ionic species (alkali and alkaline earth metal salts) and optically-active centers (organic dyes and lanthanide ions) are described. A useful qualitative relationship deduced between the emission quantum yield of the ordered hybrid materials and the degree of order of the hydrogen-bonded network is highlighted. © 2018 The Chemical Society of Japan & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Rigid Dipeptide Mimics: Synthesis of Enantiopure 5- and 7-Benzyl and 5,7-Dibenzyl Indolizidinone Amino Acids via Enolization and Alkylation of delta-Oxo alpha,omega-Di-[N-(9-(9-phenylfluorenyl))amino]azelate Esters.

PubMed

Polyak, Felix; Lubell, William D.

1998-08-21

Azabicyclo[X.Y.0]alkane amino acids are tools for constructing mimics of peptide structure and templates for generating combinatorial libraries for drug discovery. Our methodology for synthesizing these conformationally rigid dipeptides has been elaborated such that alkyl groups can be appended onto the heterocycle to generate mimics of peptide backbone and side-chain structure. Inexpensive glutamic acid was employed as chiral educt in a Claisen condensation/ketone alkylation/reductive amination/lactam cyclization sequence that furnished alkyl-branched azabicyclo[4.3.0]alkane amino acid. Enantiopure 5-benzyl-, 7-benzyl-, and 5,7-dibenzylindolizidinone amino acids 2-4 were stereoselectively synthesized via efficient reaction sequences featuring the alkylation of di-tert-butyl alpha,omega-di-[N-(PhF)amino]azelate delta-ketone 5. A variety of alkyl halides were readily added to the enolate of ketone 5 to provide mono- and dialkylated ketones 6 and 7. Hydride additions to 6 and 7, methanesulfonations, and intramolecular S(N)2 displacements by the PhF amine gave 5-alkylprolines that were converted by lactam cyclizations into 7- and 5-benzyl-, as well as 5,7-dibenzyl-2-oxo-3-N-(BOC)amino-1-azabicyclo[4.3.0]nonane-9-carboxylate methyl esters 10, 11, and 14. Epimerization of the alkyl-branched stereocenter via an iminium-enaminium equilibrium proved effective for controlling diastereoselectivity in reductive aminations with 6 and 7 in order to furnish 5-alkylprolines that were similarly converted to 7- benzyl- and 5,7-dibenzylindolizidinone N-(BOC)amino esters 10 and 14. Ester hydrolysis with hydroxide ion and potassium trimethylsilanolate then gave enantiopure indolizidinone amino acids 2-4. Epimerization at C-9 of benzylindolizidinone amino esters was also used to provide alternative diastereomers of 10, 11, and 14. This practical methodology for introducing side-chain groups onto the heterocycle with regioselective and diastereoselective control is designed to enhance

Substituent effect on the thermodynamic solubility of structural analogs: relative contribution of crystal packing and hydration.

PubMed

Ozaki, Shunsuke; Nakagawa, Yoshiaki; Shirai, Osamu; Kano, Kenji

2014-11-01

Thermodynamic analysis of the solubility of benzoylphenylurea (BPU) derivatives was conducted to investigate the relative importance of crystal packing and hydration for improving solubility with minor structural modification. The contribution of crystal packing to solubility was evaluated from the change in Gibbs energy on the transition from the crystalline to liquid state. Hydration Gibbs energy was estimated using a linear free-energy relationship between octanol-water partition coefficients and gas-water partition coefficients. The established solubility model satisfactorily explained the relative thermodynamic solubility of the model compounds and revealed that crystal packing and hydration equally controlled solubility of the structural analogs. All hydrophobic substituents were undesirable for solubility in terms of hydration, as expected. On the other hand, some of these hydrophobic substituents destabilized crystal packing and improved the solubility of the BPU derivatives when their impact on crystal packing exceeded their negative influence on hydration. The replacement of a single substituent could cause more than a 10-fold enhancement in thermodynamic solubility; this degree of improvement was comparable to that generally achieved by amorphous formulations. Detailed analysis of thermodynamic solubility will allow us to better understand the true substituent effect and design drug-like candidates efficiently. © 2014 Wiley Periodicals, Inc. and the American Pharmacists Association.

Hydrophile-lipophile balance of alkyl ethoxylated surfactants as a function of intermolecular energies.

