Theoretical studies of alkyl radicals in the NaY and HY zeolites.

PubMed

Ghandi, Khashayar; Zahariev, Federico E; Wang, Yan Alexander

2005-08-18

Interplay of quantum mechanical calculations and experimental data on hyperfine coupling constants of ethyl radical in zeolites at several temperatures was engaged to study the geometries and binding energies and to predict the temperature dependence of hyperfine splitting of a series of alkyl radicals in zeolites for the first time. The main focus is on the hyperfine interaction of alkyl radicals in the NaY and HY zeolites. The hyperfine splitting for neutral free radicals and free radical cations is predicted for different zeolite environments. This information can be used to establish the nature of the muoniated alkyl radicals in the NaY and HY zeolites via muSR experiments. The muon hyperfine coupling constants of the ethane radical cation in these zeolites are very large with relatively little dependence on temperature. It was found that the intramolecular dynamics of alkyl free radicals are only weakly affected by their strong binding to zeolites. In contrast, the substrate binding has a significant effect on their intermolecular dynamics.

Total OH reactivity as a constraint of model calculated peroxy radical production, and the catalytic efficiency of NOx in O3 production in a boreal forest environment.

NASA Astrophysics Data System (ADS)

Javed, M. U.; Hens, K.; Martinez, M.; Kubistin, D.; Novelli, A.; Beygi, Z. H.; Axinte, R.; Nölscher, A. C.; Sinha, V.; Song, W.; Johnson, A. M.; Auld, J.; Bohn, B.; Sander, R.; Taraborrelli, D.; Williams, J.; Fischer, H.; Lelieveld, J.; Harder, H.

2016-12-01

Peroxy radicals play a key role in ozone (O3) production and hydroxyl (OH) recycling influencing the self-cleansing capacity and air quality. Organic peroxy radical (RO2) concentrations are estimated by three different approaches for a boreal forest, based on the field campaign HUMPPA-COPEC 2010 in Southern Finland. RO2 concentrations were simulated by a box model constrained by the comprehensive dataset from the campaign and cross-checked against the photostationary state (PSS) of NOx [= nitric oxide (NO) + nitrogen dioxide (NO2)] calculations. The model simulated RO2 concentrations appear too low to explain the measured PSS of NOx. As the atmospheric RO2 production is proportional to OH loss, the total OH loss rate frequency (total OH reactivity) in the model is underestimated compared to the measurements. The total OH reactivity of the model is tuned to match the observed total OH reactivity by increasing the biogenic volatile organic compound (BVOCs) concentrations for the model simulations. The new-found simulated RO2 concentrations based on the tuned OH reactivity explain the measured PSS of NOx reasonably well. Furthermore, the sensitivity of the NOx lifetime and the catalytic efficiency of NOx (CE) in O3 production, in the context of organic alkyl nitrate (RONO2) formation, was also investigated. Based on the campaign data, it was found that the lifetime of NOx and the CE are reduced and are sensitive to the RONO2 formation under low-NOx conditions, which matches a previous model-based study.

Noo Peroxy Isomer Exposed with Velocity-Map Imaging

NASA Astrophysics Data System (ADS)

Laws, Benjamin A.; Cavanagh, Steven J.; Lewis, Brenton R.; Gibson, Stephen T.

2016-06-01

O2, a toxic gas formed in most combustion processes, plays an important role in the Earth's atmosphere due to its role in the production of both photochemical smog and tropospheric ozone. The existence of the peroxy radial, NOO, has been proposed, both as a collision reaction intermediate, and as a negative-ion in some discharge sources, in order to account for extended tails seen in some photoelectron spectra. In this work a velocity-mapped image of NO2- photodetachment measured at 519 nm, shown, reveals high-energy electron structure, that persists at detachment energies lower than the electron affinity of ONO, 2.273 eV. {b} The central ring has the spectral signature of O^-, while the outer-ripples, that appear in character to be similar to NO- detachment, are, we propose due to the NOO- peroxy radical, which is also responsible for the presence of O-. The photoelectron spectrum resolves the vibrational structure to characterize the neutral peroxy radical. The identification is further supported by ab initio calculations. The photoelectron angular distributions associated with the peroxy radical have a negative anisotropy parameter, opposite in sign to detachment from ONO^-. K. M. Ervin and J. Ho and W. C. Lineberger, J. Phys. Chem. 92, 5405 (1988). doi:10.1021/j100330a017 Research supported by the ARC DP160102585.

The photodissociation dynamics of alkyl radicals

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

Giegerich, Jens; Fischer, Ingo, E-mail: ingo.fischer@uni-wuerzburg.de

2015-01-28

The photodisscociation dynamics of the alkyl radicals i-propyl (CH(CH{sub 3}){sub 2}) and t-butyl (C(CH{sub 3}){sub 3}) are investigated by H-atom photofragment imaging. While i-propyl is excited at 250 nm, the photodynamics of t-butyl are explored over a large energy range using excitation wavelengths between 347 nm and 233 nm. The results are compared to those obtained previously for ethyl, CH{sub 3}CH{sub 2}, and to those reported for t-butyl using 248 nm excitation. The translational energy (E{sub T}) distribution of the H-atom photofragments is bimodal and appears rather similar for all three radicals. The low E{sub T} part of the distributionmore » shows an isotropic photofragment angular distribution, while the high E{sub T} part is associated with a considerable anisotropy. Thus, for t-butyl, two H-atom loss channels of roughly equal importance have been identified in addition to the CH{sub 3}-loss channel reported previously. A mechanism for the photodissociation of alkyl radicals is suggested that is based on interactions between Rydberg- and valence states.« less

Thermochemistry and kinetics for 2-butanone-1-yl radical (CH2·C(═O)CH2CH3) reactions with O2.

PubMed

Sebbar, N; Bozzelli, J W; Bockhorn, H

2014-01-09

Thermochemistry of reactants, intermediates, transition state structures, and products along with kinetics on the association of CH2·C(═O)CH2CH3 (2-butanone-1-yl) with O2 and dissociation of the peroxy adduct isomers are studied. Thermochemical properties are determined using ab initio (G3MP2B3 and G3) composite methods along with density functional theory (B3LYP/6-311g(d,p)). Entropy and heat capacity contributions versus temperature are determined from structures, vibration frequencies, and internal rotor potentials. The CH2·C(═O)CH2CH3 radical + O2 association results in a chemically activated peroxy radical with 27 kcal mol(-1) excess of energy. The chemically activated adduct can react to stabilized peroxy or hydroperoxide alkyl radical adducts, further react to lactones plus hydroxyl radical, or form olefinic ketones and a hydroperoxy radical. Kinetic parameters are determined from the G3 composite methods derived thermochemical parameters, and quantum Rice-Ramsperger-Kassel (QRRK) analysis to calculate k(E) with master equation analysis to evaluate falloff in the chemically activated and dissociation reactions. One new, not previously reported, peroxy chemistry reaction is presented. It has a low barrier path and involves a concerted reaction resulting in olefin formation, H2O elimination, and an alkoxy radical.

Reaction mechanism and kinetics of the degradation of terbacil initiated by OH radical - A theoretical study

NASA Astrophysics Data System (ADS)

Ponnusamy, S.; Sandhiya, L.; Senthilkumar, K.

2018-02-01

The reaction of terbacil with OH radical is studied by using electronic structure calculations. The reaction of terbacil with OH radical is found to proceed by H-atom abstraction, Cl-atom abstraction and OH addition reactions. The initially formed alkyl radical will undergo atmospheric transformation in the presence of molecular oxygen leading to the formation of peroxy radical. The reaction of peroxy radical with other atmospheric oxidants, such as HO2 and NO radicals is studied. The rate constant is calculated for the H-atom abstraction reactions over the temperature range of 200-1000 K. The results obtained from electronic structure calculations and kinetic study show that the H-atom abstraction reaction is more favorable. The calculated lifetime of terbacil is 24 h in normal atmospheric OH concentration. The rate constant calculated for H-atom abstraction reactions is 6 × 10-12, 4.4 × 10-12 and 3.2 × 10-12 cm3molecule-1s-1, respectively which is in agreement with the previous literature value of 1.9 × 10-12 cm3molecule-1s-1.

Ozone production in remote oceanic and industrial areas derived from ship based measurements of peroxy radicals during TexAQS 2006

NASA Astrophysics Data System (ADS)

Sommariva, R.; Brown, S. S.; Roberts, J. M.; Brookes, D. M.; Parker, A. E.; Monks, P. S.; Bates, T. S.; Bon, D.; de Gouw, J. A.; Frost, G. J.; Gilman, J. B.; Goldan, P. D.; Herndon, S. C.; Kuster, W. C.; Lerner, B. M.; Osthoff, H. D.; Tucker, S. C.; Warneke, C.; Williams, E. J.; Zahniser, M. S.

2011-03-01

During the Texas Air Quality Study II (TexAQS 2006) campaign, a PEroxy Radical Chemical Amplifier (PERCA) was deployed on the NOAA research vessel R/V Brown to measure total peroxy radicals (HO2+Σ RO2). Day-time mixing ratios of HO2+Σ RO2 between 25 and 110 ppt were observed throughout the study area - the Houston/Galveston region and the Gulf coast of the US - and analyzed in relation to measurements of nitrogen oxides, volatile organic compounds (VOC) and photolysis rates to assess radical sources and sinks in the region. The measurements of HO2+Σ RO2 were used to calculate the in-situ net photochemical formation of ozone. Measured median values ranged from 0.6 ppb/h in clean oceanic air masses up to several tens of ppb/h in the most polluted industrial areas. The results are consistent with previous studies and generally agree with observations made during the previous TexAQS 2000 field campaign. The net photochemical ozone formation rates determined at Barbours Cut, a site immediately south of the Houston Ship Channel, were analyzed in relation to local wind direction and VOC reactivity to understand the relationship between ozone formation and local VOC emissions. The measurements of HO2+Σ RO2 made during the R/V Brown TexAQS 2006 cruise indicate that ozone formation is NOx-limited in the Houston/Galveston region and influenced by highly reactive hydrocarbons, especially alkenes from urban and industrial sources and their photo-oxidation products, such as formaldehyde.

Ozone production in remote oceanic and industrial areas derived from ship based measurements of peroxy radicals during TexAQS 2006

NASA Astrophysics Data System (ADS)

Sommariva, R.; Brown, S. S.; Roberts, J. M.; Brookes, D. M.; Parker, A. E.; Monks, P. S.; Bates, T. S.; Bon, D.; de Gouw, J. A.; Frost, G. J.; Gilman, J. B.; Goldan, P. D.; Herndon, S. C.; Kuster, W. C.; Lerner, B. M.; Osthoff, H. D.; Tucker, S. C.; Warneke, C.; Williams, E. J.; Zahniser, M. S.

2010-10-01

During the Texas Air Quality Study II (TexAQS 2006) campaign, a PEroxy Radical Chemical Amplifier (PERCA) was deployed on the NOAA research vessel R/V Brown to measure total peroxy radicals (HO2+ΣRO2). Day-time mixing ratios of HO2+ΣRO2 between 25 and 110 ppt were observed throughout the study area - the Houston/Galveston region and the Gulf coast of the U.S. - and analyzed in relation to measurements of nitrogen oxides, volatile organic compounds (VOC) and photolysis rates to assess radical sources and sinks in the region. The measurements of HO2+ΣRO2 were used to calculate the in-situ net photochemical formation of ozone. Measured median values ranged from 0.6 ppb/h in clean oceanic air masses up to several tens of ppb/h in the most polluted industrial areas. The results are consistent with previous studies and generally agree with observations made during the previous TexAQS 2000 field campaign. The net photochemical ozone formation rates determined at Barbours Cut, a site immediately south of the Houston Ship Channel, were analyzed in relation to local wind direction and VOC reactivity to understand the relationship between ozone formation and local VOC emissions. The measurements of HO2+ΣRO2 made during the R/V Brown TexAQS 2006 cruise indicate that ozone formation is NOx-limited in the Houston/Galveston region and influenced by highly reactive hydrocarbons, especially alkenes from urban and industrial sources and their photooxidation products, such as formaldehyde.

Large enhancement in the heterogeneous oxidation rate of organic aerosols by hydroxyl radicals in the presence of nitric oxide

DOE PAGES

Richards-Henderson, Nicole K.; Goldstein, Allen H.; Wilson, Kevin R.

2015-10-27

In this paper we report an unexpectedly large acceleration in the effective heterogeneous OH reaction rate in the presence of NO. This 10–50 fold acceleration originates from free radical chain reactions, propagated by alkoxy radicals that form inside the aerosol by the reaction of NO with peroxy radicals, which do not appear to produce chain terminating products (e.g., alkyl nitrates), unlike gas phase mechanisms. Lastly, a kinetic model, constrained by experiments, suggests that in polluted regions heterogeneous oxidation plays a much more prominent role in the daily chemical evolution of organic aerosol than previously believed.

Mild and Low-Pressure fac-Ir(ppy)3 -Mediated Radical Aminocarbonylation of Unactivated Alkyl Iodides through Visible-Light Photoredox Catalysis.

PubMed

Chow, Shiao Y; Stevens, Marc Y; Åkerbladh, Linda; Bergman, Sara; Odell, Luke R

2016-06-27

A novel, mild and facile preparation of alkyl amides from unactivated alkyl iodides employing a fac-Ir(ppy)3 -catalyzed radical aminocarbonylation protocol has been developed. Using a two-chambered system, alkyl iodides, fac-Ir(ppy)3 , amines, reductants, and CO gas (released ex situ from Mo(CO)6 ), were combined and subjected to an initial radical reductive dehalogenation generating alkyl radicals, and a subsequent aminocarbonylation with amines affording a wide range of alkyl amides in moderate to excellent yields. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Artifacts Generated During Azoalkane Peroxy Radical Oxidative Stress Testing of Pharmaceuticals Containing Primary and Secondary Amines.

PubMed

Nefliu, Marcela; Zelesky, Todd; Jansen, Patrick; Sluggett, Gregory W; Foti, Christopher; Baertschi, Steven W; Harmon, Paul A

2015-12-01

We report artifactual degradation of pharmaceutical compounds containing primary and secondary amines during peroxy radical-mediated oxidative stress carried out using azoalkane initiators. Two degradation products were detected when model drug compounds dissolved in methanol/water were heated to 40°C with radical initiators such as 2,2'-azobis(2-methylpropionitrile) (AIBN). The primary artifact was identified as an α-aminonitrile generated from the reaction of the amine group of the model drug with formaldehyde and hydrogen cyanide, generated as byproducts of the stress reaction. A minor artifact was generated from the reaction between the amine group and isocyanic acid, also a byproduct of the stress reaction. We report the effects of pH, initiator/drug molar ratio, and type of azoalkane initiator on the formation of these artifacts. Mass spectrometry and nuclear magnetic resonance were used for structure elucidation, whereas mechanistic studies, including stable isotope labeling experiments, cyanide analysis, and experiments exploring the effects of butylated hydroxyanisole addition, were employed to support the degradation pathways. © 2015 Wiley Periodicals, Inc. and the American Pharmacists Association.

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

Kinetic and Spectroscopic Studies of Peroxy Radical Reactions Related to Tropospheric Photo-Oxidation Chemistry

NASA Astrophysics Data System (ADS)

Jenkin, Michael Edwin

1991-05-01

Available from UMI in association with The British Library. Over the past 30 years, man has become increasingly aware that the presence of relatively small quantities of pollutants in the atmosphere as a result of his activities, can have a profound impact on both its chemistry, and its meteorology. Photochemistry in the atmosphere is not restricted to the behaviour of pollutants; indeed, certain photochemical phenomena necessarily occur naturally in a "pollution free" atmosphere. It is the interaction of the photochemistry of trace pollutants with the naturally established chemistry, either inhibiting or exaggerating natural processes, which has given rise to the environment-threatening consequences. The chemistry that leads to the phenomena mentioned above is complex, involving many hundreds of chemical reactions of reactive atomic and radical species. Over the years, a great deal of chemical kinetic data for elementary atmospheric reactions has accumulated^{(5,6)} , and the fundamental gas phase chemistry is well established. Computer models provide a useful means of assembling these data, and describing the likely behaviour and interconversion of various atmospheric pollutants, thereby enabling policy decision. For these models to be truly predictive, however, they must be based, first on reliable field measurements of primary trace pollutants and, secondly, on accurate kinetic and mechanistic data for key reactions of atmospheric importance. The work presented in this dissertation is concerned with the kinetics and mechanisms of reactions of the hydroperoxy radical (HO_2), and various organic peroxy radicals (RO_2) which are formed as intermediates in the atmospheric oxidation of volatile organic compounds. In the sections that follow, our current understanding of the chemistry in general of the lower atmosphere (0-50 km) will be discussed in some detail, but with particular reference to the role played by HO_2 and RO_2 radicals. (Abstract shortened by UMI.).

Composite wastewater treatment by aerated electrocoagulation and modified peroxi-coagulation processes.

PubMed

Kumar, Abhijeet; Nidheesh, P V; Suresh Kumar, M

2018-08-01

Treatment of composite wastewater generating from the industrial estates is a great challenge. The present study examines the applicability of aerated electrocoagulation and modified peroxi-coagulation processes for removing color and COD from composite wastewater. Iron plates were used as anodes and cathodes in both electrochemical processes and experiments were carried out in a working volume of 2 L. Aeration enhanced the efficiency of electrocoagulation process significantly. More than 50% of COD and 60% of color were removed after 1 h of electrocoagulation process operated at pH 3 and applied voltage of 1 V. Efficiency of the modified peroxi-coagulation process was significantly higher than that of aerated electrocoagulation. COD and color removal efficiencies of the modified peroxi-coagulation process were found as 77.7% and 97%, respectively after 1 h of electrolysis operated at 1 V, solution pH 3 and 50 mM hydrogen peroxide addition. This improved efficiency of modified peroxi-coagulation compared to aerated electrocoagulation is mainly due to the attack of in-situ generated hydroxyl radicals. Copyright © 2018 Elsevier Ltd. All rights reserved.

Chlorine atom-initiated low-temperature oxidation of prenol and isoprenol: The effect of C=C double bonds on the peroxy radical chemistry in alcohol oxidation

DOE PAGES

Welz, Oliver; Savee, John D.; Osborn, David L.; ...

2014-07-04

The chlorine atom-initiated oxidation of two unsaturated primary C5 alcohols, prenol (3-methyl-2-buten-1-ol, (CH 3) 2CCHCH 2OH) and isoprenol (3-methyl-3-buten-1-ol, CH 2C(CH 3)CH 2CH 2OH), is studied at 550 K and low pressure (8 Torr). The time- and isomer-resolved formation of products is probed with multiplexed photoionization mass spectrometry (MPIMS) using tunable vacuum ultraviolet ionizing synchrotron radiation. The peroxy radical chemistry of the unsaturated alcohols appears much less rich than that of saturated C4 and C5 alcohols. The main products observed are the corresponding unsaturated aldehydes – prenal (3-methyl-2-butenal) from prenol oxidation and isoprenal (3-methyl-3-butenal) from isoprenol oxidation. No significant productsmore » arising from QOOH chemistry are observed. These results can be qualitatively explained by the formation of resonance stabilized allylic radicals via H-abstraction in the Cl + prenol and Cl + isoprenol initiation reactions. The loss of resonance stabilization upon O 2 addition causes the energies of the intermediate wells, saddle points, and products to increase relative to the energy of the initial radicals and O 2. These energetic shifts make most product channels observed in the peroxy radical chemistry of saturated alcohols inaccessible for these unsaturated alcohols. The experimental findings are underpinned by quantum-chemical calculations for stationary points on the potential energy surfaces for the reactions of the initial radicals with O 2. Under our conditions, the dominant channels in prenol and isoprenol oxidation are the chain-terminating HO 2-forming channels arising from radicals, in which the unpaired electron and the –OH group are on the same carbon atom, with stable prenal and isoprenal co-products, respectively. These results suggest that the presence of C=C double bonds in alcohols will reduce low-temperature reactivity during autoignition.« less

Kinetic and spectroscopic studies of peroxy radical reactions related to tropospheric photo-oxidation chemistry

NASA Astrophysics Data System (ADS)

Jenkin, Michael Edwin

Over the past 30 years, man has become increasingly aware that the presence of relatively small quantities of pollutants in the atmosphere as a result of his activities, can have a profound impact on both its chemistry, and its meteorology. Photochemistry in the atmosphere is not restricted to the behavior of pollutants; indeed, certain photochemical phenomena necessarily occur naturally in a 'pollution free' atmosphere. It is the interaction of the photochemistry of trace pollutants with the naturally established chemistry, either inhibiting or exaggerating natural processes, which has given rise to the environment threatening consequences. The chemistry that leads to the phenomena mentioned above is complex, involving many hundreds of chemical reactions of reactive atomic and radical species. Over the years, a great deal of chemical kinetic data for elementary atmospheric reactions has accumulated, and the fundamental gas phase chemistry is well established. Computer models provide a useful means of assembling these data, and describing the likely behavior and interconversion of various atmospheric pollutants, thereby enabling policy decision. For these models to be truly predictive, however, they must be based, first on reliable field measurements of primary trace pollutants and, secondly, on accurate kinetic and mechanistic data for key reactions of atmospheric importance. The work presented in this dissertation is concerned with the kinetics and mechanisms of reactions of the hydroperoxy radial (HO2), and various organic peroxy radicals (RO2), which are formed as intermediates in the atmospheric oxidation of volatile organic compounds. In the sections that follow, our current understanding of the chemistry in general of the lower atmosphere (0-50 km) will be discussed in some detail, but with particular reference to the role played by HO2 and RO2 radicals.

Asymmetric radical alkylation of N-sulfinimines under visible light photocatalytic conditions.

PubMed

Garrido-Castro, Alberto F; Choubane, Houcine; Daaou, Mortada; Maestro, M Carmen; Alemán, José

2017-07-06

In this communication, a new photocatalytic strategy for the addition of alkyl-radical derivatives to N-sulfinimines with complete diastereoselectivity and moderate to good yields is presented. This is the first asymmetric photocatalytic addition to N-sulfinimines under visible light irradiation with smooth conditions and functional group tolerance.

Measurement of peroxy radicals in the urban atmosphere by PERCA-LIF technique

NASA Astrophysics Data System (ADS)

Sadanaga, Y.; Matsumoto, J.; Sakurai, K.; Kato, S.; Nomaguchi, T.; Bandow, H.; Kajii, Y.

2002-12-01

A new instrument has been developed for measuring peroxy radicals (RO2) using the Chemical Amplifier-Laser Induced Fluorescence (PERCA-LIF) technique. RO2 was converted to NO2 via a chain reaction by the addition of NO and CO in a 1/4" Teflon tube. NO2 was detected by LIF using Nd:YAG laser (532 nm, 5W at 10kHz). More selective detection of NO2 is enabled by the LIF than by luminol chemiluminescence because of free from the interference by other oxidants when using luminol. LIF technique can be more sensitive detection of NO2 than the luminol detector. Optimum conditions were investigated by varying reaction time (i.e. the length of reaction tube) and the concentrations of NO and CO. Maximum chain length of approximately 300 was obtained in dry conditions using a H2O/O2 simultaneous photolysis method. Experiments were performed to characterize the dependence of the chain length on humidity for this instrument. In August 2002, RO2 measurements were performed in Osaka using this method. Maximum concentrations of RO2 in the daytime were approximately 100 pptv. Nighttime observations were also conducted and significant concentrations of RO2 were detected just after the sunset. Existence of formation processes in the dark condition was investigated.

Understanding Trends in Autoignition of Biofuels: Homologous Series of Oxygenated C5 Molecules

DOE PAGES

Ciesielski, Peter N.; Robichaud, David J.; Kim, Seonah; ...

2017-07-05

Oxygenated biofuels provide a renewable, domestic source of energy that can enable adoption of advanced, high-efficiency internal combustion engines, such as those based on homogeneously charged compression ignition (HCCI). Of key importance to such engines is the cetane number (CN) of the fuel, which is determined by the autoignition of the fuel under compression at relatively low temperatures (550-800 K). For the plethora of oxygenated biofuels possible, it is desirable to know the ignition delay times and the CN of these fuels to help guide conversion strategies so as to focus efforts on the most desirable fuels. For alkanes, themore » chemical pathways leading to radical chain-branching reactions giving rise to low-temperature autoignition are well-known and are highly coincident with the buildup of reactive radicals such as OH. Key in the mechanisms leading to chain branching are the addition of molecular oxygen to alkyl radicals and the rearrangement and dissociation of the resulting peroxy radials. Prediction of the temperature and pressure dependence of reactions that lead to the buildup of reactive radicals requires a detailed understanding of the potential energy surfaces (PESs) of these reactions. In this study, we used quantum mechanical modeling to systematically compare the effects of oxygen functionalities on these PESs and associated kinetics so as to understand how they affect experimental trends in autoignition and CN. The molecules studied here include pentane, pentanol, pentanal, 2-heptanone, methylpentyl ether, methyl hexanoate, and pentyl acetate. All have a saturated five-carbon alkyl chain with an oxygen functional group attached to the terminal carbon atom. The results of our systematic comparison may be summarized as follows: (1) Oxygen functionalities activate C-H bonds by lowering the bond dissociation energy (BDE) relative to alkanes. (2) The R-OO bonds in peroxy radicals adjacent to carbonyl groups are weaker than corresponding alkyl

Understanding Trends in Autoignition of Biofuels: Homologous Series of Oxygenated C5 Molecules

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

Ciesielski, Peter N.; Robichaud, David J.; Kim, Seonah

Oxygenated biofuels provide a renewable, domestic source of energy that can enable adoption of advanced, high-efficiency internal combustion engines, such as those based on homogeneously charged compression ignition (HCCI). Of key importance to such engines is the cetane number (CN) of the fuel, which is determined by the autoignition of the fuel under compression at relatively low temperatures (550-800 K). For the plethora of oxygenated biofuels possible, it is desirable to know the ignition delay times and the CN of these fuels to help guide conversion strategies so as to focus efforts on the most desirable fuels. For alkanes, themore » chemical pathways leading to radical chain-branching reactions giving rise to low-temperature autoignition are well-known and are highly coincident with the buildup of reactive radicals such as OH. Key in the mechanisms leading to chain branching are the addition of molecular oxygen to alkyl radicals and the rearrangement and dissociation of the resulting peroxy radials. Prediction of the temperature and pressure dependence of reactions that lead to the buildup of reactive radicals requires a detailed understanding of the potential energy surfaces (PESs) of these reactions. In this study, we used quantum mechanical modeling to systematically compare the effects of oxygen functionalities on these PESs and associated kinetics so as to understand how they affect experimental trends in autoignition and CN. The molecules studied here include pentane, pentanol, pentanal, 2-heptanone, methylpentyl ether, methyl hexanoate, and pentyl acetate. All have a saturated five-carbon alkyl chain with an oxygen functional group attached to the terminal carbon atom. The results of our systematic comparison may be summarized as follows: (1) Oxygen functionalities activate C-H bonds by lowering the bond dissociation energy (BDE) relative to alkanes. (2) The R-OO bonds in peroxy radicals adjacent to carbonyl groups are weaker than corresponding alkyl

Intermediates in the reaction of substrate-free cytochrome P450cam with peroxy acetic acid.

PubMed

Schünemann, V; Jung, C; Trautwein, A X; Mandon, D; Weiss, R

2000-08-18

Freeze-quenched intermediates of substrate-free cytochrome 57Fe-P450(cam) in reaction with peroxy acetic acid as oxidizing agent have been characterized by EPR and Mossbauer spectroscopy. After 8 ms of reaction time the reaction mixture consists of approximately 90% of ferric low-spin iron with g-factors and hyperfine parameters of the starting material; the remaining approximately 10% are identified as a free radical (S' = 1/2) by its EPR and as an iron(IV) (S= 1) species by its Mossbauer signature. After 5 min of reaction time the intermediates have disappeared and the Mossbauer and EPR-spectra exhibit 100% of the starting material. We note that the spin-Hamiltonian analysis of the spectra of the 8 ms reactant clearly reveals that the two paramagnetic species, e.g. the ferryl (iron(IV)) species and the radical, are not exchanged coupled. This led to the conclusion that under the conditions used, peroxy acetic acid oxidized a tyrosine residue (probably Tyr-96) into a tyrosine radical (Tyr*-96), and the iron(III) center of substrate-free P450(cam) to iron(IV).

Cobalt-catalyzed cross-coupling reactions of alkyl halides with allylic and benzylic Grignard reagents and their application to tandem radical cyclization/cross-coupling reactions.

PubMed

Ohmiya, Hirohisa; Tsuji, Takashi; Yorimitsu, Hideki; Oshima, Koichiro

2004-11-05

Details of cobalt-catalyzed cross-coupling reactions of alkyl halides with allylic Grignard reagents are disclosed. A combination of cobalt(II) chloride and 1,2-bis(diphenylphosphino)ethane (DPPE) or 1,3-bis(diphenylphosphino)propane (DPPP) is suitable as a precatalyst and allows secondary and tertiary alkyl halides--as well as primary ones--to be employed as coupling partners for allyl Grignard reagents. The reaction offers a facile synthesis of quaternary carbon centers, which has practically never been possible with palladium, nickel, and copper catalysts. Benzyl, methallyl, and crotyl Grignard reagents can all couple with alkyl halides. The benzylation definitely requires DPPE or DPPP as a ligand. The reaction mechanism should include the generation of an alkyl radical from the parent alkyl halide. The mechanism can be interpreted in terms of a tandem radical cyclization/cross-coupling reaction. In addition, serendipitous tandem radical cyclization/cyclopropanation/carbonyl allylation of 5-alkoxy-6-halo-4-oxa-1-hexene derivatives is also described. The intermediacy of a carbon-centered radical results in the loss of the original stereochemistry of the parent alkyl halides, creating the potential for asymmetric cross-coupling of racemic alkyl halides.

Spectroscopic detection, characterization and dynamics of free radicals relevant to combustion processes

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

Miller, Terry

2015-06-04

Combustion chemistry is enormously complex. The chemical mechanisms involve a multitude of elementary reaction steps and a comparable number of reactive intermediates, many of which are free radicals. Computer simulations based upon these mechanisms are limited by the validity of the mechanisms and the parameters characterizing the properties of the intermediates and their reactivity. Spectroscopy can provide data for sensitive and selective diagnostics to follow their reactions. Spectroscopic analysis also provides detailed parameters characterizing the properties of these intermediates. These parameters serve as experimental gold standards to benchmark predictions of these properties from large-scale, electronic structure calculations. This work hasmore » demonstrated the unique capabilities of near-infrared cavity ringdown spectroscopy (NIR CRDS) to identify, characterize and monitor intermediates of key importance in complex chemical reactions. Our studies have focussed on the large family of organic peroxy radicals which are arguably themost important intermediates in combustion chemistry and many other reactions involving the oxidation of organic compounds. Our spectroscopic studies have shown that the NIR Ã - ˜X electronic spectra of the peroxy radicals allows one to differentiate among chemical species in the organic peroxy family and also determine their isomeric and conformic structure in many cases. We have clearly demonstrated this capability on saturated and unsaturated peroxy radicals and β-hydroxy peroxy radicals. In addition we have developed a unique dual wavelength CRDS apparatus specifically for the purpose of measuring absolute absorption cross section and following the reaction of chemical intermediates. The utility of the apparatus has been demonstrated by measuring the cross-section and self-reaction rate constant for ethyl peroxy.« less

Thermochemical and kinetic analyses on oxidation of isobutenyl radical and 2-hydroperoxymethyl-2-propenyl radical.

PubMed

Zheng, X L; Sun, H Y; Law, C K

2005-10-13

In recognition of the importance of the isobutene oxidation reaction in the preignition chemistry associated with engine knock, the thermochemistry, chemical reaction pathways, and reaction kinetics of the isobutenyl radical oxidation at low to intermediate temperature range were computationally studied, focusing on both the first and the second O2 addition to the isobutenyl radical. The geometries of reactants, important intermediates, transition states, and products in the isobutenyl radical oxidation system were optimized at the B3LYP/6-311G(d,p) and MP2(full)/6-31G(d) levels, and the thermochemical properties were determined on the basis of ab initio, density functional theory, and statistical mechanics. Enthalpies of formation for several important intermediates were calculated using isodesmic reactions at the DFT and the CBS-QB3 levels. The kinetic analysis of the first O2 addition to the isobutenyl radical was performed using enthalpies at the CBS-QB3 and G3(MP2) levels. The reaction forms a chemically activated isobutenyl peroxy adduct which can be stabilized, dissociate back to reactants, cyclize to cyclic peroxide-alkyl radicals, and isomerize to the 2-hydroperoxymethyl-2-propenyl radical that further undergoes another O2 addition. The reaction channels for isomerization and cyclization and further dissociation on this second O2 addition were analyzed using enthalpies at the DFT level with energy corrections based on similar reaction channels for the first O2 addition. The high-pressure limit rate constants for each reaction channel were determined as functions of temperature by the canonical transition state theory for further kinetic model development.

Free-radical chemistry of sulfite.

PubMed Central

Neta, P; Huie, R E

1985-01-01

The free-radical chemistry of sulfite oxidation is reviewed. Chemical transformations of organic and biological molecules induced by sulfite oxidation are summarized. The kinetics of the free-radical oxidations of sulfite are discussed, as are the kinetics of the reactions of the sulfite-derived radicals SO3 and the peroxy derivative SO5 with organic compounds. PMID:3830699

Free Radical Mechanisms in Autoxidation Processes.

ERIC Educational Resources Information Center

Simic, Michael G.

1981-01-01

Discusses the use of steady-state radiation chemistry and pulse radiolysis for the generation of initial free radicals and formation of peroxy radicals in the autoxidation process. Provides information regarding the autoxidation process. Defines autoxidation reactions and antioxidant action. (CS)

Electrografting of alkyl films at low driving force by diverting the reactivity of aryl radicals derived from diazonium salts.

PubMed

Hetemi, Dardan; Kanoufi, Frédéric; Combellas, Catherine; Pinson, Jean; Podvorica, Fetah I

2014-11-25

Alkyl and partial perfluoroalkyl groups are strongly attached to carbon surfaces through (i) the abstraction of the iodine atom from an iodoalkane by the sterically hindered 2,6-dimethylphenyl radical and (ii) the reaction of the ensuing alkyl radical with the carbon surface. Since the 2,6-dimethylphenyl radical is obtained at -0.25 V/Ag/AgCl by reducing the corresponding diazonium salt, the electrografting reaction is facilitated by ∼1.7 V by comparison with the direct electrografting of the iodo compounds. Layers of various thicknesses, including monolayers, are obtained by controlling the time duration of the electrolysis. The grafted films are characterized by electrochemistry, IR, XPS, ellipsometry, and water contact angles.

Measurements of Peroxy Radicals and Related Species At A Rural Site During The Escompte Campaign

NASA Astrophysics Data System (ADS)

Pinceloup, S.; Laverdet, G.; Le Bras, G.

The chemical amplifier technique has been used to measure peroxy radicals (RO2) concentrations at a rural site (Dupail), located 35 km North East of Marseille, during the ESCOMPTE campaign in June-July 2001. Daily profiles of RO2 and also ozone and NOx concentrations have been recorded everyday including those of the four in- tensive observation periods (IOP). The NOx levels were most of the time lower than a few ppbv, ie characteristic of a rural site. Typical diurnal profiles of RO2 were ob- served with maxima in the range 40-180 pptv. The RO2 signals were corrected from the influence of relative humidity based on calibration of the chemical amplifier in separate laboratory experiments under controlled water vapor concentrations. Prelim- inary interpretation of the data shows very different ratios of photochemically pro- duced/transported ozone related to meteorological conditions. Further interpretation of the data is underway integrating additional measurements of a large variety of hy- drocarbons as well as some hydroperoxides and aldehydes made at the site by other groups. The results of the comparison of calculated steady state concentrations of RO2 and ozone production rate with the measured values will be presented and discussed in relation with our understanding of the tropospheric ozone production.

Engaging unactivated alkyl, alkenyl and aryl iodides in visible-light-mediated free radical reactions

NASA Astrophysics Data System (ADS)

Nguyen, John D.; D'Amato, Erica M.; Narayanam, Jagan M. R.; Stephenson, Corey R. J.

2012-10-01

Radical reactions are a powerful class of chemical transformations. However, the formation of radical species to initiate these reactions has often required the use of stoichiometric amounts of toxic reagents, such as tributyltin hydride. Recently, the use of visible-light-mediated photoredox catalysis to generate radical species has become popular, but the scope of these radical precursors has been limited. Here, we describe the identification of reaction conditions under which photocatalysts such as fac-Ir(ppy)3 can be utilized to form radicals from unactivated alkyl, alkenyl and aryl iodides. The generated radicals undergo reduction via hydrogen atom abstraction or reductive cyclization. The reaction protocol utilizes only inexpensive reagents, occurs under mild reaction conditions, and shows exceptional functional group tolerance. Reaction efficiency is maintained upon scale-up and decreased catalyst loading, and the reaction time can be significantly shortened when the reaction is performed in a flow reactor.

Hydroxy nitrate production in the OH-initiated oxidation of alkenes

NASA Astrophysics Data System (ADS)

Teng, A. P.; Crounse, J. D.; Lee, L.; St. Clair, J. M.; Cohen, R. C.; Wennberg, P. O.

2014-03-01

Alkenes generally react rapidly by addition of OH and subsequently O2 to form beta hydroxy peroxy radicals. These peroxy radicals react with NO to form beta hydroxy nitrates with a branching ratio α. We quantify α for C2-C8 alkenes at 296 K ±3 and 993 hPa. The branching ratio can be expressed as α = (0.042 ± 0.008) × N - (0.11 ± 0.04) where N is the number of heavy atoms (excluding the peroxy moiety), and listed errors are 2σ. These branching ratios are larger than previously reported and are similar to those for peroxy radicals formed from H abstraction from alkanes. We find the isomer distributions of beta hydroxy nitrates formed under NO-dominated peroxy radical chemistry to be similar to the isomer distribution of hydroxy hydroperoxides produced under HO2-dominated peroxy radical chemistry. With the assumption of unity yield for the hydroperoxides, this implies that the branching ratio to form beta hydroxy nitrates from primary, secondary, and tertiary RO2 are similar. Deuterium substitution enhances the branching ratio to form hydroxy nitrates in both propene and isoprene by a factor of ~1.5. These observations provide further evidence for importance of the ROONO lifetime in determining the branching ratio to form alkyl nitrates. We use these measurements to re-evaluate the role of alkene chemistry in the Houston region. We find that small alkenes play a larger role in oxidant formation than previously recognized.

Diastereoselective radical addition to γ-alkyl-α-methylene-γ-butyrolactams and the synthesis of a chiral pyroglutamic acid derivative.

PubMed

Yajima, Tomoko; Yoshida, Eriko; Hamano, Masako

2013-01-01

The cis- and trans-stereoselective radical additions to α-methylene-γ-alkyl- γ-lactams were investigated and the scope and limitation of the reaction were also revealed. This stereoselective radical reaction was used for synthesis of chiral pyroglutamic acid derivatives starting from a commercially available chiral amino acid.

Chemiluminescence Study of the Autoxidation of cis-1,4-Polyisoprene

NASA Technical Reports Server (NTRS)

Mendenhall, G. David; Nathan, Richard A.; Golub, Morton A.

1978-01-01

The free-radical mechanism for the autoxidation of cis-1,4-polyisoprene (natural rubber or its synthetic counterpart) has been investigated extensively. An important feature of this mechanism, and indeed also of the autoxidation of hydrocarbons generally, is that it is a chain process propagated by alkyl and peroxy radicals and terminated through bimolecular reactions involving these same radicals. In the usual oxidation situation, that is, at all oxygen pressures greater than a few torr, the alkyl radicals are rapidly converted to peroxy radicals, and the termination step proceeds almost exclusively through the latter radicals. The bimolecular decay of the peroxy radicals is accompanied by a weak emission of light or chemiluminescence. Kinetic evidence is consistent with an electronically excited ketone produced in the termination reaction as the source of the emission. The first observation of chemiluminescence from the oxidative degradation of polymers was reported by Ashby, who dealt mainly with polypropylene but made passing mention of several other polymers. Subsequently, a number of papers have appeared dealing with oxidative chemiluminescence from a variety of polymers. In this paper we report the first detailed study of the chemiluminescence emitted in the autoxidation of cis-1,4-polyisoprene. The chemiluminescence technique is extremely sensitive and can follow rates of oxidation that are too slow to be measured conveniently by other means. This work thus offered the potential of throwing new light on the autoxidation of cis-1,4-polyisoprene, especially in the very early stages or under ambient conditions where conventional spectroscopic procedures are rather insensitive.

Comparison of COD removal from pharmaceutical wastewater by electrocoagulation, photoelectrocoagulation, peroxi-electrocoagulation and peroxi-photoelectrocoagulation processes.

PubMed

Farhadi, Sajjad; Aminzadeh, Behnoush; Torabian, Ali; Khatibikamal, Vahid; Alizadeh Fard, Mohammad

2012-06-15

This work makes a comparison between electrocoagulation (EC), photoelectrocoagulation, peroxi-electrocoagulation and peroxi-photoelectrocoagulation processes to investigate the removal of chemical oxygen demand (COD) from pharmaceutical wastewater. The effects of operational parameters such as initial pH, current density, applied voltage, amount of hydrogen peroxide and electrolysis time on COD removal efficiency were investigated and the optimum operating range for each of these operating variables was experimentally determined. In electrocoagulation process, the optimum values of pH and voltage were determined to be 7 and 40 V, respectively. Desired pH and hydrogen peroxide concentration in the Fenton-based processes were found to be 3 and 300 mg/L, respectively. The amounts of COD, pH, electrical conductivity, temperature and total dissolved solids (TDS) were on-line monitored. Results indicated that under the optimum operating range for each process, the COD removal efficiency was in order of peroxi-electrocoagulation > peroxi-photoelectrocoagulation > photoelectrocoagulation>electrocoagulation. Finally, a kinetic study was carried out using the linear pseudo-second-order model and results showed that the pseudo-second-order equation provided the best correlation for the COD removal rate. Copyright © 2012 Elsevier B.V. All rights reserved.

Diastereoselective radical addition to γ-alkyl-α-methylene-γ-butyrolactams and the synthesis of a chiral pyroglutamic acid derivative

PubMed Central

Yoshida, Eriko; Hamano, Masako

2013-01-01

Summary The cis- and trans-stereoselective radical additions to α-methylene-γ-alkyl- γ-lactams were investigated and the scope and limitation of the reaction were also revealed. This stereoselective radical reaction was used for synthesis of chiral pyroglutamic acid derivatives starting from a commercially available chiral amino acid. PMID:23946839

Silyl Radical Activation of Alkyl Halides in Metallaphotoredox Catalysis: A Unique Pathway for Cross-Electrophile Coupling.

PubMed

Zhang, Patricia; Le, Chi Chip; MacMillan, David W C

2016-07-06

A strategy for cross-electrophile coupling has been developed via the merger of photoredox and transition metal catalysis. In this report, we demonstrate the use of commercially available tris(trimethylsilyl)silane with metallaphotoredox catalysis to efficiently couple alkyl bromides with aryl or heteroaryl bromides in excellent yields. We hypothesize that a photocatalytically generated silyl radical species can perform halogen-atom abstraction to activate alkyl halides as nucleophilic cross-coupling partners. This protocol allows the use of mild yet robust conditions to construct Csp(3)-Csp(2) bonds generically via a unique cross-coupling pathway.

Fate of the CHBrsub2O radical in air

NASA Technical Reports Server (NTRS)

Bayes, K. D.; Friedl, R. F.

2003-01-01

Trace amounts of bromoform in air have been photolyzed at 266 and 303 nm to form Br atoms and CHBr2 radicals. The Br concentration as a funtion of time is followed by resonance fluorescence. The CHBr2 radicals react with O2 in the air to form peroxy radicals.

The interaction of radiation-generated radicals with myoglobin in aqueous solution—V. The indirect action of 2-methyl-2-hydroxypropyl radicals on oxymyoglobin

NASA Astrophysics Data System (ADS)

Whitburn, Kevin D.; Hoffman, Morton Z.

The interaction of radiation-generated 2-methyl-2-hydroxypropyl radicals (derived from t-butyl alcohol) with oxymyoglobin has been examined at pH 7.3. In N 2O-saturated solutions, oxymyoglobin is converted to the ferri and ferryl derivatives of myoglobin; the production of ferrylmyoglobin is essentially eliminated when catalase is present in solution during irradiation. In deaerated solutions containing catalase, oxymyoglobin is converted to both ferro- and ferrimyoglobin during irradiation. When added O 2 is initially present, all compositional changes occur after irradiation; the presence of catalase diminishes, but does not eliminate, the extent of these postirradiation conversions of oxymyoglobin to the ferri and ferryl derivatives. These observations are interpreted in terms of the scavenging of the 2-methyl-2-hydroxypropyl radicals by O 2 to generate their peroxy analogs, which causes a displacement of the equilibrium between oxy- and ferromyoglobin. The peroxy radicals decay to produce H 2O 2, an organic peroxide, and other products. These peroxides subsequently react with ferromyoglobin to produce the ferryl form; the rate of the reaction increases with decreasing [O 2] as [ferromyoglobin] increases. This reaction is sufficiently fast in deaerated solution that substantial conversion of ferromyoglobin to ferrylmyoglobin occurs during the time of irradiation. The formation of the ferryl derivative in the presence of unconverted ferromyoglobin drives a concurrent synproportion reaction which produces ferrimyoglobin. Overall, no direct interaction of 2-methyl-2-hydroxypropyl radicals, nor their peroxy analogs, with myoglobin is indicated; all reactivity is accountable by the peroxide products of these radicals.

Alkyl radical generation by an intramolecular homolytic substitution reaction between iron (II) and trialkylsulfonium groups.

PubMed

Jungen, Stefan; Chen, Peter

2018-05-16

Intramolecular, homolytic substitution reactions between iron (II) species and various trialkylsulfonium groups were directly observed in the gas phase upon collision induced dissociation. In spite of the notoriously low reduction potential of trialkylsulfonium species and the mismatched oxidation potential of iron (II), the reactions proceed at moderate collision energies, forming an alkyl radical as well as a thioether coordinated to the iron. In contrast to classical homolytic substitutions, the attacking radical is a "metalloradical", namely iron (II) that is oxidized to iron (III) during the reaction. With this process we demonstrate that the conceptually analogous, putative radical generation step in Radical S-Adenosyl Methionine Enzymes is possible and plausible. Further, we show that this kind of reaction only occurs in constrained systems with a defined geometry. Combining experimental measurements with DFT studies and NBO analyses allowed us to gain insights into the reactivity and transition states of these systems. Based on our findings, we challenge the notion of a collinear transition state in the radical generation step of Radical SAM Enzymes and propose it to be bent instead. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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.

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.

Peroxy radical detection by chemical amplification (PERCA)

NASA Technical Reports Server (NTRS)

Stedman, D. H.

1986-01-01

Important reactions of atmospheric free radicals are the chain oxidation of NO and CO. Thus: H2O + NO yields OH + NO2; OH + CO yields H + CO2; H + O2 + M yields HO2 + M. In most models, the need to know the free radical concentration could also be described as the need to know the rate of the above oxidation chain in the atmosphere. It is the total rate of this chain (also carried by RO2 and RO) which was measured using the PERCA. The PERCA is thus essentially a RO sub X meter. The PERCA works by adding excess CO (10%) and NO (5ppm) to a stream of air and measuring the NO2 produced after 3s of reaction time. Since other processes produce NO2, the chain reaction is modulated by switching the CO for N2. The chain length is limited by the reaction OH + NO yields HONO and is modeled to be somewhat over 1000. Measured chain lengths agree with the modeled numbers.

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

Understanding in situ ozone production in the summertime through radical observations and modelling studies during the Clean air for London project (ClearfLo)

NASA Astrophysics Data System (ADS)

Whalley, Lisa K.; Stone, Daniel; Dunmore, Rachel; Hamilton, Jacqueline; Hopkins, James R.; Lee, James D.; Lewis, Alastair C.; Williams, Paul; Kleffmann, Jörg; Laufs, Sebastian; Woodward-Massey, Robert; Heard, Dwayne E.

2018-02-01

Measurements of OH, HO2, RO2i (alkene and aromatic-related RO2) and total RO2 radicals taken during the ClearfLo campaign in central London in the summer of 2012 are presented. A photostationary steady-state calculation of OH which considered measured OH reactivity as the OH sink term and the measured OH sources (of which HO2+ NO reaction and HONO photolysis dominated) compared well with the observed levels of OH. Comparison with calculations from a detailed box model utilising the Master Chemical Mechanism v3.2, however, highlighted a substantial discrepancy between radical observations under lower NOx conditions ([NO] < 1 ppbv), typically experienced during the afternoon hours, and indicated that the model was missing a significant peroxy radical sink; the model overpredicted HO2 by up to a factor of 10 at these times. Known radical termination steps, such as HO2 uptake on aerosols, were not sufficient to reconcile the model-measurement discrepancies alone, suggesting other missing termination processes. This missing sink was most evident when the air reaching the site had previously passed over central London to the east and when elevated temperatures were experienced and, hence, contained higher concentrations of VOCs. Uncertainties in the degradation mechanism at low NOx of complex biogenic and diesel related VOC species, which were particularly elevated and dominated OH reactivity under these easterly flows, may account for some of the model-measurement disagreement. Under higher [NO] (> 3 ppbv) the box model increasingly underpredicted total [RO2]. The modelled and observed HO2 were in agreement, however, under elevated NO concentrations ranging from 7 to 15 ppbv. The model uncertainty under low NO conditions leads to more ozone production predicted using modelled peroxy radical concentrations ( ˜ 3 ppbv h-1) versus ozone production from peroxy radicals measured ( ˜ 1 ppbv h-1). Conversely, ozone production derived from the predicted peroxy radicals is up

Identification and yields of 1,4-hydroxynitrates formed from the reactions of C8-C16 n-alkanes with OH radicals in the presence of NO(x).

PubMed

Yeh, Geoffrey K; Ziemann, Paul J

2014-09-25

A series of C8-C16 n-alkanes were reacted with OH radicals in the presence of NOx in an environmental chamber and particulate 1,4-hydroxynitrate reaction products were collected by filtration, extracted, and analyzed by high-performance liquid chromatography with UV absorption and electron ionization mass spectrometry (HPLC/UV/MS). Observed mass spectral patterns can be explained by using proposed ion fragmentation mechanisms, permitting the identification of each hydroxynitrate isomer. Reversed-phase retention of these compounds was dictated by the length of the longer of two alkyl chains attached to the 1,4-hydroxynitrate subunit. 1,4-Hydroxynitrates were quantified in particles using an authentic analytical standard for calibration, and the results were combined with gas chromatography measurements of the n-alkanes to determine the molar yields. Yields based on analyses of particles increased with increasing carbon number from 0.00 for C8 to an average plateau value of 0.130 ± 0.008 for C14-C16, due primarily to corresponding increases in gas-to-particle partitioning. The value at the plateau, where essentially all 1,4-hydroxynitrates were in particles, was equal to the average total yield of C14-C16 1,4-hydroxynitrates. The average branching ratio for the formation of C14-C16 1,4-hydroxynitrates from the reaction of NO with the corresponding 1,4-hydroxyperoxy radicals was 0.184 ± 0.011. This value is ∼20% higher than the plateau value of 0.15 for reactions of secondary 1,2-hydroxyperoxy radicals and ∼40% lower than the plateau value of 0.29 for reactions of secondary alkyl peroxy radicals, both of which were reported previously. The branching ratios determined here were used with values reported previously to calculate the yields of C7-C18 alkyl nitrates, 1,4-hydroxynitrates, and 1,4-hydroxycarbonyls, the three products formed from the reactions of these n-alkanes.

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.

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.

Investigation of the antioxidant and radical scavenging activities of some phenolic Schiff bases with different free radicals.

PubMed

Marković, Zoran; Đorović, Jelena; Petrović, Zorica D; Petrović, Vladimir P; Simijonović, Dušica

2015-11-01

The antioxidant properties of some phenolic Schiff bases in the presence of different reactive particles such as (•)OH, (•)OOH, (CH2=CH-O-O(•)), and (-•)O2 were investigated. The thermodynamic values, ΔH BDE, ΔH IP, and ΔH PA, were used for this purpose. Three possible mechanisms for transfer of hydrogen atom, concerted proton-electron transfer (CPET), single electron transfer followed by proton transfer (SET-PT), and sequential proton loss electron transfer (SPLET) were considered. These mechanisms were tested in solvents of different polarity. On the basis of the obtained results it was shown that SET-PT antioxidant mechanism can be the dominant mechanism when Schiff bases react with radical cation, while SPLET and CPET are competitive mechanisms for radical scavenging of hydroxy radical in all solvents under investigation. Examined Schiff bases react with the peroxy radicals via SPLET mechanism in polar and nonpolar solvents. The superoxide radical anion reacts with these Schiff bases very slowly.

Evaluated rate constants for selected HCFC's and HFC's with OH and O((sup)1D)

NASA Technical Reports Server (NTRS)

Hampson, Robert F.; Kurylo, Michael J.; Sander, Stanley P.

1990-01-01

The chemistry of HCFC's and HFC's in the troposphere is controlled by reactions with OH in which a hydrogen atom is abstracted from the halocarbon to form water and a halo-alkyl radical. The halo-alkyl radical subsequently reacts with molecular oxygen to form a peroxy radical. The reactions of HCFC's and HFC's with O(exp1D) atoms are unimportant in the troposphere, but may be important in producing active chlorine of OH in the stratosphere. Here, the rate constants for the reactions of OH and O(exp1D) with many HFC's and HCFC's are evaluated. Recommendations are given for the five HCFC's and three HFC's specified by AFEAS as primary alternatives as well as for all other isomers of C1 and C2 HCFC's and HFC's where rate data exist. In addition, recommendations are included for CH3CCl3, CH2Cl2, and CH4.

Products of BVOC oxidation: ozone and organic aerosols

NASA Astrophysics Data System (ADS)

Wildt, Jürgen; Andres, Stefanie; Carriero, Giulia; Ehn, Mikael; Fares, Silvano; Hoffmann, Thorsten; Hacker, Lina; Kiendler-Scharr, Astrid; Kleist, Einhard; Paoletti, Elena; Pullinen, Iida; Rohrer, Franz; Rudich, Yinon; Springer, Monika; Tillmann, Ralf; Wahner, Andreas; Wu, Cheng; Mentel, Thomas

2015-04-01

Biogenic Volatile Organic Compounds (BVOC) are important precursors in photochemical O3 and secondary organic aerosol (SOA) formation. We conducted a series of laboratory experiments with OH-induced oxidation of monoterpenes to elucidate pathways and efficiencies of O3 and SOA formation. At high NOx conditions ([BVOC] / [NOx] < 7 ppbC / ppb) photochemical ozone formation was observed. For -pinene as individual BVOC as well as for the monoterpene mixes emitted from different plant species we observed increasing ozone formation with increasing [NOX]. Between 2 and 3 O3-molecules were formed from 1 monoterpene when ozone formation was BVOC limited. Under such high NOX conditions, new particle formation was suppressed. Increasing [BVOC] / [NOX] ratios caused increasing efficiency of new particle formation indicating that peroxy radicals are the key intermediates in both, photochemical ozone- and new particle formation. The classical chemistry of peroxy radicals is well established (e.g. Master Chemical Mechanism). Peroxy radicals are produced by addition of molecular oxygen to the alkyl radical formed after OH attack at the BVOC. They either react with NO which leads to ozone formation or they react with other peroxy radicals and form chemically stable products (hydroperoxides, alkoholes and ketones). Much less knowledge exists on such reactions for Highly Oxidized Peroxy Radicals, (HOPR). Such HOPR were observed during ozonolysis of several volatiles and, in case of monoterpenes as precursors, they can contain more than 12 Oxygen atoms (Mentel et al., 2015). Although the OH-initiated formation of HOPR is yet not fully understood, their basic gas phase reactions seem to follow classical photochemical rules. In reactions with NO they can act as precursor for O3 and in reactions with other HOPR or with classical less oxidized peroxy radicals they can form highly oxidized stable products and alkoxy radicals. In addition, HOPR-HOPR reactions lead to the formation of

One-step formation of bifunctionnal aryl/alkyl grafted films on conducting surfaces by the reduction of diazonium salts in the presence of alkyl iodides.

PubMed

Hetemi, Dardan; Hazimeh, Hassan; Decorse, Philippe; Galtayries, Anouk; Combellas, Catherine; Kanoufi, Frédéric; Pinson, Jean; Podvorica, Fetah I

2015-05-19

The formation of partial perfluoroalkyl or alkyl radicals from partial perfluoroalkyl or alkyl iodides (ICH2CH2C6F13 and IC6H13) and their reaction with surfaces takes place at low driving force (∼-0.5 V/SCE) when the electrochemical reaction is performed in acetonitrile in the presence of diazonium salts (ArN2(+)), at a potential where the latter is reduced. By comparison to the direct grafting of ICH2CH2C6F13, this corresponds to a gain of ∼2.1 V in the case of 4-nitrobenzenediazonium. Such electrochemical reaction permits the modification of gold surfaces (and also carbon, iron, and copper) with mixed aryl-alkyl groups (Ar = 3-CH3-C6H4, 4-NO2-C6H4, and 4-Br-C6H4, R = C6H13 or (CH2)2-C6F13). These strongly bonded mixed layers are characterized by IRRAS, XPS, ToF-SIMS, ellipsometry, water contact angles, and cyclic voltammetry. The relative proportions of grafted aryl and alkyl groups can be varied along with the relative concentrations of diazonium and iodide components in the grafting solution. The formation of the films is assigned to the reaction of aryl and alkyl radicals on the surface and on the first grafted layer. The former is obtained from the electrochemical reduction of the diazonium salt; the latter results from the abstraction of an iodine atom by the aryl radical. The mechanism involved in the growth of the film provides an example of complex surface radical chemistry.

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.

Highly Oxidizing Surface Radicals in Lunar Dust

NASA Astrophysics Data System (ADS)

Kulahci, I.; Freund, F. T.; Bose, M.; Loftus, D. J.

2007-12-01

Lunar rocks are generally believed to be very "dry" with little or no evidence for hydroxyl as indicators of traces of dissolved H2O. The absence of hydroxyl, however, is not a sure sign of the absence of dissolved H2O. The reason is that hydroxyl pairs in the structure of host minerals, O3X-OH HO-XO3, with X=Si4+, Al3+ etc., tend to undergo an electronic rearrangement (redox conversion) in the course of which two oxygen anions are oxidized from the 2- to the 1- valence, forming a peroxy link, O3X-OO-XO3, plus an H2 molecule. If the H2 molecules diffuse out (which they are expected to do from lunar rocks and lunar fines over the course of 4 Gyrs), the peroxy links remain as the only "memory" of a former solute H2O content. Hard UV causes peroxy links to dissociate. In the process an electron from a neighboring O2- jumps into the broken peroxy bond. This is equivalent to forming an O-, e.g. a defect electron in the oxygen anion sublattice. Such defect electrons, also known as positive holes or pholes for short, represent highly mobile charge carriers. When trapped at the surface of dust grains, these charge carriers turn into highly reactive, highly oxidizing O- radicals, which are of concern because of their toxicity when lunar dust is inhaled by astronauts. We propose a device to measure the UV-activation of peroxy links by dusting lunar fines onto a polyethylene base plate with Au electrodes sputtered onto both ends and an ammeter connecting the two electrodes. One end of the dust layer will be exposed to the ambient UV radiation, while the remainder will be shaded. During the lunar night no current is expected to flow between the two Au electrodes. During passage through the night-day terminator, a current is expected to flow between the Au electrodes carried by defect electrons activated in the irradiated portion of the dust layer. Such a current would be an indicator that lunar fines and, by implication, lunar rocks contain peroxy links as a memory of a former

OH, HO2, and HO2* Radical Chemistry During PROPHET-AMOS 2016: Measurements and Model Comparison

NASA Astrophysics Data System (ADS)

Bottorff, B.; Lew, M.; Rickly, P.; Stevens, P. S.

2017-12-01

The hydroxyl (OH) and peroxy radicals, both the hydroperoxy radical (HO2) and organic peroxy radicals (RO2), play an important role in atmospheric chemistry. In addition to controlling lifetimes of many trace gases important to issues of global climate change, reactions of these radicals can also lead to the production of ozone and secondary organic aerosols in the atmosphere. Previous measurements of these radicals in remote forest environments have shown serious discrepancies with modeled concentrations. These results bring into question our understanding of the atmospheric chemistry of isoprene and other biogenic VOCs under low NOX conditions. In the summer of 2016, OH, HO2 and HO2* (HO2 + αRO2) radicals were measured using the Indiana University Laser-Induced Fluorescence Fluorescence Assay by Gas Expansion (LIF-FAGE) technique as part of the Program for Research on Oxidants: PHtochemistry, Emissions, and Transport- Atmospheric Measurements of Oxidants in Summer (PROPHET-AMOS). This campaign took place in a forested area in northern Michigan characterized by high mixing ratios of isoprene and low mixing ratios of NOX. Ambient measurements from this campaign will be compared to previous measurements at this site and to modeled predictions using both the Regional Atmospheric Chemistry Mechanism (RACM2) and the Master Chemical Mechanism. Potential interferences associated with the OH measurements will also be examined.

Gas-Phase Ozonolysis of Cycloalkenes: Formation of Highly Oxidized RO2 Radicals and Their Reactions with NO, NO2, SO2, and Other RO2 Radicals.

PubMed

Berndt, Torsten; Richters, Stefanie; Kaethner, Ralf; Voigtländer, Jens; Stratmann, Frank; Sipilä, Mikko; Kulmala, Markku; Herrmann, Hartmut

2015-10-15

The gas-phase reaction of ozone with C5-C8 cycloalkenes has been investigated in a free-jet flow system at atmospheric pressure and a temperature of 297 ± 1 K. Highly oxidized RO2 radicals bearing at least 5 O atoms in the molecule and their subsequent reaction products were detected in most cases by means of nitrate-CI-APi-TOF mass spectrometry. Starting from a Criegee intermediate after splitting-off an OH-radical, the formation of these RO2 radicals can be explained via an autoxidation mechanism, meaning RO2 isomerization (ROO → QOOH) and subsequently O2 addition (QOOH + O2 → R'OO). Time-dependent RO2 radical measurements concerning the ozonolysis of cyclohexene indicate rate coefficients of the intramolecular H-shifts, ROO → QOOH, higher than 1 s(-1). The total molar yield of highly oxidized products (predominantly RO2 radicals) from C5-C8 cycloalkenes in air is 4.8-6.0% affected with a calibration uncertainty by a factor of about two. For the most abundant RO2 radical from cyclohexene ozonolysis, O,O-C6H7(OOH)2O2 ("O,O" stands for two O atoms arising from the ozone attack), the determination of the rate coefficients of the reaction with NO2, NO, and SO2 yielded (1.6 ± 0.5) × 10(-12), (3.4 ± 0.9) × 10(-11), and <10(-14) cm(3) molecule(-1) s(-1), respectively. The reaction of highly oxidized RO2 radicals with other peroxy radicals (R'O2) leads to detectable accretion products, RO2 + R'O2 → ROOR' + O2, which allows to acquire information on peroxy radicals not directly measurable with the nitrate ionization technique applied here. Additional experiments using acetate as the charger ion confirm conclusively the existence of highly oxidized RO2 radicals and closed-shell products. Other reaction products, detectable with this ionization technique, give a deeper insight in the reaction mechanism of cyclohexene ozonolysis.

Oxidative 1,2-carboamination of alkenes with alkyl nitriles and amines toward γ-amino alkyl nitriles

NASA Astrophysics Data System (ADS)

Liu, Yan-Yun; Yang, Xu-Heng; Song, Ren-Jie; Luo, Shenglian; Li, Jin-Heng

2017-04-01

Difunctionalization of alkenes has become a powerful tool for quickly increasing molecular complexity in synthesis. Despite significant progress in the area of alkene difunctionalization involving the incorporation of a nitrogen atom across the C-C double bonds, approaches for the direct 1,2-carboamination of alkenes to produce linear N-containing molecules are scarce and remain a formidable challenge. Here we describe a radical-mediated oxidative intermolecular 1,2-alkylamination of alkenes with alkyl nitriles and amines involving C(sp3)-H oxidative functionalization catalysed by a combination of Ag2CO3 with iron Lewis acids. This three-component alkene 1,2-alkylamination method is initiated by the C(sp3)-H oxidative radical functionalization, which enables one-step formation of two new chemical bonds, a C-C bond and a C-N bond, to selectively produce γ-amino alkyl nitriles.

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.

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 photochemical alkylation and reduction of heteroarenes.

PubMed

McCallum, T; Pitre, S P; Morin, M; Scaiano, J C; Barriault, L

2017-11-01

The functionalization of heteroarenes has been integral to the structural diversification of medicinally active molecules such as quinolines, pyridines, and phenanthridines. Electron-deficient heteroarenes are electronically compatible to react with relatively nucleophilic free radicals such as hydroxyalkyl. However, the radical functionalization of such heteroarenes has been marked by the use of transition-metal catalyzed processes that require initiators and stoichiometric oxidants. Herein, we describe the photochemical alkylation of quinolines, pyridines and phenanthridines, where through direct excitation of the protonated heterocycle, alcohols and ethers, such as methanol and THF, can serve as alkylating agents. We also report the discovery of a photochemical reduction of these heteroarenes using only iPrOH and HCl. Mechanistic studies to elucidate the underlying mechanism of these transformations, and preliminary results on catalytic methylations are also reported.

Nuclear Resonance Vibrational Spectroscopic Definition of Peroxy Intermediates in Nonheme Iron Sites.

PubMed

Sutherlin, Kyle D; Liu, Lei V; Lee, Yong-Min; Kwak, Yeonju; Yoda, Yoshitaka; Saito, Makina; Kurokuzu, Masayuki; Kobayashi, Yasuhiro; Seto, Makoto; Que, Lawrence; Nam, Wonwoo; Solomon, Edward I

2016-11-02

Fe III -(hydro)peroxy intermediates have been isolated in two classes of mononuclear nonheme Fe enzymes that are important in bioremediation: the Rieske dioxygenases and the extradiol dioxygenases. The binding mode and protonation state of the peroxide moieties in these intermediates are not well-defined, due to a lack of vibrational structural data. Nuclear resonance vibrational spectroscopy (NRVS) is an important technique for obtaining vibrational information on these and other intermediates, as it is sensitive to all normal modes with Fe displacement. Here, we present the NRVS spectra of side-on Fe III -peroxy and end-on Fe III -hydroperoxy model complexes and assign these spectra using calibrated DFT calculations. We then use DFT calculations to define and understand the changes in the NRVS spectra that arise from protonation and from opening the Fe-O-O angle. This study identifies four spectroscopic handles that will enable definition of the binding mode and protonation state of Fe III -peroxy intermediates in mononuclear nonheme Fe enzymes. These structural differences are important in determining the frontier molecular orbitals available for reactivity.

An oxygen radical absorbance capacity-like assay that directly quantifies the antioxidant's scavenging capacity against AAPH-derived free radicals.

PubMed

Kohri, Shunji; Fujii, Hirotada; Oowada, Shigeru; Endoh, Nobuyuki; Sueishi, Yoshimi; Kusakabe, Miku; Shimmei, Masashi; Kotake, Yashige

2009-03-15

A new method is proposed for the evaluation of oxygen radical absorbance capacity (ORAC). The current fluorescence-based ORAC assay (ORAC-FL) is an indirect method that monitors the antioxidant's ability to protect the fluorescent probe from free radical-mediated damage, and an azo-radical initiator, AAPH (2,2-azobis(2-amidinopropane) dihydrochloride), has been used as a thermal free radical source. The new ORAC assay employs a short in situ photolysis of AAPH to generate free radicals. The electron paramagnetic resonance (EPR) spin trapping method was employed to identify and quantify AAPH radicals. In the presence of antioxidant, the level of AAPH radicals was decreased, and ORAC-EPR values were calculated following a simple kinetic formulation. Alkyl-oxy radical was identified as the sole decomposition product from AAPH; therefore, we concluded that ORAC-FL is the assay equivalent to alkyl-oxy radical scavenging capacity measurement. ORAC-EPR results for several antioxidants and human serum indicated that the overall tendency is in agreement with ORAC-FL, but absolute values showed significant discrepancies. ORAC-EPR is a rapid and simple method that is especially suitable for thermally labile biological specimens because the sample heating is not required for free radical production.

An assessment of potential degradation products in the gas-phase reactions of alternative fluorocarbons in the troposphere

NASA Technical Reports Server (NTRS)

Niki, Hiromi

1990-01-01

Tropospheric chemical transformations of alternative hydrofluorocarbons (HCF's) and hydrochlorofluorocarbons (HCFC's) are governed by hydroxyl radical initiated oxidation processes, which are likely to be analogous to those known for alkanes and chloroalkanes. A schematic diagram is used to illustrate plausible reaction mechanisms for their atmospheric degradation, where R, R', and R'' denote the F- and/or Cl-substituted alkyl groups derived from HCF's and HCFC's subsequent th the initial H atom abstraction by HO radicals. At present, virtually no kinetic data exist for the majority of these reactions, particularly for those involving RO. Potential degradation intermediates and final products include a large variety of fluorine- and/or chlorine-containing carbonyls, acids, peroxy acids, alcohols, hydrogen peroxides, nitrates and peroxy nitrates, as summarized in the attached table. Probably atmospheric lifetimes of these compounds were also estimated. For some carbonyl and nitrate products shown in this table, there seem to be no significant gas-phase removal mechanisms. Further chemical kinetics and photochemical data are needed to quantitatively assess the atmospheric fate of HCF's and HCFC's, and of the degradation products postulated in this report.

Effective treatment of PAH contaminated Superfund site soil with the peroxy-acid process.

PubMed

Scott Alderman, N; N'Guessan, Adeola L; Nyman, Marianne C

2007-07-31

Peroxy-organic acids are formed by the chemical reaction between organic acids and hydrogen peroxide. The peroxy-acid process was applied to two Superfund site soils provided by the U.S. Environmental Protection Agency (EPA). Initial small-scale experiments applied ratios of 3:5:7 (v/v/v) or 3:3:9 (v/v/v) hydrogen peroxide:acetic acid:deionized (DI) water solution to 5g of Superfund site soil. The experiment using 3:5:7 (v/v/v) ratio resulted in an almost complete degradation of the 14 EPA regulated polycyclic aromatic hydrocarbons (PAHs) in Bedford LT soil during a 24-h reaction period, while the 3:3:9 (v/v/v) ratio resulted in no applicable degradation in Bedford LT lot 10 soil over the same reaction period. Specific Superfund site soil characteristics (e.g., pH, total organic carbon content and particle size distribution) were found to play an important role in the availability of the PAHs and the efficiency of the transformation during the peroxy-acid process. A scaled-up experiment followed treating 150g of Bedford LT lot 10 soil with and without mixing. The scaled-up processes applied a 3:3:9 (v/v/v) solution resulting in significant decrease in PAH contamination. These findings demonstrate the peroxy-acid process as a viable option for the treatment of PAH contaminated soils. Further work is necessary in order to elucidate the mechanisms of this process.

Alkyl hydrogen atom abstraction reactions of the CN radical with ethanol

NASA Astrophysics Data System (ADS)

Athokpam, Bijyalaxmi; Ramesh, Sai G.

2018-04-01

We present a study of the abstraction of alkyl hydrogen atoms from the β and α positions of ethanol by the CN radical in solution using the Empirical Valence Bond (EVB) method. We have built separate 2 × 2 EVB models for the Hβ and Hα reactions, where the atom transfer is parameterized using ab initio calculations. The intra- and intermolecular potentials of the reactant and product molecules were modelled with the General AMBER Force Field, with some modifications. We have carried out the dynamics in water and chloroform, which are solvents of contrasting polarity. We have computed the potential of mean force for both abstractions in each of the solvents. They are found to have a small and early barrier along the reaction coordinate with a large energy release. Analyzing the solvent structure around the reaction system, we have found two solvents to have little effect on either reaction. Simulating the dynamics from the transition state, we also study the fate of the energies in the HCN vibrational modes. The HCN molecule is born vibrationally hot in the CH stretch in both reactions and additionally in the HCN bends for the Hα abstraction reaction. In the early stage of the dynamics, we find that the CN stretch mode gains energy at the expense of the energy in CH stretch mode.

Nuclear Resonance Vibrational Spectroscopic Definition of Peroxy Intermediates in Nonheme Iron Sites

DOE PAGES

Sutherlin, Kyle D.; Liu, Lei V.; Lee, Yong-Min; ...

2016-11-02

Fe III-(hydro)peroxy intermediates have been isolated in two classes of mononuclear nonheme Fe enzymes that are important in bioremediation: the Rieske dioxygenases and the extradiol dioxygenases. The binding mode and protonation state of the peroxide moieties in these intermediates are not well-defined, due to a lack of vibrational structural data. Nuclear resonance vibrational spectroscopy (NRVS) is an important technique for obtaining vibrational information on these and other intermediates, as it is sensitive to all normal modes with Fe displacement. Here in this paper, we present the NRVS spectra of side-on Fe III-peroxy and end-on Fe III-hydroperoxy model complexes and assignmore » these spectra using calibrated DFT calculations. We then use DFT calculations to define and understand the changes in the NRVS spectra that arise from protonation and from opening the Fe–O–O angle. This study identifies four spectroscopic handles that will enable definition of the binding mode and protonation state of Fe III-peroxy intermediates in mononuclear nonheme Fe enzymes. These structural differences are important in determining the frontier molecular orbitals available for reactivity.« less

Nuclear Resonance Vibrational Spectroscopic Definition of Peroxy Intermediates in Nonheme Iron Sites

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

Sutherlin, Kyle D.; Liu, Lei V.; Lee, Yong-Min

Fe III-(hydro)peroxy intermediates have been isolated in two classes of mononuclear nonheme Fe enzymes that are important in bioremediation: the Rieske dioxygenases and the extradiol dioxygenases. The binding mode and protonation state of the peroxide moieties in these intermediates are not well-defined, due to a lack of vibrational structural data. Nuclear resonance vibrational spectroscopy (NRVS) is an important technique for obtaining vibrational information on these and other intermediates, as it is sensitive to all normal modes with Fe displacement. Here in this paper, we present the NRVS spectra of side-on Fe III-peroxy and end-on Fe III-hydroperoxy model complexes and assignmore » these spectra using calibrated DFT calculations. We then use DFT calculations to define and understand the changes in the NRVS spectra that arise from protonation and from opening the Fe–O–O angle. This study identifies four spectroscopic handles that will enable definition of the binding mode and protonation state of Fe III-peroxy intermediates in mononuclear nonheme Fe enzymes. These structural differences are important in determining the frontier molecular orbitals available for reactivity.« less

Direct β-Alkylation of Aldehydes via Photoredox Organocatalysis

PubMed Central

2015-01-01

Direct β-alkylation of saturated aldehydes has been accomplished by synergistically combining photoredox catalysis and organocatalysis. Photon-induced enamine oxidation provides an activated β-enaminyl radical intermediate, which readily combines with a wide range of Michael acceptors to produce β-alkyl aldehydes in a highly efficient manner. Furthermore, this redox-neutral, atom-economical C–H functionalization protocol can be achieved both inter- and intramolecularly. Mechanistic studies by various spectroscopic methods suggest that a reductive quenching pathway is operable. PMID:24754456

Enhanced Synthesis of Alkyl Amino Acids in Miller's 1958 H2S Experiment

NASA Technical Reports Server (NTRS)

Parker, Eric T.; Cleaves, H. James; Callahan, Michael P.; Dworkin, James P.; Glavin, Daniel P.; Lazcano, Antonio; Bada, Jeffrey L.

2011-01-01

Stanley Miller's 1958 H2S-containing experiment, which included a simulated prebiotic atmosphere of methane (CH4), ammonia (NH3), carbon dioxide (CO2), and hydrogen sulfide (H2S) produced several alkyl amino acids, including the alpha-, beta-, and gamma-isomers of aminobutyric acid (ABA) in greater relative yields than had previously been reported from his spark discharge experiments. In the presence of H2S, aspariic and glutamic acids could yield alkyl amino acids via the formation of thioimide intermediates. Radical chemistry initiated by passing H2S through a spark discharge could have also enhanced alkyl amino acid synthesis by generating alkyl radicals that can help form the aldehyde and ketone precursors to these amino acids. We propose mechanisms that may have influenced the synthesis of certain amino acids in localized environments rich in H2S and lightning discharges, similar to conditions near volcanic systems on the early Earth, thus contributing to the prebiotic chemical inventory of the primordial Earth.

Kinetics of the Reaction of CH3O2 Radicals with OH Studied over the 292-526 K Temperature Range.

PubMed

Yan, Chao; Kocevska, Stefani; Krasnoperov, Lev N

2016-08-11

Reaction of methyl peroxy radicals with hydroxyl radicals, CH3O2 + OH → CH3O + HO2 (1a) and CH3O2 + OH → CH2OO + H2O (1b) was studied using pulsed laser photolysis coupled to transient UV-vis absorption spectroscopy over the 292-526 K temperature range and pressure 1 bar (bath gas He). Hydroxyl radicals were generated in the reaction of electronically excited oxygen atoms O((1)D), produced in the photolysis of N2O at 193.3 nm, with H2O. Methyl peroxy radicals were generated in the reaction of methyl radicals, CH3, produced in the photolysis of acetone at 193.3 nm, and subsequent reaction of CH3 with O2. Temporal profiles of OH were monitored via transient absorption of light from a DC discharge H2O/Ar low-pressure resonance lamp at ca. 308 nm. The absolute intensity of the photolysis light was determined by accurate in situ actinometry based on the ozone formation in the presence of molecular oxygen. The overall rate constant of the reaction is k1a+1b = (8.4 ± 1.7) × 10(-11)(T/298 K)(-0.81) cm(3) molecule(-1) s(-1) (292-526 K). The branching ratio of channel 1b at 298 K is less than 5%.

Role of the reaction of stabilized Criegee intermediates with peroxy radicals in particle formation and growth in air.

PubMed

Zhao, Yue; Wingen, Lisa M; Perraud, Véronique; Greaves, John; Finlayson-Pitts, Barbara J

2015-05-21

Ozonolysis of alkenes is an important source of secondary organic aerosol (SOA) in the atmosphere. However, the mechanisms by which stabilized Criegee intermediates (SCI) react to form and grow the particles, and in particular the contributions from oligomers, are not well understood. In this study, ozonolysis of trans-3-hexene (C6H12), as a proxy for small alkenes, was investigated with an emphasis on the mechanisms of particle formation and growth. Ozonolysis experiments were carried out both in static Teflon chambers (18-20 min reaction times) and in a glass flow reactor (24 s reaction time) in the absence and presence of OH or SCI scavengers, and under different relative humidity (RH) conditions. The chemical composition of polydisperse and size-selected SOA particles was probed using different mass spectrometric techniques and infrared spectroscopy. Oligomers having SCI as the chain unit are found to be the dominant components of such SOA particles. The formation mechanism for these oligomers suggested by our results follows the sequential addition of SCI to organic peroxy (RO2) radicals, in agreement with previous studies by Moortgat and coworkers. Smaller particles are shown to have a relatively greater contribution from longer oligomers. Higher O/C ratios are observed in smaller particles and are similar to those of oligomers resulting from RO2 + nSCI, supporting a significant role for longer oligomers in particle nucleation and early growth. Under atmospherically relevant RH of 30-80%, water vapor suppresses oligomer formation through scavenging SCI, but also enhances particle nucleation. Under humid conditions, or in the presence of formic or hydrochloric acid as SCI scavengers, peroxyhemiacetals are formed by the acid-catalyzed particle phase reaction between oligomers from RO2 + nSCI and a trans-3-hexene derived carbonyl product. In contrast to the ozonolysis of trans-3-hexene, oligomerization involving RO2 + nSCI does not appear to be prevalent in the

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.

Multiple free-radical scavenging capacity in serum

PubMed Central

Oowada, Shigeru; Endo, Nobuyuki; Kameya, Hiromi; Shimmei, Masashi; Kotake, Yashige

2012-01-01

We have developed a method to determine serum scavenging-capacity profile against multiple free radical species, namely hydroxyl radical, superoxide radical, alkoxyl radical, alkylperoxyl radical, alkyl radical, and singlet oxygen. This method was applied to a cohort of chronic kidney disease patients. Each free radical species was produced with a common experimental procedure; i.e., uv/visible-light photolysis of free-radical precursor/sensitizer. The decrease in free-radical concentration by the presence of serum was quantified with electron spin resonance spin trapping method, from which the scavenging capacity was calculated. There was a significant capacity change in the disease group (n = 45) as compared with the healthy control group (n = 30). The percent values of disease’s scavenging capacity with respect to control group indicated statistically significant differences in all free-radical species except alkylperoxyl radical, i.e., hydroxyl radical, 73 ± 12% (p = 0.001); superoxide radical, 158 ± 50% (p = 0.001); alkoxyl radical, 121 ± 30% (p = 0.005); alkylperoxyl radical, 123 ± 32% (p>0.1); alkyl radical, 26 ± 14% (p = 0.001); and singlet oxygen, 57 ± 18% (p = 0.001). The scavenging capacity profile was illustrated using a radar chart, clearly demonstrating the characteristic change in the disease group. Although the cause of the scavenging capacity change by the disease state is not completely understood, the profile of multiple radical scavenging capacities may become a useful diagnostic tool. PMID:22962529

Spin labeled antioxidants protect bacteria against the toxicity of alkylating antitumor drug CCNU.

PubMed

Gadjeva, Vesselina; Lazarova, Grozdanka; Zheleva, Antoaneta

2003-10-15

We have studied the toxic effect of the alkylating antitumor drug N'-cyclohexyl-N-(2-chloroethyl)-N-nitrosourea (lomustine, CCNU) on Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) strains, alone and in presence of oxygen radical-scavenging substances [Vitamin E, stable nitroxyl radical 2,2,6,6-tetramethylpiperidine-N-oxyl (TMPO), and spin labeled (nitroxyl free radical moiety containing) analogues of CCNU] and compared with that of the alkylating antitumor drug 5-(3,3-dimethyltriazene-1-yl)-imidazole-4-carboxamide (dacarbazine, DTIC). All spin labeled compounds tested were almost no toxic at doses of 50-500 microM/ml, whereas the alkylating antitumor drug CCNU showed toxicity in a dose dependent manner. Even low doses of spin labeled nitrosoureas provided protection against the toxicity caused by the antitumor drug CCNU alone. The lowest toxicity against E. coli and S. aureus were achieved when 500 microM/ml of CCNU was combined with 200 microM/ml of spin labeled nitrosourea N-[N'-(2-chloroethyl)-N'-nitrosocarbamoyl]-glycine amid of 2,2,6,6-tetramethyl-4-aminopiperidine-1-oxyl (SLCNUgly). A combination of TMPO with vitamin E completely abolished the toxicity of CCNU. Endogenous formation of oxygen radicals and their possible involvement in CCNU toxicity towards the bacteria strains tested have been also discussed.

Exploring the chemical kinetics of partially oxidized intermediates by combining experiments, theory, and kinetic modeling.

PubMed

Hoyermann, Karlheinz; Mauß, Fabian; Olzmann, Matthias; Welz, Oliver; Zeuch, Thomas

2017-07-19

Partially oxidized intermediates play a central role in combustion and atmospheric chemistry. In this perspective, we focus on the chemical kinetics of alkoxy radicals, peroxy radicals, and Criegee intermediates, which are key species in both combustion and atmospheric environments. These reactive intermediates feature a broad spectrum of chemical diversity. Their reactivity is central to our understanding of how volatile organic compounds are degraded in the atmosphere and converted into secondary organic aerosol. Moreover, they sensitively determine ignition timing in internal combustion engines. The intention of this perspective article is to provide the reader with information about the general mechanisms of reactions initiated by addition of atomic and molecular oxygen to alkyl radicals and ozone to alkenes. We will focus on critical branching points in the subsequent reaction mechanisms and discuss them from a consistent point of view. As a first example of our integrated approach, we will show how experiment, theory, and kinetic modeling have been successfully combined in the first infrared detection of Criegee intermediates during the gas phase ozonolysis. As a second example, we will examine the ignition timing of n-heptane/air mixtures at low and intermediate temperatures. Here, we present a reduced, fuel size independent kinetic model of the complex chemistry initiated by peroxy radicals that has been successfully applied to simulate standard n-heptane combustion experiments.

Photoredox Generated Radicals in Csp2-Csp3 Bond Construction

NASA Astrophysics Data System (ADS)

Primer, David Neal

The routine application of Csp3-hybridized nucleophiles in cross-coupling has been an ongoing pursuit in the agrochemical, pharmaceutical, and materials science industries for over 40 years. Unfortunately, despite numerous attempts to circumvent the problems associated with alkyl nucleophiles, application of these reagents in transition metal-catalyzed C-C bond-forming reactions has remained largely restricted. In recent years, many chemists have noted the lack of reliable, turnkey reactions that exist for the installation of Csp3-hybridized centers--reactions that would be useful for delivering molecules with enhanced three-dimensional topology and altered chemical properties. As such, a general method for alkyl nucleophile activation in cross-coupling would offer access to a host of compounds inaccessible by other means. From a mechanistic standpoint, the continued failure of alkylmetallics is inherent to the high energy intermediates associated with a traditional transmetalation. To overcome this problem, we have pioneered an alternate, single-electron pathway involving 1) initial oxidation of an alkylmetallic reagent, 2) oxidative alkyl radical capture at a metal center, and 3) subsequent reduction of the metal center to return its initial oxidation state. This series of steps constitutes a formal transmetalation that avoids the energy-demanding steps that plague a traditional anionic approach. Under this enabling paradigm, a host of alkyl precursors (alkyl-trifluoroborates and -silicates) have been generally used in cross-coupling for the first time. In summary, the synergistic use of an Ir photoredox catalyst and a Ni cross-coupling catalyst to mediate the cross-coupling of (hetero)aryl bromides with diverse alkyl radical precursors will be discussed. Methods for coupling various trifluoroborate classes (alpha-alkoxy, alpha-trifluoromethyl, secondary and tertiary alkyl) will be covered, focusing on their complementarity to traditional protocols. Finally, a

Alkyl nitrate formation from the reactions of C8-C14 n-alkanes with OH radicals in the presence of NO(x): measured yields with essential corrections for gas-wall partitioning.

PubMed

Yeh, Geoffrey K; Ziemann, Paul J

2014-09-18

In this study, C8-C14 n-alkanes were reacted with OH radicals in the presence of NO(x) in a Teflon film environmental chamber and isomer-specific yields of alkyl nitrates were determined using gas chromatography. Because results indicated significant losses of alkyl nitrates to chamber walls, gas-wall partitioning was investigated by monitoring the concentrations of a suite of synthesized alkyl nitrates added to the chamber. Gas-to-wall partitioning increased with increasing carbon number and with proximity of the nitrooxy group to the terminal carbon, with losses as high as 86%. The results were used to develop a structure-activity model to predict the effects of carbon number and isomer structure on gas-wall partitioning, which was used to correct the measured yields of alkyl nitrate isomers formed in chamber reactions. The resulting branching ratios for formation of secondary alkyl nitrates were similar for all isomers of a particular carbon number, and average values, which were almost identical to alkyl nitrate yields, were 0.219, 0.206, 0.254, 0.291, and 0.315 for reactions of n-octane, n-decane, n-dodecane, n-tridecane, and n-tetradecane, respectively. The increase in average branching ratios and alkyl nitrate yields with increasing carbon number to a plateau value of ∼0.30 at about C13-C14 is consistent with predictions of a previously developed model, indicating that the model is valid for alkane carbon numbers ≥C3.

Structure of free radicals in irradiated acetyl-L-leucine single crystals at 77 K

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

Almanov, G.A.; Bogdanchikov, G.A.; Usov, O.M.

1988-09-01

By using the EPR method, two types of radicals are observed, which are formed in acetyl-L-leucine single crystals irradiated at 77K. These are alkyl type radicals (CH/sub 3/)/sub 2/CCH/sub 2/CH(NHCOCH/sub 3/)COOH and peptide group radicals. When the crystals are defrozen to room temperatures, the radicals of the second type disappear without formation of paramagnetic particles. Two possible structures of the peptide group radicals were studied by the INDO method. On defreezing to room temperature, the alkyl group radical is retained, while the peptide radical disappears without formation of paramagnetic particles. For the protonated form of the anion-radical, a better agreementmore » is observed between the theoretically calculated and the experimentally obtained HFI constants. The quantum chemical analysis of the possible structures of the peptide group radicals indicates that the formation of the protonated form of the anion-radical is energetically favorable.« less

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.

Radical chemistry of artemisinin

NASA Astrophysics Data System (ADS)

Denisov, Evgenii T.; Solodova, S. L.; Denisova, Taisa G.

2010-12-01

The review summarizes physicochemical characteristics of the natural sesquiterpene peroxide artemisinin. The kinetic schemes of transformations of artemisinin radicals under anaerobic conditions are presented and analyzed. The sequence of radical reactions of artemisinin in the presence of oxygen is considered in detail. Special emphasis is given to the intramolecular chain oxidation resulting in the transformation of artemisinin into polyatomic hydroperoxide. The kinetic characteristics of elementary reaction steps involving alkyl, alkoxyl, and peroxyl radicals generated from artemisinin are discussed. The results of testing of artemisinin and its derivatives for the antimalarial activity and the scheme of the biochemical synthesis of artemisinin in nature are considered.

Absolute rate expressions for hydrogen atom abstraction from molybdenum hydrides by carbon-centered radicals

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

Franz, J.A.; Linehan, J.C.; Birnbaum, J.C.

1999-10-27

A new family of basis rate expressions for hydrogen atom abstraction by primary, secondary, and tertiary alkyl radicals in dodecane and benzyl radical in benzene from the molybdenum hydride Cp*Mo-(CO){sub 3}H and for reactions of a primary alkyl radical with CpMo(CO){sub 3}H in dodecane are reported (Cp* = {eta}{sup 5}-pentamethylcyclopentadienyl, Cp = {eta}{sup 5}-cyclopentadienyl). Rate expressions for reaction of primary, secondary, and tertiary radical clocks with Cp*Mo(CO){sub 3}H were as follows: for hex-5-enyl, log(k/M{sup {minus}1} s{sup {minus}1}) = (9.27 {+-} 0.13) {minus} (1.36 {+-} 0.22)/{theta}, {theta} = 2.303RT kcal/mol; for hept-6-en-2-yl, log(k/M{sup {minus}1} s{sup {minus}1}) = (9.12 {+-} 0.42) {minus}more » (1.91 {+-} 0.74)/{theta}; and for 2-methylhept-6-en-2-yl, log(k/M{sup {minus}1} s{sup {minus}1}) = (9.36 {+-} 0.18) {minus} (3.19 {+-} 0.30)/{theta} (errors are 2{sigma}). Hydrogen atom abstraction from CpMo(CO){sub 3}H by hex-5-enyl is described by log(k/M{sup {minus}1} s{sup {minus}1}) = (9.53 {+-} 0.34) {minus} (1.24 {+-} 0.62)/{theta}. Relative rate constants for 1{degree}:2{degree}:3{degree} alkyl radicals were found to be 26:7:1 at 298 K. Benzyl radical was found to react 1.4 times faster than tertiary alkyl radical. The much higher selectivities for CP*Mo(CO){sub 3}H than those observed for main group hydrides (Bu{sub 3}SnH, PhSeH, PhSH) with alkyl radicals, together with the very fast benzyl hydrogen-transfer rate, suggest the relative unimportance of simple enthalpic effects and the dominance of steric effects for the early transition-state hydrogen transfers. Hydrogen abstraction from Cp*Mo(CO){sub 3}H by benzyl radicals is described by log(k/M{sup {minus}1} s{sup {minus}1}) = (8.89 {+-} 0.22) {minus} (2.31 {+-} 0.33)/{theta}.« less

Catalytic alkylation of remote C-H bonds enabled by proton-coupled electron transfer

NASA Astrophysics Data System (ADS)

Choi, Gilbert J.; Zhu, Qilei; Miller, David C.; Gu, Carol J.; Knowles, Robert R.

2016-11-01

Despite advances in hydrogen atom transfer (HAT) catalysis, there are currently no molecular HAT catalysts that are capable of homolysing the strong nitrogen-hydrogen (N-H) bonds of N-alkyl amides. The motivation to develop amide homolysis protocols stems from the utility of the resultant amidyl radicals, which are involved in various synthetically useful transformations, including olefin amination and directed carbon-hydrogen (C-H) bond functionalization. In the latter process—a subset of the classical Hofmann-Löffler-Freytag reaction—amidyl radicals remove hydrogen atoms from unactivated aliphatic C-H bonds. Although powerful, these transformations typically require oxidative N-prefunctionalization of the amide starting materials to achieve efficient amidyl generation. Moreover, because these N-activating groups are often incorporated into the final products, these methods are generally not amenable to the direct construction of carbon-carbon (C-C) bonds. Here we report an approach that overcomes these limitations by homolysing the N-H bonds of N-alkyl amides via proton-coupled electron transfer. In this protocol, an excited-state iridium photocatalyst and a weak phosphate base cooperatively serve to remove both a proton and an electron from an amide substrate in a concerted elementary step. The resultant amidyl radical intermediates are shown to promote subsequent C-H abstraction and radical alkylation steps. This C-H alkylation represents a catalytic variant of the Hofmann-Löffler-Freytag reaction, using simple, unfunctionalized amides to direct the formation of new C-C bonds. Given the prevalence of amides in pharmaceuticals and natural products, we anticipate that this method will simplify the synthesis and structural elaboration of amine-containing targets. Moreover, this study demonstrates that concerted proton-coupled electron transfer can enable homolytic activation of common organic functional groups that are energetically inaccessible using

Catalytic alkylation of remote C-H bonds enabled by proton-coupled electron transfer.

PubMed

Choi, Gilbert J; Zhu, Qilei; Miller, David C; Gu, Carol J; Knowles, Robert R

2016-11-10

Despite advances in hydrogen atom transfer (HAT) catalysis, there are currently no molecular HAT catalysts that are capable of homolysing the strong nitrogen-hydrogen (N-H) bonds of N-alkyl amides. The motivation to develop amide homolysis protocols stems from the utility of the resultant amidyl radicals, which are involved in various synthetically useful transformations, including olefin amination and directed carbon-hydrogen (C-H) bond functionalization. In the latter process-a subset of the classical Hofmann-Löffler-Freytag reaction-amidyl radicals remove hydrogen atoms from unactivated aliphatic C-H bonds. Although powerful, these transformations typically require oxidative N-prefunctionalization of the amide starting materials to achieve efficient amidyl generation. Moreover, because these N-activating groups are often incorporated into the final products, these methods are generally not amenable to the direct construction of carbon-carbon (C-C) bonds. Here we report an approach that overcomes these limitations by homolysing the N-H bonds of N-alkyl amides via proton-coupled electron transfer. In this protocol, an excited-state iridium photocatalyst and a weak phosphate base cooperatively serve to remove both a proton and an electron from an amide substrate in a concerted elementary step. The resultant amidyl radical intermediates are shown to promote subsequent C-H abstraction and radical alkylation steps. This C-H alkylation represents a catalytic variant of the Hofmann-Löffler-Freytag reaction, using simple, unfunctionalized amides to direct the formation of new C-C bonds. Given the prevalence of amides in pharmaceuticals and natural products, we anticipate that this method will simplify the synthesis and structural elaboration of amine-containing targets. Moreover, this study demonstrates that concerted proton-coupled electron transfer can enable homolytic activation of common organic functional groups that are energetically inaccessible using

Cyclopentadienone Oxidation Reaction Kinetics and Thermochemistry for the Alcohols, Hydroperoxides, and Vinylic, Alkoxy, and Alkylperoxy Radicals.

PubMed

Yommee, Suriyakit; Bozzelli, Joseph W

2016-01-28

Cyclopentadienone has one carbonyl and two olefin groups resulting in 4n + 2 π-electrons in a cyclic five-membered ring structure. Thermochemical and kinetic parameters for the initial reactions of cyclopentadienone radicals with O2 and the thermochemical properties for cyclopentadienone-hydroperoxides, alcohols, and alkenyl, alkoxy, and peroxy radicals were determined by use of computational chemistry. The CBS-QB3 composite and B3LYP density functional theory methods were used to determine the enthalpies of formation (ΔfH°298) using the isodesmic reaction schemes with several work reactions for each species. Entropy and heat capacity, S°(T) and Cp°(T) (50 K ≤ T ≤ 5000 K) are determined using geometric parameters, internal rotor potentials, and frequencies from B3LYP/6-31G(d,p) calculations. Standard enthalpies of formation are reported for parent molecules as cyclopentadienone, cyclopentadienone with alcohol, hydroperoxide substituents, and the cyclopentadienone-yl vinylic, alkoxy, and peroxy radicals corresponding to loss of a hydrogen atom from the carbon and oxygen sites. Entropy and heat capacity vs temperature also are reported for the parent molecules and for radicals. The thermochemical analysis shows The R(•) + O2 well depths are deep, on the order of 50 kcal mol(-1), and the R(•) + O2 reactions to RO + O (chain branching products) for cyclopentadienone-2-yl and cyclopentadienone-3-yl have unusually low reaction (ΔHrxn) enthalpies, some 20 or so kcal/mol below the entrance channels. Chemical activation kinetics using quantum RRK analysis for k(E) and master equation for falloff are used to show that significant chain branching as a function of temperature and pressure can occur when these vinylic radicals are formed.