PubMed

Urbina-Villalba, G; Rogel, E; Márquez, M L; Reif, I

1994-06-01

The semiempirical MNDO method has been used in order to examine the variation of the molecular properties of hydrocarbons CnH2n + 2 (with 1 < or = n < or = 19) and ethylene oxide chains CH3(CH2CH2O)mCH3 (with 1 < or = m < or = 19) as a function of their molecular length. Least-square fits of those properties have been calculated, along with two mathematical relations between the hydrophile-lipophile balance of alkyl-phenol ethoxylated surfactants and (1) the ratio of molecular lengths between their lipophilic and hydrophilic branches; (2) the intermolecular energies between the molecules of surfactant, water and hexane.

Sleep-inducing N-alkyl-5-[m-(trifluoromethyl)phenyl]-5-hydroxy-2-pyrrolidinones and N-alkyl-3-(trifluoromethyl)cinnamamides.

PubMed

Houlihan, W J; Gogerty, J H; Ryan, E A; Schmitt, G

1985-01-01

A series of N-alkyl-3-[m-(trifluoromethyl)phenyl]-5-hydroxy-2-pyrrolidinones and N-alkyl-3-(trifluoromethyl)-cinnamamides were prepared and screened in a series of tests designed to detect potential sleep inducers. The more active members of the series were evaluated for their ability to induce sleep in Cebus monkeys. The most active compound, N-methyl-5-[m-(trifluoromethyl)phenyl]-5-hydroxy-2-pyrrolidinone, was equal to methaqualone.

Dielectric relaxation of alkyl chains in graphite oxide and n-alkylammonium halides

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ai, Xiaoqian; Tian, Yuchen; Gu, Min, E-mail: mgu@nju.edu.cn

2016-05-15

The dynamic of n-alkylammonium halides and n-alkylammonium cations (n = 12, 14, 16, 18) intercalated in graphite oxide (GO) have been investigated with complex impedance spectroscopy. X-ray diffraction, X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy, elemental analysis and thermogravimetry served to characterize the materials. The intercalated alkylammonium cations distributes as monolayers (when n = 12, 14 or 16) or bilayers (when n = 18), with their long axis parallel to GO layers, and with cations of headgroups bonded ionically to C-O{sup -} groups of GO; backbones of the confined molecules remain free. All halides and intercalation compounds suffer dielectric loss atmore » low temperature. Arrhenius plots of the thermal dependence of the loss peaks, which are asymmetric, produce apparent activation energies that rise with increasing n. Ngai’s correlated-state model helps to correct for effects of dipole-dipole interaction, leading to virtually identical values for actual activation energy of 110 meV ± 5%; the values are also almost the same as the barrier energy for internal rotation in the alkyl macromolecule. We conclude that the relaxation of the alkylammonium cations arises not from C{sub 3} reorientation of the CH{sub 3} at its headgroup, but from small-angle wobbling around its major axis, an intrinsic motion.« less

Computational study on the effects of substituent and heteroatom on physical properties and solar cell performance in donor-acceptor conjugated polymers based on benzodithiophene.

PubMed

Zhang, Lvyong; Shen, Wei; He, Rongxing; Liu, Xiaorui; Fu, Zhiyong; Li, Ming

2014-11-01

Computationally driven material design has attracted increasing interest to accelerate the search for optimal conjugated donor materials in bulk heterojunction organic solar cells. A series of novel copolymers containing benzo[1,2-b:4,5-b']dithiophene (BDT) and thieno[3,4-c]pyrrole-4,6-dione (TPD) derivatives were simulated by density functional theory (DFT) and time-dependent density functional theory (TD-DFT). We performed a systematic study on the influences on molecular geometry parameters, electronic properties, optical properties, photovoltaic performances, and intermolecular stacking as well as hole mobility when different chalcogenophenes in TPD derivatives were used and functional groups with different electron-withdrawing abilities such as alkyl, fluorine, sufonyl, and cyano were introduced to the nitrogen positions in electron-deficient units. The substitution position of electron-withdrawing groups may cause little steric hindrance to the neighboring donor units, especially fluorine and cyano group. It was found that the incorporation of these new electron-deficient substituents and sulfur-selenium exchange can be applicable to further modify and optimize existing molecular structures. Our findings will provide valuable guidance and chemical methodologies for a judicious material design of conjugated polymers for solar cell applications with desirable photovoltaic characteristics.

Synthesis and characterization of chitosan alkyl urea.