Growing up Radical: Investigation of Benzyl-Like Radicals with Increasing Chain Lengths

NASA Astrophysics Data System (ADS)

Korn, Joseph A.; Jawad, Khadija M.; Hewett, Daniel M.; Zwier, Timothy S.

2015-06-01

Combustion processes involve complex chemistry including pathways leading to polyaromatic hydrocarbons (PAHs) from small molecule precursors. Resonance stabilized radicals (RSRs) likely play an important role in the pathways to PAHs due to their unusual stability. Benzyl radical is a prototypical RSR that is stabilized by conjugation with the phenyl ring. Earlier work on α-methyl benzyl radical showed perturbations to the spectroscopy due to a hindered methyl rotor. If the alkyl chain is lengthened then multiple conformations become possible. This talk will discuss the jet-cooled spectroscopy of α-ethyl benzyl radical and α-propyl benzyl radical produced from the discharge of 1-phenyl propanol and 1-phenyl butanol respectively. Electronic spectra were obtained via resonant two-photon ionization, and IR spectra were obtained by resonant ion-dip infrared spectroscopy. Kidwell, N. M.; Reilly, N. J.; Nebgen, B.; Mehta-Hurt, D. N.; Hoehn, R. D.; Kokkin, D. L.; McCarthy, M. C.; Slipchenko, L. V.; Zwier, T. S. The Journal of Physical Chemistry A 2013, 117, 13465.

Combined chemical and mechanical effects on free radicals in UHMWPE joints during implantation.

PubMed

Jahan, M S; Wang, C; Schwartz, G; Davidson, J A

1991-08-01

An electron spin resonance (ESR) technique is employed to determine the free radical distribution in the articulating surfaces of retrieved acetabular cups and knee-joint plateaus (retrieved after more than 6 years of implantation). Similar measurements made on samples prepared from cyclically stressed and unstressed cups, and on samples following oxidations in nitric acid and intralipid solutions provided sufficient data to gain more knowledge about the combined chemical and mechanical effects on PE free radicals during implantation. In UHMWPE free radicals are primarily initiated by gamma-ray sterilization; however, during implantation, peroxy (scission type) free radicals are formed and reach a maximum concentration level (equilibrium state) due to oxidation by chemical (hemoglobin and/or synovial fluids) environment of the joints. Subsequently, due to frictional heating and stress in the loading zones, free radical reaction is accelerated and their number is reduced only in those areas. This is consistent with the observations of a temperature rise in acetabular cups during in vitro frictional wear stress tests and in vivo telemetry observations, as reported by others. Compared with the previously reported SEM micrographs the low-free-radical regions are correlated with high-wear areas and the high-free-radical regions with the low-wear areas.

Facile synthesis of functional polyperoxides by radical alternating copolymerization of 1,3-dienes with oxygen.

PubMed

Sato, Eriko; Matsumoto, Akikazu

2009-01-01

We have developed a facile synthesis of degradable polyperoxides by the radical alternating copolymerization of 1,3-diene monomers with molecular oxygen at an atmospheric pressure. In this review, the synthesis, the degradation behavior, and the applications of functional polyperoxides are summarized. The alkyl sorbates as the conjugated 1,3-dienes gave a regiospecific alternating copolymer by exclusive 5,4-addition during polymerization and the resulting polyperoxides decomposed by the homolysis of a peroxy linkage followed by successive beta-scissions. The preference of 5,4-addition was well rationalized by theoretical calculations. The degradation of the polyperoxides occurred with various stimuli, such as heating, UV irradiation, a redox reaction with amines, and an enzyme reaction. The various functional polyperoxides were synthesized by following two methods, one is the direct copolymerization of functional 1,3-dienes, and the other is the functionalization of the precursor polyperoxides. Water soluble polyperoxides were also prepared, and the LCST behavior and the application to a drug carrier in the drug delivery system were investigated. In order to design various types of degradable polymers and gels we developed a method for the introduction of dienyl groups into the precursor polymers. The resulting dienyl-functionalized polymers were used for the degradable gels. The degradable branched copolymers showed a microphase-separated structure, which changed owing to the degradation of the polyperoxide segments. Copyright 2009 The Japan Chemical Journal Forum and Wiley Periodicals, Inc.

Ozone decomposition in aqueous acetate solutions

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

Sehested, K.; Holcman, J.; Bjergbakke, E.

1987-01-01

The acetate radical ion reacts with ozone with a rate constant of k = (1.5 +/- 0.5) x 10Z dmT mol s . The products from this reaction are CO2, HCHO, and O2 . By subsequent reaction of the peroxy radical with ozone the acetate radical ion is regenerated through the OH radical. A chain decomposition of ozone takes place. It terminates when the acetate radical ion reacts with oxygen forming the unreactive peroxy acetate radical. The chain is rather short as oxygen is developed, as a result of the ozone consumption. The inhibiting effect of acetate on the ozonemore » decay is rationalized by OH scavenging by acetate and successive reaction of the acetate radical ion with oxygen. Some products from the bimolecular disappearance of the peroxy acetate radicals, however, react further with ozone, reducing the effectiveness of the stabilization.« less

Sulfur Dioxide Accelerates the Heterogeneous Oxidation Rate of Organic Aerosol by Hydroxyl Radicals

DOE PAGES

Richards-Henderson, Nicole K.; Goldstein, Allen H.; Wilson, Kevin R.

2016-03-08

There remains considerable uncertainty in how anthropogenic gas phase emissions alter the oxidative aging of organic aerosols in the troposphere. Here we observe a 10-20 fold acceleration in the effective heterogeneous OH oxidation rate of organic aerosol in the presence of SO 2. This acceleration originates from the radical chain reactions propagated by alkoxy radicals, which are formed efficiently inside the particle by the reaction of peroxy radicals with SO 2. As the OH approaches atmospheric concentrations, the radical chain length increases, transforming the aerosol at rates predicted to be up to 10 times the OH-aerosol collision frequency. Model predictions,more » constrained by experiments over orders of magnitude changes in [OH] and [SO 2], suggest that in polluted regions the heterogeneous processing of organic aerosols by OH ([SO 2] ≥ 40 ppb) occur on similar time scales as analogous gas-phase oxidation reactions. These results provide evidence for a previously unidentified mechanism by which organic aerosol oxidation is enhanced by anthropogenic gas phase emissions. (Chemical Equation Presented).« less

Reactions of hydroxyalkyl radicals with cysteinyl peptides in a nanoESI plume.

PubMed

Stinson, Craig A; Xia, Yu

2014-07-01

In biological systems, carbon-centered small molecule radicals are primarily formed via external radiation or internal radical reactions. These radical species can react with a variety of biomolecules, most notably nucleic acids, the consequence of which has possible links to gene mutation and cancer. Sulfur-containing peptides and proteins are reactive toward a variety of radical species and many of them behave as radical scavengers. In this study, the reactions between alkyl alcohol carbon-centered radicals (e.g., •CH2OH for methanol) and cysteinyl peptides within a nanoelectrospray ionization (nanoESI) plume were explored. The reaction system involved ultraviolet (UV) irradiation of a nanoESI plume using a low pressure mercury lamp consisting of 185 and 254 nm emission bands. The alkyl alcohol was added as solvent into the nanoESI solution and served as the precursor of hydroxyalkyl radicals upon UV irradiation. The hydroxyalkyl radicals subsequently reacted with cysteinyl peptides either containing a disulfide linkage or free thiol, which led to the formation of peptide-S-hydroxyalkyl product. This radical reaction coupled with subsequent MS/MS was shown to have analytical potential by cleaving intrachain disulfide linked peptides prior to CID to enhance sequence information. Tandem mass spectrometry via collision-induced dissociation (CID), stable isotope labeling, and accurate mass measurement were employed to verify the identities of the reaction products.

Reactions of Hydroxyalkyl Radicals with Cysteinyl Peptides in a NanoESI Plume

NASA Astrophysics Data System (ADS)

Stinson, Craig A.; Xia, Yu

2014-07-01

In biological systems, carbon-centered small molecule radicals are primarily formed via external radiation or internal radical reactions. These radical species can react with a variety of biomolecules, most notably nucleic acids, the consequence of which has possible links to gene mutation and cancer. Sulfur-containing peptides and proteins are reactive toward a variety of radical species and many of them behave as radical scavengers. In this study, the reactions between alkyl alcohol carbon-centered radicals (e.g., •CH2OH for methanol) and cysteinyl peptides within a nanoelectrospray ionization (nanoESI) plume were explored. The reaction system involved ultraviolet (UV) irradiation of a nanoESI plume using a low pressure mercury lamp consisting of 185 and 254 nm emission bands. The alkyl alcohol was added as solvent into the nanoESI solution and served as the precursor of hydroxyalkyl radicals upon UV irradiation. The hydroxyalkyl radicals subsequently reacted with cysteinyl peptides either containing a disulfide linkage or free thiol, which led to the formation of peptide- S-hydroxyalkyl product. This radical reaction coupled with subsequent MS/MS was shown to have analytical potential by cleaving intrachain disulfide linked peptides prior to CID to enhance sequence information. Tandem mass spectrometry via collision-induced dissociation (CID), stable isotope labeling, and accurate mass measurement were employed to verify the identities of the reaction products.

Speciated Monitoring of Gas-Phase Organic Peroxy Radicals by Chemical Ionization Mass Spectrometry: Cross-Reactions between CH3O2, CH3(CO)O2, (CH3)3CO2, and c-C6H11O2.

PubMed

Nozière, Barbara; Hanson, David R

2017-11-09

Organic peroxy radicals ("RO 2 ", with R organic) are key intermediates in most oxygen-rich systems, where organic compounds are oxidized (natural environment, flames, combustion engines, living organisms, etc). But, until recently, techniques able to monitor simultaneously and distinguish between RO 2 species ("speciated" detection) have been scarce, which has limited the understanding of complex systems containing these radicals. Mass spectrometry using proton transfer ionization has been shown previously to detect individual gas-phase RO 2 separately. In this work, we illustrate its ability to speciate and monitor several RO 2 simultaneously by investigating reactions involving CH 3 O 2 , CH 3 C(O)O 2 , c-C 6 H 11 O 2 , and (CH 3 ) 3 CO 2 . The detection sensitivity of each of these radicals was estimated by titration with NO to between 50 and 1000 Hz/ppb, with a factor from 3 to 5 of uncertainties, mostly due to the uncertainties in knowing the amounts of added NO. With this, the RO 2 concentration in the reactor was estimated between 1 × 10 10 and 1 × 10 12 molecules cm -3 . When adding a second radical species to the reactor, the kinetics of the cross-reaction could be studied directly from the decay of the first radical. The time-evolution of two and sometimes three different RO 2 was followed simultaneously, as the CH 3 O 2 produced in further reaction steps was also detected in some systems. The rate coefficients obtained are (in molecule -1 cm 3 s -1 ): k CH3O2+CH3C(O)O2 = 1.2 × 10 -11 , k CH3O2+t-butylO2 = 3.0 × 10 -15 , k c-hexylO2+CH3O2 = 1.2 × 10 -13 , k t-butylO2+CH3C(O)O2 = 3.7 × 10 -14 , and k c-hexylO2+t-butylO2 = 1.5 × 10 -15 . In spite of their good comparison with the literature and good reproducibility, large uncertainties (×5/5) are recommended on these results because of those in the detection sensitivities. This work is a first illustration of the potential applications of this technique for the investigation of organic radicals in

Bioefficacy of Graviola leaf extracts in scavenging free radicals and upregulating antioxidant genes.

PubMed

Son, Yu-Ra; Choi, Eun-Hye; Kim, Goon-Tae; Park, Tae-Sik; Shim, Soon-Mi

2016-02-01

The aims of this study were to determine bioactive components of Graviola leaf extracts and to examine the radical scavenging capacity, gene expression and transcription factors of antioxidant enzymes. Rutin, kaempferol-rutinoside, and vitamin U were identified from the steaming and 50% EtOH extracts of Graviola leaves. Graviola leaf extracts effectively scavenged peroxy and nitrogen radicals. 50% EtOH of Graviola leaves provided a 1-2.9 times higher trolox equivalent than the steaming extract. It also had a higher VCEAC. Graviola leaf extracts reduced the generation of reactive oxygen species (ROS) induced by H2O2 in a dose-dependent manner. The 50% EtOH extract of Graviola leaves upregulated SOD1 and Nrf2, but catalase and HMOX1 were not altered by the 50% EtOH extract of Graviola leaves.

Transient alkylaminium radicals in n-hexane. Condensed-phase ion-molecule reactions

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

Werst, D.W.; Trifunac, A.D.

Time-resolved fluorescence detected magnetic resonance (FDMR) is used to observe alkylaminium radicals formed in n-hexane solutions by electron pulse radiolysis. The ease of observation of aminium radical FDMR signals increases with increasing alkyl substitution of the amine solutes. The results are discussed in terms of the ion-molecule reactions, such as proton transfer, which compete with the electron-transfer processes, i.e, the electron transfer from solute molecules to n-hexane radical cations and geminate recombination.

Hydroxy nitrate production in the OH-initiated oxidation of alkenes

NASA Astrophysics Data System (ADS)

Teng, A. P.; Crounse, J. D.; Lee, L.; St. Clair, J. M.; Cohen, R. C.; Wennberg, P. O.

2015-04-01

Alkenes are oxidized rapidly in the atmosphere by addition of OH and subsequently O2 leading to the formation of β-hydroxy peroxy radicals. These peroxy radicals react with NO to form β-hydroxy nitrates with a branching ratio α. We quantify α for CM2-C8 alkenes at 295 K ± 3 and 993 hPa. The branching ratio can be expressed as α = (0.045 ± 0.016) × N - (0.11 ± 0.05) where N is the number of heavy atoms (excluding the peroxy moiety), and listed errors are 2σ. These branching ratios are larger than previously reported and are similar to those for peroxy radicals formed from H abstraction from alkanes. We find the isomer distributions of β-hydroxy nitrates formed under NO-dominated peroxy radical chemistry to be different than the isomer distribution of hydroxy hydroperoxides produced under HO2-dominated peroxy radical chemistry. Assuming unity yield for the hydroperoxides implies that the branching ratio to form β-hydroxy nitrates increases with substitution of RO2. Deuterium substitution enhances the branching ratio to form hydroxy nitrates in both propene and isoprene by a factor of ~ 1.5. The role of alkene chemistry in the Houston region is re-evaluated using the RONO2 branching ratios reported here. Small alkenes are found to play a significant role in present-day oxidant formation more than a decade (2013) after the 2000 Texas Air Quality Study identified these compounds as major contributors to photochemical smog in Houston.

Decomposition and reactivity of tellurium alkyls in the liquid and gas phases; dihex-5-enyltellurium and dipent-4-enyltellurium as mechanistic probes

NASA Astrophysics Data System (ADS)

Bell, William; McQueen, A. Ewan D.; Walton, John C.; Foster, Douglas F.; Cole-Hamilton, David J.; Hails, Janet E.

1992-02-01

The new tellurium alkyls, dihex-5-enyltellurium and dipent-4-enyltellurium have been prepared and pyrolysed in the gas and liquid phases. in the liquid phase, at 200°C some decomposition occurs but the main isolated products are the tellurium alkyls, bis(cyclopentylmethyl)tellurium and 2-methyltelluracyclopentane respectively. A further product, cyclopentylmethylhex-5-enyltellurium is observed as an intermediate in the rearrangement of dihex-5-enyltellurium, whilst (2-telluracyclopentylmethyl)pent-4-enyltellurium together with pent-1-ene and 1,4-pentadiene is obtained from dipent-4-enyltellurium. These products are interpreted as providing direct evidence for initial homolytic cleavage of the Te-C bonds followed by cyclisation of some of the formed radicals and radical chain reactions. In the gas phase, at 500°C similar products to those obtained in the liquid phase are formed from dipent-4-enyltellurium, although not compounds containing more than one Te atom. Dihex-5-enyltellurium, however, decomposes completely in the gas phase at 700°C to give a mixture of hydrocarbons. Substantial quantities of methylcyclopentane and methylenecyclopentane again confirm that a free radical pathway makes a major contribution to the mechanism. The origin of the other products, especially cyclohexene (the major C 6 product) and cyclohexane is also interpreted in terms of a free radical mechanism leading to the 6-tellurahex-1-enyl radical which cyclises to give the 3-telluracycloheptylradical. This radical rearranges to cyclohexyl Te· which in turn acts as the source of cyclohexene and cyclohexane by H· abstraction or addition. There is little evidence that mechanisms other than free radical operate for decomposition of these metal alkyls.

Peroxy defects in Rocks and H2O2 formation on the early Earth

NASA Astrophysics Data System (ADS)

Gray, A.; Balk, M.; Mason, P.; Freund, F.; Rothschild, L.

2013-12-01

An oxygen-rich atmosphere appears to have been a prerequisite for complex life to evolve on Earth and possibly elsewhere in the Universe. The question is still shrouded in uncertainty how free oxygen became available on the early Earth. Here we study processes of peroxy defects in silicate minerals which, upon weathering, generate mobilized electronic charge carriers resulting in oxygen formation in an initially anoxic subsurface environment. Reactive Oxygen Species (ROS) are precursors to molecular oxygen during this process. Due to their toxicity they may have strongly influenced the evolution of life. ROS are generated during hydrolysis of peroxy defects, which consist of pairs of oxygen anions. A second pathway for formation occurs during (bio) transformations of iron sulphide minerals. ROS are produced and consumed by intracellular and extracellular reactions of Fe, Mn, C, N, and S species. We propose that despite an overall reducing or neutral oxidation state of the macroenvironment and the absence of free O2 in the atmosphere, microorganisms on the early Earth had to cope with ROS in their microenvironments. They were thus under evolutionary pressure to develop enzymatic and other defenses against the potentially dangerous, even lethal effects of ROS and oxygen. We have investigated how oxygen might be released through weathering and test microorganisms in contact with rock surfaces. Our results show how early Life might have adapted to oxygen. Early microorganisms must have "trained" to detoxify ROS prior to the evolution of aerobic metabolism and oxygenic photosynthesis. A possible way out of this dilemma comes from a study of igneous and high-grade metamorphic rocks, whose minerals contain a small but significant fraction of oxygen anions in the valence state 1- , forming peroxy links of the type O3Si-OO-SiO3 [1, 2]. As water hydrolyzes the peroxy links hydrogen peroxide, H2O2, forms. Continued experimental discovery of H2O2 formation at rock

HOx Radical Chemistry in an Indiana Forest Environment: Measurement and Model Comparison

NASA Astrophysics Data System (ADS)

Lew, M.; Bottorff, B.; Sigler, P. S. R.; Stevens, P. S.; Sklaveniti, S.; Leonardis, T.; Locoge, N.; Dusanter, S.; Kundu, S.; Deming, B.; Wood, E. C. D.; Gentner, D. R.

2015-12-01

Reactions of the hydroxyl (OH) and peroxy radicals (HO2 and RO2) play a central role in the chemistry of the atmosphere. In addition to controlling the lifetimes of many trace gases important to issues of global climate change, OH radical reactions initiate the oxidation of volatile organic compounds (VOCs) which can lead to the production of ozone and secondary organic aerosols in the atmosphere. Previous measurements of these radicals in forest environments characterized by high mixing ratios of isoprene and low mixing ratios of NOx have shown serious discrepancies with modeled concentrations. These results bring into question our understanding of the atmospheric chemistry of isoprene and other biogenic VOCs under low NOx conditions. In the summer of 2015, HOx radicals were measured using Laser-Induced Fluorescence Fluorescence Assay by Gas Expansion (LIF-FAGE) technique as part of the Indiana Radical, Reactivity and Ozone Production Intercomparison (IRRONIC). This campaign took place in a forested area at the Indiana Research and Teaching Preserve (IURTP) near the Bloomington campus characterized by high mixing ratios of isoprene and low mixing ratios of NOx. Supporting measurements of photolysis rates, volatile organic compounds, nitrogen oxides, and other species were used to constrain a zero-dimensional box model based on the Regional Atmospheric Chemistry Mechanism (RACM2) and the Master Chemical Mechanism (MCM).

Copper-Catalyzed Cyclopropanol Ring Opening Csp(3)-Csp(3) Cross-Couplings with (Fluoro)Alkyl Halides.

PubMed

Ye, Zhishi; Gettys, Kristen E; Shen, Xingyu; Dai, Mingji

2015-12-18

Novel and general copper-catalyzed cyclopropanol ring opening cross-coupling reactions with difluoroalkyl bromides, perfluoroalkyl iodides, monofluoroalkyl bromides, and 2-bromo-2-alkylesters to synthesize various β-(fluoro)alkylated ketones are reported. The reactions feature mild conditions and excellent functional group compatibility and can be scaled up to gram scale. Preliminary mechanistic studies suggest the involvement of radical intermediates. The difluoroalkyl-alkyl cross-coupling products can also be readily converted to more valuable and diverse gem-difluoro-containing compounds by taking advantage of the carbonyl group resulting from cyclopropanol ring opening.

Development of nitroxide radicals-containing polymer for scavenging reactive oxygen species from cigarette smoke

NASA Astrophysics Data System (ADS)

Yoshitomi, Toru; Kuramochi, Kazuhiro; Binh Vong, Long; Nagasaki, Yukio

2014-06-01

We developed a nitroxide radicals-containing polymer (NRP), which is composed of poly(4-methylstyrene) possessing nitroxide radicals as a side chain via amine linkage, to scavenge reactive oxygen species (ROS) from cigarette smoke. In this study, the NRP was coated onto cigarette filters and its ROS-scavenging activity from streaming cigarette smoke was evaluated. The intensity of electron spin resonance signals of the NRP in the filter decreased after exposure to cigarette smoke, indicating consumption of nitroxide radicals. To evaluate the ROS-scavenging activity of the NRP-coated filter, the amount of peroxy radicals in an extract of cigarette smoke was measured using UV-visible spectrophotometry and 1,1-diphenyl-2-picrylhydrazyl (DPPH). The absorbance of DPPH at 517 nm decreased with exposure to cigarette smoke. When NRP-coated filters were used, the decrease in the absorbance of DPPH was prevented. In contrast, both poly[4-(cyclohexylamino)methylstyrene]- and poly(acrylic acid)-coated filters, which have no nitroxide radical, did not show any effect, indicating that the nitroxide radicals in the NRP scavenge the ROS in cigarette smoke. As a result, the extract of cigarette smoke passed through the NRP-coated filter has a lower cellular toxicity than smoke passed through poly[4-(cyclohexylamino)methylstyrene]- and poly(acrylic acid)-coated filters. Accordingly, NRP is a promising material for ROS scavenging from cigarette smoke.

Evaluation of free radical scavenging and anti-oxidative capacity of polydatin-nanostructured lipid carriers

NASA Astrophysics Data System (ADS)

Meng, Xiang-Ping; Shi, Fan; Li, Hai-Jie; Yin, Li-De; Wang, Yi-Fei; Wang, Zhi-ping; Chen, Tong-sheng

2016-10-01

Cellular damage induced by free-radicals like reactive oxygen species has been implicated in several diseases. 2, 2-azobis(2-amidino-propane) dihydrochloride(AAPH) generates two potent ROS capable of inducing lipid peroxidation: alkoxy radical(RO-) and peroxy radical (ROO-). These radicals are similar to those that are physiologically active and thus might initiate a cascade of intracellular toxic events leading to oxidation, lipid peroxidation, DNA damage and subsequent cell death. Hence naturally anti-oxidant play a vital role in combating these conditions. In this study, polydatin loaded nanostructured lipid carriers (Pol-NLC) was prepared by hot melting and then high pressure homogenization technique. The effects of Pol-NLC on free radical scavenging and anti-oxidative capacity is investigated. The particle size and zeta potential of Pol-NLC were 113.9 +/- 1.1 nm and -16.3 1 +/- 0.27 mV, respectively. By free radical scavenging assays, the IC50 value of Pol-NLC were 28.71, 9.83 μg/mL with DPPH, ABTS assay respectively, and 0.143 mg ferrous sulfate/1 mg Pol-NLC with FRAP assay. These results indicated that the antioxidant properties of Pol-NLC hold great potential used as an alternative to more toxic synthetic anti-oxidants as an additive in food, cosmetic and pharmaceutical preparations for the oxidative diseases treatment.

Tested Demonstrations: The Effect of Free Radical Stability on the Rate of Bromination of Hydrocarbons.

ERIC Educational Resources Information Center

Gilbert, George L., Ed.; And Others

1980-01-01

Presents a demonstration of the effect of alkyl free radical stability on the rate of free radical halogenation of hydrocarbons. The arenes toluene, ethylbenzene and comene are photobrominated comparatively, using an overhead projector both to provide a light source for the chemical reaction and to project the results on a screen. (CS)

Relationship between Antimalarial Activity and Heme Alkylation for Spiro- and Dispiro-1,2,4-Trioxolane Antimalarials▿

PubMed Central

Creek, Darren J.; Charman, William N.; Chiu, Francis C. K.; Prankerd, Richard J.; Dong, Yuxiang; Vennerstrom, Jonathan L.; Charman, Susan A.

2008-01-01

The reaction of spiro- and dispiro-1,2,4-trioxolane antimalarials with heme has been investigated to provide further insight into the mechanism of action for this important class of antimalarials. A series of trioxolanes with various antimalarial potencies was found to be unreactive in the presence of Fe(III) hemin, but all were rapidly degraded by reduced Fe(II) heme. The major reaction product from the heme-mediated degradation of biologically active trioxolanes was an alkylated heme adduct resulting from addition of a radical intermediate. Under standardized reaction conditions, a correlation (R2 = 0.88) was found between the extent of heme alkylation and in vitro antimalarial activity, suggesting that heme alkylation may be related to the mechanism of action for these trioxolanes. Significantly less heme alkylation was observed for the clinically utilized artemisinin derivatives compared to the equipotent trioxolanes included in this study. PMID:18268087

Tunneling in hydrogen-transfer isomerization of n-alkyl radicals.

PubMed

Sirjean, Baptiste; Dames, Enoch; Wang, Hai; Tsang, Wing

2012-01-12

The role of quantum tunneling in hydrogen shift in linear heptyl radicals is explored using multidimensional, small-curvature tunneling method for the transmission coefficients and a potential energy surface computed at the CBS-QB3 level of theory. Several one-dimensional approximations (Wigner, Skodje and Truhlar, and Eckart methods) were compared to the multidimensional results. The Eckart method was found to be sufficiently accurate in comparison to the small-curvature tunneling results for a wide range of temperature, but this agreement is in fact fortuitous and caused by error cancellations. High-pressure limit rate constants were calculated using the transition state theory with treatment of hindered rotations and Eckart transmission coefficients for all hydrogen-transfer isomerizations in n-pentyl to n-octyl radicals. Rate constants are found in good agreement with experimental kinetic data available for n-pentyl and n-hexyl radicals. In the case of n-heptyl and n-octyl, our calculated rates agree well with limited experimentally derived data. Several conclusions made in the experimental studies of Tsang et al. (Tsang, W.; McGivern, W. S.; Manion, J. A. Proc. Combust. Inst. 2009, 32, 131-138) are confirmed theoretically: older low-temperature experimental data, characterized by small pre-exponential factors and activation energies, can be reconciled with high-temperature data by taking into account tunneling; at low temperatures, transmission coefficients are substantially larger for H-atom transfers through a five-membered ring transition state than those with six-membered rings; channels with transition ring structures involving greater than 8 atoms can be neglected because of entropic effects that inhibit such transitions. The set of computational kinetic rates were used to derive a general rate rule that explicitly accounts for tunneling. The rate rule is shown to reproduce closely the theoretical rate constants.

Pentan isomers compound flame front structure

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

Mansurov, Z.A.; Mironenko, A.W.; Bodikov, D.U.

1995-08-13

The fuels (hexane, pentane, diethyl ether) and conditions investigated in this study are relevant to engine knock in spark- ignition engines. A review is provided of the field of low temperature hydrocarbon oxidation. Studies were made of radical and stable intermediate distribution in the front of cool flames: Maximum concentrations of H atoms and peroxy radicals were observed in the luminous zone of the cool flame front. Peroxy radicals appear before the luminous zone at 430 K due to diffusion. H atoms were found in cool flames of butane and hexane. H atoms diffuses from the luminous zone to themore » side of the fresh mixture, and they penetrate into the fresh mixture to a small depth. Extension of action sphear of peroxy radicals in the fresh mixture is much greater than that of H atoms due to their small activity and high concentrations.« less

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

Spectroscopic evidence of α-methylbenzyl radical in the gas phase

NASA Astrophysics Data System (ADS)

Lee, Gi Woo; Ahn, Hyeon Geun; Kim, Tae Kyu; Lee, Sang Kuk

2008-11-01

We report the observation of the spectroscopic evidence of the α-methylbenzyl radical in a corona excited supersonic expansion using a pinhole-type glass nozzle for the first time. The precursors, toluene, ethylbenzene, and isopropylbenzene, seeded in a large amount of inert carrier gas helium, were electrically discharged to produce benzyl-type radicals as a result of the breaking off of a C-H or a C-C bond from the alkyl chain. The vibronic emission spectra, obtained in the visible region from the precursors, were compared to identify the species generated in the corona discharge of the precursors, from which we found the spectroscopic evidence of the α-methylbenzyl radical.

Reactions of OH radicals with 2-methyl-1-butyl, neopentyl and 1-hexyl nitrates. Structure-activity relationship for gas-phase reactions of OH with alkyl nitrates: An update

NASA Astrophysics Data System (ADS)

Bedjanian, Yuri; Morin, Julien; Romanias, Manolis N.

2018-05-01

The kinetics of the reactions 2-methyl-1-butyl (2M1BNT), neopentyl (NPTNT) and 1-hexyl nitrates (1HXNT) with OH radicals has been studied using a low pressure flow tube reactor combined with a quadrupole mass spectrometer. The rate constants of the title reactions were determined under pseudo-first order conditions from kinetics of OH consumption in excess of nitrates. The overall rate coefficients, k2M1BNT = 1.54 × 10-14 (T/298)4.85 exp (1463/T) (T = 278-538 K), kNPTNT = 1.39 × 10-14 (T/298)4.89 exp (1189/T) (T = 278-500 K) and k1HXNT = 2.23 × 10-13 (T/298)2.83 exp (853/T) cm3molecule-1s-1 (T = 306-538 K) (with conservative 15% uncertainty), were determined at a total pressure of 1 Torr of helium. The yield of trimethylacetaldehyde ((CH3)3CCHO), resulting from the abstraction by OH of an α-hydrogen atom in neopentyl nitrate, followed by α-substituted alkyl radical decomposition, was determined as 0.31 ± 0.06 at T = 298 K. The calculated tropospheric lifetimes of 2M1BNT, NPTNT and 1HXNT indicate that reaction of these nitrates with OH represents an important sink of these compounds in the atmosphere. Based on the available kinetic data, we have updated the structure-activity relationship (SAR) for reactions of alkyl nitrates with OH at T = 298 K. Good agreement (within 20%) is obtained between experimentally measured rate constants (total and that for H-atom abstraction from α carbon) and those calculated from SAR using new substituents factors for almost all the experimental data available.

Alkyl nitrate (C1-C3) depth profiles in the tropical Pacific Ocean

NASA Astrophysics Data System (ADS)

Dahl, E. E.; Yvon-Lewis, S. A.; Saltzman, E. S.

2007-01-01

This paper reports the first depth profile measurements of methyl, ethyl, isopropyl and n-propyl nitrates in the tropical Pacific Ocean. Depth profile measurements were made at 22 stations during the Project Halocarbon Air Sea Exchange cruise, in warm pool, equatorial, subequatorial, and gyre waters. The highest concentrations, up to several hundred pM of methyl nitrate, were observed in the central Pacific within 8 degrees of the equator. In general, alkyl nitrate levels were highest in the surface mixed layer, and decreased with depth below the mixed layer. The spatial distribution of the alkyl nitrates suggests that there is a strong source associated with biologically productive ocean regions, that is characterized by high ratios of methyl:ethyl nitrate. However, the data do not allow discrimination between direct biological emissions and photochemistry as production mechanisms. Alkyl nitrates were consistently detectable at several hundred meters depth. On the basis of the estimated chemical loss rate of these compounds, we conclude that deep water alkyl nitrates must be produced in situ. Possible sources include free radical processes initiated by radioactive decay or cosmic rays, enzymatically mediated reactions involving bacteria, or unidentified chemical mechanisms involving dissolved organic matter.

Mycothiol-Deficient Mycobacterium smegmatis Mutants Are Hypersensitive to Alkylating Agents, Free Radicals, and Antibiotics

PubMed Central

Rawat, Mamta; Newton, Gerald L.; Ko, Mary; Martinez, Gladys J.; Fahey, Robert C.; Av-Gay, Yossef

2002-01-01

Mycothiol (MSH; 1d-myo-inosityl 2-[N-acetyl-l-cysteinyl]amido-2-deoxy-α-d-glucopyranoside) is the major low-molecular-weight thiol produced by mycobacteria. Mutants of Mycobacterium smegmatis mc2155 deficient in MSH production were produced by chemical mutagenesis as well as by transposon mutagenesis. One chemical mutant (mutant I64) and two transposon mutants (mutants Tn1 and Tn2) stably deficient in MSH production were isolated by screening for reduced levels of MSH content. The MSH contents of transposon mutants Tn1 and Tn2 were found to be less than 0.1% that of the parent strain, and the MSH content of I64 was found to be 1 to 5% that of the parent strain. All three strains accumulated 1d-myo-inosityl 2-deoxy-α-d-glucopyranoside to levels 20- to 25-fold the level found in the parent strain. The cysteine:1d-myo-inosityl 2-amino-2-deoxy-α-d-glucopyranoside ligase (MshC) activities of the three mutant strains were ≤2% that of the parent strain. Phenotypic analysis revealed that these MSH-deficient mutants possess increased susceptibilities to free radicals and alkylating agents and to a wide range of antibiotics including erythromycin, azithromycin, vancomycin, penicillin G, rifamycin, and rifampin. Conversely, the mutants possess at least 200-fold higher levels of resistance to isoniazid than the wild type. We mapped the mutation in the chemical mutant by sequencing the mshC gene and showed that a single amino acid substitution (L205P) is responsible for reduced MSH production and its associated phenotype. Our results demonstrate that there is a direct correlation between MSH depletion and enhanced sensitivity to toxins and antibiotics. PMID:12384335

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...

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.

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...

The rotational spectrum of the water-hydroperoxy radical (H2O-HO2) complex.

PubMed

Suma, Kohsuke; Sumiyoshi, Yoshihiro; Endo, Yasuki

2006-03-03

Peroxy radicals and their derivatives are elusive but important intermediates in a wide range of oxidation processes. We observed pure rotational transitions of the water-hydroperoxy radical complex, H2O-HO2, in a supersonic jet by means of a Fourier transform microwave spectrometer combined with a double-resonance technique. The observed rotational transitions were found to split into two components because of the internal rotation of the water moiety. The molecular constants for the two components were determined precisely, supporting a molecular structure in which HO2 acts as a proton donor to form a nearly planar five-membered ring, and one hydrogen atom of water sticks out from the ring plane. The structure and the spectral splittings due to internal rotation provide information on the nature of the bonding interaction between open- and closed-shell species, and they also provide accurate transition frequencies that are applicable to remote sensing of this complex, which may elucidate its potential roles in atmospheric and combustion chemistry.

Isoprenoid Alcohols are Susceptible to Oxidation with Singlet Oxygen and Hydroxyl Radicals.

PubMed

Komaszylo Née Siedlecka, Joanna; Kania, Magdalena; Masnyk, Marek; Cmoch, Piotr; Lozinska, Iwona; Czarnocki, Zbigniew; Skorupinska-Tudek, Karolina; Danikiewicz, Witold; Swiezewska, Ewa

2016-02-01

Isoprenoids, as common constituents of all living cells, are exposed to oxidative agents--reactive oxygen species, for example, singlet oxygen or hydroxyl radicals. Despite this fact, products of oxidation of polyisoprenoids have never been characterized. In this study, chemical oxidation of isoprenoid alcohols (Prenol-2 and -10) was performed using singlet oxygen (generated in the presence of hydrogen peroxide/molybdate or upon photochemical reaction in the presence of porphyrin), oxygen (formed upon hydrogen peroxide dismutation) or hydroxyl radical (generated by the hydrogen peroxide/sonication, UV/titanium dioxide or UV/hydrogen peroxide) systems. The structure of the obtained products, hydroxy-, peroxy- and heterocyclic derivatives, was studied with the aid of mass spectrometry (MS) and nuclear magnetic resonance (NMR) methods. Furthermore, mass spectrometry with electrospray ionization appeared to be a useful analytical tool to detect the products of oxidation of isoprenoids (ESI-MS analysis), as well as to establish their structure on the basis of the fragmentation spectra of selected ions (ESI-MS/MS analysis). Taken together, susceptibility of polyisoprenoid alcohols to various oxidizing agents was shown for the first time.

Evaluation of free radical scavenging capacity and antioxidative damage effect of resveratrol-nanostructured lipid carriers

NASA Astrophysics Data System (ADS)

Jin, Ju; Shi, Fan; Li, Qiu-wen; Li, Pei-shan; Chen, Tong-sheng; Wang, Yi-fei; Wang, Zhi-ping

2016-03-01

Cellular damage induced by free-radicals like reactive oxygen species has been implicated in several diseases. 2, 2-azobis(2-amidino-propane) dihydrochloride(AAPH) generates two potent ROS capable of inducing lipid peroxidation: alkoxy radical(RO-) and peroxy radical(ROO-). These radicals are similar to those that are physiologically active and thus might initiate a cascade of intracellular toxic events leading to oxidation, lipid peroxidation, DNA damage and subsequent cell death. Hence naturally anti-oxidant play a vital role in combating these conditions. In this study, resveratrol loaded nanostructured lipid carriers (Res-NLC) was prepared by hot melting and then high pressure homogenization technique. The effects of Res-NLC on free radical scavenging capacity and antioxidative damage is investigated. The particle size and zeta potential of Res-NLC were 139.3 ± 1.7 nm and -11.21 ± 0.41 mV, respectively. By free radical scavenging assays, the IC50 value of Res-NLC were 19.25, 5.29 μg/mL with DPPH, ABTS assay respectively, and 0.161 mg ferrous sulfate/1 mg Res-NLC with FRAP assay; and by AAPH-induced oxidative injury cell model assay, Res-NLC showed the strong protective effect against the human liver tumor HepG2 cell oxidative stress damage. These results indicated that the antioxidant properties of Res-NLC hold great potential used as an alternative to more toxic synthetic antioxidants as an additive in food, cosmetic and pharmaceutical preparations for the oxidative diseases treatment.

Deuterium Substitution used as a Tool for Investigating Mechanisms of Gas-Phase Free-Radical Reactions

NASA Technical Reports Server (NTRS)

Wine, P. H.; Hynes, A. J.; Nicovich, J. M.

1997-01-01

Results are presented and discussed for a number of gas phase free radical reactions where H/D isotope effects provide valuable mechanistic insights. The cases considered are (1) the reactions of OH, NO3, and Cl with atmospheric reduced sulfur compounds, (2) the reactions of OH and OD with CH3CN and CD3CN, and (3) the reactions of alkyl radicals with HBr and DBr.

Degradation and biodegradability improvement of the olive mill wastewater by peroxi-electrocoagulation/electrooxidation-electroflotation process with bipolar aluminum electrodes.

PubMed

Esfandyari, Yahya; Mahdavi, Yousef; Seyedsalehi, Mahdi; Hoseini, Mohammad; Safari, Gholam Hossein; Ghozikali, Mohammad Ghanbari; Kamani, Hossein; Jaafari, Jalil

2015-04-01

Olive mill wastewater is considered as one of the most polluting effluents of the food industry and constitutes a source of important environmental problems. In this study, the removal of pollutants (chemical oxygen demand (COD), biochemical oxygen demand (BOD5), polyphenols, turbidity, color, total suspended solids (TSS), and oil and grease) from olive oil mill processing wastewater by peroxi-electrocoagulation/electrooxidation-electroflotation process with bipolar aluminum electrodes was evaluated using a pilot continuous reactor. In the electrochemical unit, aluminum (Al), stainless steel, and RuO2/Ti plates were used. The effects of pH, hydrogen peroxide doses, current density, NaCl concentrations, and reaction times were studied. Under optimal conditions of pH 4, current density of 40 mA/m(2), 1000 mg/L H2O2, 1 g/L NaCl, and 30-min reaction time, the peroxi-electrochemical method yielded very effective removal of organic pollution from the olive mill wastewater diluted four times. The treatment process reduced COD by 96%, BOD5 by 93.6%, total, polyphenols by 94.4%, color by 91.4%, turbidity by 88.7, suspended solids by 97% and oil and grease by 97.1%. The biodegradability index (BOD5/COD) increased from 0.29 to 0.46. Therefore, the peroxi-electrocoagulation/electrooxidation-electroflotation process is considered as an effective and feasible process for pre-treating olive mill wastewater, making possible a post-treatment of the effluent in a biological system.

Suppression of new particle formation from monoterpene oxidation by NOx

NASA Astrophysics Data System (ADS)

Wildt, J.; Mentel, T. F.; Kiendler-Scharr, A.; Hoffmann, T.; Andres, S.; Ehn, M.; Kleist, E.; Müsgen, P.; Rohrer, F.; Rudich, Y.; Springer, M.; Tillmann, R.; Wahner, A.

2013-10-01

The impact of nitrogen oxides (NOx = NO + NO2) on new particle formation (NPF) and on photochemical ozone production from real plant volatile organic compound (BVOC) emissions was studied in a laboratory set up. At high NOx conditions (BVOC/NOx < 7, NOx > 23 ppb) no new particles were formed. Instead photochemical ozone formation was observed resulting in higher hydroxyl radical (OH) and lower nitrogen monoxide (NO) concentrations. As soon as [NO] was reduced to below 1 ppb by OH reactions, NPF was observed. Adding high amounts of NOx caused NPF orders of magnitude slower than in analogous experiments at low NOx conditions (NOx ~ 300 ppt), although OH concentrations were higher. Varying NO2 photolysis enabled showing that NO was responsible for suppression of NPF suggesting that peroxy radicals are involved in NPF. The rates of NPF and photochemical ozone production were related by power law dependence with an exponent of approximately -2. This exponent indicated that the overall peroxy radical concentration must have been the same whenever NPF appeared. Thus permutation reactions of first generation peroxy radicals cannot be the rate limiting step in NPF from monoterpene oxidation. It was concluded that permutation reactions of higher generation peroxy radical like molecules limit the rate of new particle formation. In contrast to the strong effects on the particle numbers, the formation of particle mass was less sensitive to NOx concentrations, if at all. Only at very high NOx concentrations yields were reduced by about an order of magnitude.

[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.

Integration of CuAAC Polymerization and Controlled Radical Polymerization into Electron Transfer Mediated "Click-Radical" Concurrent Polymerization.

PubMed

Xue, Wentao; Wang, Jie; Wen, Ming; Chen, Gaojian; Zhang, Weidong

2017-03-01

The successful chain-growth copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC) polymerization employing Cu(0)/pentamethyldiethylenetriamine (PMDETA) and alkyl halide as catalyst is first investigated by a combination of nuclear magnetic resonance, gel-permeation chromatography, and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. In addition, the electron transfer mediated "click-radical" concurrent polymerization utilizing Cu(0)/PMDETA as catalyst is successfully employed to generate well-defined copolymers, where controlled CuAAC polymerization of clickable ester monomer is progressed in the main chain acting as the polymer backbone, the controlled radical polymerization (CRP) of acrylic monomer is carried out in the side chain. Furthermore, it is found that there is strong collaborative effect and compatibility between CRP and CuAAC polymerization to improve the controllability. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Suppression of new particle formation from monoterpene oxidation by NOx

NASA Astrophysics Data System (ADS)

Wildt, J.; Mentel, T. F.; Kiendler-Scharr, A.; Hoffmann, T.; Andres, S.; Ehn, M.; Kleist, E.; Müsgen, P.; Rohrer, F.; Rudich, Y.; Springer, M.; Tillmann, R.; Wahner, A.

2014-03-01

The impact of nitrogen oxides (NOx = NO + NO2) on new particle formation (NPF) and on photochemical ozone production from real plant volatile organic compound (BVOC) emissions was studied in a laboratory setup. At high NOx conditions ([BVOC] / [NOx] < 7, [NOx] > 23 ppb) new particle formation was suppressed. Instead, photochemical ozone formation was observed resulting in higher hydroxyl radical (OH) and lower nitrogen monoxide (NO) concentrations. When [NO] was reduced back to levels below 1 ppb by OH reactions, NPF was observed. Adding high amounts of NOx caused NPF to be slowed by orders of magnitude compared to analogous experiments at low NOx conditions ([NOx] ~300 ppt), although OH concentrations were higher. Varying NO2 photolysis enabled showing that NO was responsible for suppression of NPF. This suggests that peroxy radicals are involved in NPF. The rates of NPF and photochemical ozone production were related by power law dependence with an exponent approaching -2. This exponent indicated that the overall peroxy radical concentration must have been similar when NPF occurred. Thus, permutation reactions of first-generation peroxy radicals cannot be the rate limiting step in NPF from monoterpene oxidation. It was concluded that permutation reactions of higher generation peroxy-radical-like intermediates limit the rate of new particle formation. In contrast to the strong effects on the particle numbers, the formation of particle mass was substantially less sensitive to NOx concentrations. If at all, yields were reduced by about an order of magnitude only at very high NOx concentrations.

Experimental and theoretical study of oxidative stability of alkylated furans used as gasoline blend components

DOE PAGES

Christensen, Earl; Fioroni, Gina M.; Kim, Seonah; ...

2017-11-06

Alkylated furans such as 2,5-dimethylfuran and 2-methylfuran can be produced from biomass and have very attractive properties for use as spark-ignition fuel blendstocks. Their high octane numbers, relatively high energy density, low water solubility, and minimal effect on gasoline blend volatility are potentially significant advantages over alcohol-based fuels. However, prior studies have reported poor oxidative stability for furanic compound-gasoline blends, as well as the potential for the formation of dangerous organic peroxides. We show that alkylated furans have very low oxidative stability compared to conventional gasoline. Upon oxidation they form highly polar ring-opening products that can react with the startingmore » furanic compound to form dimers, trimers, and higher polymers with intact furan rings. Dimers of the starting furan compounds were also observed. These gasoline-insoluble gums can be problematic for fuel storage or in vehicle fuel systems. Evaporation to dryness under ambient conditions also produced gum with similar composition. Gums produced via evaporation were found to contain peroxides; however, whether these pose a threat of shock initiated explosion has not been determined. We also propose a density functional theory-based analysis of possible reaction pathways, showing that OH radicals can form by reaction of the alkyl group and that addition of OH radicals to the furan ring is energetically favored and leads to ring opening products. As a result, antioxidant additives can be effective at limiting the oxidation reaction in gasoline, but require much higher concentrations than are commonly used in commercial gasolines.« less

Experimental and theoretical study of oxidative stability of alkylated furans used as gasoline blend components

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

Christensen, Earl; Fioroni, Gina M.; Kim, Seonah

Alkylated furans such as 2,5-dimethylfuran and 2-methylfuran can be produced from biomass and have very attractive properties for use as spark-ignition fuel blendstocks. Their high octane numbers, relatively high energy density, low water solubility, and minimal effect on gasoline blend volatility are potentially significant advantages over alcohol-based fuels. However, prior studies have reported poor oxidative stability for furanic compound-gasoline blends, as well as the potential for the formation of dangerous organic peroxides. We show that alkylated furans have very low oxidative stability compared to conventional gasoline. Upon oxidation they form highly polar ring-opening products that can react with the startingmore » furanic compound to form dimers, trimers, and higher polymers with intact furan rings. Dimers of the starting furan compounds were also observed. These gasoline-insoluble gums can be problematic for fuel storage or in vehicle fuel systems. Evaporation to dryness under ambient conditions also produced gum with similar composition. Gums produced via evaporation were found to contain peroxides; however, whether these pose a threat of shock initiated explosion has not been determined. We also propose a density functional theory-based analysis of possible reaction pathways, showing that OH radicals can form by reaction of the alkyl group and that addition of OH radicals to the furan ring is energetically favored and leads to ring opening products. As a result, antioxidant additives can be effective at limiting the oxidation reaction in gasoline, but require much higher concentrations than are commonly used in commercial gasolines.« less

Peroxy-Titanium Complex-based inks for low temperature compliant anatase thin films.