PubMed

Wang, Jing; Jiang, Ji-Zhou; Chen, Wei; Bai, Zheng-Wu

2016-07-10

Chitosan is a versatile material employed for various purposes in many fields including the development of chiral stationary phases for enantioseparation. Chitosan alkyl urea is a kind of intermediate used to prepare enantioseparation materials. In order to synthesize the intermediates, in the present work, a new way to prepare chitosan alkyl urea has been established: chitosan was first reacted with methyl chloroformate yielding N-methoxyformylated chitosan, which was then converted to chitosan alkyl urea through amine-ester exchange reaction. With a large excess of methyl chloroformate and primary amine of low stereohindrance, the amino group in chitosan could be almost completely converted to ureido group. The as-prepared chitosan alkyl urea derivatives were characterized by IR, (1)H NMR, (13)C NMR,(1)H-(1)H COSY and (1)H-(13)C HSQC NMR spectra. The chemical shifts of hydrogen and carbon atoms of glucose unit were assigned. It was found that the degree of substitution was obviously lower if cyclopropyl amine, aniline, tert-butyl amine and diethyl amine were used as reactants for the amine-ester exchange reaction. The reason was explained with the aid of theoretical calculations. Copyright © 2016 Elsevier Ltd. All rights reserved.

Alcohols as alkylating agents in heteroarene C–H functionalization

PubMed Central

Jin, Jian; MacMillan, David W. C.

2015-01-01

Redox processes and radical intermediates are found in many biochemical processes, including deoxyribonucleotide synthesis and oxidative DNA damage1. One of the core principles that underlies DNA biosynthesis is the radical-mediated elimnation of H2O to deoxygenate ribonucleotides, an example of ‘spin-center shift’ (SCS)2, during which an alcohol C–O bond is cleaved, resulting in a carbon-centered radical intermediate. While SCS is a well-understood biochemical process, it is underutilized by the synthetic organic chemistry community. We wondered whether it would be possible to take advantage of this naturally occurring process to accomplish mild, non-traditional alkylations using alcohols as radical precursors. Considering traditional radical-based alkylation methods require the use of stoichiometric oxidants, elevated temperatures, or peroxides3–7, the development of a mild protocol using simple and abundant alkylating agents would have significant utility in the synthesis of diversely functionalized pharmacophores. In this manuscript, we describe the successful execution of this idea via the development of a dual catalytic alkylation of heteroarenes using alcohols as mild alkylating reagents. This method represents the first broadly applicable use of unactivated alcohols as latent alkylating reagents, achieved via the successful merger of photoredox and hydrogen atom transfer (HAT) catalysis. The utility of this multi-catalytic protocol has been demonstrated through the late-stage functionalization of the medicinal agents, fasudil and milrinone. PMID:26308895

Affinity alkylation of the active site of C/sub 21/ steroid side-chain cleavage cytochrome P-450 from neonatal porcine testis: a unique cysteine residue alkylated by 17-(bromoacetoxy)progesterone

DOE Office of Scientific and Technical Information (OSTI.GOV)

Onoda, M.; Haniu, M.; Yanagibashi, K.

1987-01-27

The affinity alkylating progesterone analogue 17-(bromoacetoxy)progesterone has been used to label the active site of a microsomal cytochrome P-450 enzyme from neonatal pig testis. The enzyme causes removal of the C/sub 20/ and C/sub 21/ side chains from the substrates progesterone and pregnenolone by catalyzing both 17-hydroxylase and C/sub 17,20/-lyase reactions, which produce the corresponding C/sub 1//sup 9/ steroidal precursors of testosterone. The progesterone analogue causes simultaneous inactivation of the two catalytic activities of the enzyme by a first-order kinetic process that obeys saturation kinetics. Progesterone and 17-hydroxyprogesterone each protect the enzyme against inactivation. The progesterone analogue is a competitivemore » inhibitor of the enzyme with K/sub i/ values of 8.4 ..mu..M and 7.8 ..mu..M for progesterone and 17-hydroxyprogesterone, respectively. The enzyme inactivation and kinetic data are consistent with a theory proposing that the analogue and the two substrates compete for the same active site. The radioactive analogue 17-((/sup 14/C)bromoacetoxy)progesterone causes inactivation of the enzyme with incorporation of 1.5-2.2 mol of the analogue per mole of inactivated enzyme. When this experiment is carried out in the presence of a substrate, then 0.9-1.2 mol of radioactive analogue is incorporated per mole of inactivated enzyme. The data suggest that the analogue can bind to two different sites, one of which is related to the catalytic site. Radiolabeled enzyme samples, from reactions of the /sup 14/C-labeled analogue with the enzyme alone or with enzyme in the presence of a substrate, were subjected to amino acid analysis and also in tryptic digestion and peptide mapping.« less

Spectroscopic study of 2-, 4- and 5-substituents on p Ka values of imidazole heterocycles prone to intramolecular proton-electrons transfer

NASA Astrophysics Data System (ADS)

Eseola, Abiodun O.; Obi-Egbedi, Nelson O.