PubMed

Shabanov, N S; Asvarov, A Sh; Chiolerio, A; Rabadanov, K Sh; Isaev, A B; Orudzhev, F F; Makhmudov, S Sh

2017-07-15

Stable highly crystalline titanium dioxide colloids are of paramount importance for the establishment of a solution-processable library of materials that could help in bringing the advantages of digital printing to the world of photocatalysis and solar energy conversion. Nano-sized titanium dioxide in the anatase phase was synthesized by means of hydrothermal methods and treated with hydrogen peroxide to form Peroxy-Titanium Complexes (PTCs). The influence of hydrogen peroxide on the structural, optical and rheological properties of titanium dioxide and its colloidal solutions were assessed and a practical demonstration of a low temperature compliant digitally printed anatase thin film given. Copyright © 2017 Elsevier Inc. All rights reserved.

Measurement of interferences associated with the detection of the hydroperoxy radical in the atmosphere using laser-induced fluorescence

NASA Astrophysics Data System (ADS)

Lew, Michelle M.; Dusanter, Sebastien; Stevens, Philip S.

2018-01-01

One technique used to measure concentrations of the hydroperoxy radical (HO2) in the atmosphere involves chemically converting it to OH by addition of NO and subsequent detection of OH. However, some organic peroxy radicals (RO2) can also be rapidly converted to HO2 (and subsequently OH) in the presence of NO, interfering with measurements of ambient HO2 radical concentrations. This interference must be characterized for each instrument to determine to what extent various RO2 radicals interfere with measurements of HO2 and to assess the impact of this interference on past measurements. The efficiency of RO2-to-HO2 conversion for the Indiana University laser-induced fluorescence-fluorescence assay by gas expansion (IU-FAGE) instrument was measured for a variety of RO2 radicals. Known quantities of OH and HO2 radicals were produced from the photolysis of water vapor at 184.9 nm, and RO2 radicals were produced by the reaction of several volatile organic compounds (VOCs) with OH. The conversion efficiency of RO2 radicals to HO2 was measured when NO was added to the sampling cell for conditions employed during several previous field campaigns. For these conditions, approximately 80 % of alkene-derived RO2 radicals and 20 % of alkane-derived RO2 radicals were converted to HO2. Based on these measurements, interferences from various RO2 radicals contributed to approximately 35 % of the measured HO2 signal during the Mexico City Metropolitan Area (MCMA) 2006 campaign (MCMA-2006), where the measured VOCs consisted of a mixture of saturated and unsaturated species. However, this interference can contribute more significantly to the measured HO2 signal in forested environments dominated by unsaturated biogenic emissions such as isoprene.

Observation and Modelling of the OH, HO2 and RO2 Radicals at a Regional Site of Beijing in Winter 2016.

NASA Astrophysics Data System (ADS)

Tan, Z.; Lu, K.; Ma, X.; Bohn, B.; Hofzumahaus, A.; Broch, S.; Fuchs, H.; Holland, F.; Liu, Y.; Li, X.; Novelli, A.; Rohrer, F.; Wang, H.; Wu, Y.; Shao, M.; Zeng, L.; Kiendler-Scharr, A.; Wahner, A.; Zhang, Y.

2017-12-01

A comprehensive field campaign was carried out in winter 2016 in the campus of UCAS (University of Chinese Academy of Science), located in a small town 60 km northeast of urban Beijing. Concentrations of OH, HO2 and RO2 radicals as well as the total OH reactivity were measured by a laser induced fluorescence instrument. Maximum hourly averaged OH, HO2 and RO2 radical concentrations were (3±2)×106cm-3, (8±6)×107 cm-3 and (7±5)×107 cm-3, respectively. These radical concentrations were smaller than those observed during summer because of the reduced solar radiation. A chemical modulation device to separate atmospheric OH radicals from any interfering species was applied for few days showing negligible interference for both clean and polluted air masses.HONO and HCHO photolysis were found to be the most important primary sources of ROx radicals. CO and NOx were the important OH reactants which contributed more than half of the total OH reactivity. The relative high OH concentrations in polluted episode enabled a fast oxidation of fresh emitted pollutants and the formation of secondary air products. The observed radical concentrations were compared with the results from a chemical box model. The model is capable of reproducing radical concentrations for moderate NOx conditions but larger discrepancies are observed for both low and high NOx regimes for the peroxy radical concentrations. The underestimation of RO2 radical concentrations for high NOx conditions is discussed in the context of recent campaigns.

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

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.

High-level theoretical characterization of the vinoxy radical (•CH2CHO) + O2 reaction

NASA Astrophysics Data System (ADS)

Weidman, Jared D.; Allen, Ryan T.; Moore, Kevin B.; Schaefer, Henry F.

2018-05-01

Numerous processes in atmospheric and combustion chemistry produce the vinoxy radical (•CH2CHO). To understand the fate of this radical and to provide reliable energies needed for kinetic modeling of such processes, we have examined its reaction with O2 using highly reliable theoretical methods. Utilizing the focal point approach, the energetics of this reaction and subsequent reactions were obtained using coupled-cluster theory with single, double, and perturbative triple excitations [CCSD(T)] extrapolated to the complete basis set limit. These extrapolated energies were appended with several corrections including a treatment of full triples and connected quadruple excitations, i.e., CCSDT(Q). In addition, this study models the initial vinoxy radical + O2 reaction for the first time with multireference methods. We predict a barrier for this reaction of approximately 0.4 kcal mol-1. This result agrees with experimental findings but is in disagreement with previous theoretical studies. The vinoxy radical + O2 reaction produces a 2-oxoethylperoxy radical which can undergo a number of unimolecular reactions. Abstraction of a β-hydrogen (a 1,4-hydrogen shift) and dissociation back to reactants are predicted to be competitive to each other due to their similar barriers of 21.2 and 22.3 kcal mol-1, respectively. The minimum-energy β-hydrogen abstraction pathway produces a hydroperoxy radical (QOOH) that eventually decomposes to formaldehyde, CO, and •OH. Two other unimolecular reactions of the peroxy radical are α-hydrogen abstraction (38.7 kcal mol-1 barrier) and HO2• elimination (43.5 kcal mol-1 barrier). These pathways lead to glyoxal + •OH and ketene + HO2• formation, respectively, but they are expected to be uncompetitive due to their high barriers.

Reaction between peroxynitrite and boronates: EPR spin-trapping, HPLC analyses, and quantum mechanical study of the free radical pathway

PubMed Central

Sikora, Adam; Zielonka, Jacek; Lopez, Marcos; Dybala-Defratyka, Agnieszka; Joseph, Joy; Marcinek, Andrzej; Kalyanaraman, Balaraman

2013-01-01

Recently we showed that peroxynitrite (ONOO−) reacts directly and rapidly with aromatic and aliphatic boronic acids (k ≈ 106 M−1s−1). Product analyses and substrate consumption data indicated that ONOO− reacts stoichiometrically with boronates, yielding the corresponding phenols as the major product (~85–90%), and the remaining products (10–15%) were proposed to originate from free radical intermediates (phenyl and phenoxyl radicals). Here we investigated in detail the minor, free radical pathway of boronate reaction with ONOO−. The electron paramagnetic resonance (EPR) spin-trapping technique was used to characterize the free radical intermediates formed from the reaction between boronates and ONOO−. Using 2-methyl-2-nitrosopropane (MNP) and 5-diethoxyphosphoryl-5-methyl-1-pyrroline-N-oxide (DEPMPO) spin traps, phenyl radicals were trapped and detected. Although phenoxyl radicals were not detected, the positive effects of molecular oxygen, and inhibitory effects of hydrogen atom donors (acetonitrile, and 2-propanol) and general radical scavengers (GSH, NADH, ascorbic acid and tyrosine) on the formation of phenoxyl radical-derived nitrated product, suggest that phenoxyl radical was formed as the secondary species. We propose that the initial step of the reaction involves the addition of ONOO− to the boron atom in boronates. The anionic intermediate undergoes both heterolytic (major pathway) and homolytic (minor pathway) cleavage of the peroxy (O-O) bond to form phenol and nitrite as a major product (via a non-radical mechanism), or a radical pair PhB(OH)2O•−…•NO2 as a minor product. It is conceivable that phenyl radicals are formed by the fragmentation of PhB(OH)2O•− radical anion. According to the DFT quantum mechanical calculations, the energy barrier for the dissociation of PhB(OH)2O•− radical anion to form phenyl radicals is only a few kcal/mol, suggesting rapid and spontaneous fragmentation of PhB(OH)2O•− radical anion

Efficacy of a Low Dose of Hydrogen Peroxide (Peroxy Ag⁺) for Continuous Treatment of Dental Unit Water Lines: Challenge Test with Legionella pneumophila Serogroup 1 in a Simulated Dental Unit Waterline.

PubMed

Ditommaso, Savina; Giacomuzzi, Monica; Ricciardi, Elisa; Zotti, Carla M

2016-07-22

This study was designed to examine the in vitro bactericidal activity of hydrogen peroxide against Legionella. We tested hydrogen peroxide (Peroxy Ag⁺) at 600 ppm to evaluate Legionella survival in a simulated dental treatment water system equipped with Water Hygienization Equipment (W.H.E.) device that was artificially contaminated. When Legionella pneumophila serogroup (sg) 1 was exposed to Peroxy Ag⁺ for 60 min we obtained a two decimal log reduction. High antimicrobial efficacy was obtained with extended periods of exposure: four decimal log reduction at 75 min and five decimal log reduction at 15 h of exposure. Involving a simulation device (Peroxy Ag⁺ is flushed into the simulation dental unit waterlines (DUWL)) we obtained an average reduction of 85% of Legionella load. The product is effective in reducing the number of Legionella cells after 75 min of contact time (99.997%) in the simulator device under test conditions. The Peroxy Ag⁺ treatment is safe for continuous use in the dental water supply system (i.e., it is safe for patient contact), so it could be used as a preventive option, and it may be useful in long-term treatments, alone or coupled with a daily or periodic shock treatment.

Investigation of potential interferences in the detection of atmospheric ROx radicals by laser-induced fluorescence under dark conditions

NASA Astrophysics Data System (ADS)

Fuchs, H.; Tan, Z.; Hofzumahaus, A.; Broch, S.; Dorn, H.-P.; Holland, F.; Künstler, C.; Gomm, S.; Rohrer, F.; Schrade, S.; Tillmann, R.; Wahner, A.

2015-11-01

Direct detection of highly reactive, atmospheric hydroxyl radicals (OH) is widely accomplished by laser-induced fluorescence (LIF) instruments. The technique is also suitable for the indirect measurement of HO2 and RO2 peroxy radicals by chemical conversion to OH. It requires sampling of ambient air into a low pressure cell, where OH fluorescence is detected after excitation by 308 nm laser radiation. Although the residence time of air inside the fluorescence cell is typically only on the order of milliseconds, there is potential that additional OH is internally produced, which would artificially increase the measured OH concentration. Here, we present experimental studies investigating potential interferences in the detection of OH and peroxy radicals for the LIF instruments of Forschungszentrum Jülich for nighttime conditions. For laboratory experiments, the inlet of the instrument was overflown by excess synthetic air containing one or more reactants. In order to distinguish between OH produced by reactions upstream of the inlet and artificial signals produced inside the instrument, a chemical titration for OH was applied. Additional experiments were performed in the simulation chamber SAPHIR where simultaneous measurements by an open-path differential optical absorption spectrometer (DOAS) served as reference for OH to quantify potential artifacts in the LIF instrument. Experiments included the investigation of potential interferences related to the nitrate radical (NO3, N2O5), related to the ozonolysis of alkenes (ethene, propene, 1-butene, 2,3-dimethyl-2-butene, α-pinene, limonene, isoprene), and the laser photolysis of acetone. Experiments studying the laser photolysis of acetone yield OH signals in the fluorescence cell, which are equivalent to 0.05 × 106 cm-3 OH for a mixing ratio of 5 ppbv acetone. Under most atmospheric conditions, this interference is negligible. No significant interferences were found for atmospheric concentrations of reactants

Investigation of potential interferences in the detection of atmospheric ROx radicals by laser-induced fluorescence under dark conditions

NASA Astrophysics Data System (ADS)

Fuchs, Hendrik; Tan, Zhaofeng; Hofzumahaus, Andreas; Broch, Sebastian; Dorn, Hans-Peter; Holland, Frank; Künstler, Christopher; Gomm, Sebastian; Rohrer, Franz; Schrade, Stephanie; Tillmann, Ralf; Wahner, Andreas

2016-04-01

Direct detection of highly reactive, atmospheric hydroxyl radicals (OH) is widely accomplished by laser-induced fluorescence (LIF) instruments. The technique is also suitable for the indirect measurement of HO2 and RO2 peroxy radicals by chemical conversion to OH. It requires sampling of ambient air into a low-pressure cell, where OH fluorescence is detected after excitation by 308 nm laser radiation. Although the residence time of air inside the fluorescence cell is typically only on the order of milliseconds, there is potential that additional OH is internally produced, which would artificially increase the measured OH concentration. Here, we present experimental studies investigating potential interferences in the detection of OH and peroxy radicals for the LIF instruments of Forschungszentrum Jülich for nighttime conditions. For laboratory experiments, the inlet of the instrument was over flowed by excess synthetic air containing one or more reactants. In order to distinguish between OH produced by reactions upstream of the inlet and artificial signals produced inside the instrument, a chemical titration for OH was applied. Additional experiments were performed in the simulation chamber SAPHIR where simultaneous measurements by an open-path differential optical absorption spectrometer (DOAS) served as reference for OH to quantify potential artifacts in the LIF instrument. Experiments included the investigation of potential interferences related to the nitrate radical (NO3, N2O5), related to the ozonolysis of alkenes (ethene, propene, 1-butene, 2,3-dimethyl-2-butene, α-pinene, limonene, isoprene), and the laser photolysis of acetone. Experiments studying the laser photolysis of acetone yield OH signals in the fluorescence cell, which are equivalent to 0.05 × 106 cm-3 OH for a mixing ratio of 5 ppbv acetone. Under most atmospheric conditions, this interference is negligible. No significant interferences were found for atmospheric concentrations of reactants

Synthesis and spectral properties of polymethine-cyanine dye-nitroxide radical hybrid compounds for use as fluorescence probes to monitor reducing species and radicals

NASA Astrophysics Data System (ADS)

Sato, Shingo; Tsunoda, Minoru; Suzuki, Minoru; Kutsuna, Masahiro; Takido-uchi, Kiyomi; Shindo, Mitsuru; Mizuguchi, Hitoshi; Obara, Heitaro; Ohya, Hiroaki

2009-01-01

Various hybrid compounds comprised of two types of nitroxide radicals and either a pentamethine (Cy5) or trimethine cyanine (Cy3) were synthesized. The nitroxide radicals were linked either via an ester-bond to one or two N-alkyl carboxyl-terminated groups of Cy5, or via two amido-bonds (aminocarbonyl or carbonylamino group) to the 5-position of the indolenine moieties of Cy5 and Cy3. Changes in fluorescence and ESR intensities of the hybrid compounds were measured before and after addition of Na ascorbate in PBS (pH 7.0) to reduce the radicals. Among the hybrid compounds synthesized, those that linked the nitroxide radicals via an aminocarbonyl residue at the 5-position of the indolenine moieties on Cy5 and Cy3 exhibited a 1.8- and 5.1-fold increase in fluorescence intensity with the reduction of the nitroxide segment by the addition of Na ascorbate, respectively. In contrast, fluorescence intensity was not enhanced in the other hybrid compounds. Thus, the hybrid compounds which exhibited an increase in fluorescent intensity with radical reduction can be used in the quantitative measurement of reducing species such as Fe 2+ and ascorbic acid, and hydroxyl radicals. Because these hybrid compounds have the advantage of fluorescing at longer wavelengths—661 (Cy5) or 568 (Cy3) nm, respectively, they can be used to measure radical-reducing species or radicals either in solution or in vivo.

Reassessing the atmospheric oxidation mechanism of toluene

NASA Astrophysics Data System (ADS)

Ji, Yuemeng; Zhao, Jun; Terazono, Hajime; Misawa, Kentaro; Levitt, Nicholas P.; Li, Yixin; Lin, Yun; Peng, Jianfei; Wang, Yuan; Duan, Lian; Pan, Bowen; Zhang, Fang; Feng, Xidan; An, Taicheng; Marrero-Ortiz, Wilmarie; Secrest, Jeremiah; Zhang, Annie L.; Shibuya, Kazuhiko; Molina, Mario J.; Zhang, Renyi

2017-08-01

Photochemical oxidation of aromatic hydrocarbons leads to tropospheric ozone and secondary organic aerosol (SOA) formation, with profound implications for air quality, human health, and climate. Toluene is the most abundant aromatic compound under urban environments, but its detailed chemical oxidation mechanism remains uncertain. From combined laboratory experiments and quantum chemical calculations, we show a toluene oxidation mechanism that is different from the one adopted in current atmospheric models. Our experimental work indicates a larger-than-expected branching ratio for cresols, but a negligible formation of ring-opening products (e.g., methylglyoxal). Quantum chemical calculations also demonstrate that cresols are much more stable than their corresponding peroxy radicals, and, for the most favorable OH (ortho) addition, the pathway of H extraction by O2 to form the cresol proceeds with a smaller barrier than O2 addition to form the peroxy radical. Our results reveal that phenolic (rather than peroxy radical) formation represents the dominant pathway for toluene oxidation, highlighting the necessity to reassess its role in ozone and SOA formation in the atmosphere.

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.

Structural features, kinetics and SAR study of radical scavenging and antioxidant activities of phenolic and anilinic compounds

PubMed Central

2013-01-01

Background Phenolic compounds are widely distributed in plant kingdom and constitute one of the most important classes of natural and synthetic antioxidants. In the present study fifty one natural and synthetic structurally variant phenolic, enolic and anilinic compounds were examined as antioxidants and radical scavengers against DPPH, hydroxyl and peroxyl radicals. The structural diversity of the used phenolic compounds includes monophenols with substituents frequently present in natural phenols e.g. alkyl, alkoxy, ester and carboxyl groups, besides many other electron donating and withdrawing groups, in addition to polyphenols with 1–3 hydroxyl groups and aminophenols. Some common groups e.g. alkyl, carboxyl, amino and second OH groups were incorporated in ortho, meta and para positions. Results SAR study indicates that the most important structural feature of phenolic compounds required to possess good antiradical and antioxidant activities is the presence of a second hydroxyl or an amino group in o- or p-position because of their strong electron donating effect in these positions and the formation of a stable quinone-like products upon two hydrogen-atom transfer process; otherwise, the presence of a number of alkoxy (in o or p-position) and /or alkyl groups (in o, m or p-position) should be present to stabilize the resulted phenoxyl radical and reach good activity. Anilines showed also similar structural feature requirements as phenols to achieve good activities, except o-diamines which gave low activity because of the high energy of the resulted 1,2-dimine product upon the 2H-transfer process. Enols with ene-1,2-diol structure undergo the same process and give good activity. Good correlations were obtained between DPPH inhibition and inhibition of both OH and peroxyl radicals. In addition, good correlations were obtained between DPPH inhibition and antioxidant activities in sunflower oil and liver homogenate systems. Conclusions In conclusion, the

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

The photochemical alkylation and reduction of heteroarenes† †Electronic supplementary information (ESI) available. See DOI: 10.1039/c7sc03768f Click here for additional data file.

PubMed Central

McCallum, T.; Pitre, S. P.; Morin, M.

2017-01-01

The functionalization of heteroarenes has been integral to the structural diversification of medicinally active molecules such as quinolines, pyridines, and phenanthridines. Electron-deficient heteroarenes are electronically compatible to react with relatively nucleophilic free radicals such as hydroxyalkyl. However, the radical functionalization of such heteroarenes has been marked by the use of transition-metal catalyzed processes that require initiators and stoichiometric oxidants. Herein, we describe the photochemical alkylation of quinolines, pyridines and phenanthridines, where through direct excitation of the protonated heterocycle, alcohols and ethers, such as methanol and THF, can serve as alkylating agents. We also report the discovery of a photochemical reduction of these heteroarenes using only iPrOH and HCl. Mechanistic studies to elucidate the underlying mechanism of these transformations, and preliminary results on catalytic methylations are also reported. PMID:29163892

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.

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.

Some current problems in oxidation kinetics

NASA Technical Reports Server (NTRS)

Benson, S. W.

1972-01-01

Experimental data in low temperature and high temperature oxidations are examined from the point of view of reported quantitative inconsistencies. Activation energies for tBuO2 metathesis reactions with alkanes appear to be 7 kcal/mole higher than for comparable reactions of HO2. Related isomerization reactions are examined in the light of these differences without reaching any simple conclusions. The Russell mechanism for a 6-membered, cyclic, transition state for termination of primary and secondary alkyl peroxy radicals is shown to be either inconsistent with thermochemical data, or else unique to solution reactions. Addition reactions of O3 with olefins and acetylenes are shown thermochemically to have the possibility of following concerted and biradical pathways, respectively. Recent data showing strong inhibition by PbO coated surfaces of both oxidation and pyrolysis of i-C4H10 are examined in terms of mechanism.

Hyperoxic sheep pulmonary microvascular endothelial cells generate free radicals via mitochondrial electron transport.

PubMed Central

Sanders, S P; Zweier, J L; Kuppusamy, P; Harrison, S J; Bassett, D J; Gabrielson, E W; Sylvester, J T

1993-01-01

Free radical generation by hyperoxic endothelial cells was studied using electron paramagnetic resonance (EPR) spectroscopy and the spin trap 5,5-dimethyl-1-pyrroline-N-oxide (DMPO). Studies were performed to determine the radical species produced, whether mitochondrial electron transport was involved, and the effect of the radical generation on cell mortality. Sheep pulmonary microvascular endothelial cell suspensions exposed to 100% O2 for 30 min exhibited prominent DMPO-OH and, occasionally, additional smaller DMPO-R signals thought to arise from the trapping of superoxide anion (O2-.), hydroxyl (.OH), and alkyl (.R) radicals. Superoxide dismutase (SOD) quenched both signals suggesting that the observed radicals were derived from O2-.. Studies with deferoxamine suggested that the generation of .R occurred secondary to the formation of .OH from O2-. via an iron-mediated Fenton reaction. Blocking mitochondrial electron transport with rotenone (20 microM) markedly decreased radical generation. Cell mortality increased slightly in oxygen-exposed cells. This increase was not significantly altered by SOD or deferoxamine, nor was it different from the mortality observed in air-exposed cells. These results suggest that endothelial cells exposed to hyperoxia for 30 min produce free radicals via mitochondrial electron transport, but under the conditions of these experiments, this radical generation did not appear cause cell death. PMID:8380815

Modeling the oxidative capacity of the atmosphere of the south coast air basin of California. 2. HOx radical production.

PubMed

Griffin, Robert J

2004-02-01

The production of HOx radicals in the South Coast Air Basin of California is investigated during the smog episode of September 9, 1993 using the California Institute of Technology (CIT) air-quality model. Sources of HOx(hydroxyl, hydroperoxy, and organic peroxy radicals) incorporated into the associated gas-phase chemical mechanism include the combination of excited-state singlet oxygen (formed from ozone (O3) photolysis (hv)) with water, the photolysis of nitrous acid, hydrogen peroxide (H2O2), and carbonyl compounds (formaldehyde (HCHO) or higher aldehydes and ketones), the consumption of aldehydes and alkenes (ALK) by the nitrate radical, and the consumption of alkenes by O3 and the oxygen atom (O). At a given time or location for surface cells and vertical averages, each route of HOx formation may be the greatest contributor to overall formation except HCHO-hv, H2O2-hv, and ALK-O, the latter two of which are insignificant pathways in general. The contribution of the ALK-O3 pathway is dependent on the stoichiometric yield of OH, but this pathway, at least for the studied smog episode, may not be as generally significant as previous research suggests. Future emissions scenarios yield lower total HOx production rates and a shift in the relative importance of individual pathways.

Developments in laser-induced fluorescence spectroscopy for quantitative in situ measurements of free radicals in the troposphere

NASA Astrophysics Data System (ADS)

Heard, Dwayne

2015-04-01

Photo-oxidation in the troposphere is highly complex, being initiated by short lived free radical species, in the daytime dominated by the hydroxyl radical, OH. Chemical oxidation cycles, which also involve peroxy radicals (HO2 and RO2), remove natural or anthropogenic emissions (for example methane) and generate a range of secondary products, for example ozone, nitrogen dioxide, acidic and multifunctional organic species, and secondary organic aerosol, which impact on human health and climate. Owing to their short lifetime in the atmosphere, the abundance of radicals is determined solely by their rate of chemical production and loss, and not by transport. Field measurements of the concentrations of radicals and comparison with calculations using a numerical model therefore constitutes one of the very best ways to test whether the chemistry in each of these locations is understood and accurately represented in the model. Validation of the chemistry is important, as the predictions of climate and air quality models containing this chemistry are used to drive the formulation of policy and legislation. However, in situ measurements of radical species, owing to their very low abundance (often sub part per trillion) and short lifetimes (< 1 second for OH), remain extremely challenging. Laser-induced fluorescence spectroscopy (LIF) has enjoyed considerable success worldwide for the quantitative detection of radicals in a range of environments. The radicals are either excited directly by the laser (e.g. OH, IO) or are first chemically converted to OH prior to detection (e.g. HO2, RO2). Recent developments in the LIF technique for radical detection, which uses a supersonic expansion with detection at low pressure and multi kHz pulse repetition rate tunable laser systems, will be discussed, together with calibration methods to make signals absolute, and identification of potential interferences. LIF instruments have been operated on ground, ship and aircraft platforms at a

Transition-Metal Catalysis of Nucleophilic Substitution Reactions: A Radical Alternative to SN1 and SN2 Processes.

PubMed

Fu, Gregory C

2017-07-26

Classical methods for achieving nucleophilic substitutions of alkyl electrophiles (S N 1 and S N 2) have limited scope and are not generally amenable to enantioselective variants that employ readily available racemic electrophiles. Radical-based pathways catalyzed by chiral transition-metal complexes provide an attractive approach to addressing these limitations.

Transition-Metal Catalysis of Nucleophilic Substitution Reactions: A Radical Alternative to SN1 and SN2 Processes

PubMed Central

2017-01-01

Classical methods for achieving nucleophilic substitutions of alkyl electrophiles (SN1 and SN2) have limited scope and are not generally amenable to enantioselective variants that employ readily available racemic electrophiles. Radical-based pathways catalyzed by chiral transition-metal complexes provide an attractive approach to addressing these limitations. PMID:28776010

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.

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.

Investigation of chemical and spin dynamics in micellized radical pairs by time-resolved stimulated nuclear polarization. Theory and experiment

NASA Astrophysics Data System (ADS)

Parnachev, A. P.; Bagryanskaya, E. G.; Tarasov, V. F.; Lukzen, N. N.; Sagdeev, R. Z.

1995-10-01

A numerical solution of the stochastic Liouville equation for a microreactor model is applied to the theoretical treatment of time-resolved stimulated nuclear polarization data, obtained during the investigation of micellized radical pairs, conducted in two different modes. Escape rate constants and relaxation parameters of radical pairs formed in the photolysis of methyldeoxybenzoin and benzoin in alkyl sulfate micelles of different sizes have been obtained. The conditions of the S-T 0 quantum oscillations in SNP kinetics have been determined.

Characteristics of oxidative homolytic alkylation of imidazoles and organic-inorganic hybrid extended networks from large aromatic building blocks

NASA Astrophysics Data System (ADS)

Li, Kunhao

The discovery of the dramatic in vitro antimalarial activity of 2-iodo-L-histidine and 2-fluoro-L-histidine, as well as their in vivo limitations, has prompted a systematic search for novel 2-substituted imidazoles and bioimidazoles as agents against human malaria. Previous research has shown that the regioselective alkyl free radical substitution on imidazoles and bioimidazoles could serve as a simple and efficient route to a wide variety of 2-alkylimidazoles. In this research, this methodology was successfully extended to include alkyl radicals substituted with various functional groups such as amide or ester. While this novel methodology should be of some synthetic utility when tertiary radicals are used, poorer yields are usually encountered in the cases of primary radicals. In the second part of this dissertation, a series of novel ligands containing multiple ortho-bis(organothio) groups were synthesized and their coordination and network forming properties were studied in the context of crystalline organic-inorganic hybrid extended networks. For the syntheses of HRTTs [2,3,6,7,10,11-hexakis(alkylthio)triphenylenes], a simpler, safer and higher yielding one-pot process was developed. Quenching the hexa-anions (formed when sodium methylthiolate was refluxed with hexabromotriphenylene) with alkyl halides or acid chlorides afforded HRTTs. This newly developed process was also successfully expanded to the pyrene system. In the syntheses of unsymmetrically substituted triphenlyenes, it was shown for the first time that the oxidative cyclization process is applicable to thioether containing systems, pointing to a novel strategy for the preparation of this type of unsymmetrically substituted triphenlyenes. Treating these novel ligands with various metal salts [i.e. bismuth(III) chloride and bismuth(III) bromide] under carefully controlled conditions resulted in a series of air-stable semiconductive coordination networks. Their single crystal structures were

Facile Rearrangement of 3-Oxoalkyl Radicals is Evident in Low-Temperature Gas-Phase Oxidation of Ketones

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

Scheer, Adam M.; Welz, Oliver; Sasaki, Darryl Y.

The pulsed photolytic chlorine-initiated oxidation of methyl-tert-butyl ketone (MTbuK), di-tert-butyl ketone (DTbuK), and a series of partially deuterated diethyl ketones (DEK) is studied in the gas phase at 8 Torr and 550–650 K. Products are monitored as a function of reaction time, mass, and photoionization energy using multiplexed photoionization mass spectrometry with tunable synchrotron ionizing radiation. The results establish that the primary 3-oxoalkyl radicals of those ketones, formed by abstraction of a hydrogen atom from the carbon atom in γ-position relative to the carbonyl oxygen, undergo a rapid rearrangement resulting in an effective 1,2-acyl group migration, similar to that inmore » a Dowd–Beckwith ring expansion. Without this rearrangement, peroxy radicals derived from MTbuK and DTbuK cannot undergo HO2 elimination to yield a closed-shell unsaturated hydrocarbon coproduct. However, not only are these coproducts observed, but they represent the dominant oxidation channels of these ketones under the conditions of this study. For MTbuK and DTbuK, the rearrangement yields a more stable tertiary radical, which provides the thermodynamic driving force for this reaction. Even in the absence of such a driving force in the oxidation of partially deuterated DEK, the 1,2-acyl group migration is observed. Quantum chemical (CBS-QB3) calculations show the barrier for gas-phase rearrangement to be on the order of 10 kcal mol–1. The MTbuK oxidation experiments also show several minor channels, including β-scission of the initial radicals and cyclic ether formation.« less

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.

Mass spectral analysis of long chain alkyl aromatic compounds synthesized from alpha-olefin alkylation

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

Cheng, M.T.; Hudson, J.D.

1994-12-31

Long chain alkyl aromatic compounds are important petrochemicals with many applications. They are generally synthesized by alkylating the corresponding aromatic nucleus. In this report, the authors will describe the mass spectral fragmentation of alkylphenols and alkylsalicylates.

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...

Molecular weight growth in Titan's atmosphere: Branching pathways for the reaction of 1-propynyl radical (H 3CC≡C˙) with small alkenes and alkynes

DOE PAGES

Kirk, Benjamin B.; Savee, John D.; Trevitt, Adam J.; ...

2015-07-16

The reaction of small hydrocarbon radicals (i.e. ˙CN, ˙C 2H) with trace alkenes and alkynes is believed to play an important role in molecular weight growth and ultimately the formation of Titan's characteristic haze. Current photochemical models of Titan's atmosphere largely assume hydrogen atom abstraction or unimolecular hydrogen elimination reactions dominate the mechanism, in contrast to recent experiments that reveal significant alkyl radical loss pathways during reaction of ethynyl radical (˙C 2H) with alkenes and alkynes. In this study, the trend is explored for the case of a larger ethynyl radical analogue, the 1-propynyl radical (H3CC≡C˙), a likely product frommore » the high-energy photolysis of propyne in Titan's atmosphere. Using synchrotron vacuum ultraviolet photoionization mass spectrometry, product branching ratios are measured for the reactions of 1-propynyl radical with a suite of small alkenes (ethylene and propene) and alkynes (acetylene and d 4-propyne) at 4 Torr and 300 K. Reactions of 1-propynyl radical with acetylene and ethylene form single products, identified as penta-1,3-diyne and pent-1-en-3-yne, respectively. These products form by hydrogen atom loss from the radical-adduct intermediates. The reactions of 1-propynyl radical with d4-propyne and propene form products from both hydrogen atom and methyl loss, (–H = 27%, –CH 3 = 73%) and (–H = 14%, –CH 3 = 86%), respectively. Altogether, these results indicate that reactions of ethynyl radical analogues with alkenes and alkynes form significant quantities of products by alkyl loss channels, suggesting that current photochemical models of Titan over predict both hydrogen atom production as well as the efficiency of molecular weight growth in these reactions.« less

Molecular weight growth in Titan's atmosphere: branching pathways for the reaction of 1-propynyl radical (H3CC≡C˙) with small alkenes and alkynes.

PubMed

Kirk, Benjamin B; Savee, John D; Trevitt, Adam J; Osborn, David L; Wilson, Kevin R

2015-08-28

The reaction of small hydrocarbon radicals (i.e.˙CN, ˙C2H) with trace alkenes and alkynes is believed to play an important role in molecular weight growth and ultimately the formation of Titan's characteristic haze. Current photochemical models of Titan's atmosphere largely assume hydrogen atom abstraction or unimolecular hydrogen elimination reactions dominate the mechanism, in contrast to recent experiments that reveal significant alkyl radical loss pathways during reaction of ethynyl radical (˙C2H) with alkenes and alkynes. In this study, the trend is explored for the case of a larger ethynyl radical analogue, the 1-propynyl radical (H3CC[triple bond, length as m-dash]C˙), a likely product from the high-energy photolysis of propyne in Titan's atmosphere. Using synchrotron vacuum ultraviolet photoionization mass spectrometry, product branching ratios are measured for the reactions of 1-propynyl radical with a suite of small alkenes (ethylene and propene) and alkynes (acetylene and d4-propyne) at 4 Torr and 300 K. Reactions of 1-propynyl radical with acetylene and ethylene form single products, identified as penta-1,3-diyne and pent-1-en-3-yne, respectively. These products form by hydrogen atom loss from the radical-adduct intermediates. The reactions of 1-propynyl radical with d4-propyne and propene form products from both hydrogen atom and methyl loss, (-H = 27%, -CH3 = 73%) and (-H = 14%, -CH3 = 86%), respectively. Together, these results indicate that reactions of ethynyl radical analogues with alkenes and alkynes form significant quantities of products by alkyl loss channels, suggesting that current photochemical models of Titan over predict both hydrogen atom production as well as the efficiency of molecular weight growth in these reactions.

Molecular weight growth in Titan's atmosphere: Branching pathways for the reaction of 1-propynyl radical (H 3CC≡C˙) with small alkenes and alkynes

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

Kirk, Benjamin B.; Savee, John D.; Trevitt, Adam J.

The reaction of small hydrocarbon radicals (i.e. ˙CN, ˙C 2H) with trace alkenes and alkynes is believed to play an important role in molecular weight growth and ultimately the formation of Titan's characteristic haze. Current photochemical models of Titan's atmosphere largely assume hydrogen atom abstraction or unimolecular hydrogen elimination reactions dominate the mechanism, in contrast to recent experiments that reveal significant alkyl radical loss pathways during reaction of ethynyl radical (˙C 2H) with alkenes and alkynes. In this study, the trend is explored for the case of a larger ethynyl radical analogue, the 1-propynyl radical (H3CC≡C˙), a likely product frommore » the high-energy photolysis of propyne in Titan's atmosphere. Using synchrotron vacuum ultraviolet photoionization mass spectrometry, product branching ratios are measured for the reactions of 1-propynyl radical with a suite of small alkenes (ethylene and propene) and alkynes (acetylene and d 4-propyne) at 4 Torr and 300 K. Reactions of 1-propynyl radical with acetylene and ethylene form single products, identified as penta-1,3-diyne and pent-1-en-3-yne, respectively. These products form by hydrogen atom loss from the radical-adduct intermediates. The reactions of 1-propynyl radical with d4-propyne and propene form products from both hydrogen atom and methyl loss, (–H = 27%, –CH 3 = 73%) and (–H = 14%, –CH 3 = 86%), respectively. Altogether, these results indicate that reactions of ethynyl radical analogues with alkenes and alkynes form significant quantities of products by alkyl loss channels, suggesting that current photochemical models of Titan over predict both hydrogen atom production as well as the efficiency of molecular weight growth in these reactions.« less

Photoredox Catalysis for the Generation of Carbon Centered Radicals.

PubMed

Goddard, Jean-Philippe; Ollivier, Cyril; Fensterbank, Louis

2016-09-20

Radical chemistry has witnessed over the last decades important advances that have positioned it as a methodology of choice in synthetic chemistry. A number of great attributes such as specific reactivities, the knowledge of the kinetics of most elementary processes, the functional group tolerance, and the possibility to operate cascade sequences are clearly responsible for this craze. Nevertheless, at the end of the last century, radical chemistry appeared plagued by several hurdles to overcome such as the use of environmentally problematic mediators or the impossibility of scale up. While the concept of photocatalysis was firmly established in the coordination chemistry community, its diffusion in organic synthetic chemistry remained sporadic for decades until the end of the 2000s with the breakthrough merging of organocatalysis and photocatalysis by the MacMillan group and contemporary reports by the groups of Yoon and Stephenson. Since then, photoredox catalysis has enjoyed particularly active and intense developments. It is now the topic of a still increasing number of publications featuring various applications from asymmetric synthesis, total synthesis of natural products, and polymerization to process (flow) chemistry. In this Account, we survey our own efforts in this domain, focusing on the elaboration of new photocatalytic pathways that could lead to the efficient generation of C-centered functionalized alkyl and aryl radicals. Both reductive and oxidative manifolds are accessible through photoredox catalysis, which has guided us along these lines in our projects. Thus, we studied the photocatalytic reduction of onium salts such as sulfoniums and iodoniums for the production of the elusive aryl radical intermediates. Progressing to more relevant chemistry for synthesis, we examined the cleavage of C-O and the C-Br bonds for the generation of alkyl C-centered radicals. Activated epoxides could serve as valuable substrates of a photocatalyzed variant of

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

Benzoyl radicals from (hetero)aromatic aldehydes. Decatungstate photocatalyzed synthesis of substituted aromatic ketones.

PubMed

Ravelli, Davide; Zema, Michele; Mella, Mariella; Fagnoni, Maurizio; Albini, Angelo

2010-09-21

Benzoyl radicals are generated directly from (hetero)aromatic aldehydes upon tetrabutylammonium decatungstate ((n-Bu(4)N)(4)W(10)O(32)), TBADT) photocatalysis under mild conditions. In the presence of alpha,beta-unsaturated esters, ketones and nitriles radical conjugate addition ensues and gives the corresponding beta-functionalized aryl alkyl ketones in moderate to good yields (stereoselectively in the case of 3-methylene-2-norbornanone). Due to the mild reaction conditions the presence of various functional groups on the aromatic ring is tolerated (e.g. methyl, methoxy, chloro). The method can be applied to hetero-aromatic aldehydes whether electron-rich (e.g. thiophene-2-carbaldehyde) or electron-poor (e.g. pyridine-3-carbaldehyde).

Conformation-Specific Infrared and Ultraviolet Spectroscopy of α-METHYLBENZYL Radical: Probing the State-Dependent Effects of Methyl Rocking against a Radical Site

NASA Astrophysics Data System (ADS)

Kidwell, Nathanael M.; Mehta, Deepali N.; Zwier, Timothy S.; Reilly, Neil J.; Kokkin, Damian L.; McCarthy, Michael C.

2012-06-01

Combustion processes involve a myriad of complex reaction pathways which connect smaller precursors to larger polyaromatic hydrocarbons, many of which are still unknown. In particular, benzyl-type radicals play an important role in combustible fuels due to their intrinsic resonance stabilization and consequent increase in relative concentration. Here, we present a study of the vibronic spectroscopy of α-Methylbenzyl radical (α-MeBz), in which the orientation of the methyl group adjacent to the radical site responds to the electronic interaction extending from the conjugated π-system. Probing the isolated radical, produced in an electrical discharge under jet-cooled conditions, the two-color resonant two-photon ionization, fluorescence excitation, and dispersed fluorescence spectra were obtained in order to determine the ground and excited state barriers to internal rotation and the angular change associated with electronic excitation. Resonant ion-dip infrared spectroscopy (RIDIRS) has also been implemented to elucidate the infrared signatures in the alkyl and aromatic CH stretch regions in order to probe in a complementary way the state-dependent conformational preferences of α-MeBz. We will show that the D0- and D1-RIDIR spectra report sensitively on the strong coupling between the CH stretch vibrations and the C_α-C_β torsional geometry. Furthermore, photoionization efficiency scans were carried out to reveal the adiabatic ionization threshold of α-MeBz and the quantized levels present in the radical cation state.

40 CFR 795.70 - Indirect photolysis screening test: Sunlight photolysis in waters containing dissolved humic...

Code of Federal Regulations, 2011 CFR

2011-07-01

.... (1985). (13) Mill T., Hendry D.G., Richardson H. “Free radical oxidants in natural waters.” Science, 207...)(7) of this section); peroxy radicals (RO2−) (Mill et al. (1981) under paragraph (f)(9) of this section; Mill et al. (1983) under paragraph (f)(8) of this section); hydroxyl radicals (HO−) (Mill et al...

40 CFR 795.70 - Indirect photolysis screening test: Sunlight photolysis in waters containing dissolved humic...

Code of Federal Regulations, 2010 CFR

2010-07-01

.... (1985). (13) Mill T., Hendry D.G., Richardson H. “Free radical oxidants in natural waters.” Science, 207...)(7) of this section); peroxy radicals (RO2−) (Mill et al. (1981) under paragraph (f)(9) of this section; Mill et al. (1983) under paragraph (f)(8) of this section); hydroxyl radicals (HO−) (Mill et al...

Antimalarial activity of synthetic 1,2,4-trioxanes and cyclic peroxy ketals, a quantum similarity study

NASA Astrophysics Data System (ADS)

Gironés, X.; Gallegos, A.; Carbó-Dorca, R.

2001-12-01

In this work, the antimalarial activity of two series of 20 and 7 synthetic 1,2,4-trioxanes and a set of 20 cyclic peroxy ketals are tested for correlation search by means of Molecular Quantum Similarity Measures (MQSM). QSAR models, dealing with different biological responses (IC90, IC50 and ED90) of the parasite Plasmodium Falciparum, are constructed using MQSM as molecular descriptors and are satisfactorily correlated. The statistical results of the 20 1,2,4-trioxanes are deeply analyzed to elucidate the relevant structural features in the biological activity, revealing the importance of phenyl substitutions.

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.

Formation of OH radicals in the gas phase ozonolysis of alkenes: the unexpected role of carbonyl oxides

NASA Astrophysics Data System (ADS)

Gutbrod, Roland; Schindler, Ralph N.; Kraka, Elfi; Cremer, Dieter

1996-04-01

According to CCSD(T)/TZ + 2P calculations, the decomposition of carbonyl oxide, H 2COO to HCO and OH radicals is unlikely in view of an activation enthalpy ΔΔHf0(298) of 31 kcal/mol. However, for dimethylcarbonyl oxide there is a low energy rearrangement mode ( ΔΔHf0(298): 14.4 kca/mol) which involves a H atom of ghe methyl group and which leads to a hydroperoxy methyl ethene intermediate, which in turn can decompose to OH and CH 2COCH 3 radicals ( ΔΔHf0(298): 23 kcal/mol). In the gas phase ozonolysis of alkyl substituted alkenes the formation of OH radicals is the most likely process. This has important consequences for the chemistry of the atmosphere.

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.

A Tertiary Carbon–Iron Bond as an Fe I Cl Synthon and the Reductive Alkylation of Diphosphine-Supported Iron(II) Chloride Complexes to Low-Valent Iron

DOE PAGES

Tondreau, Aaron M.; Scott, Brian L.; Boncella, James M.

2016-05-23

We explored ligand-induced reduction of ferrous alkyl complexes via homolytic cleavage of the alkyl fragment with simple chelating diphosphines. The reactivities of the sodium salts of diphenylmethane, phenyl(trimethylsilyl)methane, or diphenyl(trimethylsilyl)methane were explored in their reactivity with (py) 4FeCl 2. Furthermore, we prepared a series of monoalkylated salts of the type (py) 2FeRCl and characterized from the addition of 1 equiv of the corresponding alkyl sodium species. These complexes are isostructural and have similar magnetic properties. The double alkylation of (py) 4FeCl 2 resulted in the formation of tetrahedral high-spin iron complexes with the sodium salts of diphenylmethane and phenyl(trimethylsilyl)methane thatmore » readily decomposed. A bis(cyclohexadienyl) sandwich complex was formed with the addition of 2 equiv of the tertiary alkyl species sodium diphenyl(trimethylsilyl)methane. The addition of chelating phosphines to (py) 2FeRCl resulted in the overall transfer of Fe(I) chloride concurrent with loss of pyridine and alkyl radical. (dmpe) 2FeCl was synthesized via addition of 1 equiv of sodium diphenyl(trimethylsilyl)methane, whereas the addition of 2 equiv of the sodium compound to (dmpe) 2FeCl 2 gave the reduced Fe(0) nitrogen complex (dmpe) 2Fe(N 2). Our results demonstrate that iron–alkyl homolysis can be used to afford clean, low-valent iron complexes without the use of alkali metals.« less

Physiological Concentrations of Ascorbate Cannot Prevent the Potentially Damaging Reactions of Protein Radicals in Humans.

PubMed

Nauser, Thomas; Gebicki, Janusz M

2017-09-18

The principal initial biological targets of free radicals formed under conditions of oxidative stress are the proteins. The most common products of the interaction are carbon-centered alkyl radicals which react rapidly with oxygen to form peroxyl radicals and hydroperoxides. All these species are reactive, capable of propagating the free radical damage to enzymes, nucleic acids, lipids, and endogenous antioxidants, leading finally to the pathologies associated with oxidative stress. The best chance of preventing this chain of damage is in early repair of the protein radicals by antioxidants. Estimate of the effectiveness of the physiologically significant antioxidants requires knowledge of the antioxidant tissue concentrations and rate constants of their reaction with protein radicals. Previous studies by pulse radiolysis have shown that only ascorbate can repair the Trp and Tyr protein radicals before they form peroxyl radicals under physiological concentrations of oxygen. We have now extended this work to other protein C-centered radicals generated by hydroxyl radicals because these and many other free radicals formed under oxidative stress can produce secondary radicals on virtually any amino acid residue. Pulse radiolysis identified two classes of rate constants for reactions of protein radicals with ascorbate, a faster one in the range (9-60) × 10 7 M -1 s -1 and a slow one with a range of (0.5-2) × 10 7 M -1 s -1 . These results show that ascorbate can prevent further reactions of protein radicals only in the few human tissues where its concentration exceeds about 2.5 mM.

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

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.

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.

Radical observations during the Clean air for London project

NASA Astrophysics Data System (ADS)

Whalley, L. K.; Stone, D.; Clancy, N.; Lee, J. D.; Laufs, S.; Kleffmann, J.; Heard, D. E.

2012-12-01

With greater than 50 % of the global population residing in urban conurbations, poor urban air quality has a demonstrable effect on human health. OH and HO2 radicals, (collectively termed HOx) together with RO2 radicals, mediate virtually all of the oxidative chemistry in the atmosphere, being responsible for the transformation of primary emissions into secondary pollutants such as NO2, O3 and particulates. Understanding the chemistry of free-radicals in the atmosphere is essential in improving predictions of the lifetimes of pollutants and spatial scales of their transport within urban areas. Results from earlier field campaigns in urban and polluted regions have demonstrated the significance of HONO photolysis and alkene ozonolysis in the production of HOx radicals. In many cases, however, measurements of HONO have not been made, reducing the ability to evaluate model successes for OH in these environments. Here we present measurements of OH, HO2, RO2 and OH reactivity taken during the wintertime (January - February, 2012) and summertime (July - August, 2012) as part of the Clean air for London (ClearfLo) project in London. RO2 was detected using a newly developed flow-reactor laser-induced fluorescence technique which is able to discriminate between HO2 and organic peroxy radicals [1]. Low concentrations of radicals were observed during the wintertime, midday [OH], [HO2] and [RO2] were ~ 0.04, 0.8 and 1.5 pptv respectively, comparable to observations of radicals at other urban locations in winter [2,3,4], and which displayed a negative correlation with NO concentrations. OH reactivity was high and largely tracked the diurnal profiles of NOx and CO, with the highest reactivity ~100 s-1 observed during the morning rush hour. Analysis of factors controlling OH concentrations during the wintertime suggests that the formation of OH from the photolysis of O3 and subsequent reaction of O(1D) with H2O is a minor contribution both under high and low NOx conditions owing

[Induction of free radicals after dietary exposure by mercury contaminated rice and protective effect of coexisting selenium].