2010-02-01

New 2-(1H-imidazol-2-yl)phenols ( L1Et- L8tBuPt) bearing a phenolic proton in the vicinity of the imidazole base were prepared and characterized. Experimental studies of the dependence of their protonation/deprotonation equilibrium on substituent identities and intramolecular hydrogen bonding tendencies were carried out using electronic absorption spectroscopy at varying pH values. In order to make comparison, 2-(anthracen-10-yl)-4,5-diphenyl-1H-imidazole ( L9Anthr) bearing no phenolic proton and 4,5-diphenyl-2-(4,5-diphenyl-1H-imidazol-2-yl)-1H-imidazole ( L10BisIm) bearing two symmetrical imidazole base fragments were also prepared and experimentally investigated. DFT calculations were carried out to study frontier orbitals of the investigated molecules. While electron-releasing substituents produced increase in protonation-deprotonation p Kas for the hydroxyl group, values for the imidazole base were mainly affected by polarization of the imidazole ring aromaticity across the 2-imidazole carbon and the 4,5-imidazole carbons axis of the imidazole ring. It was concluded that electron-releasing substituents on the phenol ring and/or electron-withdrawing substituents on 4,5-imidazole carbons negatively affects donor strengths/coordination chemistries of 2-(1H-imidazol-2-yl)phenols, and vice versa. Change of substituents on the phenol ring significantly altered the donor strength of the imidazole base. The understanding of p Ka variation on account of electronic effects of substituents in this work should aid the understanding of biochemical properties and substituent environments of imidazole-containing biomacromolecules.

Rhodium-catalyzed asymmetric hydroboration of γ,δ-unsaturated amide derivatives: δ-borylated amides.

PubMed

Hoang, G L; Zhang, S; Takacs, J M

2018-05-08

γ,δ-Unsaturated amides in which the alkene moiety bears an aryl or heteroaryl substituent undergo regioselective rhodium-catalyzed δ-borylation by pinacolborane to afford chiral secondary benzylic boronic esters. The results contrast the γ-borylation of γ,δ-unsaturated amides in which the disubstituted alkene moiety bears only alkyl substituents; the reversal in regiochemistry is coupled with a reversal in the sense of π-facial selectivity.

Sontochin as a Guide to the Development of Drugs against Chloroquine-Resistant Malaria

PubMed Central

Pou, Sovitj; Winter, Rolf W.; Nilsen, Aaron; Kelly, Jane Xu; Li, Yuexin; Doggett, J. Stone; Riscoe, Erin W.; Wegmann, Keith W.; Hinrichs, David J.

2012-01-01

Sontochin was the original chloroquine replacement drug, arising from research by Hans Andersag 2 years after chloroquine (known as “resochin” at the time) had been shelved due to the mistaken perception that it was too toxic for human use. We were surprised to find that sontochin, i.e., 3-methyl-chloroquine, retains significant activity against chloroquine-resistant strains of Plasmodium falciparum in vitro. We prepared derivatives of sontochin, “pharmachins,” with alkyl or aryl substituents at the 3 position and with alterations to the 4-position side chain to enhance activity against drug-resistant strains. Modified with an aryl substituent in the 3 position of the 7-chloro-quinoline ring, Pharmachin 203 (PH-203) exhibits low-nanomolar 50% inhibitory concentrations (IC50s) against drug-sensitive and multidrug-resistant strains and in vivo efficacy against patent infections of Plasmodium yoelii in mice that is superior to chloroquine. Our findings suggest that novel 3-position aryl pharmachin derivatives have the potential for use in treating drug resistant malaria. PMID:22508305

Detection of Alkylating Agents using Electrical and Mechanical Means

NASA Astrophysics Data System (ADS)

Gerchikov, Yulia; Borzin, Elena; Gannot, Yair; Shemesh, Ariel; Meltzman, Shai; Hertzog-Ronen, Carmit; Tal, Shay; Stolyarova, Sara; Nemirovsky, Yael; Tessler, Nir; Eichen, Yoav

2011-08-01

Alkylating agents are reactive molecules having at least one polar bond between a carbon atom and a good leaving group. These often simple molecules are frequently used in organic synthesis, as sterilizing agents in agriculture and even as anticancer agents in medicine. Unfortunately, for over a century, some of the highly reactive alkylating agents are also being used as blister chemical warfare agents. Being relatively simple to make, the risk is that these will be applied by terrorists as poor people warfare agents. The detection and identification of such alkylating agents is not a simple task because of their high reactivity and simple structure of the reactive site. Here we report on new approaches to the detection and identification of such alkylating agents using electrical (organic field effect transistors) and mechanical (microcantilevers) means.

Synthesis of diketopyrrolopyrrole-based polymers with polydimethylsiloxane side chains and their application in organic field-effect transistors

NASA Astrophysics Data System (ADS)

Ohnishi, Inori; Hashimoto, Kazuhito; Tajima, Keisuke

2018-03-01

Linear polydimethylsiloxane (PDMS) was investigated as a solubilizing group for π-conjugated polymers with the aim of combining high solubility in organic solvents with the molecular packing in solid films that is advantageous for charge transport. Diketopyrrolopyrrole-based copolymers with different contents and substitution patterns of the PDMS side chains were synthesized and evaluated for application in organic field-effect transistors. The PDMS side chains greatly increased the solubility of the polymers and led to shorter d-spacings of the π-stacking in the thin films compared with polymers containing conventional branched alkyl side chains.

Safety Assessment of Alkyl PEG/PPG Ethers as Used in Cosmetics.

PubMed

Fiume, Monice M; Heldreth, Bart; Bergfeld, Wilma F; Belsito, Donald V; Hill, Ronald A; Klaassen, Curtis D; Liebler, Daniel C; Marks, James G; Shank, Ronald C; Slaga, Thomas J; Snyder, Paul W; Andersen, F Alan

2016-07-01

The Cosmetic Ingredient Review (CIR) Expert Panel assessed the safety of 131 alkyl polyethylene glycol (PEG)/polypropylene glycol ethers as used in cosmetics, concluding that these ingredients are safe in the present practices of use and concentration described in this safety assessment when formulated to be nonirritating. Most of the alkyl PEG/PPG ethers included in this review are reported to function in cosmetics as surfactants, skin-conditioning agents, and/or emulsifying agents. The alkyl PEG/PPG ethers share very similar physiochemical properties as the alkyl PEG ethers, which were reviewed previously by the CIR Expert Panel and found safe when formulated to be nonirritating. The alkyl PEG ethers differ by the inclusion of PPG repeat units, which are used to fine-tune the surfactant properties of this group. The Panel relied heavily on data on analogous ingredients, extracted from the alkyl PEG ethers and PPG reports, when making its determination of safety. © The Author(s) 2016.

Diketopyrrolopyrrole-based Conjugated Polymers Bearing Branched Oligo(Ethylene Glycol) Side Chains for Photovoltaic Devices.

PubMed

Chen, Xingxing; Zhang, Zijian; Ding, Zicheng; Liu, Jun; Wang, Lixiang

2016-08-22

Conjugated polymers are essential for solution-processable organic opto-electronic devices. In contrast to the great efforts on developing new conjugated polymer backbones, research on developing side chains is rare. Herein, we report branched oligo(ethylene glycol) (OEG) as side chains of conjugated polymers. Compared with typical alkyl side chains, branched OEG side chains endowed the resulting conjugated polymers with a smaller π-π stacking distance, higher hole mobility, smaller optical band gap, higher dielectric constant, and larger surface energy. Moreover, the conjugated polymers with branched OEG side chains exhibited outstanding photovoltaic performance in polymer solar cells. A power conversion efficiency of 5.37 % with near-infrared photoresponse was demonstrated and the device performance could be insensitive to the active layer thickness. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Cytotoxicity of alkylphenols and alkylated non-phenolics in a primary culture of rainbow trout (Onchorhynchus mykiss) hepatocytes.