PubMed

Ji, Xiu-ling; Cheng, Jin-ping; Wang, Wen-hua; Qu, Li-ya; Zhao, Xiao-xiang; Zhuang, Hui-sheng

2006-10-01

Sprague-Dawley rats were reared by environmental mercury contaminated rice to survey the potential health risk of Wanshan mercury mining area. Electron spin resonance (ESR) was introduced to detect the species and the intensities of free radicals, using spin trap 5,5-dimethyl-1-pyrroline-N-oxide (DMPO). The results showed that the mercury-contaminated rice significantly increased the levels of free radicals and MDA in rat brain at 7 days (p < 0.05). ESR spectrums showed that the principal spin adducts resulted from the trapping of alkyl free radical (alphaH = 22.7 x 10(-4)T +/- 1.6 x 10(-4)T, alphaN = 15.5 x 10(-4)T +/- 0.5 x 10(-4)T), and hydroxyl radical. Levels of free radicals and MDA increased slowly until after 90-day exposure period (83%, 100%). Element correlation analysis showed high correlations of mercury and selenium in the brain of rat fed with Wanshan rice, suggesting that the coexisting selenium in rice exhibited antagonistic effects on both mercury accumulation and toxicity. The slight increases of free radicals in rat brain at 7, 20 and 30-day exposure periods should be related with the scavenger effect of Se.

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.

The formation of quasi-alicyclic rings in alkyl-aromatic compounds

NASA Astrophysics Data System (ADS)

Straka, Pavel; Buryan, Petr; Bičáková, Olga

2018-02-01

The alkyl side chains of n-alkyl phenols, n-alkyl benzenes and n-alkyl naphthalenes are cyclised, as demonstrated by GC measurements, FTIR spectroscopy and molecular mechanics calculations. Cyclisation occurs due to the intramolecular interaction between an aromatic ring (-δ) and a hydrogen of the terminal methyl group (+δ) of an alkyl chain. In fact, conventional molecules are not aliphatic-aromatic, but quasi-alicyclic-aromatic. With the aromatic molecules formed with a quasi-alicyclic ring, the effect of van der Waals attractive forces increases not only intramolecularly but also intermolecularly. This effect is strong in molecules with propyl and higher alkyl substituents. The increase of intermolecular van der Waals attractive forces results in bi-linearity in the GC retention time of the compounds in question, observed in the dependence of the logarithm of the relative retention time on the number of carbons in a molecule in both polar and nonpolar stationary phases with both capillary and packed columns. The role of van der Waals forces has been demonstrated using the potential energies of covalent and noncovalent interactions for 2-n-alkyl phenols, n-alkyl benzenes and 1-n-alkyl- and 2-n-alkyl naphthalenes.

Measurements of free radicals in a megacity during the Clean Air for London Project

NASA Astrophysics Data System (ADS)

Heard, Dwayne; Whalley, Lisa; Stone, Daniel; Clancy, Noel; Lee, James; Kleffman, Jorg; Laufs, Sebastian; Bandy, Brian

2013-04-01

Free radicals control the photo-oxidative chemistry of the atmosphere, being responsible for the transformation of primary emissions into secondary pollutants such as NO2, O3, multifunctional species and particulates. Here we present measurements of OH, HO2 and RO2 radicals and OH reactivity recorded at North Kensington, Central London, during two Intensive Operational Periods (IOPs) of the Clear Air for London (Clearflo) project in the summer and winter of 2012. OH and HO2 were measured using laser-induced fluorescence (LIF) spectroscopy at low pressure (the FAGE technique), and RO2 was measured using the recently developed ROXLIF technique, which utilises an external flow-reactor interfaced to FAGE, and which is able to discriminate between HO2 and organic peroxy radicals. Through control of reagent gases we are further able to provide a separate measurement of those RO2 species which are known to give an interference for HO2 measurements (namely alkene, aromatic and large-chain alkane derived RO2). OH reactivity was measured using laser-flash photolysis combined with FAGE. Low concentrations of radicals were observed during the winter IOP, with mixing ratios of [OH] ~ 0.04 pptv, [HO2] ~ 0.4 pptv, and [RO2] ~ 1.6 pptv at noon, all displaying a negative correlation with NO. The photolysis of O3 and subsequent reaction of O(1D) with H2O vapour was only a minor contribution to radical production in winter, with photolysis of HONO a major radical source. The summer IOP coincided with the London Olympic Games, with a number of pollution events, with ozone peaking at 100 ppbv (exceeding EU air quality directives) and elevated radical concentrations (peak [OH] ~ 0.14 pptv, [HO2] ~ 4 pptv, [RO2] ~ 6.4 pptv) being observed. The net rate of ozone production was calculated from radical observations and agreed well with measured ozone production, suggesting that advection/dilution by continental air-masses was not playing a significant role in determining ozone

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

Protein lysine-Nζ alkylation and O-phosphorylation mediated by DTT-generated reactive oxygen species

PubMed Central

Kumar, Nigam; Ippel, Hans; Weber, Christian; Hackeng, Tilman; Mayo, Kevin H

2013-01-01

Reactive oxygen species (ROS) play crucial roles in physiology and pathology. In this report, we use NMR spectroscopy and mass spectrometry (MS) to demonstrate that proteins (galectin-1, ubiquitin, RNase, cytochrome c, myoglobin, and lysozyme) under reducing conditions with dithiothreitol (DTT) become alkylated at lysine-Nζ groups and O-phosphorylated at serine and threonine residues. These adduction reactions only occur in the presence of monophosphate, potassium, trace metals Fe/Cu, and oxygen, and are promoted by reactive oxygen species (ROS) generated via DTT oxidation. Superoxide mediates the chemistry, because superoxide dismutase inhibits the reaction, and hydroxyl and phosphoryl radicals are also likely involved. While lysine alkylation accounts for most of the adduction, low levels of phosphorylation are also observed at some serine and threonine residues, as determined by western blotting and MS fingerprinting. The adducted alkyl group is found to be a fragment of DTT that forms a Schiff base at lysine Nζ groups. Although its exact chemical structure remains unknown, the DTT fragment includes a SH group and a –CHOH–CH2– group. Chemical adduction appears to be promoted in the context of a well-folded protein, because some adducted sites in the proteins studied are considerably more reactive than others and the reaction occurs to a lesser extent with shorter, unfolded peptides and not at all with small organic molecules. A structural signature involving clusters of positively charged and other polar groups appears to facilitate the reaction. Overall, our findings demonstrate a novel reaction for DTT-mediated ROS chemistry with proteins. PMID:23315912

A new method for CH3O2 and C2H5O2 radical detection and kinetic studies of the CH3O2 self-reaction in HIRAC (Highly Instrumented Reactor for Atmospheric Chemistry)

NASA Astrophysics Data System (ADS)

Onel, L. C.; Brennan, A.; Ingham, T.; Kirk, D.; Leggott, A.; Seakins, P. W.; Whalley, L.; Heard, D. E.

2016-12-01

Peroxy (RO2) radicals such as methylperoxy (CH3O2) and ethylperoxy (C2H5O2) are significant atmospheric species in the ozone formation in the presence of NO. At low concentrations of NO, the self-reaction of RO2 and RO2 + HO2 are important radical termination reactions. Despite their importance, at present typically only the sum of RO2 is measured in the atmosphere, making no distinction between different RO2 species.A new method has been developed for the direct detection of CH3O2 and C2H5O2 by FAGE (Fluorescence Assay by Gas Expansion) by titrating the peroxy radicals to RO (R = CH3 and C2H5) by reaction with NO and then detecting the resultant RO by laser induced fluorescence. The method has the potential to directly measure atmospheric levels of CH3O2 and potentially other RO2 species. The limit of detection is 3.8 × 108 molecule cm-3 for CH3O2 and 4.9 × 109 molecule cm-3 for C2H5O2 for a signal-to-noise ratio of 2 and a 4 min averaging time. The method has been used for time-resolved monitoring of CH3O2 during its self-reaction within HIRAC at 1 bar and at room temperature to determine a rate coefficient that is lower than the range of the previous results obtained by UV absorption measurements (http://iupac.pole-ether.fr/). A range of products of the CH3O2 self-reaction were also observed for the two reaction channels, (a) leading to formaldehyde and methanol and (b) forming methoxy (CH3O) radicals, over a range of temperatures from 296 - 340 K: CH3O and HO2 radicals (from reaction of CH3O + O2) were monitored by FAGE, formaldehyde was measured by FAGE and FTIR, and methanol was observed by FTIR. Good agreement was observed between the FTIR and FAGE measurements of formaldehyde. Using the concentrations of methanol and formaldehyde, the branching ratios at room temperature have been determined and are in very good agreement with the values recommended by IUPAC. Little temperature dependence of the branching ratios has been observed from 296 K to 340 K.

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

Mechanism and kinetics of the atmospheric degradation of 2-formylcinnamaldehyde with O3 and hydroxyl OH radicals - a theoretical study

NASA Astrophysics Data System (ADS)

Thangamani, D.; Shankar, R.; Vijayakumar, S.; Kolandaivel, P.

2016-10-01

In the present investigation, the reaction mechanism and kinetics of 2-formylcinnamaldehyde (2-FC) with O3 and hydroxyl OH radicals were studied. The reaction of 2-FC with O3 radical are initiated by the formation of primary ozonide, whereas the reaction of 2-FC with the hydroxyl OH radical are initiated by two different ways: (1). H-atom abstraction by hydroxyl OH radical from the -CHO and -CH = CHCHO group of 2-FC (2). Hydroxyl OH addition to the -CH = CHCHO group to the ring-opened 2-FC. These reactions lead to the formation of an alkyl radical. The reaction pathways corresponding to the reactions between 2-FC with O3 and hydroxyl OH radicals have been analysed using density functionals of B3LYP and M06-2X level of methods with the 6-31+G(d,p) basis set. Single-point energy calculations for the most favourable reactive species are determined by B3LYP/6-311++G(d,p) and CCSD(T)/6-31+G(d,p) levels of theory. From the obtained results, the hydroxyl OH addition at C8 position of 2-FC are most favourable than the C9 position of 2-FC. The subsequent reactions of the alkyl radicals, formed from the hydroxyl OH addition at C8 position, are analysed in detail. The individual and overall rate constant for the most favourable reactions are calculated by canonical variational transition theory with small-curvature tunnelling corrections over the temperature range of 278-350 K. The calculated theoretical rate constants are in good agreement with the available experimental data. The Arrhenius plot of the rate constants with the temperature are fitted and the atmospheric lifetimes of the 2-FC with hydroxyl OH radical reaction in the troposphere calculate for the first time, which can be applied to the study on the atmospheric implications. The condensed Fukui function has been verified for the most favourable reaction sites. This study can be regarded as an attempt to investigate the O3-initiated and hydroxyl OH-initiated reaction mechanisms of 2-FC in the atmosphere.

Kinetics and characterization of radiation-induced grafting of styrene on fluoropolymers

NASA Astrophysics Data System (ADS)

Guilmeau, I.; Esnouf, S.; Betz, N.; Le Moël, A.

1997-08-01

Grafting of styrene solution onto poly(ethylene-co-tetrafluoroethylene) (ETFE) was carried out by the pre-irradiation method. ETFE films were irradiated by 1.5 MeV electron beams in air. The influence of grafting temperature (50 to 80°C) has been investigated. It was found that the saturation grafting yield and the initial rate follow an Arrhenius law. The volume grafting yields were measured by FTIR spectroscopy in transmission and by weighing and the 'surface' grafting yields by FTIR-ATR. The results showed that grafting reaction is not monomer diffusion controlled in 30 μm film, nevertheless heterogeneities are revealed. By in-situ ESR, the decay of peroxy radicals was recorded under various heating and grafting conditions. These experiments suggest that the peroxy radicals react rapidly with monomer, but do not initiate the grafting process. The propagating radicals were not detectable, which may indicate that polystyrene chains are very long.

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

Formation, Evaporation, and Hydrolysis of Organic Nitrates from Nitrate Radical Oxidation of Monoterpenes

NASA Astrophysics Data System (ADS)

Ng, N. L.; Takeuchi, M.; Eris, G.; Berkemeier, T.; Boyd, C.; Nah, T.; Xu, L.

2017-12-01

Organic nitrates play an important role in the cycling of NOx and secondary organic aerosol (SOA) formation, yet their formation mechanisms and fates remain highly uncertain. The interactions of biogenic VOCs with NO3 radicals represent a direct way for positively linking anthropogenic and biogenic emissions. Results from ambient studies suggest that organic nitrates have a relatively short lifetime, though corresponding laboratory data are limited. SOA and organic nitrates produced at night may evaporate the following morning due to increasing temperatures or dilution of semi-volatile compounds. Once formed, organic nitrates can also undergo hydrolysis in the presence of particle water. In this work, we investigate the formation, evaporation, and hydrolysis of organic nitrates generated from the nitrate radical oxidation of a-pinene, b-pinene, and limonene. Experiments are conducted in the Georgia Environmental Chamber facility (GTEC) under dry and humid conditions and different temperatures. Experiments are also designed to probe different peroxy radical pathways (RO2+HO2 vs RO2+NO3). Speciated gas-phase and particle-phase organic nitrates are continuously monitored by a Filter Inlet for Gases and AEROsols High Resolution Time-of-Flight Chemical Ionization Mass Spectrometer (FIGAERO-HR-ToF-CIMS). Bulk aerosol composition is measured by a High Resolution Time-of-Flight Aerosol Mass Spectrometer (HR-ToF-AMS). A large suite of highly oxygenated gas- and particle-phase organic nitrates are formed rapidly. We find a resistance to aerosol evaporation when it is heated. The extent of organic nitrate hydrolysis in the humid experiments is evaluated. The dynamics of the speciated organic nitrates over the course of the experiments will also be discussed. Results from this chamber study provide fundamental data for understanding the dynamics of organic nitrate aerosols over its atmospheric lifetime.

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.

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...

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 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).

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,...

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...

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

Photoionization mass spectrometry of ω -phenylalkylamines: Role of radical cation-π interaction

NASA Astrophysics Data System (ADS)

Corinti, Davide; Catone, Daniele; Turchini, Stefano; Rondino, Flaminia; Crestoni, Maria Elisa; Fornarini, Simonetta

2018-04-01

Linear ω-phenylalkylamines of increasing alkyl chain length have been investigated employing synchrotron radiation in the photon energy range from 7 to 15 eV. These molecules have received considerable interest because they bear the skeleton of biologically relevant compounds including neurotransmitters and because of the possible interaction between the amino moiety and the phenyl ring. Recently, the contribution of this interaction has been assayed in both neutral and protonated species, pointing to a role of the polymethylene chain length. In this work, the ionization energy (IE) values of benzylamine (BA), 2-phenylethylamine (2-PEA), 3-phenylpropylamine (3-PPA), and 4-phenylbutylamine (4-PBA) were investigated in order to ascertain the impact of the different alkyl chain lengths and to verify an amino radical cation-π interaction. The IEs obtained experimentally, 8.54, 8.37, 8.29, and 8.31 eV for BA, 2-PEA, 3-PPA and 4-PBA, respectively, show a decreasing trend that is discussed employing calculations at the CBS-QB3 level. Moreover, the appearance energy values for major fragments produced by the photofragmentation process are reported.

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.

Isomeric Detergent Comparison for Membrane Protein Stability: Importance of Inter-Alkyl-Chain Distance and Alkyl Chain Length

PubMed Central

Cho, Kyung Ho; Hariharan, Parameswaran; Mortensen, Jonas S.; Du, Yang; Nielsen, Anne K.; Byrne, Bernadette; Kobilka, Brian K.; Loland, Claus J.; Guan, Lan

2017-01-01

Membrane proteins encapsulated by detergent micelles are widely used for structural study. Because of their amphipathic property, detergents have the ability to maintain protein solubility and stability in an aqueous medium. However, conventional detergents have serious limitations in their scope and utility, particularly for eukaryotic membrane proteins and membrane protein complexes. Thus, a number of new agents have been devised; some have made significant contributions to membrane protein structural studies. However, few detergent design principles are available. In this study, we prepared meta and ortho isomers of the previously reported para-substituted xylene-linked maltoside amphiphiles (XMAs), along with alkyl chain-length variation. The isomeric XMAs were assessed with three membrane proteins, and the meta isomer with a C12 alkyl chain was most effective at maintaining solubility/stability of the membrane proteins. We propose that interplay between the hydrophile–lipophile balance (HLB) and alkyl chain length is of central importance for high detergent efficacy. In addition, differences in inter-alkyl-chain distance between the isomers influence the ability of the detergents to stabilise membrane proteins. PMID:27981750

Treatment of an azo dye effluent by peroxi-coagulation and its comparison to traditional electrochemical advanced processes.

PubMed

do Vale-Júnior, Edilson; da Silva, Djalma R; Fajardo, Ana S; Martínez-Huitle, Carlos A

2018-08-01

Peroxi-coagulation (PC) is an interesting new process that has not been widely studied in the literature. This work presents the application of this technology to treat an azo dye synthetic effluent, studying the effect of different parameters including initial pH, current density (j), initial dye concentration and supporting electrolyte. The two former variables significantly affected the colour removal of the wastewater, followed by the initial dye concentration and the kind of electrolyte, in a lesser extent. The optimum operating conditions achieved were initial pH of 3.0, j = 33.3 mA cm -2 , 100 mg L -1 of methyl orange (MO) and Na 2 SO 4 as supporting electrolyte. The performance of PC was also compared to other electrochemical advanced processes, under similar experimental conditions. Results indicate that the kinetic decay of the MO increases in the following order: electrocoagulation (EC) < electrochemical oxidation (EO) with electrogenerated H 2 O 2 < PC < electro-Fenton (EF). This behaviour is given to the high oxidant character of the homogenous OH radicals generated by EF and PC approaches. The EO process with production of H 2 O 2 (EO-H 2 O 2 ) is limited by mass transport and the EC, as a separation method, takes longer times to achieve similar removal results. Energy requirements about 0.06 kWh g COD -1 , 0.09 kWh g COD -1 , 0.7 kWh g COD -1 and 0.1 kWh g COD -1 were achieved for PC, EF, EO-H 2 O 2 and EC, respectively. Degradation intermediates were monitored and carboxylic acids were detected for PC and EF processes, being rapidly removed by the former technology. PC emerges as a promising and competitive alternative for wastewaters depollution, among other oxidative approaches. Copyright © 2018 Elsevier Ltd. All rights reserved.

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

Experimental and theoretical understanding of the gas phase oxidation of atmospheric amides with OH radicals: kinetics, products, and mechanisms.

PubMed

Borduas, Nadine; da Silva, Gabriel; Murphy, Jennifer G; Abbatt, Jonathan P D

2015-05-14

Atmospheric amides have primary and secondary sources and are present in ambient air at low pptv levels. To better assess the fate of amides in the atmosphere, the room temperature (298 ± 3 K) rate coefficients of five different amides with OH radicals were determined in a 1 m(3) smog chamber using online proton-transfer-reaction mass spectrometry (PTR-MS). Formamide, the simplest amide, has a rate coefficient of (4.44 ± 0.46) × 10(-12) cm(3) molec(-1) s(-1) against OH, translating to an atmospheric lifetime of ∼1 day. N-methylformamide, N-methylacetamide and propanamide, alkyl versions of formamide, have rate coefficients of (10.1 ± 0.6) × 10(-12), (5.42 ± 0.19) × 10(-12), and (1.78 ± 0.43) × 10(-12) cm(3) molec(-1) s(-1), respectively. Acetamide was also investigated, but due to its slow oxidation kinetics, we report a range of (0.4-1.1) × 10(-12) cm(3) molec(-1) s(-1) for its rate coefficient with OH radicals. Oxidation products were monitored and quantified and their time traces were fitted using a simple kinetic box model. To further probe the mechanism, ab initio calculations are used to identify the initial radical products of the amide reactions with OH. Our results indicate that N-H abstractions are negligible in all cases, in contrast to what is predicted by structure-activity relationships. Instead, the reactions proceed via C-H abstraction from alkyl groups and from formyl C(O)-H bonds when available. The latter process leads to radicals that can readily react with O2 to form isocyanates, explaining the detection of toxic compounds such as isocyanic acid (HNCO) and methyl isocyanate (CH3NCO). These contaminants of significant interest are primary oxidation products in the photochemical oxidation of formamide and N-methylformamide, respectively.

Radical scavenging activity of lipophilized products from lipase-catalyzed transesterification of triolein with cinnamic and ferulic acids.

PubMed

Choo, Wee-Sim; Birch, Edward John

2009-02-01

Lipase-catalyzed transesterification of triolein with cinnamic and ferulic acids using an immobilized lipase from Candida antarctica (E.C. 3.1.1.3) was conducted to evaluate the antioxidant activity of the lipophilized products as model systems for enhanced protection of unsaturated oil. The lipophilized products were identified using ESI-MS. Free radical scavenging activity was determined using the DPPH radical method. The polarity of the solvents proved important in determining the radical scavenging activity of the substrates. Ferulic acid showed much higher radical scavenging activity than cinnamic acid, which has limited activity. The esterification of cinnamic acid and ferulic acid with triolein resulted in significant increase and decrease in the radical scavenging activity, respectively. These opposite effects were due to the effect of addition of electron-donating alkyl groups on the predominant mechanism of reaction (hydrogen atom transfer or electron transfer) of a species with DPPH. The effect of esterification of cinnamic acid was confirmed using ethyl cinnamate which greatly enhances the radical scavenging activity. Although, compared to the lipophilized cinnamic acid product, the activity was lower. The radical scavenging activity of the main component isolated from lipophilized cinnamic acid product using solid phase extraction, monocinnamoyl dioleoyl glycerol, was as good as the unseparated mixture of lipophilized product. Based on the ratio of a substrate to DPPH concentration, lipophilized ferulic acid was a much more efficient radical scavenger than lipophilized cinnamic acid.

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

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...

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.

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.

Sticking of HO2 on fatty acids aggregates

NASA Astrophysics Data System (ADS)

Vardanega, Delphine; Briquez, Stéphane; Duflot, Denis; Monnerville, Maurice; Toubin, Céline

2015-04-01

Models of atmospheric chemistry are widely used to perform projections of future changes in the chemical composition of the global troposphere, including changes in climate related greenhouse gases and aerosol particles. However, large uncertainties are still associated with the chemistry implemented in these models, which in turn can lead to inaccurate long-term predictions. The proposed work seeks to improve our understanding of the oxidative capacity of the atmosphere, which drives the lifetime of trace gases, and therefore atmospheric composition. Recent measurements [1] of free radicals made in forested environments characterized by low levels of nitrogen oxides (NOx = NO and NO2) indicate that current models of atmospheric chemistry tend to overestimate the concentration of peroxy radicals (HO2 and RO2). An overestimation of peroxy radicals is an important issue since these radicals are the main precursors of the hydroxyl radical (OH), the most important atmospheric oxidant during daytime. This issue could lead to a significant overestimation of the oxidative capacity of the global atmosphere since more than 86% of the Earth surface is covered by forests, oceans, and polar regions. An analysis of this dataset indicates that the missing sink could be due to an underestimation of the rates of RO2+HO2 reactions, and/or the uptake of peroxy radicals onto aerosol particles. A thorough evaluation of scientific studies published in the literature shows that there is a lack of kinetic and mechanistic data to correctly assess the contribution of these two loss pathways of peroxy radicals in low NOx environments. Classical molecular dynamics simulations, using the Gromacs package [2], are performed to study the interaction of HO2 with organic (carboxylic acid) aerosols. The effect of the presence of water molecules on the surface are also be investigated. These calculations provide theoretical values for observable quantities such as uptake and mass accommodation

Synthesis of heterocyclic analogues of epibatidine via 7-azabicyclo[2.2.1]hept-2-yl radical intermediates. 1. Intermolecular reactions.

PubMed

Gómez-Sánchez, Elena; Soriano, Elena; Marco-Contelles, José

2008-09-05

The synthesis and reactivity of the 7-azabicyclo[2.2.1]hept-2-yl radical has been extensively investigated in inter- and intramolecular reaction processes for the first time. In this work we will present the preparation of the radical and its successful intermolecular reaction with radical acceptors such as tert-butylisocyanide and acrylonitrile. Computational analyses have been carried out to show and explain the mechanisms and stereochemical outcome of these transformations. Overall and from the chemical point of view, a new and convenient synthetic approach has been developed for the synthesis of exo-2-(cyano)alkyl substituted 7-azabicyclo[2.2.1]heptane derivatives, a series of compounds of wide interest for the synthesis of heterocyclic analogues of epibatidine. As a result, we describe here the synthesis of the tetrazoloepibatidines (8 and 15) and the oxadiazoloepibatidine (10).

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.

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

Isomeric Detergent Comparison for Membrane Protein Stability: Importance of Inter-Alkyl-Chain Distance and Alkyl Chain Length.

PubMed

Cho, Kyung Ho; Hariharan, Parameswaran; Mortensen, Jonas S; Du, Yang; Nielsen, Anne K; Byrne, Bernadette; Kobilka, Brian K; Loland, Claus J; Guan, Lan; Chae, Pil Seok

2016-12-14

Membrane proteins encapsulated by detergent micelles are widely used for structural study. Because of their amphipathic property, detergents have the ability to maintain protein solubility and stability in an aqueous medium. However, conventional detergents have serious limitations in their scope and utility, particularly for eukaryotic membrane proteins and membrane protein complexes. Thus, a number of new agents have been devised; some have made significant contributions to membrane protein structural studies. However, few detergent design principles are available. In this study, we prepared meta and ortho isomers of the previously reported para-substituted xylene-linked maltoside amphiphiles (XMAs), along with alkyl chain-length variation. The isomeric XMAs were assessed with three membrane proteins, and the meta isomer with a C 12 alkyl chain was most effective at maintaining solubility/stability of the membrane proteins. We propose that interplay between the hydrophile-lipophile balance (HLB) and alkyl chain length is of central importance for high detergent efficacy. In addition, differences in inter-alkyl-chain distance between the isomers influence the ability of the detergents to stabilise membrane proteins. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

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.

Computational solution of atmospheric chemistry problems

NASA Technical Reports Server (NTRS)

Jafri, J.; Ake, R. L.

1986-01-01

Extensive studies were performed on problems of interest in atmospheric chemistry. In addition to several minor projects, four major projects were performed and described (theoretical studies of ground and low-lying excited states of ClO2; ground and excited state potential energy surfaces of the methyl peroxy radical; electronic states ot the FO radical; and theoretical studies S02 (H2O) (sub n)).

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.

Barrierless Reactions with Loose Transition States Govern the Yields and Lifetimes of Organic Nitrates Derived from Isoprene

EPA Science Inventory

The chemical reaction mechanism of NO addition to two β and δ isoprene hydroxy–peroxy radical isomers is examined in detail using density functional theory, coupled cluster methods, and the energy resolved master equation formalism to provide estimates of rate co...

Investigation of the reactivity of organic materials in liquid oxygen

NASA Technical Reports Server (NTRS)

Chamberlain, D.; Irwin, K.; Kirshen, N.; Mill, T.; Stringham, R.

1970-01-01

Measurements of impact-ignition sensitivity and studies of the relative reactivity of t-butoxy and t-butyl peroxy radicals toward a variety of organic compounds reveal improved methods of selection of materials for safe use in a liquid oxygen environment.

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...

Modelling of photodegradation in solar cell modules of substrate and superstrate design made with ethylene-vinyl acetate as pottant material

NASA Technical Reports Server (NTRS)

Somersall, A. C.; Guillet, J. E.

1982-01-01

A computer model which simulates, in principle, the chemical changes in the photooxidation of hydrocarbons using as input data a set of elementary reactions, corresponding kinetic rate data and appropriate initial conditions was developed. The Model was refined and exploited to examine more closely the photooxidation and photostabilization of a hydrocarbon polymer. The results lead to the following observations. (1) The time to failure, tau sub f (chosen as the level of 5% C-H bond oxidation which is within the range anticipated for marked change in mechanical properties) varies as the inverse square root of the light intensity. However, tau sub f is almost unaffected by both the photoinitiator type and concentration. (2) The time to failure decreases with the rate of abstraction of C-H by peroxy radicals but increases with the rate of bimolecular radical termination controlled by diffusion. (3) Of the various stabilization mechanisms considered, the trapping of peroxy radicals is distinctly the most effective, although the concommitant decomposition of hydroperoxide is also desirable.

Effects of pulsed ultrasound on the adsorption of n-alkyl anionic surfactants at the gas/solution interface of cavitation bubbles.

PubMed

Yang, Limei; Sostaric, Joe Z; Rathman, James F; Kuppusamy, Periannan; Weavers, Linda K

2007-02-15

Sonolysis of argon-saturated aqueous solutions of the nonvolatile surfactants sodium dodecyl sulfate (SDS) and sodium 1-pentanesulfonate (SPSo) was investigated at three ultrasonic frequencies under both continuous wave (CW) and pulsed ultrasound. Secondary carbon-centered radicals were detected by spin trapping using 3,5-dibromo-4-nitrosobenzenesulfonic acid (DBNBS) and electron paramagnetic resonance (EPR) spectroscopy. Following sonolysis, -*CH- radicals were observed for both surfactants under both sonication modes. Under CW at 354 kHz, the maximum plateau -*CH- radical yield was higher for SPSo than for SDS, indicating that SDS, which is more surface active under equilibrium conditions, accumulates at the gas/solution interface of cavitation bubbles to a lesser degree, compared with the less surface active surfactant, SPSo. However, after sonolysis (354 kHz) under pulsed ultrasound with a pulse length of 100 ms and an interval of 500 ms, the -*CH- radical yield at the plateau concentrations was higher for SDS than for SPSo due to increased amounts of SDS accumulation on the bubble surfaces. In contrast to the findings following sonolysis at 354 kHz, sonolysis of aqueous surfactant solutions at 620 kHz and 803 kHz showed a higher -*CH- radical yield for SDS compared with SPSo under CW but lower -*CH- radical yield with increasing pulsing interval, indicating a frequency dependence on accumulation. Results indicate that pulsing the ultrasonic wave has a significant effect on the relative adsorption ability of n-alkyl surfactants at the gas/solution surface of cavitation bubbles.

Transition metal ion-assisted photochemical generation of alkyl halides and hydrocarbons from carboxylic acids.

PubMed

Carraher, Jack M; Pestovsky, Oleg; Bakac, Andreja

2012-05-21

Near-UV photolysis of aqueous solutions of propionic acid and aqueous Fe(3+) in the absence of oxygen generates a mixture of hydrocarbons (ethane, ethylene and butane), carbon dioxide, and Fe(2+). The reaction becomes mildly catalytic (about five turnovers) in the presence of oxygen which converts a portion of alkyl radicals to oxidizing intermediates that reoxidize Fe(2+). The photochemistry in the presence of halide ions (X(-) = Cl(-), Br(-)) generates ethyl halides via halogen atom abstraction from FeX(n)(3-n) by ethyl radicals. Near-quantitative yields of C(2)H(5)X are obtained at ≥0.05 M X(-). Competition experiments with Co(NH(3))(5)Br(2+) provided kinetic data for the reaction of ethyl radicals with FeCl(2+) (k = (4.0 ± 0.5) × 10(6) M(-1) s(-1)) and with FeBr(2+) (k = (3.0 ± 0.5) × 10(7) M(-1) s(-1)). Photochemical decarboxylation of propionic acid in the presence of Cu(2+) generates ethylene and Cu(+). Longer-chain acids also yield alpha olefins as exclusive products. These reactions become catalytic under constant purge with oxygen which plays a dual role. It reoxidizes Cu(+) to Cu(2+), and removes gaseous olefins to prevent accumulation of Cu(+)(olefin) complexes and depletion of Cu(2+). The results underscore the profound effect that the choice of metal ions, the medium, and reaction conditions exert on the photochemistry of carboxylic acids.

AB Initio Study of the Structure and Spectroscopic Properties of Halogenated Thioperoxy Radicals

NASA Technical Reports Server (NTRS)

Munoz, Luis A.; Binning, R. C., Jr.; Weiner, Brad R.; Ishikawa, Yasuyuki

1997-01-01

Thioperoxy (XSO or XOS) radicals exist in a variety of chemical environments, and they have as a consequence drawn some interest. HSO, an important species in the chemistry of the troposphere, has been examined both experimentally. The halogenated (X = F, Cl or Br) peroxy species and isovalent thioperoxy species have been studied less, but they too are potentially interesting because oxidized sulfur species and halogen sources are present in the atmosphere. Learning the fate of XSO and XOS radicals is important to understanding the atmospheric oxidation chemistry of sulfur compounds. Of these, FSO and ClSO are particularly interesting because they have been directly detected spectroscopically. Recent studies in our laboratory on the photochemistry of thionyl halides (X2SO; where X = F or Cl) have suggested new ways to generate XSO species. The laser-induced photodissociation of thionyl fluoride, F2SO, at 193 nm and thionyl chloride, ClSO, at 248 nm is characterized by a radical mechanism, X2SO -> XSO + X. The structure of FSO has been characterized experimentally by Endo et cd. employing microwave spectroscopy. Using the unrestricted Hartree-Fock (UHF) self-consistent field (SCF) method, Sakai and Morokuma computed the electronic structure of the ground (sup 2)A" and the first excited (sup 2)A' states of FSO. Electron correlation was not taken into account in their study. In a laser photodissociation experiment, Huber et al. identified ClSO mass spectromctrically. ClSO has also been detected in low temperature matrices by EPR and in the gas phase by far IR laser magnetic resonance. Although the structure of FSO is known in detail, the only study, experimental or theoretical, of CISO has been an ab initio HFSCF study by Hinchliffe. Electron correlation corrections were also excluded from this study. In order to better understand the isomerization and dissociation dynamics of the radical species, we have performed ab initio correlated studies of the potential energy

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

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.

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...

Prototypal dithiazolodithiazolyl radicals: synthesis, structures, and transport properties.

PubMed

Beer, Leanne; Britten, James F; Brusso, Jaclyn L; Cordes, A Wallace; Haddon, Robert C; Itkis, Mikhail E; MacGregor, Douglas S; Oakley, Richard T; Reed, Robert W; Robertson, Craig M

2003-11-26

New synthetic routes to 1,2,3-dithiazolo-1,2,3-dithiazolylium salts, based on double Herz condensations of N-alkylated 2,6-diaminopyridinium salts with sulfur monochloride, have been developed. The two prototypal 1,2,3-dithiazolo-1,2,3-dithiazolyl radicals HBPMe and HBPEt have been prepared and characterized in solution by cyclic voltammetry and EPR spectroscopy. Measured electrochemical cell potentials and computed (B3LYP/6-31G) gas-phase disproportionation enthalpies favor a low on-site Coulombic repulsion energy U in the solid state. The crystal structures of HBPR (R = Me, Et) have been determined by X-ray crystallography (at 293 K). Both consist of slipped pi-stacks of undimerized radicals, with many close intermolecular S- - -S contacts. Magnetic, conductivity, and optical measurements have been performed and the results interpreted in light of extended Hückel band calculations. The crystalline materials are paramagnetic above 100 K, with room-temperature conductivities sigma(RT) of 10(-5)-10(-6) S cm(-1); the slightly greater conductivity of the R = Et compound can be associated with a more well developed band structure. We suggest a Mott-Hubbard insulator ground state for these materials, with an on-site Coulomb repulsion energy U of about 1.0 eV.

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.

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...

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.

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

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.

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.

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.

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.

The effect of alpha-tocopherol on the oxidation and free radical decay in irradiated UHMWPE.

PubMed

Oral, Ebru; Rowell, Shannon L; Muratoglu, Orhun K

2006-11-01

We developed a radiation cross-linked ultra-high molecular weight polyethylene (UHMWPE) stabilized with alpha-tocopherol (Vitamin E) as a bearing material in total joint replacements. The stabilizing effect of alpha-tocopherol on free radical reactions in UHMWPE is not well understood. We investigated the effect of alpha-tocopherol on the oxidation and transformation of residual free radicals during real-time aging of alpha-tocopherol-doped, irradiated UHMWPE (alphaTPE) and irradiated UHMWPE (control). Samples were aged at 22 degrees C (room temperature) in air, at 40 degrees C in air and at 40 degrees C in water for 7 months. During the first month, alphaTPE showed some oxidation at the surface, which stayed constant thereafter. Control exhibited substantial oxidation in the subsurface region, which increased with time. The alkyl/allyl free radicals transformed to oxygen centered ones in both materials; this transformation occurred faster in alpha-TPE. In summary, the real-time oxidation behavior of alpha-TPE was consistent with that observed using accelerated aging methods. This new UHMWPE is oxidation resistant and is expected to maintain its properties in the long term.

Comprehensive stabilization mechanism of electron-beam irradiated polyacrylonitrile fibers to shorten the conventional thermal treatment

PubMed Central

Park, Sejoon; Yoo, Seung Hwa; Kang, Ha Ri; Jo, Seong Mu; Joh, Han-Ik; Lee, Sungho

2016-01-01

An electron beam was irradiated on polyacrylonitrile (PAN) fibers prior to thermal stabilization. The electron-beam irradiation effectively shortened the thermal stabilization process by one fourth compared with the conventional thermal stabilization process. A comprehensive mechanistic study was conducted regarding this shortening of the thermal stabilization by electron-beam irradiation. Various species of chain radicals were produced in PAN fibers by electron-beam irradiation and existed for a relatively long duration, as observed by electron spin resonance spectroscopy. Subsequently, these radicals were gradually oxidized to peroxy radicals in the presence of oxygen under storage or heating. We found that these peroxy radicals (CO) enabled such an effective shortcut of thermal stabilization by acting as intermolecular cross-linking and partial aromatization points in the low temperature range (100–130 °C) and as earlier initiation seeds of successive cyclization reactions in the next temperature range (>130–140 °C) of thermal stabilization. Finally, even at a low irradiation dose (200 kGy), followed by a short heat treatment (230 °C for 30 min), the PAN fibers were sufficiently stabilized to produce carbon fibers with tensile strength and modulus of 2.3 and 216 GPa, respectively, after carbonization. PMID:27349719

Metallaphotoredox-Catalyzed sp3–sp3 Cross-Coupling of Carboxylic Acids with Alkyl Halides

PubMed Central

Johnston, Craig P.; Smith, Russell T.; Allmendinger, Simon; MacMillan, David W. C.

2017-01-01

Over the last half-century, transition metal-mediated cross-coupling reactions have changed the way in which complex organic molecules are synthesized. Indeed, the predictable and chemoselective nature of these transformations has led to their widespread adoption across a vast array of chemical research areas1. However, the construction of sp3–sp3 bonds, a fundamental unit of organic chemistry, remains an important yet elusive objective for cross-coupling reaction engineering2. In comparison to related procedures with sp2-hybridized species, the development of methods for sp3–sp3 bond formation via transition metal catalysis has been historically hampered by deleterious side-reactions, such as β-hydride elimination with Pd-catalysis, and the reluctance of alkyl halides to undergo oxidative addition3,4. To address this issue, a number of research groups have demonstrated the feasibility of nickel-catalyzed cross-coupling processes to form sp3–sp3 bonds that utilize organometallic nucleophiles and alkyl electrophiles5–7. In particular, the coupling of alkyl halides with pregenerated organozinc8–10, Grignard11,12, and organoborane13 species has been used to furnish diverse molecular structures. However, the poor step and atom economies along with the operational difficulties associated with making, carrying, and using these sensitive coupling partners has hindered their widespread adoption. The prospect of establishing a generically useful sp3–sp3 coupling technology that employs bench-stable, native organic functional groups, without the need for pre-functionalization or substrate derivatization, would therefore be a valuable addition to fields of research that rely on organic molecule construction. Here, we demonstrate that the synergistic merger of photoredox and nickel catalysis enables the direct formation of sp3–sp3 bonds using only simple carboxylic acids and alkyl halides as the nucleophilic and electrophilic coupling partners, respectively. The

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.

The study of gamma irradiation effects on poly (glycolic acid)

NASA Astrophysics Data System (ADS)

Rao Nakka, Rajeswara; Rao Thumu, Venkatappa; Reddy SVS, Ramana; Rao Buddhiraju, Sanjeeva

2015-05-01

We have investigated the effects of gamma irradiation on chemical structure, thermal and morphological properties of biodegradable semi-crystalline poly (glycolic acid) (PGA). PGA samples were subjected to irradiation treatment using a 60Co gamma source with a delivered dose of 30, 60 and 90 kGy, respectively. Gamma irradiation induces cleavage of PGA main chains forming ∼OĊH2 and ĊH2COO∼ radicals in both amorphous and crystalline regions. The free radicals formed in the amorphous region abstract atmospheric oxygen and convert them to peroxy radicals. The peroxy radical causes chain scission at the crystal interface through hydrogen abstraction from methylene groups forming the ∼ĊHCOO∼ (I) radical. Consequently, the observed electron spin resonance (ESR) doublet of irradiated PGA is assigned to (I). The disappearance of the ESR signal above 190°C indicates that free radicals are formed in the amorphous region and decay below the melting temperature of PGA. Fourier transform infrared and optical absorption studies confirm that the ? groups are not influenced by gamma irradiation. Differential scanning calorimetry (DSC) studies showed that the melting temperature of PGA decreased from 212°C to 202°C upon irradiation. Degree of crystallinity increased initially and then decreased with an increase in radiation as per DSC and X-ray diffraction studies. Irradiation produced changes in the physical properties of PGA as well as affecting the morphology of the material.

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...

40 CFR 721.5985 - Fatty alkyl phosphate, alkali metal salt (generic).

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 31 2011-07-01 2011-07-01 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...

40 CFR 721.2094 - N,N′-di(alkyl heteromonocycle)amino chlorotriazine.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 31 2011-07-01 2011-07-01 false N,Nâ²-di(alkyl heteromonocycle)amino... Specific Chemical Substances § 721.2094 N,N′-di(alkyl heteromonocycle)amino chlorotriazine. (a) Chemical... as N,N′-di(alkyl heteromonocycle)amino chlorotriazine (PMN P-93-1369) is subject to reporting under...

40 CFR 721.2094 - N,N′-di(alkyl heteromonocycle)amino chlorotriazine.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 30 2010-07-01 2010-07-01 false N,Nâ²-di(alkyl heteromonocycle)amino... Specific Chemical Substances § 721.2094 N,N′-di(alkyl heteromonocycle)amino chlorotriazine. (a) Chemical... as N,N′-di(alkyl heteromonocycle)amino chlorotriazine (PMN P-93-1369) is subject to reporting under...

Development and field deployment of an instrument to measure ozone production rates in the troposphere

NASA Astrophysics Data System (ADS)

Sklaveniti, S.; Locoge, N.; Dusanter, S.; Leonardis, T.; Lew, M.; Bottorff, B.; Sigler, P. S. R.; Stevens, P. S.; Wood, E. C. D.; Kundu, S.; Gentner, D. R.

2015-12-01

Ozone is a greenhouse gas and a primary constituent of urban smog, irritating the respiratory system and damaging the vegetation. The current understanding of ozone chemistry in the troposphere indicates that net ozone production P(O3) occurs when peroxy radicals (HO2+RO2) react with NO producing NO2, whose photolysis leads to O3 formation. P(O3) values can be calculated from peroxy radical concentrations, either from ambient measurements or box model outputs. These two estimation methods often disagree for NOx mixing ratios higher than a few ppb, questioning our ability to measure peroxy radicals under high NOx conditions or indicating that there are still unknowns in our understanding of the radical and ozone production chemistry. Direct measurements of ozone production rates will help to address this issue and improve air quality regulations. We will present the development of an instrument for direct measurements of ozone production rates (OPR). The OPR instrument consists of three parts: (i) two quartz flow tubes sampling ambient air ("Ambient" and "Reference" flow tube), (ii) an O3-to-NO2 conversion unit, and (iii) a Cavity Attenuated Phase Shift (CAPS) monitor to measure NO2. The air in the Ambient flow tube undergoes the same photochemistry as in ambient air, while the Reference flow tube is covered by a UV filter limiting the formation of ozone. Exiting the flow tubes, ozone is converted into NO2 and the sum O3+NO2 (Ox) is measured by the CAPS monitor. The difference in Ox between the two flow tubes divided by the residence time yields the Ox production rate, P(Ox). P(O3) is assumed to be equal to P(Ox) when NO2 is efficiently photolyzed during daytime. We will present preliminary results from the Indiana Radical, Reactivity and Ozone Production Intercomparison (IRRONIC) campaign in Bloomington, Indiana, during July 2015, where ozone production rates were measured by introducing various amounts of NO inside the flow tubes to investigate the ozone

Investigation of the oxidation of methyl vinyl ketone (MVK) by OH radicals in the atmospheric simulation chamber SAPHIR

NASA Astrophysics Data System (ADS)

Fuchs, Hendrik; Albrecht, Sascha; Acir, Ismail-Hakki; Bohn, Birger; Breitenlechner, Martin; Dorn, Hans-Peter; Gkatzelis, Georgios I.; Hofzumahaus, Andreas; Holland, Frank; Kaminski, Martin; Keutsch, Frank N.; Novelli, Anna; Reimer, David; Rohrer, Franz; Tillmann, Ralf; Vereecken, Luc; Wegener, Robert; Zaytsev, Alexander; Kiendler-Scharr, Astrid; Wahner, Andreas

2018-06-01

The photooxidation of methyl vinyl ketone (MVK) was investigated in the atmospheric simulation chamber SAPHIR for conditions at which organic peroxy radicals (RO2) mainly reacted with NO (high NO case) and for conditions at which other reaction channels could compete (low NO case). Measurements of trace gas concentrations were compared to calculated concentration time series applying the Master Chemical Mechanism (MCM version 3.3.1). Product yields of methylglyoxal and glycolaldehyde were determined from measurements. For the high NO case, the methylglyoxal yield was (19 ± 3) % and the glycolaldehyde yield was (65 ± 14) %, consistent with recent literature studies. For the low NO case, the methylglyoxal yield reduced to (5 ± 2) % because other RO2 reaction channels that do not form methylglyoxal became important. Consistent with literature data, the glycolaldehyde yield of (37 ± 9) % determined in the experiment was not reduced as much as implemented in the MCM, suggesting additional reaction channels producing glycolaldehyde. At the same time, direct quantification of OH radicals in the experiments shows the need for an enhanced OH radical production at low NO conditions similar to previous studies investigating the oxidation of the parent VOC isoprene and methacrolein, the second major oxidation product of isoprene. For MVK the model-measurement discrepancy was up to a factor of 2. Product yields and OH observations were consistent with assumptions of additional RO2 plus HO2 reaction channels as proposed in literature for the major RO2 species formed from the reaction of MVK with OH. However, this study shows that also HO2 radical concentrations are underestimated by the model, suggesting that additional OH is not directly produced from RO2 radical reactions, but indirectly via increased HO2. Quantum chemical calculations show that HO2 could be produced from a fast 1,4-H shift of the second most important MVK derived RO2 species (reaction rate

40 CFR 721.520 - Alanine, N-(2-carboxyethyl)-N-alkyl-, salt.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Alanine, N-(2-carboxyethyl)-N-alkyl... Specific Chemical Substances § 721.520 Alanine, N-(2-carboxyethyl)-N-alkyl-, salt. (a) Chemical substance... alanine, N-(2-carboxyethyl)-N- alkyl-, salt (P-89-336) is subject to reporting under this section for the...

40 CFR 721.520 - Alanine, N-(2-carboxyethyl)-N-alkyl-, salt.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Alanine, N-(2-carboxyethyl)-N-alkyl... Specific Chemical Substances § 721.520 Alanine, N-(2-carboxyethyl)-N-alkyl-, salt. (a) Chemical substance... alanine, N-(2-carboxyethyl)-N- alkyl-, salt (P-89-336) is subject to reporting under this section for the...

Ni-catalyzed reductive homocoupling of unactivated alkyl bromides at room temperature and its synthetic application.

PubMed

Peng, Yu; Luo, Long; Yan, Chang-Song; Zhang, Jian-Jian; Wang, Ya-Wen

2013-11-01

A room-temperature Ni-catalyzed reductive approach to homocoupling of unactivated primary, secondary, and tertiary alkyl bromides is described. The catalytic system can be easily generated from air-stable and cheap materials and demonstrates broad functional group tolerance, thus allowing facile access to useful dimeric triterpene and lignan-like molecules. Moreover, the dimerization of tertiary bromide 6 efficiently establishes sterically hindered vicinal quaternary carbons (C3a and C3a'), which is a key linkage of intriguing bispyrrolo[2,3-b]indoline alkaloids, thereby enabling us to complete the total syntheses of racemic chimonanthine (9) and folicanthine (10). In addition, this dimerization method can be expanded to the highly stereoselective synthesis of bisperhydrofuro[2,3-b]furan (5a) and the dimeric spiroketal 5b, signifying the involvement of possible radical species.

40 CFR 721.644 - Amines, C12-14-tert-alkyl, sulfonates.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Amines, C12-14-tert-alkyl, sulfonates... Substances § 721.644 Amines, C12-14-tert-alkyl, sulfonates. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified as amines, C12-14-tert-alkyl, sulfonates (PMN...