PubMed

Tollefsen, K-E; Blikstad, Camilla; Eikvar, Sissel; Farmen Finne, Eivind; Katharina Gregersen, Inger

2008-01-01

Alkylphenols are common aquatic pollutants originating from industrial use of the compounds themselves or as biodegradation products of alkylphenol polyethoxylates. The cytotoxicity of a range of alkylphenols and alkylated non-phenolics were assessed in a primary culture of rainbow trout (Onchorhynchus mykiss) hepatocytes to construct a structure-toxicity relationship for this group of ubiquitous aquatic pollutants. Metabolic inhibition and loss of membrane integrity were used as cytotoxic endpoints through use of the cellular markers Alamar blue and 5-carboxyfluorescein diacetate acetoxymethyl ester, respectively. The results show that cytotoxicity increased with the hydrophobicity of the alkylphenols for compounds with logK(OW)<4.9. Normal chained alkylphenols, branched alkylphenols and multi-substituted alkylphenols with logK(OW)4.9 deviated clearly from this relationship. The alkylphenols displayed greater cytotoxicity than alkylated non-phenolics and it is proposed that most alkylated non-phenolic caused non-polar narcosis (baseline toxicity) whereas the alkylphenols caused polar narcosis. Observations that metabolic inhibition occurred at lower concentrations than loss of membrane integrity for most chemicals indicated that interference with cellular metabolic functions was the main cause of cytotoxicity. Metabolic inhibition corresponded better than loss of membrane integrity to reported acute toxicity to fish, although the in vivo acute toxicity of hydrophobic compounds (logK(OW)>2-3) was clearly underestimated by both endpoints.

Quantification of Alkyl Nitrates in Ambient Air by Thermal Dissociation Cavity Ring-Down Spectroscopy with Preconcentration

NASA Astrophysics Data System (ADS)

Ye, C. Z.; Osthoff, H. D.; Taha, Y. M.; Pak, J. K.; Saowapon, M. T.

2015-12-01

Alkyl nitrates (AN, molecular formula RONO2) play a crucial role in the troposphere as temporary reservoirs of nitrogen oxides (NOx =NO +NO2) and by acting as chain terminators in the photochemical production of ozone. Mixing ratios of AN in ambient air are commonly quantified by gas chromatography with electron capture or mass spectrometric detection (GC-ECD or GC-MS) coupled to purge-and-trap preconcentration, usually on Tenax sorbent, to improve the detection limits. The analysis, however, is quite laborious as there are many alkyl nitrates that are low in individual abundance (often less than 1 parts-per-trillion by volume, pptv) and that exhibit different instrumental response factors. An alternative method is to determine alkyl nitrates as a sum (ΣAN) by thermal dissociation (TD) to a common fragment (NO2), which can then be quantified with a uniform response factor by optical absorption, for example by cavity ring-down spectroscopy (CRDS). However, the determination of ΣAN by TD-CRDS is hampered by its relatively high detection limits (several 100 pptv) and secondary chemistry following TD that results in both negative and positive interferences and depends on the composition of the ambient air sampled. In this work, a TD-CRDS equipped with a Tenax preconcentration unit is described. Matrix effects are minimized by desorbing the samples from the Tenax in a background of nitrogen. The performance of the instrument, in particular the recovery from the Tenax sorbent, was evaluated by sampling laboratory-generated mixtures of alkyl and peroxyacyl nitrates. Field data from a coastal site collected during the Ozone-depleting reactions in a coastal atmosphere (ORCA) campaign, which took place at the Amphitrite Point Observatory in Ucluelet, BC, from July 6 - 31, 2015, are presented. Advantages and disadvantages of the new method are discussed.

Nanoscale supramolecular ordering in gel-surfactant complexes: Sodium alkyl sulfates in poly(diallyldimethylammonium chloride)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sokolov, E.L.; Yeh, F.; Khokhlov, A.

1996-12-25

Studies of slightly cross-linked polycationic gels interacting with anionic surfactants have been performed by using random copolymers of poly(diallyldimethylammonium chloride) (PDADMACl) and polyacrylamide (PAAm) with varying content of PDADMACl and degree of cross-linking. Gel samples which had been fully swollen in water were placed in aqueous solutions of sodium alkyl sulfates (octyl(SOS), decyl-(SDCS), dodecyl (SDS), tetradecyl (STS), and hexyl (SHS) sulfates). The degree of the sample volume contraction depends on the PDADMACl content. The collapsed gel-surfactant complexes were studied using synchrotron small-angle X-ray scattering. All studied samples containing PDADMACl exhibited pronounced supramolecular nanostructures. The gel-SDCS complex exhibited a cubic structuremore » with a periodicity (7.75 nm) of approximately 4 times the surfactant molecular length, while the gel-SDS, gel-STS, and gel-SHS complexes showed hexagonal supramolecular ordering with a periodicity of approximately 2 times the surfactant molecular length. The d spacing of the longest periodicity in the complexes was dependent on the PDADMACl content and the surfactant. The d spacing generally increased with decreasing PDADMACl (charge) content and increasing number of carbon atoms in the surfactant alkyl chain. 20 refs., 11 figs., 5 tabs.« less

Enantioselective toxicities of chiral ionic liquids 1-alkyl-3-methyl imidazolium tartrate on Scenedesmus obliquus.

PubMed

Liu, Huijun; Zhang, Xiaoqiang; Dong, Ying; Chen, Caidong; Zhu, Shimin; Ma, Xiangjuan

2015-12-01

Ionic liquids (ILs) are being used in various industries during the last few decades, while the good solubility and high stability of ILs may pose a potential threat to the aquatic environment. Effect of chiral ionic liquids (CILs) 1-alkyl-3-methyl imidazolium tartrate (RMIM T) on Scenedesmus obliquus (S.obliquus) was studied. The growth rate inhibition and cell membrane permeability increased with increasing RMIM T concentration and increasing alkyl chain lengths. The IC50 values of D-(-)-tartrate 1-hexyl-3-methyl imidazolium (D-(-)-HMIM T) were 28.30, 12.23,10.15 and 14.41 mg/L, respectively, at 24, 48, 72 and 96h. While that of L-(+)-tartrate 1-hexyl-3-methyl imidazolium (L-(+)-HMIM T) were 15.97, 7.91, 9.43 and 12.04 mg/L respectively. The concentration of chl a, chl b and chl (a+b) decreased with increasing RMIM T concentration. The chlorophyll fluorescence parameters (F0, Fv/Fm, Fv/F0, Y(II), ETR and NPQ) were affected by RMIM T, indicating that the RMIM T will damage the PSII, inhibit the transmission of excitation energy, decrease the efficiency of photosynthesis. The results showed that there were enantioselective toxicity of RMIM T to algae, and the toxicity of L-(+)-RMIM T was greater than that of D-(-)-RMIM T, but the enantioselective difference becomes smaller with increasing exposure time, and with the increasing carbon chain length of cation, indicating that cation properties may have a larger effect on toxicity than anion properties. Copyright © 2015 Elsevier B.V. All rights reserved.

Quantitative Estimation of the Electronic Effects of Substituents in Five-membered Nitrogen-containing Aromatic Heterocycles

NASA Astrophysics Data System (ADS)

Lopyrev, Valentin A.; Larina, Ludmila I.; Vakul'skaya, Tamara I.

1986-05-01

Data, characterising quantitatively the effect of substituents on the reactivity and physicochemical properties of five-membered nitrogen-containing heterocyclic compounds, which have accumulated in the literature during the last 15 years, are compiled in the review and discussed. The possibility of applying the Hammett and Jaffe equations in the determination of the direction of transmission of the electronic effects of substituents is analysed and the likely usefulness of this approach to the study of electronic influences by taking into account separately the inductive and resonance constants is demonstrated. The bibliography includes 215 references.

Alkylation of 6-mercaptopurine (6-MP) with N-alkyl-N-alkoxycarbonylaminomethyl chlorides: S6-(N-alkyl-N-alkoxycarbonyl)aminomethyl-6-MP prodrug structure effect on the dermal delivery of 6-MP.

PubMed

Siver, K G; Sloan, K B

1990-01-01

The S6-(N-alkyl-N-alkoxycarbonyl)aminomethyl-6-MP (6-CARB-6-MP) prodrugs 5-20 were synthesized from the reaction of 6-MP with N-alkyl-N-alkyoxycarbonylaminomethyl chlorides (4) in dimethyl sulfoxide in overall yields of 5-62%, depending on the N-alkyl and the alkoxy groups involved. The derivatives were fully characterized by spectral and microanalyses. The assignment of the substitution pattern as S6-alkyl was based on comparisons of the UV, 1H NMR and 13C NMR spectra with model compounds. A S6, 9-bis-alkyl derivative was obtained from the reaction of 2 equivalents of 4 with 6-MP but the product was unstable and decomposed on standing to a 9-alkyl derivative. The 6-CARB-6-MP prodrugs reverted to 6-MP in water by an SN1-type mechanism involving unimolecular charge separation in the transition state of the rate determining step. There was no effect of dermal enzymes on the rate of hydrolysis. The solubilities in isopropyl myristate (IPM) for all of the 6-CARB-6-MP prodrugs were significantly greater than the solubility of 6-MP in IPM but only one prodrug (5) was apparently even as soluble as 6-MP in water. Selected 6-CARB-6-MP prodrugs were examined in diffusion cell experiments. Only the N-methyl-N-methoxycarbonyl derivative 5 gave a steady-state rate of delivery of 6-MP from IPM that was significantly greater than the steady-state rate of delivery of 6-MP from 6-MP in IPM. All the other derivatives gave steady-state rates of delivery of 6-MP from IPM that were either not significantly different, or were significantly lower than the rate obtained from 6-MP in IPM. In all cases, the effect of the 6-CARB-6-MP:IPM suspensions on the permeability of the skin, as determined by the second application flux of theophylline:propylene glycol, was of the same magnitude as the effect of IPM alone.