40 CFR 721.644 - Amines, C12-14-tert-alkyl, sulfonates.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Amines, C12-14-tert-alkyl, sulfonates... Substances § 721.644 Amines, C12-14-tert-alkyl, sulfonates. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified as amines, C12-14-tert-alkyl, sulfonates (PMN...

Copper-Catalyzed Intermolecular Amidation and Imidation of Unactivated Alkanes

PubMed Central

2015-01-01

We report a set of rare copper-catalyzed reactions of alkanes with simple amides, sulfonamides, and imides (i.e., benzamides, tosylamides, carbamates, and phthalimide) to form the corresponding N-alkyl products. The reactions lead to functionalization at secondary C–H bonds over tertiary C–H bonds and even occur at primary C–H bonds. [(phen)Cu(phth)] (1-phth) and [(phen)Cu(phth)2] (1-phth2), which are potential intermediates in the reaction, have been isolated and fully characterized. The stoichiometric reactions of 1-phth and 1-phth2 with alkanes, alkyl radicals, and radical probes were investigated to elucidate the mechanism of the amidation. The catalytic and stoichiometric reactions require both copper and tBuOOtBu for the generation of N-alkyl product. Neither 1-phth nor 1-phth2 reacted with excess cyclohexane at 100 °C without tBuOOtBu. However, the reactions of 1-phth and 1-phth2 with tBuOOtBu afforded N-cyclohexylphthalimide (Cy-phth), N-methylphthalimide, and tert-butoxycyclohexane (Cy-OtBu) in approximate ratios of 70:20:30, respectively. Reactions with radical traps support the intermediacy of a tert-butoxy radical, which forms an alkyl radical intermediate. The intermediacy of an alkyl radical was evidenced by the catalytic reaction of cyclohexane with benzamide in the presence of CBr4, which formed exclusively bromocyclohexane. Furthermore, stoichiometric reactions of [(phen)Cu(phth)2] with tBuOOtBu and (Ph(Me)2CO)2 at 100 °C without cyclohexane afforded N-methylphthalimide (Me-phth) from β-Me scission of the alkoxy radicals to form a methyl radical. Separate reactions of cyclohexane and d12-cyclohexane with benzamide showed that the turnover-limiting step in the catalytic reaction is the C–H cleavage of cyclohexane by a tert-butoxy radical. These mechanistic data imply that the tert-butoxy radical reacts with the C–H bonds of alkanes, and the subsequent alkyl radical combines with 1-phth2 to form the corresponding N-alkyl imide product

In Vitro Antimicrobial Bioassays, DPPH Radical Scavenging Activity, and FTIR Spectroscopy Analysis of Heliotropium bacciferum.

PubMed

Ahmad, Sohail; AbdEl-Salam, Naser M; Ullah, Riaz

2016-01-01

The present study deals with the antimicrobial, antioxidant, and functional group analysis of Heliotropium bacciferum extracts. Disc diffusion susceptibility method was followed for antimicrobial assessment. Noteworthy antimicrobial activities were recorded by various plant extracts against antibiotic resistant microorganisms. Plant flower extracts antioxidant activity was investigated against 2, 2-diphenyl-1-picryl hydrazyl radical by ultraviolet spectrophotometer (517 nm). Plant extracts displayed noteworthy radical scavenging activities at all concentrations (25-225 μg/mL). Notable activities were recorded by crude, chloroform and ethyl acetate extracts up to 88.27% at 225 μg/mL concentration. Compounds functional groups were examined by Fourier transform infrared spectroscopic studies. Alkanes, alkenes, alkyl halides, amines, carboxylic acids, amides, esters, alcohols, phenols, nitrocompounds, and aromatic compounds were identified by FTIR analysis. Thin layer chromatography bioautography was carried out for all plant extracts. Different bands were separated by various solvent systems. The results of the current study justify the use of Heliotropium bacciferum in traditional remedial herbal medicines.

Synthesis and electronic structure determination of N-alkyl-substituted bis(imino)pyridine iron imides exhibiting spin crossover behavior.

PubMed

Bowman, Amanda C; Milsmann, Carsten; Bill, Eckhard; Turner, Zoë R; Lobkovsky, Emil; DeBeer, Serena; Wieghardt, Karl; Chirik, Paul J

2011-11-02

Three new N-alkyl substituted bis(imino)pyridine iron imide complexes, ((iPr)PDI)FeNR ((iPr)PDI = 2,6-(2,6-(i)Pr(2)-C(6)H(3)-N═CMe)(2)C(5)H(3)N; R = 1-adamantyl ((1)Ad), cyclooctyl ((Cy)Oct), and 2-adamantyl ((2)Ad)) were synthesized by addition of the appropriate alkyl azide to the iron bis(dinitrogen) complex, ((iPr)PDI)Fe(N(2))(2). SQUID magnetic measurements on the isomeric iron imides, ((iPr)PDI)FeN(1)Ad and ((iPr)PDI)FeN(2)Ad, established spin crossover behavior with the latter example having a more complete spin transition in the experimentally accessible temperature range. X-ray diffraction on all three alkyl-substituted bis(imino)pyridine iron imides established essentially planar compounds with relatively short Fe-N(imide) bond lengths and two-electron reduction of the redox-active bis(imino)pyridine chelate. Zero- and applied-field Mössbauer spectroscopic measurements indicate diamagnetic ground states at cryogenic temperatures and established low isomer shifts consistent with highly covalent molecules. For ((iPr)PDI)FeN(2)Ad, Mössbauer spectroscopy also supports spin crossover behavior and allowed extraction of thermodynamic parameters for the S = 0 to S = 1 transition. X-ray absorption spectroscopy and computational studies were also performed to explore the electronic structure of the bis(imino)pyridine alkyl-substituted imides. An electronic structure description with a low spin ferric center (S = 1/2) antiferromagnetically coupled to an imidyl radical (S(imide) = 1/2) and a closed-shell, dianionic bis(imino)pyridine chelate (S(PDI) = 0) is favored for the S = 0 state. An iron-centered spin transition to an intermediate spin ferric ion (S(Fe) = 3/2) accounts for the S = 1 state observed at higher temperatures. Other possibilities based on the computational and experimental data are also evaluated and compared to the electronic structure of the bis(imino)pyridine iron N-aryl imide counterparts.

Radical distinction: Support for radical left and radical right parties in Europe

PubMed Central

Burgoon, Brian; van Elsas, Erika J; van de Werfhorst, Herman G

2017-01-01

Support for radical parties on both the left and right is on the rise, fueling intuition that both radicalisms have similar underpinnings. Indeed, existing studies show that radical left and right voters have overlapping positions and preferences. In this article, however, we focus on the differences in the voting bases of such parties. We show that radical left and right voters have sharply diverging ideological profiles. When it comes to the historical traditions of the ‘left’ and ‘right’, these voters differ radically from each other. Both groups express the traditions associated with their mainstream counterparts—particularly with respect to (non-)egalitarian, (non-)altruistic, and (anti-)cosmopolitan values. Such differences also explain why radical left voters tend to be more, not less, educated than mainstream or radical right voters. PMID:29187802

Radical distinction: Support for radical left and radical right parties in Europe.

PubMed

Rooduijn, Matthijs; Burgoon, Brian; van Elsas, Erika J; van de Werfhorst, Herman G

2017-12-01

Support for radical parties on both the left and right is on the rise, fueling intuition that both radicalisms have similar underpinnings. Indeed, existing studies show that radical left and right voters have overlapping positions and preferences. In this article, however, we focus on the differences in the voting bases of such parties. We show that radical left and right voters have sharply diverging ideological profiles. When it comes to the historical traditions of the 'left' and 'right', these voters differ radically from each other. Both groups express the traditions associated with their mainstream counterparts-particularly with respect to (non-)egalitarian, (non-)altruistic, and (anti-)cosmopolitan values. Such differences also explain why radical left voters tend to be more, not less, educated than mainstream or radical right voters.

Effects of star-shape poly(alkyl methacrylate) arm uniformity on lubricant properties

DOE PAGES

Robinson, Joshua W.; Qu, Jun; Erck, Robert; ...

2016-03-29

Star-shaped poly(alkyl methacrylate)s (PAMAs) were prepared and blended into an additive-free engine oil to assess the structure property relationship between macromolecular structure and lubricant performance. These additives were designed with a comparable number of repeating units per arm and the number of arms was varied between 3 and 6. Well-defined star-shaped PAMAs were synthesized by atom transfer radical polymerization (ATRP) via a core-first strategy from multi-functional headgroups. Observations of the polymer-oil blends suggest that stars with less than four arms are favorable as a viscosity index improver (VII), and molecular weight dominates viscosity-related effects over other structural features. Star-shaped PAMAs,more » as oil additives, effectively reduce the friction coefficient in both mixed and boundary lubrication regime. Several analogs outperformed commercial VIIs in both viscosity and friction performance. Furthermore, increased wear rates were observed for these star-shaped PAMAs in the boundary lubrication regime suggesting pressure-sensitive conformations may exist.« less

Alkylation sensitivity screens reveal a conserved cross-species functionome

PubMed Central

Svilar, David; Dyavaiah, Madhu; Brown, Ashley R.; Tang, Jiang-bo; Li, Jianfeng; McDonald, Peter R.; Shun, Tong Ying; Braganza, Andrea; Wang, Xiao-hong; Maniar, Salony; St Croix, Claudette M.; Lazo, John S.; Pollack, Ian F.; Begley, Thomas J.; Sobol, Robert W.

2013-01-01

To identify genes that contribute to chemotherapy resistance in glioblastoma, we conducted a synthetic lethal screen in a chemotherapy-resistant glioblastoma derived cell line with the clinical alkylator temozolomide (TMZ) and an siRNA library tailored towards “druggable” targets. Select DNA repair genes in the screen were validated independently, confirming the DNA glycosylases UNG and MYH as well as MPG to be involved in the response to high dose TMZ. The involvement of UNG and MYH is likely the result of a TMZ-induced burst of reactive oxygen species. We then compared the human TMZ sensitizing genes identified in our screen with those previously identified from alkylator screens conducted in E. coli and S. cerevisiae. The conserved biological processes across all three species composes an Alkylation Functionome that includes many novel proteins not previously thought to impact alkylator resistance. This high-throughput screen, validation and cross-species analysis was then followed by a mechanistic analysis of two essential nodes: base excision repair (BER) DNA glycosylases (UNG, human and mag1, S. cerevisiae) and protein modification systems, including UBE3B and ICMT in human cells or pby1, lip22, stp22 and aim22 in S. cerevisiae. The conserved processes of BER and protein modification were dual targeted and yielded additive sensitization to alkylators in S. cerevisiae. In contrast, dual targeting of BER and protein modification genes in human cells did not increase sensitivity, suggesting an epistatic relationship. Importantly, these studies provide potential new targets to overcome alkylating agent resistance. PMID:23038810

Regulation of DNA Alkylation Damage Repair: Lessons and Therapeutic Opportunities

PubMed Central

Soll, Jennifer M.; Sobol, Robert W.; Mosammaparast, Nima

2016-01-01

Alkylation chemotherapy is one of the most widely used systemic therapies for cancer. While somewhat effective, clinical responses and toxicities of these agents are highly variable. A major contributing factor for this variability is the numerous distinct lesions that are created upon alkylation damage. These adducts activate multiple repair pathways. There is mounting evidence that the individual pathways function cooperatively, suggesting that coordinated regulation of alkylation repair is critical to prevent toxicity. Furthermore, some alkylating agents produce adducts that overlap with newly discovered methylation marks, making it difficult to distinguish between bona fide damaged bases and so called ‘epigenetic’ adducts. We discuss new efforts aimed at deciphering the mechanisms that regulate these repair pathways, emphasizing their implications for cancer chemotherapy. PMID:27816326

Palladium-catalyzed Heck-type cross-couplings of unactivated alkyl iodides.

PubMed

McMahon, Caitlin M; Alexanian, Erik J

2014-06-02

A palladium-catalyzed, intermolecular Heck-type coupling of alkyl iodides and alkenes is described. This process is successful with a variety of primary and secondary unactivated alkyl iodides as reaction partners, including those with hydrogen atoms in the β position. The mild catalytic conditions enable intermolecular C-C bond formations with a diverse set of alkyl iodides and alkenes, including substrates containing base- or nucleophile-sensitive functionality. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Compositions for labeling .beta.-amyloid plaques and neurofibrillary tangles

DOEpatents

Barrio, Jorge R [Agoura Hills, CA; Petric, Andrej [Ljubljana, SI; Satyamurthy, Nagichettiar [Los Angeles, CA; Small, Gary W [Los Angeles, CA; Cole, Gregory M [Santa Monica, CA; Huang, Sung-Cheng [Sherman Oaks, CA

2008-03-11

Compositions useful for labeling .beta.-amyloid plaques and neurofibrillary tangles are provided. The compositions comprises compounds of formula (I): ##STR00001## wherein R.sub.1 is selected from the group consisting of --C(O)-alkyl, --C(O)-alkylenyl-R.sub.4, --C(O)O-alkyl, --C(O)O-alkylenyl-R.sub.4, --C.dbd.C(CN).sub.2-alkyl, --C.dbd.C(CN).sub.2-alkylenyl-R.sub.4, ##STR00002## wherein R.sub.4 is a radical selected from the group consisting of alkyl, substituted alkyl, aryl and substituted aryl; R.sub.5 is a radical selected from the group consisting of --NH.sub.2, --OH, --SH, --NH-alkyl, --NHR.sub.4, --NH-alkylenyl-R.sub.4, --O-alkyl, --O-alkylenyl-R.sub.4, --S-alkyl, and --S-alkylenyl-R.sub.4; R.sub.6 is a radical selected from the group consisting of --CN, --COOH, --C(O)O-alkyl, --C(O)O-alkylenyl-R.sub.4, --C(O)-alkyl, --C(O)-alkylenyl-R.sub.4, --C(O)-halogen, --C(O)NH-alkyl, --C(O)NH-alkylenyl-R.sub.4 and --C(O)NH.sub.2; R.sub.7 is a radical selected from the group consisting of O, NH, and S; and R.sub.8 is N, O or S; and R.sub.2 is selected from the group consisting of alkyl and alkylenyl-R.sub.10 and R.sub.3 is alkylenyl-R.sub.10, wherein R.sub.10 is selected from the group consisting of --OH, --OTs, halogen, spiperone, spiperone ketal, and spiperone-3-yl, or R.sub.2 and R.sub.3 together form a heterocyclic ring, optionally substituted with at least one radical selected from the group consisting of alkyl, alkoxy, OH, OTs, halogen, alkyl-R.sub.10, carbonyl, spiperone, spiperone ketal and spiperone-3-yl, and further wherein one or more of the hydrogen, halogen or carbon atoms are optionally replaced with a radiolabel.

Catalytic hydrogenation activity and electronic structure determination of bis(arylimidazol-2-ylidene)pyridine cobalt alkyl and hydride complexes.

PubMed

Yu, Renyuan Pony; Darmon, Jonathan M; Milsmann, Carsten; Margulieux, Grant W; Stieber, S Chantal E; DeBeer, Serena; Chirik, Paul J

2013-09-04

The bis(arylimidazol-2-ylidene)pyridine cobalt methyl complex, ((iPr)CNC)CoCH3, was evaluated for the catalytic hydrogenation of alkenes. At 22 °C and 4 atm of H2 pressure, ((iPr)CNC)CoCH3 is an effective precatalyst for the hydrogenation of sterically hindered, unactivated alkenes such as trans-methylstilbene, 1-methyl-1-cyclohexene, and 2,3-dimethyl-2-butene, representing one of the most active cobalt hydrogenation catalysts reported to date. Preparation of the cobalt hydride complex, ((iPr)CNC)CoH, was accomplished by hydrogenation of ((iPr)CNC)CoCH3. Over the course of 3 h at 22 °C, migration of the metal hydride to the 4-position of the pyridine ring yielded (4-H2-(iPr)CNC)CoN2. Similar alkyl migration was observed upon treatment of ((iPr)CNC)CoH with 1,1-diphenylethylene. This reactivity raised the question as to whether this class of chelate is redox-active, engaging in radical chemistry with the cobalt center. A combination of structural, spectroscopic, and computational studies was conducted and provided definitive evidence for bis(arylimidazol-2-ylidene)pyridine radicals in reduced cobalt chemistry. Spin density calculations established that the radicals were localized on the pyridine ring, accounting for the observed reactivity, and suggest that a wide family of pyridine-based pincers may also be redox-active.

Chiral Alkyl Halides: Underexplored Motifs in Medicine

PubMed Central

Gál, Bálint; Bucher, Cyril; Burns, Noah Z.

2016-01-01

While alkyl halides are valuable intermediates in synthetic organic chemistry, their use as bioactive motifs in drug discovery and medicinal chemistry is rare in comparison. This is likely attributable to the common misconception that these compounds are merely non-specific alkylators in biological systems. A number of chlorinated compounds in the pharmaceutical and food industries, as well as a growing number of halogenated marine natural products showing unique bioactivity, illustrate the role that chiral alkyl halides can play in drug discovery. Through a series of case studies, we demonstrate in this review that these motifs can indeed be stable under physiological conditions, and that halogenation can enhance bioactivity through both steric and electronic effects. Our hope is that, by placing such compounds in the minds of the chemical community, they may gain more traction in drug discovery and inspire more synthetic chemists to develop methods for selective halogenation. PMID:27827902

Changes in Reactivity as Chemistry Becomes Confined to an Interface. The Case of Free Radical Oxidation of C 30H 62 Alkane by OH

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

Houle, Frances A.; Wiegel, Aaron A.; Wilson, Kevin R.

Here, we examine in a simple organic aerosol the transition between heterogeneous chemistry under well-mixed conditions to chemistry under interfacial confinement. A single reaction mechanism, shown to reproduce observed OH oxidation chemistry for liquid and semisolid C 30H 62, is used in reaction-diffusion simulations to explore reactivity over a broad viscosity range. The results show that when internal mixing of the aerosol is fast and the particle interface is enriched in C-H groups, ketone and alcohol products, formed via peroxy radical disproportionation, predominate. As viscosity increases the reactions become confined to a shell at the gas-aerosol interface. The confinement ismore » accompanied by emergence of acyloxy reaction pathways that are particularly active when the shell is 1 nm or less. We quantify this trend using a reaction-diffusion index, allowing the parts of the mechanism that control reactivity as viscosity increases to be identified.« less

Changes in Reactivity as Chemistry Becomes Confined to an Interface. The Case of Free Radical Oxidation of C 30H 62 Alkane by OH

DOE PAGES

Houle, Frances A.; Wiegel, Aaron A.; Wilson, Kevin R.

2018-02-14

Here, we examine in a simple organic aerosol the transition between heterogeneous chemistry under well-mixed conditions to chemistry under interfacial confinement. A single reaction mechanism, shown to reproduce observed OH oxidation chemistry for liquid and semisolid C 30H 62, is used in reaction-diffusion simulations to explore reactivity over a broad viscosity range. The results show that when internal mixing of the aerosol is fast and the particle interface is enriched in C-H groups, ketone and alcohol products, formed via peroxy radical disproportionation, predominate. As viscosity increases the reactions become confined to a shell at the gas-aerosol interface. The confinement ismore » accompanied by emergence of acyloxy reaction pathways that are particularly active when the shell is 1 nm or less. We quantify this trend using a reaction-diffusion index, allowing the parts of the mechanism that control reactivity as viscosity increases to be identified.« less

Selective sp3 C-H alkylation via polarity-match-based cross-coupling.

PubMed

Le, Chip; Liang, Yufan; Evans, Ryan W; Li, Ximing; MacMillan, David W C

2017-07-06

The functionalization of carbon-hydrogen (C-H) bonds is one of the most attractive strategies for molecular construction in organic chemistry. The hydrogen atom is considered to be an ideal coupling handle, owing to its relative abundance in organic molecules and its availability for functionalization at almost any stage in a synthetic sequence. Although many C-H functionalization reactions involve C(sp 3 )-C(sp 2 ) coupling, there is a growing demand for C-H alkylation reactions, wherein sp 3 C-H bonds are replaced with sp 3 C-alkyl groups. Here we describe a polarity-match-based selective sp 3 C-H alkylation via the combination of photoredox, nickel and hydrogen-atom transfer catalysis. This methodology simultaneously uses three catalytic cycles to achieve hydridic C-H bond abstraction (enabled by polarity matching), alkyl halide oxidative addition, and reductive elimination to enable alkyl-alkyl fragment coupling. The sp 3 C-H alkylation is highly selective for the α-C-H of amines, ethers and sulphides, which are commonly found in pharmaceutically relevant architectures. This cross-coupling protocol should enable broad synthetic applications in de novo synthesis and late-stage functionalization chemistry.

mTOR target NDRG1 confers MGMT-dependent resistance to alkylating chemotherapy.

PubMed

Weiler, Markus; Blaes, Jonas; Pusch, Stefan; Sahm, Felix; Czabanka, Marcus; Luger, Sebastian; Bunse, Lukas; Solecki, Gergely; Eichwald, Viktoria; Jugold, Manfred; Hodecker, Sibylle; Osswald, Matthias; Meisner, Christoph; Hielscher, Thomas; Rübmann, Petra; Pfenning, Philipp-Niklas; Ronellenfitsch, Michael; Kempf, Tore; Schnölzer, Martina; Abdollahi, Amir; Lang, Florian; Bendszus, Martin; von Deimling, Andreas; Winkler, Frank; Weller, Michael; Vajkoczy, Peter; Platten, Michael; Wick, Wolfgang

2014-01-07

A hypoxic microenvironment induces resistance to alkylating agents by activating targets in the mammalian target of rapamycin (mTOR) pathway. The molecular mechanisms involved in this mTOR-mediated hypoxia-induced chemoresistance, however, are unclear. Here we identify the mTOR target N-myc downstream regulated gene 1 (NDRG1) as a key determinant of resistance toward alkylating chemotherapy, driven by hypoxia but also by therapeutic measures such as irradiation, corticosteroids, and chronic exposure to alkylating agents via distinct molecular routes involving hypoxia-inducible factor (HIF)-1alpha, p53, and the mTOR complex 2 (mTORC2)/serum glucocorticoid-induced protein kinase 1 (SGK1) pathway. Resistance toward alkylating chemotherapy but not radiotherapy was dependent on NDRG1 expression and activity. In posttreatment tumor tissue of patients with malignant gliomas, NDRG1 was induced and predictive of poor response to alkylating chemotherapy. On a molecular level, NDRG1 bound and stabilized methyltransferases, chiefly O(6)-methylguanine-DNA methyltransferase (MGMT), a key enzyme for resistance to alkylating agents in glioblastoma patients. In patients with glioblastoma, MGMT promoter methylation in tumor tissue was not more predictive for response to alkylating chemotherapy in patients who received concomitant corticosteroids.

Aag DNA Glycosylase Promotes Alkylation-Induced Tissue Damage Mediated by Parp1

PubMed Central

Calvo, Jennifer A.; Moroski-Erkul, Catherine A.; Lake, Annabelle; Eichinger, Lindsey W.; Shah, Dharini; Jhun, Iny; Limsirichai, Prajit; Bronson, Roderick T.; Christiani, David C.; Meira, Lisiane B.; Samson, Leona D.

2013-01-01

Alkylating agents comprise a major class of front-line cancer chemotherapeutic compounds, and while these agents effectively kill tumor cells, they also damage healthy tissues. Although base excision repair (BER) is essential in repairing DNA alkylation damage, under certain conditions, initiation of BER can be detrimental. Here we illustrate that the alkyladenine DNA glycosylase (AAG) mediates alkylation-induced tissue damage and whole-animal lethality following exposure to alkylating agents. Aag-dependent tissue damage, as observed in cerebellar granule cells, splenocytes, thymocytes, bone marrow cells, pancreatic β-cells, and retinal photoreceptor cells, was detected in wild-type mice, exacerbated in Aag transgenic mice, and completely suppressed in Aag −/− mice. Additional genetic experiments dissected the effects of modulating both BER and Parp1 on alkylation sensitivity in mice and determined that Aag acts upstream of Parp1 in alkylation-induced tissue damage; in fact, cytotoxicity in WT and Aag transgenic mice was abrogated in the absence of Parp1. These results provide in vivo evidence that Aag-initiated BER may play a critical role in determining the side-effects of alkylating agent chemotherapies and that Parp1 plays a crucial role in Aag-mediated tissue damage. PMID:23593019

mTOR target NDRG1 confers MGMT-dependent resistance to alkylating chemotherapy

PubMed Central

Weiler, Markus; Blaes, Jonas; Pusch, Stefan; Sahm, Felix; Czabanka, Marcus; Luger, Sebastian; Bunse, Lukas; Solecki, Gergely; Eichwald, Viktoria; Jugold, Manfred; Hodecker, Sibylle; Osswald, Matthias; Meisner, Christoph; Hielscher, Thomas; Rübmann, Petra; Pfenning, Philipp-Niklas; Ronellenfitsch, Michael; Kempf, Tore; Schnölzer, Martina; Abdollahi, Amir; Lang, Florian; Bendszus, Martin; von Deimling, Andreas; Winkler, Frank; Weller, Michael; Vajkoczy, Peter; Platten, Michael; Wick, Wolfgang

2014-01-01

A hypoxic microenvironment induces resistance to alkylating agents by activating targets in the mammalian target of rapamycin (mTOR) pathway. The molecular mechanisms involved in this mTOR-mediated hypoxia-induced chemoresistance, however, are unclear. Here we identify the mTOR target N-myc downstream regulated gene 1 (NDRG1) as a key determinant of resistance toward alkylating chemotherapy, driven by hypoxia but also by therapeutic measures such as irradiation, corticosteroids, and chronic exposure to alkylating agents via distinct molecular routes involving hypoxia-inducible factor (HIF)-1alpha, p53, and the mTOR complex 2 (mTORC2)/serum glucocorticoid-induced protein kinase 1 (SGK1) pathway. Resistance toward alkylating chemotherapy but not radiotherapy was dependent on NDRG1 expression and activity. In posttreatment tumor tissue of patients with malignant gliomas, NDRG1 was induced and predictive of poor response to alkylating chemotherapy. On a molecular level, NDRG1 bound and stabilized methyltransferases, chiefly O6-methylguanine-DNA methyltransferase (MGMT), a key enzyme for resistance to alkylating agents in glioblastoma patients. In patients with glioblastoma, MGMT promoter methylation in tumor tissue was not more predictive for response to alkylating chemotherapy in patients who received concomitant corticosteroids. PMID:24367102

Selective sp3 C-H alkylation via polarity-match-based cross-coupling

NASA Astrophysics Data System (ADS)

Le, Chip; Liang, Yufan; Evans, Ryan W.; Li, Ximing; MacMillan, David W. C.

2017-07-01

The functionalization of carbon-hydrogen (C-H) bonds is one of the most attractive strategies for molecular construction in organic chemistry. The hydrogen atom is considered to be an ideal coupling handle, owing to its relative abundance in organic molecules and its availability for functionalization at almost any stage in a synthetic sequence. Although many C-H functionalization reactions involve C(sp3)-C(sp2) coupling, there is a growing demand for C-H alkylation reactions, wherein sp3 C-H bonds are replaced with sp3 C-alkyl groups. Here we describe a polarity-match-based selective sp3 C-H alkylation via the combination of photoredox, nickel and hydrogen-atom transfer catalysis. This methodology simultaneously uses three catalytic cycles to achieve hydridic C-H bond abstraction (enabled by polarity matching), alkyl halide oxidative addition, and reductive elimination to enable alkyl-alkyl fragment coupling. The sp3 C-H alkylation is highly selective for the α-C-H of amines, ethers and sulphides, which are commonly found in pharmaceutically relevant architectures. This cross-coupling protocol should enable broad synthetic applications in de novo synthesis and late-stage functionalization chemistry.

Radical chemistry at a rural site (Wangdu) in the North China Plain: observation and model calculations of OH, HO2 and RO2 radicals

NASA Astrophysics Data System (ADS)

Tan, Zhaofeng; Fuchs, Hendrik; Lu, Keding; Hofzumahaus, Andreas; Bohn, Birger; Broch, Sebastian; Dong, Huabin; Gomm, Sebastian; Häseler, Rolf; He, Lingyan; Holland, Frank; Li, Xin; Liu, Ying; Lu, Sihua; Rohrer, Franz; Shao, Min; Wang, Baolin; Wang, Ming; Wu, Yusheng; Zeng, Limin; Zhang, Yinsong; Wahner, Andreas; Zhang, Yuanhang

2017-01-01

production at high NOx found in this study is consistent with the results from other field campaigns in urban environments, which underlines the need for better understanding of the peroxy radical chemistry for high NOx conditions.

Methods for labeling .beta.-amyloid plaques and neurofibrillary tangles

DOEpatents

Barrio, Jorge R.; Petric, Andrej; Satyamurthy, Nagichettiar; Small, Gary W.; Cole, Gregory M.; Huang, Sung-Cheng

2003-12-09

A method for labeling .beta.-amyloid plaques and neurofibrillary tangles in vivo and in vitro, comprises contacting a compound of formula (I): ##STR1## with mammalian tissue. In formula (I), R.sub.1 is selected from the group consisting of --C(O)-alkyl, --C(O)-alkylenyl-R.sub.4, --C(O)O-alkyl, --C(O)O-alkylenyl-R.sub.4, --C.dbd.C(CN).sub.2 -alkyl, --C.dbd.C(CN).sub.2 -alkylenyl-R.sub.4, ##STR2## R.sub.4 is a radical selected from the group consisting of alkyl, substituted alkyl, aryl and substituted aryl; R.sub.5 is a radical selected from the group consisting of --NH.sub.2, --OH, --SH, --NH-alkyl, --NHR.sub.4, --NH-alkylenyl-R.sub.4, --O-alkyl, --O-alkylenyl-R.sub.4, --S-alkyl, and --S-alkylenyl-R.sub.4 ; R.sub.6 is a radical selected from the group consisting of --CN, --COOH, --C(O)O-alkyl, --C(O)O-alkylenyl-R.sub.4, --C(O)-alkyl, --C(O)-alkylenyl-R.sub.4, --C(O)-halogen, --C(O)NH, --C(O)NH-alkyl, --C(O)NH-alkylenyl-R.sub.4 ; R.sub.7 is a radical selected from the group consisting of O, NH, and S; and R.sub.8 is N, O or S. R.sub.2 and R.sub.3 are each independently selected from the group consisting of alkyl and alkylenyl-R.sub.10, wherein R.sub.10 is selected from the group consisting of --OH, --OTs, halogen, spiperone, spiperone ketal and spiperone-3-yl. Alternatively, R.sub.2 and R.sub.3 together form a heterocyclic ring, optionally substituted with at least one radical selected from the group consisting of alkyl, alkoxy, OH, OTs, halogen, alkylenyl-R.sub.10, carbonyl, spiperone, spiperone ketal and spiperone-3-yl. In the compounds of formula (I), one or more of the hydrogen, halogen or carbon atoms can, optionally, be replaced with a radiolabel.

Methods for labeling .beta.-amyloid plaques and neurofibrillary tangles

DOEpatents

Barrio, Jorge R.; Petric, Andrej; Satyamurthy, Nagichettiar; Small, Gary W.; Cole, Gregory M.; Huang, Sung-Cheng

2001-01-01

A method for labeling .beta.-amyloid plaques and neurofibrillary tangles in vivo and in vitro, comprises contacting a compound of formula (I): ##STR1## with mammalian tissue. In formula (I), R.sub.1 is selected from the group consisting of --C(O)-alkyl, --C(O)-alkylenyl-R.sub.4, --C(O)O-alkyl, --C(O)O-alkylenyl-R.sub.4, --C.dbd.C(CN).sub.2 -alkyl, --C.dbd.C(CN).sub.2 -alkylenyl-R.sub.4 , ##STR2## R.sub.4 is a radical selected from the group consisting of alkyl, substituted alkyl, aryl and substituted aryl; R.sub.5, is a radical selected from the group consisting of --NH.sub.2, --OH, --SH, --NH-alkyl, --NHR.sub.4, --NH-alkylenyl-R.sub.4, --O-alkyl, --O-alkylenyl-R.sub.4, --S-alkyl, and --S-alkylenyl-R.sub.4 ; R.sub.6 is a radical selected from the group consisting of --CN, --COOH, --C(O)O-alkyl, --C(O)O-alkylenyl-R.sub.4, --C(O)-alkyl, --C(O)-alkylenyl-R.sub.4, --C(O)-halogen, --C(O)NH , --C(O)NH-alkyl, --C(O)NH-alkylenyl-R.sub.4 ; R.sub.7 is a radical selected from the group consisting of O, NH, and S; and R.sub.8 is N, O or S. R.sub.2 and R.sub.3 are each independently selected from the group consisting of alkyl and alkylenyl-R.sub.10, wherein R.sub.10 is selected from the group consisting of --OH, --OTs, halogen, spiperone, spiperone ketal and spiperone-3-yl. Alternatively, R.sub.2 and R.sub.3 together form a heterocyclic ring, optionally substituted with at least one radical selected from the group consisting of alkyl, alkoxy, OH, OTs, halogen, alkylenyl-R.sub.10, carbonyl, spiperone, spiperone ketal and spiperone-3-yl. In the compounds of formula (I), one or more of the hydrogen, halogen or carbon atoms can, optionally, be replaced with a radiolabel.

The Impact of Commonly Used Alkylating Agents on Artifactual Peptide Modification.

PubMed

Hains, Peter G; Robinson, Phillip J

2017-09-01

Iodoacetamide is by far the most commonly used agent for alkylation of cysteine during sample preparation for proteomics. An alternative, 2-chloroacetamide, has recently been suggested to reduce the alkylation of residues other than cysteine, such as the N-terminus, Asp, Glu, Lys, Ser, Thr, and Tyr. Here we show that although 2-chloroacetamide reduces the level of off-target alkylation, it exhibits a range of adverse effects. The most significant of these is methionine oxidation, which increases to a maximum of 40% of all Met-containing peptides, compared with 2-5% with iodoacetamide. Increases were also observed for mono- and dioxidized tryptophan. No additional differences between the alkylating reagents were observed for a range of other post-translational modifications and digestion parameters. The deleterious effects were observed for 2-chloroacetamide from three separate suppliers. The adverse impact of 2-chloroacetamide on methionine oxidation suggests that it is not the ideal alkylating reagent for proteomics.

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.

40 CFR 721.10517 - Alkyl methacrylates, polymer with substituted carbomonocycle, hydroxymethyl acrylamide and...

Code of Federal Regulations, 2013 CFR

2013-07-01

... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Alkyl methacrylates, polymer with... Substances § 721.10517 Alkyl methacrylates, polymer with substituted carbomonocycle, hydroxymethyl acrylamide... reporting. (1) The chemical substance identified generically as alkyl methacrylates, polymer with...

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.

40 CFR 721.3900 - Alkyl polyethylene glycol phosphate, potassium salt.

Code of Federal Regulations, 2012 CFR

2012-07-01

..., potassium salt. 721.3900 Section 721.3900 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Specific Chemical Substances § 721.3900 Alkyl polyethylene glycol phosphate, potassium salt. (a) Chemical... as alkyl polyethylene glycol phosphate, potassium salt (P-90-481), is subject to reporting under this...

40 CFR 721.3900 - Alkyl polyethylene glycol phosphate, potassium salt.

Code of Federal Regulations, 2013 CFR

2013-07-01

..., potassium salt. 721.3900 Section 721.3900 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Specific Chemical Substances § 721.3900 Alkyl polyethylene glycol phosphate, potassium salt. (a) Chemical... as alkyl polyethylene glycol phosphate, potassium salt (P-90-481), is subject to reporting under this...

40 CFR 721.3900 - Alkyl polyethylene glycol phosphate, potassium salt.

Code of Federal Regulations, 2014 CFR

2014-07-01

..., potassium salt. 721.3900 Section 721.3900 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Specific Chemical Substances § 721.3900 Alkyl polyethylene glycol phosphate, potassium salt. (a) Chemical... as alkyl polyethylene glycol phosphate, potassium salt (P-90-481), is subject to reporting under this...

40 CFR 721.3900 - Alkyl polyethylene glycol phosphate, potassium salt.

Code of Federal Regulations, 2011 CFR

2011-07-01

..., potassium salt. 721.3900 Section 721.3900 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Specific Chemical Substances § 721.3900 Alkyl polyethylene glycol phosphate, potassium salt. (a) Chemical... as alkyl polyethylene glycol phosphate, potassium salt (P-90-481), is subject to reporting under this...

When alcohol is the answer: trapping, identifying and quantifying simple alkylating species in aqueous environments

PubMed Central

Penketh, P. G.; Shyam, K.; Baumann, R. P; Zhu, Rui; Ishiguro, K.; Sartorelli, A. C.; Ratner, E. S.

2016-01-01

Alkylating agents are a significant class of environmental carcinogens as well as commonly used anticancer therapeutics. Traditional alkylating activity assays have utilized the colorimetric reagent 4-(4-nitrobenzyl)pyridine (4NBP). However, 4NBP based assays have a relatively low sensitivity towards harder, more oxophilic alkylating species and are not well suited for the identification of the trapped alkyl moiety due to adduct instability. Herein we describe a method using water as the trapping agent which permits the trapping of simple alkylating electrophiles with a comparatively wide range of softness/hardness and permits the identification of donated simple alkyl moieties. PMID:27188264

Extended exposure to alkylator chemotherapy: delayed appearance of myelodysplasia.

PubMed

Chamberlain, Marc C; Raizer, Jeffrey

2009-06-01

A case series of gliomas treated with alkylator-based chemotherapy who subsequently developed myelodysplastic syndrome (tMDS) or acute myelocytic leukemia (AML). Alkylator-based chemotherapy is recognized to be leukemogenic; however, it is infrequently described as a delayed consequence of anti-glioma treatment. Seven patients (4 men; 3 women) ages 34-69 years (median 44), with gliomas (3 Grade 2; 4 Grade 3) were treated with surgery, all but one with involved-field radiotherapy and all with alkylator-based chemotherapy (temozolomide; 6 patients, nitrosoureas; 5 patients, both agents; 5 patients). Exposure to alkylator-based chemotherapy ranged from 8 to 30 months (median 24). The diagnosis of tMDS was determined by bone marrow biopsy in 7 patients. Seven patients showed chromosomal abnormalities consistent with chemotherapy induced MDS. Three patients were diagnosed with AML as well (in two determined by bone marrow and one at autopsy). Interval from last chemotherapy exposure to diagnosis of tMDS/AML ranged from 3 to 31 months (median 24 months). Two patients were treated with bone marrow transplantation and 5 received supportive care only. Five patients have died, 2 as a consequence of recurrent brain tumor, 1 as a complication of transplantation, and 2 due to AML. Although rare, induction of tMDS/AML following extended use of alkylator-based chemotherapy may become more relevant with the evolving practice to treat gliomas for protracted periods. Future work to determine at risk patients would be important.

Alkyl Glucosides in Contact Dermatitis.

PubMed

Loranger, Camille; Alfalah, Maisa; Ferrier Le Bouedec, Marie-Christine; Sasseville, Denis

Ecologically sound because they are synthesized from natural and renewable sources, the mild surfactants alkyl glucosides are being rediscovered by the cosmetic industry. They are currently found in rinse-off products such as shampoos, liquid cleansers, and shower gels, but also in leave-on products that include moisturizers, deodorants, and sunscreens. During the past 15 years, numerous cases of allergic contact dermatitis have been published, mostly to lauryl and decyl glucosides, and these compounds are considered emergent allergens. Interestingly, the sunscreen Tinosorb M contains decyl glucoside as a hidden allergen, and most cases of allergic contact dermatitis reported to this sunscreen ingredient are probably due to sensitization to decyl glucoside. This article will review the chemistry of alkyl glucosides, their sources of exposure, as well as their cutaneous adverse effects reported in the literature and encountered in various patch testing centers.

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.

Selective sp3 C–H alkylation via polarity-match-based cross-coupling

PubMed Central

Le, Chip; Liang, Yufan; Evans, Ryan W.; Li, Ximing; MacMillan, David W. C.

2017-01-01

The functionalization of carbon–hydrogen (C–H) bonds is one of the most attractive strategies for molecular construction in organic chemistry. The hydrogen atom is considered to be an ideal coupling handle, owing to its relative abundance in organic molecules and its availability for functionalization at almost any stage in a synthetic sequence1. Although many C–H functionalization reactions involve C(sp3)–C(sp2) coupling, there is a growing demand for C–H alkylation reactions, wherein sp3 C–H bonds are replaced with sp3 C–alkyl groups. Here we describe a polarity-match-based selective sp3 C–H alkylation via the combination of photoredox, nickel and hydrogen-atom transfer catalysis. This methodology simultaneously uses three catalytic cycles to achieve hydridic C–H bond abstraction (enabled by polarity matching), alkyl halide oxidative addition, and reductive elimination to enable alkyl–alkyl fragment coupling. The sp3 C–H alkylation is highly selective for the α-C–H of amines, ethers and sulphides, which are commonly found in pharmaceutically relevant architectures. This cross-coupling protocol should enable broad synthetic applications in de novo synthesis and late-stage functionalization chemistry. PMID:28636596

Discovery and identification of a series of alkyl decalin isomers in petroleum geological samples.

PubMed

Wang, Huitong; Zhang, Shuichang; Weng, Na; Zhang, Bin; Zhu, Guangyou; Liu, Lingyan

2015-07-07

The comprehensive two-dimensional gas chromatography/time-of-flight mass spectrometry (GC × GC/TOFMS) has been used to characterize a crude oil and a source rock extract sample. During the process, a series of pairwise components between monocyclic alkanes and mono-aromatics have been discovered. After tentative assignments of decahydronaphthalene isomers, a series of alkyl decalin isomers have been synthesized and used for identification and validation of these petroleum compounds. From both the MS and chromatography information, these pairwise compounds were identified as 2-alkyl-decahydronaphthalenes and 1-alkyl-decahydronaphthalenes. The polarity of 1-alkyl-decahydronaphthalenes was stronger. Their long chain alkyl substituent groups may be due to bacterial transformation or different oil cracking events. This systematic profiling of alkyl-decahydronaphthalene isomers provides further understanding and recognition of these potential petroleum biomarkers.

Infrared laser spectroscopy of the n-propyl and i-propyl radicals: Stretch-bend Fermi coupling in the alkyl CH stretch region

DOE PAGES

Franke, Peter R.; Tabor, Daniel P.; Moradi, Christopher P.; ...

2016-12-13

The n-propyl and i-propyl radicals were generated in the gas phase via pyrolysis of n-butyl nitrite [CH 3(CH 2) 3ONO] and i-butyl nitrite [(CH 3) 2CHCH 2ONO], respectively. Nascent radicals were promptly solvated by a beam of He nanodroplets, and the infrared spectra of the radicals were recorded in the CH stretching region. Several previously unreported bands are observed between 2800 and 3150 cm –1. The CH stretching modes observed above 3000 cm –1 are in excellent agreement with CCSD(T) anharmonic frequencies computed using second-order vibrational perturbation theory. However, between 2800 and 3000 cm –1, the spectra of n- andmore » i-propyl radicals become congested and difficult to assign due to the presence of multiple anharmonic resonance polyads. To model the spectrally congested region, Fermi and Darling-Dennison resonances are treated explicitly using “dressed” Hamiltonians and CCSD(T) quartic force fields in the normal mode representation, and the agreement with experiment is less than satisfactory. Computations employing local mode effective Hamiltonians reveal the origin of the spectral congestion to be strong coupling between the high frequency CH stretching modes and the lower frequency CH n bending/scissoring motions. The most significant coupling is between stretches and bends localized on the same CH 2/CH 3 group. As a result, spectral simulations using the local mode approach are in excellent agreement with experiment.« less

Infrared laser spectroscopy of the n-propyl and i-propyl radicals: Stretch-bend Fermi coupling in the alkyl CH stretch region

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

Franke, Peter R.; Tabor, Daniel P.; Moradi, Christopher P.

The n-propyl and i-propyl radicals were generated in the gas phase via pyrolysis of n-butyl nitrite [CH 3(CH 2) 3ONO] and i-butyl nitrite [(CH 3) 2CHCH 2ONO], respectively. Nascent radicals were promptly solvated by a beam of He nanodroplets, and the infrared spectra of the radicals were recorded in the CH stretching region. Several previously unreported bands are observed between 2800 and 3150 cm –1. The CH stretching modes observed above 3000 cm –1 are in excellent agreement with CCSD(T) anharmonic frequencies computed using second-order vibrational perturbation theory. However, between 2800 and 3000 cm –1, the spectra of n- andmore » i-propyl radicals become congested and difficult to assign due to the presence of multiple anharmonic resonance polyads. To model the spectrally congested region, Fermi and Darling-Dennison resonances are treated explicitly using “dressed” Hamiltonians and CCSD(T) quartic force fields in the normal mode representation, and the agreement with experiment is less than satisfactory. Computations employing local mode effective Hamiltonians reveal the origin of the spectral congestion to be strong coupling between the high frequency CH stretching modes and the lower frequency CH n bending/scissoring motions. The most significant coupling is between stretches and bends localized on the same CH 2/CH 3 group. As a result, spectral simulations using the local mode approach are in excellent agreement with experiment.« less

When alcohol is the answer: Trapping, identifying and quantifying simple alkylating species in aqueous environments.

PubMed

Penketh, Philip G; Shyam, Krishnamurthy; Baumann, Raymond P; Zhu, Rui; Ishiguro, Kimiko; Sartorelli, Alan C; Ratner, Elena S

2016-09-01

Alkylating agents are a significant class of environmental carcinogens as well as commonly used anticancer therapeutics. Traditional alkylating activity assays have utilized the colorimetric reagent 4-(4-nitrobenzyl)pyridine (4NBP). However, 4NBP based assays have a relatively low sensitivity towards harder, more oxophilic alkylating species and are not well suited for the identification of the trapped alkyl moiety due to adduct instability. Herein we describe a method using water as the trapping agent which permits the trapping of simple alkylating electrophiles with a comparatively wide range of softness/hardness and permits the identification of donated simple alkyl moieties. Copyright © 2016 Elsevier Inc. All rights reserved.

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.

Catalytic Hydrogenation Activity and Electronic Structure Determination of Bis(arylimidazol-2-ylidene)pyridine Cobalt Alkyl and Hydride Complexes

PubMed Central

Yu, Renyuan Pony; Darmon, Jonathan M.; Milsmann, Carsten; Margulieux, Grant W.; E. Stieber, S. Chantal; DeBeer, Serena

2013-01-01

The bis(arylimidazol-2-ylidene)pyridine cobalt methyl complex, (iPrCNC)CoCH3, was evaluated for the catalytic hydrogenation of alkenes. At 22 °C and 4 atm of H2 pressure, (iPrCNC)CoCH3 is an effective pre-catalyst for the hydrogenation of sterically hindered, unactivated alkenes such as trans-methylstilbene, 1-methyl-1-cyclohexene and 2,3-dimethyl-2-butene, representing one of the most active cobalt hydrogenation catalysts reported to date. Preparation of the cobalt hydride complex, (iPrCNC)CoH was accomplished by hydrogenation of (iPrCNC)CoCH3. Over the course of 3 hours at 22 °C, migration of the metal-hydride to the 4-position of the pyridine ring yielded (4-H2-iPrCNC)CoN2. Similar alkyl migration was observed upon treatment of (iPrCNC)CoH with 1,1-diphenylethylene. This reactivity raised the question as to whether this class of chelate is redoxactive, engaging in radical chemistry with the cobalt center. A combination of structural, spectroscopic and computational studies was conducted and provided definitive evidence for bis(arylimidazol-2-ylidene)pyridine radicals in reduced cobalt chemistry. Spin density calculations established that the radicals were localized on the pyridine ring, accounting for the observed reactivity and suggest a wide family of pyridine-based pincers may also be redox active. PMID:23968297

Hybrid ligand-alkylating agents targeting telomeric G-quadruplex structures.