Ultrasound promoted N-alkylation of pyrrole using potassium superoxide as base in crown ether.

PubMed

Yim, E S; Park, M K; Han, B H

1997-04-01

Ultrasound accelerates the N-alkylation of pyrrole by alkylating reagents using potassium superoxide as base in the presence of 18-crown-6. A much lower yield of N-alkylated pyrrole was realized in the absence of ultrasound. N-alkylating reagents employed for pyrrole are methyl iodide, ethyl bromide, benzyl bromide, as well as acrylonitrile allyl cyanide and methyl acrylate. In an extension of this work, we have found that ultrasound was not necessary for the N-alkylation of indole and alkyl amine, such as diphenyl amine and piperidine with alkyl halides using our reagents. In all cases we observed that the 18-crown-6 catalyzed N-alkylation reaction gives higher yields of N-alkylated products than that without crown ether, when potassium superoxide was used as base. These observations are probably due to the potassium-crown complex which can be released when the reaction goes to completion.

Bifunctional Molybdenum Polyoxometalates for the Combined Hydrodeoxygenation and Alkylation of Lignin-Derived Model Phenolics.

PubMed

Anderson, Eric; Crisci, Anthony; Murugappan, Karthick; Román-Leshkov, Yuriy

2017-05-22

Reductive catalytic fractionation of biomass has recently emerged as a powerful lignin extraction and depolymerization method to produce monomeric aromatic oxygenates in high yields. Here, bifunctional molybdenum-based polyoxometalates supported on titania (POM/TiO 2 ) are shown to promote tandem hydrodeoxygenation (HDO) and alkylation reactions, converting lignin-derived oxygenated aromatics into alkylated benzenes and alkylated phenols in high yields. In particular, anisole and 4-propylguaiacol were used as model compounds for this gas-phase study using a packed-bed flow reactor. For anisole, 30 % selectivity for alkylated aromatic compounds (54 % C-alkylation of the methoxy groups by methyl balance) with an overall 72 % selectivity for HDO at 82 % anisole conversion was observed over H 3 PMo 12 O 40 /TiO 2 at 7 h on stream. Under similar conditions, 4-propylguaiacol was mainly converted into 4-propylphenol and alkylated 4-propylphenols with a selectivity to alkylated 4-propylphenols of 42 % (77 % C-alkylation) with a total HDO selectivity to 4-propylbenzene and alkylated 4-propylbenzenes of 4 % at 92 % conversion (7 h on stream). Higher catalyst loadings pushed the 4-propylguaiacol conversion to 100 % and resulted in a higher selectivity to propylbenzene of 41 %, alkylated aromatics of 21 % and alkylated phenols of 17 % (51 % C-alkylation). The reactivity studies coupled with catalyst characterization revealed that Lewis acid sites act synergistically with neighboring Brønsted acid sites to simultaneously promote alkylation and hydrodeoxygenation activity. A reaction mechanism is proposed involving activation of the ether bond on a Lewis acid site, followed by methyl transfer and C-alkylation. Mo-based POMs represent a versatile catalytic platform to simultaneously upgrade lignin-derived oxygenated aromatics into alkylated arenes. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

40 CFR 721.5985 - Fatty alkyl phosphate, alkali metal salt (generic).

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Fatty alkyl phosphate, alkali metal... Specific Chemical Substances § 721.5985 Fatty alkyl phosphate, alkali metal salt (generic). (a) Chemical... as a fatty alkyl phosphate, alkali metal salt (PMN P-99-0385) is subject to reporting under this...