PubMed

Doria, Filippo; Nadai, Matteo; Folini, Marco; Di Antonio, Marco; Germani, Luca; Percivalle, Claudia; Sissi, Claudia; Zaffaroni, Nadia; Alcaro, Stefano; Artese, Anna; Richter, Sara N; Freccero, Mauro

2012-04-14

The synthesis, physico-chemical properties and biological effects of a new class of naphthalene diimides (NDIs) capable of reversibly binding telomeric DNA and alkylate it through an electrophilic quinone methide moiety (QM), are reported. FRET and circular dichroism assays showed a marked stabilization and selectivity towards telomeric G4 DNA folded in a hybrid topology. NDI-QMs' alkylating properties revealed a good reactivity on single nucleosides and selectivity towards telomeric G4. A selected NDI was able to significantly impair the growth of melanoma cells by causing telomere dysfunction and down-regulation of telomerase expression. These findings points to our hybrid ligand-alkylating NDIs as possible tools for the development of novel targeted anticancer therapies. This journal is © The Royal Society of Chemistry 2012

Alkyl Azides, Diazides, Haloazides and Bridged Polycyclic Diazides

DTIC Science & Technology

1991-05-16

temperature. Most of the methyl ether was removed during this process. The ehtyl ether was distilled from the reaction mixture using a water aspirator into a...Street PROGRAM IPROJECT ITASK IWORK li1111? ArliiqIoh, VA 22217-5000 EILIMENT NO I NO. I oACCESSION P10) Alkyl Azides, Dlazides, laloazides and...REPRODUCE LEGIBLY. ALKYL AZIDES, DIAZIDES, HALOAZIDES AND BRIDGED POLYCYCLIC DIAZIDES Final REPORTe July 1, 1989-November 14, 1990 A6jd.%4gi0 F’or

Enantiomerically Pure Acetals in Organic Synthesis: Resolutions and Diastereoselective Alkylations of Alpha-Hydroxy Esters

DTIC Science & Technology

1990-01-01

sensitivity of the alkylating agent to the reaction conditions. In either case , a decision was made to use 5-iodo-2- methyl -l-pentene as the alkylating ...agent, and the reaction conditions. In most cases the diastereomeric products of the alkylation were also separated by column chromatography. This...equatorially substituted product. Oxidation of the alcohol to the ketone followed by treatment with an alkyl Grignard reagent gave only the product which

In Vitro Antimicrobial Bioassays, DPPH Radical Scavenging Activity, and FTIR Spectroscopy Analysis of Heliotropium bacciferum

PubMed Central

2016-01-01

The present study deals with the antimicrobial, antioxidant, and functional group analysis of Heliotropium bacciferum extracts. Disc diffusion susceptibility method was followed for antimicrobial assessment. Noteworthy antimicrobial activities were recorded by various plant extracts against antibiotic resistant microorganisms. Plant flower extracts antioxidant activity was investigated against 2, 2-diphenyl-1-picryl hydrazyl radical by ultraviolet spectrophotometer (517 nm). Plant extracts displayed noteworthy radical scavenging activities at all concentrations (25–225 μg/mL). Notable activities were recorded by crude, chloroform and ethyl acetate extracts up to 88.27% at 225 μg/mL concentration. Compounds functional groups were examined by Fourier transform infrared spectroscopic studies. Alkanes, alkenes, alkyl halides, amines, carboxylic acids, amides, esters, alcohols, phenols, nitrocompounds, and aromatic compounds were identified by FTIR analysis. Thin layer chromatography bioautography was carried out for all plant extracts. Different bands were separated by various solvent systems. The results of the current study justify the use of Heliotropium bacciferum in traditional remedial herbal medicines. PMID:27597961

Free Radical Chemistry Enabled by Visible Light-Induced Electron Transfer.

PubMed

Staveness, Daryl; Bosque, Irene; Stephenson, Corey R J

2016-10-18

temperature conditions. Evolving from this work, a new avenue toward atom transfer radical addition (ATRA) chemistry was developed, enabling dual functionalization of both double and triple bonds. Importantly, we have also expanded our portfolio to target clinically relevant scaffolds. Photoredox catalysis proved effective in generating high value fluorinated alkyl radicals through the use of abundantly available starting materials, providing access to libraries of trifluoromethylated (hetero)arenes as well as intriguing gem-difluoro benzyl motifs via a novel photochemical radical Smiles rearrangement. Finally, we discuss a photochemical strategy toward sustainable lignin processing through selective C-O bond cleavage methodology. The collection of these efforts is meant to highlight the potential for visible light-mediated radical chemistry to impact a variety of industrial sectors.

Free Radical Chemistry Enabled by Visible Light-Induced Electron Transfer

PubMed Central

2016-01-01

-mediated, ambient temperature conditions. Evolving from this work, a new avenue toward atom transfer radical addition (ATRA) chemistry was developed, enabling dual functionalization of both double and triple bonds. Importantly, we have also expanded our portfolio to target clinically relevant scaffolds. Photoredox catalysis proved effective in generating high value fluorinated alkyl radicals through the use of abundantly available starting materials, providing access to libraries of trifluoromethylated (hetero)arenes as well as intriguing gem-difluoro benzyl motifs via a novel photochemical radical Smiles rearrangement. Finally, we discuss a photochemical strategy toward sustainable lignin processing through selective C–O bond cleavage methodology. The collection of these efforts is meant to highlight the potential for visible light-mediated radical chemistry to impact a variety of industrial sectors. PMID:27529484

40 CFR 721.5860 - Methylphenol, bis(sub-sti-tuted)alkyl.

Code of Federal Regulations, 2010 CFR

2010-07-01

... SUBSTANCES CONTROL ACT SIGNIFICANT NEW USES OF CHEMICAL SUBSTANCES Significant New Uses for Specific Chemical Substances § 721.5860 Methylphenol, bis(sub-sti-tuted)alkyl. (a) Chemical substance and significant new uses...-ed)alkyl (P-84-417) is subject to reporting under this section for the significant new uses described...

Photoionization mass spectrometric measurements of initial reaction pathways in low-temperature oxidation of 2,5-dimethylhexane

DOE PAGES

Rotavera, Brandon; Zádor, Judit; Welz, Oliver; ...

2014-09-19

The product formation from R + O 2 reactions relevant to low-temperature autoignition chemistry was studied for 2,5-dimethylhexane, a symmetrically branched octane isomer, at 550 and 650 K using Cl-atom initiated oxidation and multiplexed photoionization mass spectrometry (MPIMS). The interpretation of time- and photon-energy-resolved mass spectra led to three specific results important to characterizing the initial oxidation steps: (1) quantified isomer-resolved branching ratios for HO 2 + alkene channels; (2) 2,2,5,5-tetramethyltetrahydrofuran is formed in substantial yield from addition of O 2 to tertiary 2,5-dimethylhex-2-yl followed by isomerization of the resulting ROO adduct to tertiary hydroperoxyalkyl (QOOH) and exhibits a positivemore » dependence on temperature over the range covered leading to a higher flux relative to aggregate cyclic ether yield. The higher relative flux is explained by a 1,5-hydrogen atom shift reaction that converts the initial primary alkyl radical (2,5-dimethylhex-1-yl) to the tertiary alkyl radical 2,5-dimethylhex-2-yl, providing an additional source of tertiary alkyl radicals. Furthermore, quantum-chemical and master-equation calculations of the unimolecular decomposition of the primary alkyl radical reveal that isomerization to the tertiary alkyl radical is the most favorable pathway, and is favored over O 2-addition at 650 K under the conditions herein. The isomerization pathway to tertiary alkyl radicals therefore contributes an additional mechanism to 2,2,5,5-tetramethyltetrahydrofuran formation; (3) carbonyl species (acetone, propanal, and methylpropanal) consistent with β-scission of QOOH radicals were formed in significant yield, indicating unimolecular QOOH decomposition into carbonyl + alkene + OH.« less

Intramolecular homolytic displacements. 30. Functional decarbonylative transformations of aldehydes via homolytically induced decomposition of unsaturated peroxyacetals

PubMed

Degueil-Castaing; Moutet; Maillard

2000-06-30

Homolytically induced decompositions of unsaturated peroxyacetals, synthesized from aldehydes, gave alkoxyalkoxyl radicals that yielded alkyl radicals by rapid beta-scission. The latter radicals could react with several types of "transfer agents" to smoothly bring about homolytic decarbonylative functional group transformations of aldehydes into halides, hydrocarbons, xanthates, alkanenitriles, 2-alkyl-3-chloromaleic anhydrides, 1-phenylalk-1-ynes, and ethyl 2-alkylpropenoates.

Study of the impact of organic nitrate production on ozone production in a southeastern mixed forest environment using a 0-D photochemical model

NASA Astrophysics Data System (ADS)

Mcavey, K. M.; Groff, C. J.; Xiong, F.; Seeley, J. V.; Starn, T.; Feiner, P. A.; Zhang, L.; Brune, W. H.; Baumann, K.; Misztal, P. K.; Koss, A.; De Gouw, J. A.; Olson, K. F.; Goldstein, A. H.; Bertman, S. B.; Shepson, P. B.

2014-12-01

Organic nitrates (RONO2 + ROONO2) act as an important sink for both organic alkoxy and peroxy and NOx (NO+NO2) radicals, and thus their production can have a significant limiting impact on ozone production. However, there remains significant uncertainty on the formation yields and fates of organic nitrates in the atmosphere. This certainly applies to the biogenic volatile organic compounds (BVOCs), which can often be the dominant reaction partner for OH and thus precursors to the peroxy radicals that produce ozone. Observations of BVOCs and total isoprene and monoterpene nitrates were measured as part of the Southern Oxidant and Aerosol Study in the summer of 2013, at the SEARCH Centreville site in rural, central Alabama. A 0-D box model was constructed to observe the effect of individual and total organic nitrates on ozone production potential, to determine the relative importance of each species in organic nitrate formation. Here we examine the impact of yield uncertainty, and secondary oxidation reactions that might release NOx from the primary organic nitrates.

From old alkylating agents to new minor groove binders.

PubMed

Puyo, Stéphane; Montaudon, Danièle; Pourquier, Philippe

2014-01-01

Alkylating agents represent the oldest class of anticancer agents with the approval of mechloretamine by the FDA in 1949. Even though their clinical use is far beyond the use of new targeted therapies, they still occupy a major place in the treatment of specific malignancies, sometimes representing the unique option for the treatment of refractory tumors. Here, we are reviewing the major classes of alkylating agents, with a particular focus on the latest generations of compounds that specifically target the minor groove of the DNA. These naturally occurring derivatives have a unique mechanism of action that explains the recent regain of interest in developing new classes of alkylating agents that could be used in combination with other anticancer drugs to enhance tumor response in the clinic. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.

Methods of producing alkylated hydrocarbons from an in situ heat treatment process liquid

DOEpatents

Roes, Augustinus Wilhelmus Maria [Houston, TX; Mo, Weijian [Sugar Land, TX; Muylle, Michel Serge Marie [Houston, TX; Mandema, Remco Hugo [Houston, TX; Nair, Vijay [Katy, TX

2009-09-01

A method for producing alkylated hydrocarbons is disclosed. Formation fluid is produced from a subsurface in situ heat treatment process. The formation fluid is separated to produce a liquid stream and a first gas stream. The first gas stream includes olefins. The liquid stream is fractionated to produce at least a second gas stream including hydrocarbons having a carbon number of at least 3. The first gas stream and the second gas stream are introduced into an alkylation unit to produce alkylated hydrocarbons. At least a portion of the olefins in the first gas stream enhance alkylation.

40 CFR 721.3812 - Substituted phenols and formaldehyde polymer, alkylated (generic).

Code of Federal Regulations, 2010 CFR

2010-07-01

... polymer, alkylated (generic). 721.3812 Section 721.3812 Protection of Environment ENVIRONMENTAL PROTECTION... New Uses for Specific Chemical Substances § 721.3812 Substituted phenols and formaldehyde polymer... substance identified generically as substituted phenols and formaldehyde polymer, alkylated (PMN P-00-0542...

40 CFR 721.3812 - Substituted phenols and formaldehyde polymer, alkylated (generic).

Code of Federal Regulations, 2011 CFR

2011-07-01

... polymer, alkylated (generic). 721.3812 Section 721.3812 Protection of Environment ENVIRONMENTAL PROTECTION... New Uses for Specific Chemical Substances § 721.3812 Substituted phenols and formaldehyde polymer... substance identified generically as substituted phenols and formaldehyde polymer, alkylated (PMN P-00-0542...

40 CFR 721.3812 - Substituted phenols and formaldehyde polymer, alkylated (generic).

Code of Federal Regulations, 2014 CFR

2014-07-01

... polymer, alkylated (generic). 721.3812 Section 721.3812 Protection of Environment ENVIRONMENTAL PROTECTION... New Uses for Specific Chemical Substances § 721.3812 Substituted phenols and formaldehyde polymer... substance identified generically as substituted phenols and formaldehyde polymer, alkylated (PMN P-00-0542...

40 CFR 721.3812 - Substituted phenols and formaldehyde polymer, alkylated (generic).

Code of Federal Regulations, 2013 CFR

2013-07-01

... polymer, alkylated (generic). 721.3812 Section 721.3812 Protection of Environment ENVIRONMENTAL PROTECTION... New Uses for Specific Chemical Substances § 721.3812 Substituted phenols and formaldehyde polymer... substance identified generically as substituted phenols and formaldehyde polymer, alkylated (PMN P-00-0542...

40 CFR 721.3812 - Substituted phenols and formaldehyde polymer, alkylated (generic).

Code of Federal Regulations, 2012 CFR

2012-07-01

... polymer, alkylated (generic). 721.3812 Section 721.3812 Protection of Environment ENVIRONMENTAL PROTECTION... New Uses for Specific Chemical Substances § 721.3812 Substituted phenols and formaldehyde polymer... substance identified generically as substituted phenols and formaldehyde polymer, alkylated (PMN P-00-0542...

Alkylation Induced DNA Repair and Mutagenesis in Escherichia coli.

DTIC Science & Technology

1987-11-23

III (Gates and inn, 1977), Micrococcus luteus UV endo- nuclease (Grossman et al, 1978) and bacteriophage T UV endonuclease (Warner et al, 1980) have DNA...34, Garland Publishing, Inc. New York & London USA. Ather, A., Z. Ahmed and S. Riazxxddin, 1984. Adaptive response of Micrococcus luteus to alkylating...Laval, J., 3. Pierre and F. Laval. 1981. Release of 7-nmthylguanine residues frain alkylated ENA by extracts of Micrococcus luteus and Escherichia

40 CFR 721.10621 - Distillation bottoms, alkylated benzene by-product (generic).

Code of Federal Regulations, 2014 CFR

2014-07-01

... benzene by-product (generic). 721.10621 Section 721.10621 Protection of Environment ENVIRONMENTAL... Significant New Uses for Specific Chemical Substances § 721.10621 Distillation bottoms, alkylated benzene by... substance identified generically as distillation bottoms, alkylated benzene by-product (PMN P-12-196) is...

40 CFR 721.10621 - Distillation bottoms, alkylated benzene by-product (generic).

Code of Federal Regulations, 2013 CFR

2013-07-01

... benzene by-product (generic). 721.10621 Section 721.10621 Protection of Environment ENVIRONMENTAL... Significant New Uses for Specific Chemical Substances § 721.10621 Distillation bottoms, alkylated benzene by... substance identified generically as distillation bottoms, alkylated benzene by-product (PMN P-12-196) is...

40 CFR 721.10702 - Polyfluorinated alkyl thio polyacrylic acid-acrylamide (generic).

Code of Federal Regulations, 2014 CFR

2014-07-01

... acid-acrylamide (generic). 721.10702 Section 721.10702 Protection of Environment ENVIRONMENTAL... Significant New Uses for Specific Chemical Substances § 721.10702 Polyfluorinated alkyl thio polyacrylic acid... substance identified generically as polyfluorinated alkyl thio polyacrylic acid-acrylamide (PMN P-11-534) is...

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.

Thermodynamic Interactions between Polystyrene and Long-Chain Poly(n-Alkyl Acrylates) Derived from Plant Oils.

PubMed

Wang, Shu; Robertson, Megan L

2015-06-10

Vegetable oils and their fatty acids are promising sources for the derivation of polymers. Long-chain poly(n-alkyl acrylates) and poly(n-alkyl methacrylates) are readily derived from fatty acids through conversion of the carboxylic acid end-group to an acrylate or methacrylate group. The resulting polymers contain long alkyl side-chains with around 10-22 carbon atoms. Regardless of the monomer source, the presence of alkyl side-chains in poly(n-alkyl acrylates) and poly(n-alkyl methacrylates) provides a convenient mechanism for tuning their physical properties. The development of structured multicomponent materials, including block copolymers and blends, containing poly(n-alkyl acrylates) and poly(n-alkyl methacrylates) requires knowledge of the thermodynamic interactions governing their self-assembly, typically described by the Flory-Huggins interaction parameter χ. We have investigated the χ parameter between polystyrene and long-chain poly(n-alkyl acrylate) homopolymers and copolymers: specifically we have included poly(stearyl acrylate), poly(lauryl acrylate), and their random copolymers. Lauryl and stearyl acrylate were chosen as model alkyl acrylates derived from vegetable oils and have alkyl side-chain lengths of 12 and 18 carbon atoms, respectively. Polystyrene is included in this study as a model petroleum-sourced polymer, which has wide applicability in commercially relevant multicomponent polymeric materials. Two independent methods were employed to measure the χ parameter: cloud point measurements on binary blends and characterization of the order-disorder transition of triblock copolymers, which were in relatively good agreement with one another. The χ parameter was found to be independent of the alkyl side-chain length (n) for large values of n (i.e., n > 10). This behavior is in stark contrast to the n-dependence of the χ parameter predicted from solubility parameter theory. Our study complements prior work investigating the interactions between

SERIES: Genomic instability in cancer Balancing repair and tolerance of DNA damage caused by alkylating agents

PubMed Central

Fu, Dragony; Calvo, Jennifer A.; Samson, Leona D

2013-01-01

Alkylating agents comprise 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 an organism's favorable response to alkylating agents. Furthermore, an individual's response 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. PMID:22237395

Isoprene photochemistry over the Amazon rainforest

PubMed Central

Liu, Yingjun; Brito, Joel; Dorris, Matthew R.; Rivera-Rios, Jean C.; Seco, Roger; Bates, Kelvin H.; Artaxo, Paulo; Duvoisin, Sergio; Keutsch, Frank N.; Kim, Saewung; Goldstein, Allen H.; Guenther, Alex B.; Manzi, Antonio O.; Souza, Rodrigo A. F.; Springston, Stephen R.; Watson, Thomas B.; McKinney, Karena A.

2016-01-01

Isoprene photooxidation is a major driver of atmospheric chemistry over forested regions. Isoprene reacts with hydroxyl radicals (OH) and molecular oxygen to produce isoprene peroxy radicals (ISOPOO). These radicals can react with hydroperoxyl radicals (HO2) to dominantly produce hydroxyhydroperoxides (ISOPOOH). They can also react with nitric oxide (NO) to largely produce methyl vinyl ketone (MVK) and methacrolein (MACR). Unimolecular isomerization and bimolecular reactions with organic peroxy radicals are also possible. There is uncertainty about the relative importance of each of these pathways in the atmosphere and possible changes because of anthropogenic pollution. Herein, measurements of ISOPOOH and MVK + MACR concentrations are reported over the central region of the Amazon basin during the wet season. The research site, downwind of an urban region, intercepted both background and polluted air masses during the GoAmazon2014/5 Experiment. Under background conditions, the confidence interval for the ratio of the ISOPOOH concentration to that of MVK + MACR spanned 0.4–0.6. This result implies a ratio of the reaction rate of ISOPOO with HO2 to that with NO of approximately unity. A value of unity is significantly smaller than simulated at present by global chemical transport models for this important, nominally low-NO, forested region of Earth. Under polluted conditions, when the concentrations of reactive nitrogen compounds were high (>1 ppb), ISOPOOH concentrations dropped below the instrumental detection limit (<60 ppt). This abrupt shift in isoprene photooxidation, sparked by human activities, speaks to ongoing and possible future changes in the photochemistry active over the Amazon rainforest. PMID:27185928

Isoprene photochemistry over the Amazon rainforest.

PubMed

Liu, Yingjun; Brito, Joel; Dorris, Matthew R; Rivera-Rios, Jean C; Seco, Roger; Bates, Kelvin H; Artaxo, Paulo; Duvoisin, Sergio; Keutsch, Frank N; Kim, Saewung; Goldstein, Allen H; Guenther, Alex B; Manzi, Antonio O; Souza, Rodrigo A F; Springston, Stephen R; Watson, Thomas B; McKinney, Karena A; Martin, Scot T

2016-05-31

Isoprene photooxidation is a major driver of atmospheric chemistry over forested regions. Isoprene reacts with hydroxyl radicals (OH) and molecular oxygen to produce isoprene peroxy radicals (ISOPOO). These radicals can react with hydroperoxyl radicals (HO2) to dominantly produce hydroxyhydroperoxides (ISOPOOH). They can also react with nitric oxide (NO) to largely produce methyl vinyl ketone (MVK) and methacrolein (MACR). Unimolecular isomerization and bimolecular reactions with organic peroxy radicals are also possible. There is uncertainty about the relative importance of each of these pathways in the atmosphere and possible changes because of anthropogenic pollution. Herein, measurements of ISOPOOH and MVK + MACR concentrations are reported over the central region of the Amazon basin during the wet season. The research site, downwind of an urban region, intercepted both background and polluted air masses during the GoAmazon2014/5 Experiment. Under background conditions, the confidence interval for the ratio of the ISOPOOH concentration to that of MVK + MACR spanned 0.4-0.6. This result implies a ratio of the reaction rate of ISOPOO with HO2 to that with NO of approximately unity. A value of unity is significantly smaller than simulated at present by global chemical transport models for this important, nominally low-NO, forested region of Earth. Under polluted conditions, when the concentrations of reactive nitrogen compounds were high (>1 ppb), ISOPOOH concentrations dropped below the instrumental detection limit (<60 ppt). This abrupt shift in isoprene photooxidation, sparked by human activities, speaks to ongoing and possible future changes in the photochemistry active over the Amazon rainforest.

Isoprene photochemistry over the Amazon rainforest

NASA Astrophysics Data System (ADS)

Liu, Yingjun; Brito, Joel; Dorris, Matthew R.; Rivera-Rios, Jean C.; Seco, Roger; Bates, Kelvin H.; Artaxo, Paulo; Duvoisin, Sergio; Keutsch, Frank N.; Kim, Saewung; Goldstein, Allen H.; Guenther, Alex B.; Manzi, Antonio O.; Souza, Rodrigo A. F.; Springston, Stephen R.; Watson, Thomas B.; McKinney, Karena A.; Martin, Scot T.

2016-05-01

Isoprene photooxidation is a major driver of atmospheric chemistry over forested regions. Isoprene reacts with hydroxyl radicals (OH) and molecular oxygen to produce isoprene peroxy radicals (ISOPOO). These radicals can react with hydroperoxyl radicals (HO2) to dominantly produce hydroxyhydroperoxides (ISOPOOH). They can also react with nitric oxide (NO) to largely produce methyl vinyl ketone (MVK) and methacrolein (MACR). Unimolecular isomerization and bimolecular reactions with organic peroxy radicals are also possible. There is uncertainty about the relative importance of each of these pathways in the atmosphere and possible changes because of anthropogenic pollution. Herein, measurements of ISOPOOH and MVK + MACR concentrations are reported over the central region of the Amazon basin during the wet season. The research site, downwind of an urban region, intercepted both background and polluted air masses during the GoAmazon2014/5 Experiment. Under background conditions, the confidence interval for the ratio of the ISOPOOH concentration to that of MVK + MACR spanned 0.4-0.6. This result implies a ratio of the reaction rate of ISOPOO with HO2 to that with NO of approximately unity. A value of unity is significantly smaller than simulated at present by global chemical transport models for this important, nominally low-NO, forested region of Earth. Under polluted conditions, when the concentrations of reactive nitrogen compounds were high (>1 ppb), ISOPOOH concentrations dropped below the instrumental detection limit (<60 ppt). This abrupt shift in isoprene photooxidation, sparked by human activities, speaks to ongoing and possible future changes in the photochemistry active over the Amazon rainforest.

Versatile assembly of p-carboxylatocalix[4]arene-O-alkyl ethers

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

Kennedy, Stuart; Teat, Simon J.; Dalgarno, Scott J.

Crystallisation of lower-rim tetra-O-alkylated p-carboxylatocalix[4]arenes from pyridine results in the formation of both bi-layer and pillar type supramolecular motifs. Full alkylation at the calixarene lower rim has significant influence over the supramolecular self-assembly motif, including preclusion of pyridine guest molecules from the calixarene cavity in the solid state.

40 CFR 721.10044 - Metal oxide, modified with alkyl and vinyl terminated polysiloxanes (generic).

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Metal oxide, modified with alkyl and... SUBSTANCES Significant New Uses for Specific Chemical Substances § 721.10044 Metal oxide, modified with alkyl... to reporting. (1) The chemical substance identified generically as metal oxide, modified with alkyl...

Safety Assessment of Alkyl Ethylhexanoates as Used in Cosmetics.

PubMed

Fiume, Monice; 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

2015-01-01

The Cosmetic Ingredient Review (CIR) Expert Panel (Panel) assessed the safety of 16 alkyl ethylhexanoates for use in cosmetics, concluding that these ingredients are safe in cosmetic formulations in the present practices of use and concentrations when formulated to be nonirritating. The alkyl ethylhexanoates primarily function as skin-conditioning agents in cosmetics. The highest concentration of use reported for any of the alkyl ethylhexanoates is 77.3% cetyl ethylhexanoate in rinse-off formulations used near the eye, and the highest leave-on use reported is 52% cetyl ethylhexanoate in lipstick formulations. The Panel reviewed available animal and clinical data related to these ingredients, and the similarities in structure, properties, functions, and uses of ingredients from previous CIR assessments on constituent alcohols that allowed for extrapolation of the available toxicological data to assess the safety of the entire group. © The Author(s) 2015.

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%.

Extensive reprogramming of the genetic code for genetically encoded synthesis of highly N-alkylated polycyclic peptidomimetics.

PubMed

Kawakami, Takashi; Ishizawa, Takahiro; Murakami, Hiroshi

2013-08-21

Cyclic structures can increase the proteolytic stability and conformational rigidity of peptides, and N-alkylation of the peptide backbone can make peptides more cell-permeable and resistant to proteolysis. Therefore, cyclic N-alkyl amino acids are expected to be useful building blocks to increase simultaneously these pharmacological properties of peptides. In this study, we screened various cyclic N-alkyl amino acids for their ribosomal incorporation into peptides and identified cyclic N-alkyl amino acids that can be efficiently and successively incorporated. We also demonstrated genetic code reprogramming for reassigning 16 NNU codons to 16 different cyclic N-alkyl amino acids with high fidelity to synthesize highly N-alkylated polycyclic peptidomimetics and an mRNA-displayed library of completely N-alkylated polycyclic peptidomimetics by using our recently developed TRAP (transcription/translation coupled with association of puromycin linker) display. In vitro selection from a highly diverse library of such completely N-alkylated polycyclic peptidomimetics could become a powerful means to discover small-molecule ligands such as drug candidates that can be targeted to biomolecules inside living cells.

Stochastic resonance algorithm applied to quantitative analysis for weak chromatographic signals of alkyl halides and alkyl benzenes in water samples.

PubMed

Xiang, Suyun; Wang, Wei; Xia, Jia; Xiang, Bingren; Ouyang, Pingkai

2009-09-01

The stochastic resonance algorithm is applied to the trace analysis of alkyl halides and alkyl benzenes in water samples. Compared to encountering a single signal when applying the algorithm, the optimization of system parameters for a multicomponent is more complex. In this article, the resolution of adjacent chromatographic peaks is first involved in the optimization of parameters. With the optimized parameters, the algorithm gave an ideal output with good resolution as well as enhanced signal-to-noise ratio. Applying the enhanced signals, the method extended the limit of detection and exhibited good linearity, which ensures accurate determination of the multicomponent.

Persistence of DNA adducts, hypermutation and acquisition of cellular resistance to alkylating agents in glioblastoma.

PubMed

Head, R J; Fay, M F; Cosgrove, L; Y C Fung, K; Rundle-Thiele, D; Martin, J H

2017-12-02

Glioblastoma is a lethal form of brain tumour usually treated by surgical resection followed by radiotherapy and an alkylating chemotherapeutic agent. Key to the success of this multimodal approach is maintaining apoptotic sensitivity of tumour cells to the alkylating agent. This initial treatment likely establishes conditions contributing to development of drug resistance as alkylating agents form the O 6 -methylguanine adduct. This activates the mismatch repair (MMR) process inducing apoptosis and mutagenesis. This review describes key juxtaposed drivers in the balance between alkylation induced mutagenesis and apoptosis. Mutations in MMR genes are the probable drivers for alkylation based drug resistance. Critical to this interaction are the dose-response and temporal interactions between adduct formation and MMR mutations. The precision in dose interval, dose-responses and temporal relationships dictate a role for alkylating agents in either promoting experimental tumour formation or inducing tumour cell death with chemotherapy. Importantly, this resultant loss of chemotherapeutic selective pressure provides opportunity to explore novel therapeutics and appropriate combinations to minimise alkylation based drug resistance and tumour relapse.

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.

Safety Assessment of Alkyl PEG Sulfosuccinates as Used in Cosmetics.

PubMed

Johnson, Wilbur; 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

2015-09-01

The Cosmetic Ingredient Review (CIR) Expert Panel (Panel) reviewed the safety of alkyl polyethylene glycol (PEG) sulfosuccinates, which function in cosmetics mostly as surfactants/cleansing agents. Although these ingredients may cause ocular and skin irritation, dermal penetration is unlikely because of the substantial polarity and molecular size of these ingredients. The Panel considered the negative oral carcinogenicity and reproductive and developmental toxicity data on chemically related laureths (PEG lauryl ethers) and negative repeated dose toxicity and skin sensitization data on disodium laureth sulfosuccinate supported the safety of these alkyl PEG sulfosuccinates in cosmetic products, but. The CIR Expert Panel concluded that the alkyl PEG sulfosuccinates are safe in the present practices of use and concentration when formulated to be nonirritating. © The Author(s) 2015.

ATM regulates 3-Methylpurine-DNA glycosylase and promotes therapeutic resistance to alkylating agents

PubMed Central

Agnihotri, Sameer; Burrell, Kelly; Buczkowicz, Pawel; Remke, Marc; Golbourn, Brian; Chornenkyy, Yevgen; Gajadhar, Aaron; Fernandez, Nestor A.; Clarke, Ian D.; Barszczyk, Mark S.; Pajovic, Sanja; Ternamian, Christian; Head, Renee; Sabha, Nesrin; Sobol, Robert W.; Taylor, Michael D; Rutka, James T.; Jones, Chris; Dirks, Peter B.; Zadeh, Gelareh; Hawkins, Cynthia

2014-01-01

Alkylating agents are a frontline therapy for the treatment of several aggressive cancers including pediatric glioblastoma, a lethal tumor in children. Unfortunately, many tumors are resistant to this therapy. We sought to identify ways of sensitizing tumor cells to alkylating agents while leaving normal cells unharmed; increasing therapeutic response while minimizing toxicity. Using a siRNA screen targeting over 240 DNA damage response genes, we identified novel sensitizers to alkylating agents. In particular the base excision repair (BER) pathway, including 3-methylpurine-DNA glycosylase (MPG), as well as ataxia telangiectasia mutated (ATM) were identified in our screen. Interestingly, we identified MPG as a direct novel substrate of ATM. ATM-mediated phosphorylation of MPG was required for enhanced MPG function. Importantly, combined inhibition or loss of MPG and ATM resulted in increased alkylating agent-induced cytotoxicity in vitro and prolonged survival in vivo. The discovery of the ATM-MPG axis will lead to improved treatment of alkylating agent-resistant tumors. PMID:25100205

Polyimides and Process for Preparing Polyimides Having Thermal-Oxidative Stability

NASA Technical Reports Server (NTRS)

Meador, Mary Ann B. (Inventor)

2001-01-01

Polyimides and the process for preparing polyimides having improved thermal-oxidative stability derived from the polymerization of effective amounts of one or more of the polyamines such as the aromatic diamines, one or more of the tetracarboxylic dianhydrides and a novel dicarboxylic endcap having formula with an R1 group of either hydrogen or an alkyl radical of one to four carbons, an R2 group of either OH, NH2, F, or Cl radical, an R3 group of either H, OH, NH2, F, Cl or an alkylene radical, an R4 group of either an alkyl, aryl, aryloxy, nitro, F, or Cl radical, and/or an R5 group of either H, alkyl, aryl, alkoxy, aryloxy, nitro, F, or Cl radical. The polyimides are useful particularly in the preparation of prepegs and PMR composites.

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.

Preparation, characterization and magnetic behavior of a spin-labelled physical hydrogel containing a chiral cyclic nitroxide radical unit fixed inside the gelator molecule.

PubMed

Takemoto, Yusa; Yamamoto, Takayuki; Ikuma, Naohiko; Uchida, Yoshiaki; Suzuki, Katsuaki; Shimono, Satoshi; Takahashi, Hiroki; Sato, Nobuhiro; Oba, Yojiro; Inoue, Rintaro; Sugiyama, Masaaki; Tsue, Hirohito; Kato, Tatsuhisa; Yamauchi, Jun; Tamura, Rui

2015-07-21

An optically active amphiphilic nitroxide radical compound [(S,S,R)-], which contains a paramagnetic (2S,5S)-2,5-dimethyl-2,5-diphenylpyrrolidine-N-oxyl radical group fixed in the inner position together with a hydrophobic long alkyl chain and a hydrophilic (R)-alanine residue in the opposite terminal positions, was found to serve as a low-molecular-weight gelator in H2O to give rise to a spin-labelled physical hydrogel. Characterization of the hydrogel was performed by microscopic (SEM, TEM and AFM) techniques, XRD and SAXS measurements, and IR, UV and CD spectroscopies. The gel-sol transition temperature was determined by EPR spectral line-width (ΔHpp) analysis. Measurement of the temperature dependence of relative paramagnetic susceptibility (χrel) for the hydrogel and sol phases was achieved by means of the double-integration of VT-EPR spectra.

Carbon Kinetic Isotope Effects in the Oxidation of Atmospheric Alkane and Aromatic Hydrocarbons by Hydroxyl Radicals

NASA Astrophysics Data System (ADS)

Anderson, R. S.; Thompson, A. E.; Rudolph, J.; Huang, L.

2001-12-01

To interpret measurements of stable carbon isotope ratios of ambient NMHC, we need to understand the isotopic composition of the emissions, and the isotope fractionation associated with the removal of NMHC from the atmosphere. Oxidation by OH-radicals is by far the most important atmospheric process for removal of NMHC. In this presentation measurements of the kinetic isotope effects (KIEs) for the reactions of hydroxyl radicals with several C5-C8 alkanes, including cyclic, branched and straight-chain alkanes, as well as C6-C9 aromatics are presented. All KIEs are positive: compounds containing only 12C atoms react faster than 13C labelled compounds. KIEs for light n-alkanes are typically between 1.5-4‰ and are larger than mass dependent collision frequencies, deviating from the collision frequency as carbon number increases. For n-alkanes there is no statistically significant difference between the KIEs of structural isomers. KIEs for the reactions of light alkenes and aromatics with OH-radicals are considerably higher than for alkane reactions, ranging from 3-18‰ . The KIEs for the aromatic reactions can be described by a 33.3+/-2.0‰ fractionation for the addition of an OH-radical to the aromatic ring and an inverse dependency on the number of carbon atoms, added to the mass dependent collision frequency. There are indications for minor structure specific effects, however the deviations from the idealised inverse carbon number dependence is relatively small and the limited number of studied alkyl benzenes does not yet allow the identification of systematic dependencies.

Synthesis and Performance of a Biomimetic Indicator for Alkylating Agents.

PubMed

Provencher, Philip A; Love, Jennifer A

2015-10-02

4-(4-Nitrobenzyl)pyridine (NBP) is a colorimetric indicator compound for many types of carcinogenic alkylating agents. Because of the similar reactivity of NBP and guanine in DNA, NBP serves as a DNA model. NBP assays are used in the toxicological screening of pharmaceutical compounds, detection of chemical warfare agents, environmental hygiene technology, preliminary toxicology tests, mutagenicity of medicinal compounds, and other chemical analyses. Nevertheless, the use of NBP as a DNA model suffers from the compound's low water solubility, its lack of reactive oxygen sites, and dissimilar steric encumbrance compared to DNA. We report herein the design and synthesis of NBP derivatives that address some of these issues. These derivatives have been tested in solution and found to be superior in the colorimetric assay of the alkylating anticancer drug cyclophosphamide. The derivatives have also been integrated into a polymeric silica material which changes color upon the exposure to dangerous alkylating agents, such as iodomethane vapor, without the need for an exogenous base. This material modernizes the NBP assay from a time-consuming laboratory analysis to a real-time solid state sensor, which requires neither solvent nor additional reagents and can detect both gas- and solution-phase alkylating agents.

ATM regulates 3-methylpurine-DNA glycosylase and promotes therapeutic resistance to alkylating agents.

PubMed

Agnihotri, Sameer; Burrell, Kelly; Buczkowicz, Pawel; Remke, Marc; Golbourn, Brian; Chornenkyy, Yevgen; Gajadhar, Aaron; Fernandez, Nestor A; Clarke, Ian D; Barszczyk, Mark S; Pajovic, Sanja; Ternamian, Christian; Head, Renee; Sabha, Nesrin; Sobol, Robert W; Taylor, Michael D; Rutka, James T; Jones, Chris; Dirks, Peter B; Zadeh, Gelareh; Hawkins, Cynthia

2014-10-01

Alkylating agents are a first-line therapy for the treatment of several aggressive cancers, including pediatric glioblastoma, a lethal tumor in children. Unfortunately, many tumors are resistant to this therapy. We sought to identify ways of sensitizing tumor cells to alkylating agents while leaving normal cells unharmed, increasing therapeutic response while minimizing toxicity. Using an siRNA screen targeting over 240 DNA damage response genes, we identified novel sensitizers to alkylating agents. In particular, the base excision repair (BER) pathway, including 3-methylpurine-DNA glycosylase (MPG), as well as ataxia telangiectasia mutated (ATM), were identified in our screen. Interestingly, we identified MPG as a direct novel substrate of ATM. ATM-mediated phosphorylation of MPG was required for enhanced MPG function. Importantly, combined inhibition or loss of MPG and ATM resulted in increased alkylating agent-induced cytotoxicity in vitro and prolonged survival in vivo. The discovery of the ATM-MPG axis will lead to improved treatment of alkylating agent-resistant tumors. Inhibition of ATM and MPG-mediated BER cooperate to sensitize tumor cells to alkylating agents, impairing tumor growth in vitro and in vivo with no toxicity to normal cells, providing an ideal therapeutic window. ©2014 American Association for Cancer Research.

Near Infrared Spectroscopic Identification of Alkyl Aromatic Esters and Phenyl Ketones

NASA Astrophysics Data System (ADS)

Nelyubov, D. V.; Vazhenin, D. A.; Kudriavtsev, A. A.; Buzolina, A. Yu.

2018-03-01

Bands characterizing the content of carbon atoms in alkyl (7177-7205 cm-1) and phenyl structural fragments (9175-9192 cm-1) in organic molecules were revealed by studying the near infrared spectra of such compounds. The optical density at the maxima of these absorption bands was shown to depend strongly on the fraction of carbon atoms in the corresponding fragments. The developed models proved to be adequate for determining the fraction of carbon atoms in alkyl aromatic esters and phenyl ketones. The feasibility of modeling the molecular structure of alkyl aromatic esters using regression models was demonstrated for the product of the condensation of oleic acid and benzyl alcohol.

Fe-Catalyzed C–C Bond Construction from Olefins via Radicals

PubMed Central

2017-01-01

This Article details the development of the iron-catalyzed conversion of olefins to radicals and their subsequent use in the construction of C–C bonds. Optimization of a reductive diene cyclization led to the development of an intermolecular cross-coupling of electronically-differentiated donor and acceptor olefins. Although the substitution on the donor olefins was initially limited to alkyl and aryl groups, additional efforts culminated in the expansion of the scope of the substitution to various heteroatom-based functionalities, providing a unified olefin reactivity. A vinyl sulfone acceptor olefin was developed, which allowed for the efficient synthesis of sulfone adducts that could be used as branch points for further diversification. Moreover, this reactivity was extended into an olefin-based Minisci reaction to functionalize heterocyclic scaffolds. Finally, mechanistic studies resulted in a more thorough understanding of the reaction, giving rise to the development of a more efficient second-generation set of olefin cross-coupling conditions. PMID:28094980

Chemical evolution of gaseous air pollutants down-wind of tropical megacities: Mexico City case study

NASA Astrophysics Data System (ADS)

Madronich, Sasha

The photochemical evolution of a polluted air parcel originating in a tropical megacity was modeled for 3 days using a box model with detailed gas-phase chemistry. The parcel was initialized with concentrations typically observed in Mexico City for nitrogen oxides (80 parts per billion on a molar basis, or ppbv), carbon monoxide (3000 ppbv), non-methane hydrocarbons (1700 ppb on a carbon basis, or ppbC) and formaldehyde (23.9 ppbv). Vigorous ozone production occurred during day 1, followed by gradual net destruction during the next 2 days. Other major inorganic products were nitric acid and hydrogen peroxide (35 and 16 ppbv, respectively at the end of day 3), while organic products included ketones (83 ppbv), organic hydroperoxides (25 ppbv), peroxyacyl nitrates (28 ppbv), aldehydes (18 ppbv), organic acids (16 ppbv), alkyl nitrates (10 ppbv) and alcohols (0.2 ppbv). Also produced was multitude of different polyfunctional compounds, present individually at small concentrations, but with significant summed concentrations (68, 49 and 1.5 ppbC, respectively, for compounds having 2, 3 or 4 functional groups), which could contribute to the formation of secondary aerosols. The overall reactivity of the parcel (daytime concentrations of hydroxy, hydroperoxy and organic peroxy radicals; and cumulative hydroxyl radical loss rates) remained relatively constant and high on days 2 and 3. This persistent gas-phase reactivity suggests that urban areas could affect regional and global tropospheric chemistry. However, it remains unclear whether heterogeneous losses, on aerosol particles, reduce this reactivity while simultaneously changing aerosol chemical, microphysical and radiative properties relevant to weather and climate.

Electrochemical and thermal grafting of alkyl grignard reagents onto (100) silicon surfaces.

PubMed

Vegunta, Sri Sai S; Ngunjiri, Johnpeter N; Flake, John C

2009-11-03

Passivation of (100) silicon surfaces using alkyl Grignard reagents is explored via electrochemical and thermal grafting methods. The electrochemical behavior of silicon in methyl or ethyl Grignard reagents in tetrahydrofuran is investigated using cyclic voltammetry. Surface morphology and chemistry are investigated using atomic force microscopy, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy (XPS). Results show that electrochemical pathways provide an efficient and more uniform passivation method relative to thermal methods, and XPS results demonstrate that electrografted terminations are effective at limiting native oxide formation for more than 55 days in ambient conditions. A two-electron per silicon mechanism is proposed for electrografting a single (1:1) alkyl group per (100) silicon atom. The mechanism includes oxidation of two Grignard species and subsequent hydrogen abstraction and alkylation reaction resulting in a covalent attachment of alkyl groups with silicon.

Deciphering the genomic targets of alkylating polyamide conjugates using high-throughput sequencing

PubMed Central

Chandran, Anandhakumar; Syed, Junetha; Taylor, Rhys D.; Kashiwazaki, Gengo; Sato, Shinsuke; Hashiya, Kaori; Bando, Toshikazu; Sugiyama, Hiroshi

2016-01-01

Chemically engineered small molecules targeting specific genomic sequences play an important role in drug development research. Pyrrole-imidazole polyamides (PIPs) are a group of molecules that can bind to the DNA minor-groove and can be engineered to target specific sequences. Their biological effects rely primarily on their selective DNA binding. However, the binding mechanism of PIPs at the chromatinized genome level is poorly understood. Herein, we report a method using high-throughput sequencing to identify the DNA-alkylating sites of PIP-indole-seco-CBI conjugates. High-throughput sequencing analysis of conjugate 2 showed highly similar DNA-alkylating sites on synthetic oligos (histone-free DNA) and on human genomes (chromatinized DNA context). To our knowledge, this is the first report identifying alkylation sites across genomic DNA by alkylating PIP conjugates using high-throughput sequencing. PMID:27098039

Synthesis and evaluation of novel caged DNA alkylating agents bearing 3,4-epoxypiperidine structure.

PubMed

Kawada, Yuji; Kodama, Tetsuya; Miyashita, Kazuyuki; Imanishi, Takeshi; Obika, Satoshi

2012-07-14

Previously, we reported that the 3,4-epoxypiperidine structure, whose design was based on the active site of DNA alkylating antitumor antibiotics, azinomycins A and B, possesses prominent DNA cleavage activity. In this report, novel caged DNA alkylating agents, which were designed to be activated by UV irradiation, were synthesized by the introduction of four photo-labile protecting groups to a 3,4-epoxypiperidine derivative. The DNA cleavage activity and cytotoxicity of the caged DNA alkylating agents were examined under UV irradiation. Four caged DNA alkylating agents showed various degrees of bioactivity depending on the photosensitivity of the protecting groups.

Profound impairment of adaptive immune responses by alkylating chemotherapy

PubMed Central

Litterman, Adam J.; Zellmer, David M.; Grinnen, Karen L.; Hunt, Matthew A.; Dudek, Arkadiusz Z.; Salazar, Andres M.; Ohlfest, John R.

2013-01-01

Cancer vaccines have overall had a record of failure as an adjuvant therapy for malignancies that are treated with alkylating chemotherapy, and the contribution of standard treatment to that failure remains unclear. Vaccines aim to harness the proliferative potential of the immune system by expanding a small number of tumor-specific lymphocytes into a large number of anti-tumor effectors. Clinical trials are often conducted after treatment with alkylating chemotherapy, given either as standard therapy or for immunomodulatory effect. There is mounting evidence for synergy between chemotherapy and adoptive immunotherapy or vaccination against self-antigens; however, the impact of chemotherapy on lymphocytes primed against tumor neo-antigens remains poorly defined. We report here that clinically relevant dosages of standard alkylating chemotherapies such as temozolomide and cyclophosphamide significantly inhibit the proliferative abilities of lymphocytes in mice. This proliferative impairment was long lasting and led to quantitative and qualitative defects in B and T cell responses to neo-antigen vaccines. High affinity responder lymphocytes receiving the strongest proliferative signals from vaccines experienced the greatest DNA damage responses, skewing the response toward lower affinity responders with inferior functional characteristics. Together these defects lead to inferior efficacy and overall survival in murine tumor models treated by neo-antigen vaccines. These results suggest that clinical protocols for cancer vaccines should be designed to avoid exposing responder lymphocytes to alkylating chemotherapy. PMID:23686484

Persubstituted p-benzoquinone monoxime alkyl ethers and their molecular structure

NASA Astrophysics Data System (ADS)

Slaschinin, D. G.; Alemasov, Y. A.; Ilushkin, D. I.; Sokolenko, W. A.; Tovbis, M. S.; Kirik, S. D.

2012-05-01

Theoretical and experimental approaches were applied for the investigation of the reactivity of persubstituted 4-nitrosophenols in the reaction with alkyl iodides, in particular the potassium salt of 2,6-di(alkoxycarbonyl)-3,5-dimethyl-4-nitrosophenol. Hartre-Fock calculations showed that the anion negative charge was located mostly on the oxygen of hydroxyl group, while estimation of the total energy of the alkylated products pointed out the benefit of alkylation on the oxygen atom of the nitroso group yielding p-benzoquinone monoxime alkyl ethers. Methylation and ethylation of persubstituted nitrosophenols were carried out. The products obtained were investigated using X-ray diffraction, 1Н NMR spectroscopy and mass spectrometry. The crystal structure of the methyl ether of 2,6-di(alkoxycarbonyl)-3,5-dimethyl-1,4-benzoquinone-1-oxime (С15H19NO6) (I) was determined by the X-ray powder diffraction technique. The unit cell parameters were: a = 7.3322(6) Å, b = 10.5039(12) Å, c = 21.1520(20) Å, β = 93.742(6)°, V = 1625.58(2) Å3Z = 4, Sp.Gr. P21/c. The structure modeling was made in direct space by the Monte-Carlo approach using rigid and soft restrictions. The structure refinement was completed by the Rietveld method. It was established that the alkylation occurred on the oxygen atom of the nitroso group. The molecules (I) in the crystal structure were packed in columns along the axis a with pairwise convergence in a column up to the distance of 3.63 Å due to a 180° turn of every second molecule around the column axis. In the molecular structure the methyloxime group was oriented in the benzene plane and had π-conjugation with the ring. The ethoxycarbonyl groups were turned nearly perpendicular to the ring. Other compounds obtained had the structure of the alkyl ethers of 1.4-benzoquinone-1-oxime, which was proved by 1Н NMR spectroscopy and mass-spectrometry.

Carbon kinetic isotope effects in the gas-phase reactions of aromatic hydrocarbons with the OH radical at 296 +/- 4 K

NASA Astrophysics Data System (ADS)

Anderson, Rebecca S.; Iannone, Richard; Thompson, Alexandra E.; Rudolph, Jochen; Huang, Lin

2004-08-01

The carbon kinetic isotope effects (KIEs) of the room temperature reactions of benzene and several light alkyl benzenes with OH radicals were studied in a reaction chamber at ambient pressure using gas chromatography coupled with online combustion and isotope ratio mass spectrometry (GCC-IRMS). The KIEs are reported in per mil according to $\\varepsilon$ (‰) = (KIE - 1) × 1000, where KIE = k12/k13. The following average KIEs were obtained, (all in ‰): benzene 7.53 +/- 0.50; toluene 5.95 +/- 0.28; ethylbenzene 4.34 +/- 0.28; o-xylene 4.27 +/- 0.05, p-xylene 4.83 +/- 0.81; o-ethyltoluene 4.71 +/- 0.12 and 1,2,4-trimethylbenzene 3.18 +/- 0.09. Our KIE value for benzene + OH agrees with the only reported value known to us [Rudolph et al., 2000]. It is shown that measurements of the stable carbon isotope ratios of light aromatic compounds should be extremely useful to study atmospheric processing by the OH radical.

Direct Evidence of Solution-Mediated Superoxide Transport and Organic Radical Formation in Sodium-Oxygen Batteries.

PubMed

Xia, Chun; Fernandes, Russel; Cho, Franklin H; Sudhakar, Niranjan; Buonacorsi, Brandon; Walker, Sean; Xu, Meng; Baugh, Jonathan; Nazar, Linda F

2016-09-07

Advanced large-scale electrochemical energy storage requires cost-effective battery systems with high energy densities. Aprotic sodium-oxygen (Na-O2) batteries offer advantages, being comprised of low-cost elements and possessing much lower charge overpotential and higher reversibility compared to their lithium-oxygen battery cousins. Although such differences have been explained by solution-mediated superoxide transport, the underlying nature of this mechanism is not fully understood. Water has been suggested to solubilize superoxide via formation of hydroperoxyl (HO2), but direct evidence of these HO2 radical species in cells has proven elusive. Here, we use ESR spectroscopy at 210 K to identify and quantify soluble HO2 radicals in the electrolyte-cold-trapped in situ to prolong their lifetime-in a Na-O2 cell. These investigations are coupled to parallel SEM studies that image crystalline sodium superoxide (NaO2) on the carbon cathode. The superoxide radicals were spin-trapped via reaction with 5,5-dimethyl-pyrroline N-oxide at different electrochemical stages, allowing monitoring of their production and consumption during cycling. Our results conclusively demonstrate that transport of superoxide from cathode to electrolyte leads to the nucleation and growth of NaO2, which follows classical mechanisms based on the variation of superoxide content in the electrolyte and its correlation with the crystallization of cubic NaO2. The changes in superoxide content upon charge show that charge proceeds through the reverse solution process. Furthermore, we identify the carbon-centered/oxygen-centered alkyl radicals arising from attack of these solubilized HO2 species on the diglyme solvent. This is the first direct evidence of such species, which are likely responsible for electrolyte degradation.

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.

Effect of Molecular Interactions on Electron-Transfer and Antioxidant Activity of Bis(alkanol)selenides: A Radiation Chemical Study.

PubMed

Kumar, Pavitra V; Singh, Beena G; Phadnis, Prasad P; Jain, Vimal K; Priyadarsini, K Indira

2016-08-16

Understanding electron-transfer processes is crucial for developing organoselenium compounds as antioxidants and anti-inflammatory agents. To find new redox-active selenium antioxidants, we have investigated one-electron-transfer reactions between hydroxyl ((.) OH) radical and three bis(alkanol)selenides (SeROH) of varying alkyl chain length, using nanosecond pulse radiolysis. (.) OH radical reacts with SeROH to form radical adduct, which is converted primarily into a dimer radical cation (>Se∴Se<)(+) and α-{bis(hydroxyl alkyl)}-selenomethine radical along with a minor quantity of an intramolecularly stabilized radical cation. Some of these radicals have been subsequently converted to their corresponding selenoxide, and formaldehyde. Estimated yield of these products showed alkyl chain length dependency and correlated well with their antioxidant ability. Quantum chemical calculations suggested that compounds that formed more stable (>Se∴Se<)(+) , produced higher selenoxide and lower formaldehyde. Comparing these results with those for sulfur analogues confirmed for the first time the distinctive role of selenium in making such compounds better antioxidants. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The clinical pharmacology of alkylating agents in high-dose chemotherapy.

PubMed

Huitema, A D; Smits, K D; Mathôt, R A; Schellens, J H; Rodenhuis, S; Beijnen, J H

2000-08-01

Alkylating agents are widely used in high-dose chemotherapy regimens in combination with hematological support. Knowledge about the pharmacokinetics and pharmacodynamics of these agents administered in high doses is critical for the safe and efficient use of these regimens. The aim of this review is to summarize the clinical pharmacology of the alkylating agents (including the platinum compounds) in high-dose chemotherapy. Differences between conventional and high doses will be discussed.

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.

N-Alkyl-PEI Functional Iron Oxide Nanocluster for Efficient siRNA Delivery**

PubMed Central

Liu, Gang; Xie, Jin; Zhang, Fan; Wang, Zhi-Yong; Luo, Kui; Zhu, Lei; Quan, Qi-Meng; Niu, Gang; Lee, Seulki

2013-01-01

Small interfering RNA (siRNA) is an emerging class of therapeutics, working by regulating the expression of a specific gene involved in disease progression. Despite the promises, effective transport of siRNA with minimal side effects remains a challenge. In this study, a non-viral nanoparticle gene carrier has been developed and its efficiency for siRNA delivery and transfection has been validated at both in vitro and in vivo levels. Such a nanocarrier, abbreviated as Alkyl-PEI2k-IO, was constructed with a core of iron oxide (IO) and a shell of alkylated PEI2000 (Alkyl-PEI2k). It was found to be able to bind with siRNA, resulting in well-dispersed nanoparticles with a controlled clustering structure and narrow size distribution. Electrophoresis studies showed that the Alkyl-PEI2k-IOs could retard siRNA completely at N/P ratios above 10, protect siRNA from enzymatic degradation in serum and release complexed siRNA efficiently in the presence of polyanionic heparin. The knockdown efficiency of the siRNA loaded nanocarriers was assessed with 4T1 cells stably expressing luciferase (fluc-4T1) and further, with a fluc-4T1 xenograft model. Significant downregulation of luciferase was observed, and unlike the high molecular weight analogs, the Alkyl-PEI2k coated IOs showed a good biocompatibility. In conclusion, Alkyl-PEI2k-IOs demonstrate highly efficient delivery of siRNA and an innocuous toxic profile, making it a potential carrier for gene therapy. PMID:21861295

Formation of furan fatty alkyl esters from their bis-epoxide fatty esters

USDA-ARS?s Scientific Manuscript database

Reactions of epoxidized alkyl soyate with four different alcohols: ethanol, isopropyl alcohol, 2-ethylhexanol, and benzyl alcohol were investigated in the presence of Bronsted acid catalyst. Products not reported in prior studies of similar reactions were found. These were furan fatty acid alkyl est...

[Lavoisier and radicals].

PubMed

Lafont, Olivier

2007-01-01

Lavoisier and his co-workers (Guyton de Morveau, Bertholet, Fourcroy) considered that acids were constituted of oxygen and of something else that they called radicals. These radicals were known in some cases, i.e. nitrogen for nitrous acid, carbon for carbonic acid, phosphorus for phosphoric acid. In the case of sulfur, the sulfuric radical could be associated with different quantities of oxigen leading to sulfuric or sulfurous acids. In other cases radicals remained unknown at the time i.e. muriatic radical for muriatic acid, or benzoyl radical for benzoic acid. It is interesting to notice that Lavoisier evoked the case of compound radicals constituted of different substances such as carbon and hydrogen.

In vitro induction of micronuclei by monofunctional methanesulphonic acid esters: possible role of alkylation mechanisms.

PubMed

Eder, Erwin; Kütt, Wolfgang; Deininger, Christoph

2006-12-01

Six monofunctional alkylating methanesulphonates of widely varying structures were investigated in the in vitro micronucleus assay with Syrian hamster embryo fibroblast cells. The results were compared with the alkylating activities measured in the 4-(nitrobenzyl)pyridine test (NBP-test) and the N-methyl mercaptoimidazole (MMI-test) as measures for S(N)2 reactivity as well as in the triflouoroacetic acid (TFA) solvolysis and the hydrolysis reaction as measures for S(N)1 reactivity in order to provide insights into the role of alkylation mechanisms on induction of micronuclei. Moreover we compared the results of micronucleus assay with those of the Ames tests in strain TA 100 and TA1535 and with those of the SOS chromotest with the strains PQ37, PQ243, PM21 and GC 4798. The potency of methanesulphonates to induce micronuclei depended only to a certain degree, on the total alkylating activity (S(N)1 and S(N)2 reactivity). An inverse, significant correlation between the Ames test and the micronucleus assay was observed and an inverse correlation between the micronucleus assay and the SOS chromotest with the different strains. The results indicate that the primary mechanism leading to induction of micronuclei is not O-alkylation in DNA as it is the case in the Ames test with the hisG46 strains TA1535 and TA100 and not N-alkylation as with the SOS chromotest. There is evidence that protein alkylation, e.g. in the spindle apparatus in mitosis is decisive for induction of micronuclei by alkylating compounds. The structurally voluminous methanesulphonates 2-phenyl ethyl methanesulphonate and 1-phenyl-2-propyl methanesulphonate show a clear higher micronuclei inducing potency than the other tested though the bulky methanesulphonates possess a lower total alkylating activity than the others. This effect can be explained by a higher disturbance during mitosis after alkylation of the spindle apparatus with the structurally more bulky methanesulphonates.

Chemotherapy-induced pulmonary hypertension: role of alkylating agents.

PubMed

Ranchoux, Benoît; Günther, Sven; Quarck, Rozenn; Chaumais, Marie-Camille; Dorfmüller, Peter; Antigny, Fabrice; Dumas, Sébastien J; Raymond, Nicolas; Lau, Edmund; Savale, Laurent; Jaïs, Xavier; Sitbon, Olivier; Simonneau, Gérald; Stenmark, Kurt; Cohen-Kaminsky, Sylvia; Humbert, Marc; Montani, David; Perros, Frédéric

2015-02-01

Pulmonary veno-occlusive disease (PVOD) is an uncommon form of pulmonary hypertension (PH) characterized by progressive obstruction of small pulmonary veins and a dismal prognosis. Limited case series have reported a possible association between different chemotherapeutic agents and PVOD. We evaluated the relationship between chemotherapeutic agents and PVOD. Cases of chemotherapy-induced PVOD from the French PH network and literature were reviewed. Consequences of chemotherapy exposure on the pulmonary vasculature and hemodynamics were investigated in three different animal models (mouse, rat, and rabbit). Thirty-seven cases of chemotherapy-associated PVOD were identified in the French PH network and systematic literature analysis. Exposure to alkylating agents was observed in 83.8% of cases, mostly represented by cyclophosphamide (43.2%). In three different animal models, cyclophosphamide was able to induce PH on the basis of hemodynamic, morphological, and biological parameters. In these models, histopathological assessment confirmed significant pulmonary venous involvement highly suggestive of PVOD. Together, clinical data and animal models demonstrated a plausible cause-effect relationship between alkylating agents and PVOD. Clinicians should be aware of this uncommon, but severe, pulmonary vascular complication of alkylating agents. Copyright © 2015 American Society for Investigative Pathology. Published by Elsevier Inc. All rights reserved.

Pilot study of radical hysterectomy versus radical trachelectomy on sexual distress.

PubMed

Brotto, Lori A; Smith, Kelly B; Breckon, Erin; Plante, Marie

2013-01-01

Radical trachelectomy, which leaves the uterus intact, has emerged as a desirable surgical option for eligible women with early-stage cervical cancer who wish to preserve fertility. The available data suggest excellent obstetrical outcomes with radical trachelectomy, and no differences in sexual responding between radical trachelectomy and radical hysterectomy. There is a need to examine the effect of radical hysterectomy on sexual distress given that it is distinct from sexual function. Participants were 34 women diagnosed with early-stage cervical cancer. The authors report 1-month postsurgery data for 29 women (radical hysterectomy group: n = 17, M age = 41.8 years; radical trachelectomy group: n = 12, M age = 31.8 years), and 6-month follow-up data on 26 women. Whereas both groups experienced an increase in sex-related distress immediately after surgery, distress continued to increase 6 months after surgery for the radical hysterectomy group but decreased in the radical trachelectomy group. There were no between-group differences in mood, anxiety, or general measures of health. The decrease in sex-related distress in the radical trachelectomy but not in the radical hysterectomy group suggests that the preservation of fertility may have attenuated sex-related distress. Care providers should counsel women exploring surgical options for cervical cancer about potential sex distress-related sequelae.

40 CFR 721.10145 - Modified reaction products of alkyl alcohol, halogenated alkane, substituted epoxide, and amino...

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Modified reaction products of alkyl... Modified reaction products of alkyl alcohol, halogenated alkane, substituted epoxide, and amino compound... identified generically as modified reaction products of alkyl alcohol, halogenated alkane, substituted...

40 CFR 721.10145 - Modified reaction products of alkyl alcohol, halogenated alkane, substituted epoxide, and amino...

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Modified reaction products of alkyl... Modified reaction products of alkyl alcohol, halogenated alkane, substituted epoxide, and amino compound... identified generically as modified reaction products of alkyl alcohol, halogenated alkane, substituted...

Catalytic enantioselective synthesis of atropisomeric biaryls by a cation-directed O-alkylation

NASA Astrophysics Data System (ADS)

Jolliffe, John D.; Armstrong, Roly J.; Smith, Martin D.

2017-06-01

Axially chiral biaryls, as exemplified by 1,1‧-bi-2-naphthol (BINOL), are key components of catalysts, natural products and medicines. These materials are synthesized conventionally in enantioenriched form through metal-mediated cross coupling, de novo construction of an aromatic ring, point-to-axial chirality transfer or an atropselective transformation of an existing biaryl. Here, we report a highly enantioselective organocatalytic method for the synthesis of atropisomeric biaryls by a cation-directed O-alkylation. Treatment of racemic 1-aryl-2-tetralones with a chiral quinidine-derived ammonium salt under basic conditions in the presence of an alkylating agent leads to atropselective O-alkylation with e.r. up to 98:2. Oxidation with DDQ gives access to C2-symmetric and non-symmetric BINOL derivatives without compromising e.r. We propose that the chiral ammonium counterion differentiates between rapidly equilibrating atropisomeric enolates, leading to highly atropselective O-alkylation. This dynamic kinetic resolution process offers a general approach to the synthesis of enantioenriched atropisomeric materials.

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.

21 CFR 176.120 - Alkyl ketene dimers.

Code of Federal Regulations, 2010 CFR

2010-04-01

..., processing, preparing, treating, packaging, transporting, or holding food, subject to the provisions of this... paperboard. (c) The alkyl ketene dimers may be used in the form of an aqueous emulsion which may contain...

Isoprene photochemistry over the Amazon rainforest

DOE PAGES

Liu, Yingjun; Brito, Joel; Dorris, Matthew R.; ...

2016-05-31

Isoprene photooxidation is a major driver of atmospheric chemistry over forested regions. Isoprene reacts with hydroxyl radicals (OH) and molecular oxygen to produce isoprene peroxy radicals (ISOPOO). These radicals can react with hydroperoxyl radicals (HO 2) to dominantly produce hydroxyhydroperoxides (ISOPOOH). They can also react with nitric oxide (NO) to largely produce methyl vinyl ketone (MVK) and methacrolein (MACR). Unimolecular isomerization and bimolecular reactions with organic peroxy radicals are also possible. There is uncertainty about the relative importance of each of these pathways in the atmosphere and possible changes because of anthropogenic pollution. Herein, measurements of ISOPOOH and MVK +more » MACR concentrations are reported over the central region of the Amazon basin during the wet season. The research site, downwind of an urban region, intercepted both background and polluted air masses during the GoAmazon2014/5 Experiment. Under background conditions, the confidence interval for the ratio of the ISOPOOH concentration to that of MVK + MACR spanned 0.4–0.6. This result implies a ratio of the reaction rate of ISOPOO with HO2 to that with NO of approximately unity. Also, a value of unity is significantly smaller than simulated at present by global chemical transport models for this important, nominally low-NO, forested region of Earth. Under polluted conditions, when the concentrations of reactive nitrogen compounds were high (>1 ppb), ISOPOOH concentrations dropped below the instrumental detection limit (<60 ppt). In conclusion, this abrupt shift in isoprene photooxidation, sparked by human activities, speaks to ongoing and possible future changes in the photochemistry active over the Amazon rainforest.« less

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

Liu, Yingjun; Brito, Joel; Dorris, Matthew R.

Isoprene photooxidation is a major driver of atmospheric chemistry over forested regions. Isoprene reacts with hydroxyl radicals (OH) and molecular oxygen to produce isoprene peroxy radicals (ISOPOO). These radicals can react with hydroperoxyl radicals (HO 2) to dominantly produce hydroxyhydroperoxides (ISOPOOH). They can also react with nitric oxide (NO) to largely produce methyl vinyl ketone (MVK) and methacrolein (MACR). Unimolecular isomerization and bimolecular reactions with organic peroxy radicals are also possible. There is uncertainty about the relative importance of each of these pathways in the atmosphere and possible changes because of anthropogenic pollution. Herein, measurements of ISOPOOH and MVK +more » MACR concentrations are reported over the central region of the Amazon basin during the wet season. The research site, downwind of an urban region, intercepted both background and polluted air masses during the GoAmazon2014/5 Experiment. Under background conditions, the confidence interval for the ratio of the ISOPOOH concentration to that of MVK + MACR spanned 0.4–0.6. This result implies a ratio of the reaction rate of ISOPOO with HO2 to that with NO of approximately unity. Also, a value of unity is significantly smaller than simulated at present by global chemical transport models for this important, nominally low-NO, forested region of Earth. Under polluted conditions, when the concentrations of reactive nitrogen compounds were high (>1 ppb), ISOPOOH concentrations dropped below the instrumental detection limit (<60 ppt). In conclusion, this abrupt shift in isoprene photooxidation, sparked by human activities, speaks to ongoing and possible future changes in the photochemistry active over the Amazon rainforest.« less

Enantioconvergent Cross-Couplings of Racemic Alkylmetal Reagents with Unactivated Secondary Alkyl Electrophiles: Catalytic Asymmetric Negishi α-Alkylations of N-Boc-pyrrolidine

PubMed Central

Cordier, Christopher J.; Lundgren, Rylan J.; Fu, Gregory C.

2013-01-01

Although enantioconvergent alkyl-alkyl couplings of racemic electrophiles have been developed, there have been no reports of the corresponding reactions of racemic nucleophiles. Herein, we describe Negishi cross-couplings of racemic α-zincated N-Boc-pyrrolidine with unactivated secondary halides, thus providing a one-pot, catalytic asymmetric method for the synthesis of a range of 2-alkylpyrrolidines (an important family of target molecules) from N-Boc-pyrrolidine, a commercially available precursor. Preliminary mechanistic studies indicate that two of the most straightforward mechanisms for enantioconvergence (a dynamic kinetic resolution of the organometallic coupling partner and a simple β-hydride elimination/β-migratory insertion pathway) are unlikely to be operative. PMID:23869442

46 CFR 151.50-86 - Alkyl (C7-C9) nitrates.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 46 Shipping 5 2011-10-01 2011-10-01 false Alkyl (C7-C9) nitrates. 151.50-86 Section 151.50-86... CARRYING BULK LIQUID HAZARDOUS MATERIAL CARGOES Special Requirements § 151.50-86 Alkyl (C7-C9) nitrates. (a) The carriage temperature of octyl nitrates must be maintained below 100 °C (212 °F) in order to...

46 CFR 151.50-86 - Alkyl (C7-C9) nitrates.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 46 Shipping 5 2014-10-01 2014-10-01 false Alkyl (C7-C9) nitrates. 151.50-86 Section 151.50-86... CARRYING BULK LIQUID HAZARDOUS MATERIAL CARGOES Special Requirements § 151.50-86 Alkyl (C7-C9) nitrates. (a) The carriage temperature of octyl nitrates must be maintained below 100 °C (212 °F) in order to...

46 CFR 151.50-86 - Alkyl (C7-C9) nitrates.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 46 Shipping 5 2012-10-01 2012-10-01 false Alkyl (C7-C9) nitrates. 151.50-86 Section 151.50-86... CARRYING BULK LIQUID HAZARDOUS MATERIAL CARGOES Special Requirements § 151.50-86 Alkyl (C7-C9) nitrates. (a) The carriage temperature of octyl nitrates must be maintained below 100 °C (212 °F) in order to...

46 CFR 151.50-86 - Alkyl (C7-C9) nitrates.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 46 Shipping 5 2013-10-01 2013-10-01 false Alkyl (C7-C9) nitrates. 151.50-86 Section 151.50-86... CARRYING BULK LIQUID HAZARDOUS MATERIAL CARGOES Special Requirements § 151.50-86 Alkyl (C7-C9) nitrates. (a) The carriage temperature of octyl nitrates must be maintained below 100 °C (212 °F) in order to...

46 CFR 151.50-86 - Alkyl (C7-C9) nitrates.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 46 Shipping 5 2010-10-01 2010-10-01 false Alkyl (C7-C9) nitrates. 151.50-86 Section 151.50-86... CARRYING BULK LIQUID HAZARDOUS MATERIAL CARGOES Special Requirements § 151.50-86 Alkyl (C7-C9) nitrates. (a) The carriage temperature of octyl nitrates must be maintained below 100 °C (212 °F) in order to...

40 CFR 721.10417 - Biphenyl alkyl morpholino ketone (generic) (P-11-338).

Code of Federal Regulations, 2014 CFR

2014-07-01

... (generic) (P-11-338). 721.10417 Section 721.10417 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Specific Chemical Substances § 721.10417 Biphenyl alkyl morpholino ketone (generic) (P-11-338). (a... generically as biphenyl alkyl morpholino ketone (PMN P-11-338) is subject to reporting under this section for...

40 CFR 721.10417 - Biphenyl alkyl morpholino ketone (generic) (P-11-338).

Code of Federal Regulations, 2013 CFR

2013-07-01

... (generic) (P-11-338). 721.10417 Section 721.10417 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Specific Chemical Substances § 721.10417 Biphenyl alkyl morpholino ketone (generic) (P-11-338). (a... generically as biphenyl alkyl morpholino ketone (PMN P-11-338) is subject to reporting under this section for...

40 CFR 721.10417 - Biphenyl alkyl morpholino ketone (generic) (P-11-338).

Code of Federal Regulations, 2012 CFR

2012-07-01

... (generic) (P-11-338). 721.10417 Section 721.10417 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Specific Chemical Substances § 721.10417 Biphenyl alkyl morpholino ketone (generic) (P-11-338). (a... generically as biphenyl alkyl morpholino ketone (PMN P-11-338) is subject to reporting under this section for...

Spatially-dependent alkyl quinolone signaling responses to antibiotics in Pseudomonas aeruginosa swarms.

PubMed

Morales-Soto, Nydia; Dunham, Sage J B; Baig, Nameera F; Ellis, Joseph F; Madukoma, Chinedu S; Bohn, Paul W; Sweedler, Jonathan V; Shrout, Joshua D

2018-03-27

There is a general lack of understanding about how communities of bacteria respond to exogenous toxins such as antibiotics. Most of our understanding of community-level stress responses comes from the study of stationary biofilm communities. Although several community behaviors and production of specific biomolecules affecting biofilm development and associated behavior have been described for Pseudomonas aeruginosa and other bacteria, we have little appreciation for the production and dispersal of secreted metabolites within the 2D and 3D spaces they occupy as they colonize, spread, and grow on surfaces. Here we specifically studied the phenotypic responses and spatial variability of alkyl quinolones, including the Pseudomonas quinolone signal (PQS) and members of the alkyl hydroxyquinoline (AQNO) subclass, in P. aeruginosa plate-assay swarming communities. We found that PQS production was not a universal signaling response to antibiotics as tobramycin elicited an alkyl quinolone response while carbenicillin did not. We also found that PQS and AQNO profiles in response to tobramycin were markedly distinct and influenced these swarms on different spatial scales. The distribution of alkyl quinolones varied by several orders of magnitude within the same swarm. At some tobramycin exposures, P. aeruginosa swarms produced alkyl quinolones in the range of 150 µM PQS and 400 µM AQNO that accumulated as aggregates. Our collective findings show that the distribution of alkyl quinolones can vary by several orders of magnitude within the same swarming community.  More notably, our results suggest that multiple intercellular signals acting on different spatial scales can be triggered by one common cue. Published under license by The American Society for Biochemistry and Molecular Biology, Inc.

EPR investigation of gamma irradiated single crystal guaifenesin: A combined experimental and computational study

NASA Astrophysics Data System (ADS)

Tasdemir, Halil Ugur; Sayin, Ulku; Türkkan, Ercan; Ozmen, Ayhan

2016-04-01

Gamma irradiated single crystal of Guaifenesin (Glyceryl Guaiacolate), an important expectorant drug, were investigated with Electron Paramagnetic Resonance (EPR) spectroscopy between 123 and 333 K temperature at different orientations in the magnetic field. Considering the chemical structure and the experimental spectra of the gamma irradiated single crystal of guaifenesin sample, we assumed that alkoxy or alkyl-type paramagnetic species may be produced by irradiation. Depending on this assumption, eight possible alkoxy and alkyl-type radicals were modeled and EPR parameters of these modeled radicals were calculated using the B3LYP/6-311++G(d,p)-level of density functional theory (DFT). Theoretically calculated values of alkyl-type modeled radical(R3) are in good agreement with experimentally determined EPR parameters of single crystal. Furthermore, simulation spectra which are obtained by using the theoretical initial values are well matched with the experimental spectra. It was determined that a stable Cα •H2αCβHβCγH2γ (R3) alkyl radical was produced in the host crystal as a result of gamma irradiation.

Endocrine disrupting potential of PAHs and their alkylated analogues associated with oil spills.

PubMed

Lee, Sangwoo; Hong, Seongjin; Liu, Xiaoshan; Kim, Cheolmin; Jung, Dawoon; Yim, Un Hyuk; Shim, Won Joon; Khim, Jong Seong; Giesy, John P; Choi, Kyungho

2017-09-20

Polycyclic aromatic hydrocarbons (PAHs) and alkylated PAHs are known to be major toxic contaminants in spills of petroleum hydrocarbons (oil). Spilled oil undergoes weathering and over time, PAHs go through a series of compositional changes. PAHs can disrupt endocrine functions, and the type of functions affected and associated potencies vary with the type and alkylation status of PAH. In this study, the potential of five major PAHs of crude oil, i.e., naphthalene, fluorene, dibenzothiophene, phenanthrene, and chrysene, and their alkylated analogues (n = 25), to disrupt endocrine functions was evaluated by use of MVLN-luc and H295R cell lines. In the MVLN-luc bioassay, seven estrogen receptor (ER) agonists were detected among 30 tested PAHs. The greatest ER-mediated potency was observed for 1-methylchrysene (101.4%), followed by phenanthrene and its alkylated analogues (range of %-E2max from 1.6% to 47.3%). In the H295R bioassay, significantly greater syntheses of steroid hormones were observed for 20 PAHs. For major PAHs and their alkylated analogues, disruption of steroidogenesis appeared to be more significant than ER-mediated effects. The number and locations of alkyl-moieties alone could not explain differences in the types or the potencies of toxicities. This observation shows that disruption of endocrine functions by some constituents of oil spills could be underestimated if only parent compounds are considered in assessments of hazard and risk.

'Petite' mutagenesis and mitotic crossing-over in yeast by DNA-targeted alkylating agents.

PubMed

Ferguson, L R; Turner, P M; Gourdie, T A; Valu, K K; Denny, W A

1989-12-01

Although the biological properties (cytotoxicity, mutagenicity and carcinogenicity) of alkylating agents result from their bonding interactions with DNA, such compounds generally do not show any special binding affinity for DNA. A series of acridine-linked aniline mustards of widely-varying alkylator reactivity have been designed as DNA-directed alkylating agents. We have considered whether such DNA targeting has an effect on mutagenic properties by evaluating this series of drugs in comparison with their untargeted counterparts for toxic, recombinogenic and mutagenic properties in Saccharomyces cerevisiae strain D5. The simple untargeted aniline mustards are effective inducers of mitotic crossing-over in this strain, but resemble other reported alkylators in being rather inefficient inducers of the "petite" or mitochondrial mutation in yeast. However, the majority of the DNA-targeted mustards were very efficient petite mutagens, while showing little evidence of mitotic crossing-over or other nuclear events. The 100% conversion of cells into petites and the lack of a differential between growing and non-growing cells are similar to the effects of the well characterised mitochondrial mutagen ethidium bromide. These data suggest very different modes of action between the DNA-targeted alkylators and their non-targeted counterparts.

Practical Alkoxythiocarbonyl Auxiliaries for Iridium(I)-Catalyzed C-H Alkylation of Azacycles.

PubMed

Tran, Anh T; Yu, Jin-Quan

2017-08-21

The development of new and practical 3-pentoxythiocarbonyl auxiliaries for Ir I -catalyzed C-H alkylation of azacycles is described. This method allows for the α-C-H alkylation of a variety of substituted pyrrolidines, piperidines, and tetrahydroisoquinolines through alkylation with alkenes. While the practicality of these simple carbamate-type auxiliaries is underscored by the ease of installation and removal, the method's utility is demonstrated in its ability to functionalize biologically relevant l-proline and l-trans-hydroxyproline, delivering unique 2,5-dialkylated amino acid analogues that are not accessible by other C-H functionalization methods. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Alkylation effects on the energy transfer of highly vibrationally excited naphthalene.

PubMed

Hsu, Hsu Chen; Tsai, Ming-Tsang; Dyakov, Yuri A; Ni, Chi-Kung

2011-11-04

The energy transfer of highly vibrationally excited isomers of dimethylnaphthalene and 2-ethylnaphthalene in collisions with krypton were investigated using crossed molecular beam/time-of-flight mass spectrometer/time-sliced velocity map ion imaging techniques at a collision energy of approximately 300 cm(-1). Angular-resolved energy-transfer distribution functions were obtained directly from the images of inelastic scattering. The results show that alkyl-substituted naphthalenes transfer more vibrational energy to translational energy than unsubstituted naphthalene. Alkylation enhances the V→T energy transfer in the range -ΔE(d)=-100~-1500 cm(-1) by approximately a factor of 2. However, the maximum values of V→T energy transfer for alkyl-substituted naphthalenes are about 1500~2000 cm(-1), which is similar to that of naphthalene. The lack of rotation-like wide-angle motion of the aromatic ring and no enhancement in very large V→T energy transfer, like supercollisions, indicates that very large V→T energy transfer requires special vibrational motions. This transfer cannot be achieved by the low-frequency vibrational motions of alkyl groups. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Thermal and UV Hydrosilylation of Alcohol-Based Bifunctional Alkynes on Si (111) surfaces: How surface radicals influence surface bond formation.

PubMed

Khung, Y L; Ngalim, S H; Scaccabarozi, A; Narducci, D

2015-06-12

Using two different hydrosilylation methods, low temperature thermal and UV initiation, silicon (111) hydrogenated surfaces were functionalized in presence of an OH-terminated alkyne, a CF3-terminated alkyne and a mixed equimolar ratio of the two alkynes. XPS studies revealed that in the absence of premeditated surface radical through low temperature hydrosilylation, the surface grafting proceeded to form a Si-O-C linkage via nucleophilic reaction through the OH group of the alkyne. This led to a small increase in surface roughness as well as an increase in hydrophobicity and this effect was attributed to the surficial etching of silicon to form nanosize pores (~1-3 nm) by residual water/oxygen as a result of changes to surface polarity from the grafting. Furthermore in the radical-free thermal environment, a mix in equimolar of these two short alkynes can achieve a high contact angle of ~102°, comparable to long alkyl chains grafting reported in literature although surface roughness was relatively mild (rms = ~1 nm). On the other hand, UV initiation on silicon totally reversed the chemical linkages to predominantly Si-C without further compromising the surface roughness, highlighting the importance of surface radicals determining the reactivity of the silicon surface to the selected alkynes.

Thermal and UV Hydrosilylation of Alcohol-Based Bifunctional Alkynes on Si (111) surfaces: How surface radicals influence surface bond formation

PubMed Central

Khung, Y. L.; Ngalim, S. H.; Scaccabarozi, A.; Narducci, D.

2015-01-01

Using two different hydrosilylation methods, low temperature thermal and UV initiation, silicon (111) hydrogenated surfaces were functionalized in presence of an OH-terminated alkyne, a CF3-terminated alkyne and a mixed equimolar ratio of the two alkynes. XPS studies revealed that in the absence of premeditated surface radical through low temperature hydrosilylation, the surface grafting proceeded to form a Si-O-C linkage via nucleophilic reaction through the OH group of the alkyne. This led to a small increase in surface roughness as well as an increase in hydrophobicity and this effect was attributed to the surficial etching of silicon to form nanosize pores (~1–3 nm) by residual water/oxygen as a result of changes to surface polarity from the grafting. Furthermore in the radical-free thermal environment, a mix in equimolar of these two short alkynes can achieve a high contact angle of ~102°, comparable to long alkyl chains grafting reported in literature although surface roughness was relatively mild (rms = ~1 nm). On the other hand, UV initiation on silicon totally reversed the chemical linkages to predominantly Si-C without further compromising the surface roughness, highlighting the importance of surface radicals determining the reactivity of the silicon surface to the selected alkynes. PMID:26067470

RAIN REPELLENT

DTIC Science & Technology

COATINGS, *RAINDROPS, *SILANES, *ULTRASONIC RADIATION, ACIDS, AEROSOLS, ALKOXY RADICALS, ALKYL RADICALS, CHLORIDES, FILMS, FLUORIDES, GLASS, LIQUIDS...MATERIALS, METHYL RADICALS, MIXTURES, ORGANIC COMPOUNDS, SALTS, STABILITY, STORAGE, SURFACES

DNA Damage Induced by Alkylating Agents and Repair Pathways

PubMed Central

Kondo, Natsuko; Takahashi, Akihisa; Ono, Koji; Ohnishi, Takeo

2010-01-01

The cytotoxic effects of alkylating agents are strongly attenuated by cellular DNA repair processes, necessitating a clear understanding of the repair mechanisms. Simple methylating agents form adducts at N- and O-atoms. N-methylations are removed by base excision repair, AlkB homologues, or nucleotide excision repair (NER). O6-methylguanine (MeG), which can eventually become cytotoxic and mutagenic, is repaired by O6-methylguanine-DNA methyltransferase, and O6MeG:T mispairs are recognized by the mismatch repair system (MMR). MMR cannot repair the O6MeG/T mispairs, which eventually lead to double-strand breaks. Bifunctional alkylating agents form interstrand cross-links (ICLs) which are more complex and highly cytotoxic. ICLs are repaired by complex of NER factors (e.g., endnuclease xeroderma pigmentosum complementation group F-excision repair cross-complementing rodent repair deficiency complementation group 1), Fanconi anemia repair, and homologous recombination. A detailed understanding of how cells cope with DNA damage caused by alkylating agents is therefore potentially useful in clinical medicine. PMID:21113301

Structural Characterization of N-Alkylated Twisted Amides: Consequences for Amide Bond Resonance and N-C Cleavage.

PubMed

Hu, Feng; Lalancette, Roger; Szostak, Michal

2016-04-11

Herein, we describe the first structural characterization of N-alkylated twisted amides prepared directly by N-alkylation of the corresponding non-planar lactams. This study provides the first experimental evidence that N-alkylation results in a dramatic increase of non-planarity around the amide N-C(O) bond. Moreover, we report a rare example of a molecular wire supported by the same amide C=O-Ag bonds. Reactivity studies demonstrate rapid nucleophilic addition to the N-C(O) moiety of N-alkylated amides, indicating the lack of n(N) to π*(C=O) conjugation. Most crucially, we demonstrate that N-alkylation activates the otherwise unreactive amide bond towards σ N-C cleavage by switchable coordination. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

REVISITING CLASSICAL NUCLEOPHILIC SUBSTITUTIONS IN AQUEOUS MEDIUM: MICROWAVE-ASSISTED SYNTHESIS OF ALKYL AZIDES

EPA Science Inventory

An efficient and clean synthesis of alkyl azides using microwave (MW) radiation is described in aqueous medium by reacting alkyl halides or tosylates with alkali azides. This general and expeditious MW-enhanced approach to nucleophilic substitution reactions is applicable to the ...

The [C{sub 6}H{sub 10}]{sup {sm{underscore}bullet}+} hypersurface: The parent radical cation Diels-Alder reaction

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

Hoffmann, M.; Schaefer, H.F. III

1999-07-21

Various possible reaction pathways between ethene and butadiene radical cation (cis- and trans-), have been investigated at different levels of theory up to UCCSD(T)/DZP/UMP2(fc)/DZP and with density functional theory at B3LYP/DZP. A stepwise addition involving open chain intermediates and leading to the Diels-Alder product, the cyclohexene radical cation, was found to have a total activation barrier {Delta}G{sup 298{ne}} = 6.3 kcal mol{sup {minus}1} and a change in free Gibbs energy, {Delta}G{sup 298}, of {minus}33.5 kcal mol{sup {minus}1}. On the E{degree} potential energy surface, all transition states are lower in energy than separated ethene and butadiene, the exothermicity {Delta}E = -45.6more » kcal mol{sup {minus}1}. A more direct path could be characterized as stepwise with one intermediate only at the SCF level but not at electron-correlated levels and hence might actually be a concerted strongly asynchronous addition with a very small or no activation barrier (UCCSD(T)/DZP/UHF/6-31G* gives a {Delta}G{sup 298{ne}} of 0.8 kcal mol{sup {minus}1}). The critical step for another alternative, the cyclobutanation-vinylcyclobutane/cyclohexene rearrangement, is a 1,3-alkyl shift which involves a barrier ({Delta}G{sup 298{ne}}) only 1.7 kcal mol{sup {minus}1} higher than that of stop use addition for both cis-, and trans-butadiene radical cation. However, from the (ethene and trans-butadiene) reactions, ring expansion of the vinylcyclobutane radical cation intermediate, to a methylene cyclopentane radical cation, requires an activation only 1.3 kcal mol{sup {minus}1} larger than for (trans-butadiene radical). While cis/trans isomerization of free butadiene radical cation requires a high activation (24.9 kcal mol{sup {minus}1}), a reaction sequence involving addition of ethene (to stepwise give an open chain intermediate and vinyl cyclobutane radical cation) has a barrier of only 3.5 kcal mol{sup {minus}1} ({Delta}G{sup 298{ne}}). This sequence also makes ethene

Enhanced Oxidation of Isoprene and Monoterpenes in High and Low NOx Conditions

NASA Astrophysics Data System (ADS)

Tokarek, T. W.; Gilman, J.; Lerner, B. M.; Koss, A.; Yuan, B.; Taha, Y. M.; Osthoff, H. D.; Warneke, C.; De Gouw, J. A.

2015-12-01

In the troposphere, the photochemical oxidation of volatile organic compounds (VOCs) is primarily initiated by their reactions with the hydroxyl radical (OH) which yields peroxy radicals (HO2 and RO2). Concentrations of OH and the rates of VOC oxidation depend on the efficiency of peroxy radical recycling to OH. Radical recycling mainly occurs through reaction of HO2 with NO to produce NO2 and, ultimately, ozone (O3). Hence, the rate of VOC oxidation is dependent on NOx (=NO+NO2) concentration. The Shale Oil and Natural Gas Nexus (SONGNEX) campaign was conducted from March 17 to April 29, 2015 with the main goal of identifying and quantifying industrial sources of pollutants throughout the United States, in particular those associated with the production of oil and natural gas. In this work, a case study of biogenic VOC oxidation within and outside a power plant plume in the Haynesville basin near the border of Texas and Louisiana is presented. Isoprene, monoterpenes and their oxides were measured by H3O+ chemical ionization mass spectrometry (H3O+ CIMS) in high time resolution (1 s). Further, an improved Whole Air Sampler (iWAS) was used to collect samples for post-flight analysis by gas chromatography mass spectrometric detection (GC-MS) and yielded speciated quantification of biogenic VOCs. The monoterpene oxide to monoterpene ratio follows the spatial extent of the plume as judged by another tracer (NOx), tracking the enhancement of oxidation rates by NOx. The observations are rationalized with the aid of box modeling using the Master Chemical Mechanism (MCM).

The high-temperature oxidation of aromatic hydrocarbons

NASA Technical Reports Server (NTRS)

Brezinsky, K.

1986-01-01

Chemical mechanisms of the atmospheric pressure, high-temperature (875-1500 K) gas-phase oxidation of benzene, toluene, ethylbenzene, and propylbenzene are described and discussed. Oxidation trends evident from turbulent flow reactor experiments serve as the basis for the mechanisms of the oxidation of benzene and alkylated aromatics. The potential effects of very high temperatures and pressures on the chemistry of oxidation of aromatics are described. The oxidation of benzene and phenyl radical has been found to proceed in a stepwise C6-C5-C4 sequence. Species profiles obtained from flow-reactor experiments suggest that the oxidation of benzene and phenyl radical follows the generalized route via phenoxy, cyclopentadienyl and butadienyl radical. The oxidation of the C4 species branches into multiple pathways that yield copious amounts of ethylene and acetylene. Certain major trends are evident: the alkylated aromatics on initial attack either form styrene, benzyl radical or benzene. The styrene reacts further to produce a benzyl radical or benzene. The oxidation of an alkylated aromatic hydrocarbon appears eventually to reduce to the oxidation of either phenyl radical or benzene.

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.

Lithiated imines: solvent-dependent aggregate structures and mechanisms of alkylation.

PubMed

Zuend, Stephan J; Ramirez, Antonio; Lobkovsky, Emil; Collum, David B

2006-05-03

We describe efforts to understand the structure and reactivity of lithiated cyclohexanone N-cyclohexylimine. The lithioimine affords complex solvent-dependent distributions of monomers, dimers, and trimers in a number of ethereal solvents. Careful selection of solvent provides exclusively monosolvated dimers. Rate studies on the C-alkylations reveal chronic mixtures of monomer- and dimer-based pathways. We explore the factors influencing reactants and alkylation transition structures and the marked differences between lithioimines and isostructural lithium dialkylamides with the aid of density functional theory calculations.

40 CFR 721.950 - Sodium salt of an alkylated, sulfonated aromatic (generic name).

Code of Federal Regulations, 2010 CFR

2010-07-01

..., sulfonated aromatic (generic name). 721.950 Section 721.950 Protection of Environment ENVIRONMENTAL... Significant New Uses for Specific Chemical Substances § 721.950 Sodium salt of an alkylated, sulfonated... chemical substance identified generically as a sodium salt of an alkylated, sulfonated aromatic (PMN P-84...

40 CFR 721.950 - Sodium salt of an alkylated, sulfonated aromatic (generic name).

Code of Federal Regulations, 2011 CFR

2011-07-01

..., sulfonated aromatic (generic name). 721.950 Section 721.950 Protection of Environment ENVIRONMENTAL... Significant New Uses for Specific Chemical Substances § 721.950 Sodium salt of an alkylated, sulfonated... chemical substance identified generically as a sodium salt of an alkylated, sulfonated aromatic (PMN P-84...

Comparison of the reactivity of alkyl and alkyl amine precursors with native oxide GaAs(100) and InAs(100) surfaces

NASA Astrophysics Data System (ADS)

Henegar, A. J., , Dr.; Gougousi, T., , Prof.

2016-12-01

In this manuscript we compare the interaction of alkyl (trimethyl aluminum) and alkyl amine (tetrakis dimethylamino titanium) precursors during thermal atomic layer deposition with III-V native oxides. For that purpose we deposit Al2O3 and TiO2, using H2O as the oxidizer, on GaAs(100) and InAs(100) native oxide surfaces. We find that there are distinct differences in the behavior of the two films. For the Al2O3 ALD very little native oxide removal happens after the first few ALD cycles while the interaction of the alkyl amine precursor for TiO2 and the native oxides continues well after the surface has been covered with 2 nm of TiO2. This difference is traced to the superior properties of Al2O3 as a diffusion barrier. Differences are also found in the behavior of the arsenic oxides of the InAs and GaAs substrates. The arsenic oxides from the InAs surface are found to mix more efficiently in the growing dielectric film than those from the GaAs surface. This difference is attributed to lower native oxide stability as well as an initial diffusion path formation by the indium oxides.

Lanthanide alkyl and silyl compounds: Synthesis, reactivity and catalysts for green

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

Pindwal, Aradhana

2016-01-01

The last few decades have witnessed enormous research in the field of organometallic lanthanide chemistry. Our research group has developed a few rare earth alkyl compounds containing tris(dimethylsilyl)methyl ligand and explored their reactivity. This thesis focusses on extending the study of lanthanide alkyl and silyl compounds to develop strategies for their synthesis and explore their reactivity and role as catalysts in processes such as hydrosilylation and cross-dehydrocoupling.

Expanding Radical SAM Chemistry by Using Radical Addition Reactions and SAM Analogues.

PubMed

Ji, Xinjian; Li, Yongzhen; Xie, Liqi; Lu, Haojie; Ding, Wei; Zhang, Qi

2016-09-19

Radical S-adenosyl-l-methionine (SAM) enzymes utilize a [4Fe-4S] cluster to bind SAM and reductively cleave its carbon-sulfur bond to produce a highly reactive 5'-deoxyadenosyl (dAdo) radical. In almost all cases, the dAdo radical abstracts a hydrogen atom from the substrates or from enzymes, thereby initiating a highly diverse array of reactions. Herein, we report a change of the dAdo radical-based chemistry from hydrogen abstraction to radical addition in the reaction of the radical SAM enzyme NosL. This change was achieved by using a substrate analogue containing an olefin moiety. We also showed that two SAM analogues containing different nucleoside functionalities initiate the radical-based reactions with high efficiencies. The radical adduct with the olefin produced in the reaction was found to undergo two divergent reactions, and the mechanistic insights into this process were investigated in detail. Our study demonstrates a promising strategy in expanding radical SAM chemistry, providing an effective way to access nucleoside-containing compounds by using radical SAM-dependent reactions. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Binding of alkylphenols and alkylated non-phenolics to rainbow trout (Oncorhynchus mykiss) hepatic estrogen receptors.

PubMed

Tollefsen, Knut-Erik; Julie Nilsen, Anja

2008-02-01

Alkylphenols are well-known endocrine disrupters, mediating effects through the estrogen receptor (ER). In the present work, the interaction of alkylphenols and alkylated non-phenolics with hepatic rainbow trout (Oncorhynchus mykiss) estrogen receptors (rtERs) was determined. The role of alkyl chain length and branching, substituent position, number of alkylated groups, and the requirement of a phenolic ring structure was assessed. The results showed that the rtERs bound most alkylphenols, although with 20,000 to 2 million times lower affinity than the endogenous estrogen 17beta-estradiol. Mono-substituted alkylphenols with moderate (C4-C6) and long (C8 and C12) alkyl chain length in the para position exhibited the highest affinity for the rtERs. Substitution with multiple alkyl groups, presence of substituents in the ortho- and meta-position, and lack of a hydroxyl group on the benzene ring reduced the binding affinity. The rtERs resembled the reported binding specificity of the human ER for alkylphenols, although some exceptions were identified.

Antioxidant properties of ferulic acid and its related compounds.

PubMed

Kikuzaki, Hiroe; Hisamoto, Masashi; Hirose, Kanae; Akiyama, Kayo; Taniguchi, Hisaji

2002-03-27

Antioxidant activity of 24 ferulic acid related compounds together with 6 gallic acid related compounds was evaluated using several different physical systems as well as their radical scavenging activity. The radical scavenging activity on 1,1-diphenyl-2-picrylhydrazyl (DPPH) decreased in the order caffeic acid > sinapic acid > ferulic acid > ferulic acid esters > p-coumaric acid. In bulk methyl linoleate, test hydroxycinnamic acids and ferulic acid esters showed antioxidant activity in parallel with their radical scavenging activity. In an ethanol-buffer solution of linoleic acid, the activity of test compounds was not always associated with their radical scavenging activity. Ferulic acid was most effective among the tested phenolic acids. Esterification of ferulic acid resulted in increasing activity. The activity of alkyl ferulates was somewhat influenced by the chain length of alcohol moiety. When the inhibitory effects of alkyl ferulates against oxidation of liposome induced by AAPH were tested, hexyl, octyl, and 2-ethyl-1-hexyl ferulates were more active than the other alkyl ferulates. Furthermore, lauryl gallate is most effective among the tested alkyl gallates. These results indicated that not only the radical scavenging activity of antioxidants, but also their affinity with lipid substrates, might be important factors in their activity.

40 CFR 721.9220 - Reaction products of secondary alkyl amines with a substituted benzenesulfonic acid and sulfuric...

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Reaction products of secondary alkyl... Reaction products of secondary alkyl amines with a substituted benzenesulfonic acid and sulfuric acid... substances identified generically as reaction products of secondary alkyl amines with a substituted...