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Sample records for acid base reaction

  1. Investigating Students' Reasoning about Acid-Base Reactions

    ERIC Educational Resources Information Center

    Cooper, Melanie M.; Kouyoumdjian, Hovig; Underwood, Sonia M.

    2016-01-01

    Acid-base chemistry is central to a wide range of reactions. If students are able to understand how and why acid-base reactions occur, it should provide a basis for reasoning about a host of other reactions. Here, we report the development of a method to characterize student reasoning about acid-base reactions based on their description of…

  2. Acid-base bifunctional catalytic surfaces for nucleophilic addition reactions.

    PubMed

    Motokura, Ken; Tada, Mizuki; Iwasawa, Yasuhiro

    2008-09-01

    This article illustrates the modification of oxide surfaces with organic amine functional groups to create acid-base bifunctional catalysts, summarizing our previous reports and also presenting new data. Immobilization of organic amines as bases on inorganic solid-acid surfaces afforded highly active acid-base bifunctional catalysts, which enabled various organic transformations including C--C coupling reactions, though these reactions did not proceed with either the homogeneous amine precursors or the acidic supports alone. Spectroscopic characterization, such as by solid-state MAS NMR and FTIR, revealed not only the interactions between acidic and basic sites but also bifunctional catalytic reaction mechanisms.

  3. Wang-Landau Reaction Ensemble Method: Simulation of Weak Polyelectrolytes and General Acid-Base Reactions.

    PubMed

    Landsgesell, Jonas; Holm, Christian; Smiatek, Jens

    2017-02-14

    We present a novel method for the study of weak polyelectrolytes and general acid-base reactions in molecular dynamics and Monte Carlo simulations. The approach combines the advantages of the reaction ensemble and the Wang-Landau sampling method. Deprotonation and protonation reactions are simulated explicitly with the help of the reaction ensemble method, while the accurate sampling of the corresponding phase space is achieved by the Wang-Landau approach. The combination of both techniques provides a sufficient statistical accuracy such that meaningful estimates for the density of states and the partition sum can be obtained. With regard to these estimates, several thermodynamic observables like the heat capacity or reaction free energies can be calculated. We demonstrate that the computation times for the calculation of titration curves with a high statistical accuracy can be significantly decreased when compared to the original reaction ensemble method. The applicability of our approach is validated by the study of weak polyelectrolytes and their thermodynamic properties.

  4. Acid-Base Pairs in Lewis Acidic Zeolites Promote Direct Aldol Reactions by Soft Enolization.

    PubMed

    Lewis, Jennifer D; Van de Vyver, Stijn; Román-Leshkov, Yuriy

    2015-08-17

    Hf-, Sn-, and Zr-Beta zeolites catalyze the cross-aldol condensation of aromatic aldehydes with acetone under mild reaction conditions with near quantitative yields. NMR studies with isotopically labeled molecules confirm that acid-base pairs in the Si-O-M framework ensemble promote soft enolization through α-proton abstraction. The Lewis acidic zeolites maintain activity in the presence of water and, unlike traditional base catalysts, in acidic solutions.

  5. A computational study of ultrafast acid dissociation and acid-base neutralization reactions. I. The model

    NASA Astrophysics Data System (ADS)

    Maurer, Patrick; Thomas, Vibin; Rivard, Ugo; Iftimie, Radu

    2010-07-01

    Ultrafast, time-resolved investigations of acid-base neutralization reactions have recently been performed using systems containing the photoacid 8-hydroxypyrene-1,3,6-trisulfonic acid trisodium salt (HPTS) and various Brønsted bases. Two conflicting neutralization mechanisms have been formulated by Mohammed et al. [Science 310, 83 (2005)] and Siwick et al. [J. Am. Chem. Soc. 129, 13412 (2007)] for the same acid-base system. Herein an ab initio molecular dynamics based computational model is formulated, which is able to investigate the validity of the proposed mechanisms in the general context of ground-state acid-base neutralization reactions. Our approach consists of using 2,4,6-tricyanophenol (exp. pKa≅1) as a model for excited-state HPTS∗ (pKa≅1.4) and carboxylate ions for the accepting base. We employ our recently proposed dipole-field/quantum mechanics (QM) treatment [P. Maurer and R. Iftimie, J. Chem. Phys. 132, 074112 (2010)] of the proton donor and acceptor molecules. This approach allows one to tune the free energy of neutralization to any desired value as well as model initial nonequilibrium hydration effects caused by a sudden increase in acidity, making it possible to achieve a more realistic comparison with experimental data than could be obtained via a full-QM treatment of the entire system. It is demonstrated that the dipole-field/QM model reproduces correctly key properties of the 2,4,6-tricyanophenol acid molecule including gas-phase proton dissociation energies and dipole moments, and condensed-phase hydration structure and pKa values.

  6. Students' Understanding of Acid, Base and Salt Reactions in Qualitative Analysis.

    ERIC Educational Resources Information Center

    Tan, Kim-Chwee Daniel; Goh, Ngoh-Khang; Chia, Lian-Sai; Treagust, David F.

    2003-01-01

    Uses a two-tier, multiple-choice diagnostic instrument to determine (n=915) grade 10 students' understanding of the acid, base, and salt reactions involved in basic qualitative analysis. Reports that many students did not understand the formation of precipitates and the complex salts, acid/salt-base reactions, and thermal decomposition involved in…

  7. Proton exchange in acid-base complexes induced by reaction coordinates with heavy atom motions

    NASA Astrophysics Data System (ADS)

    Alavi, Saman; Taghikhani, Mahdi

    2012-06-01

    We extend previous work on nitric acid-ammonia and nitric acid-alkylamine complexes to illustrate that proton exchange reaction coordinates involve the rocking motion of the base moiety in many double hydrogen-bonded gas phase strong acid-strong base complexes. The complexes studied involve the biologically and atmospherically relevant glycine, formic, acetic, propionic, and sulfuric acids with ammonia/alkylamine bases. In these complexes, the magnitude of the imaginary frequencies associated with the proton exchange transition states are <400 cm-1. This contrasts with widely studied proton exchange reactions between symmetric carboxylic acid dimers or asymmetric DNA base pair and their analogs where the reaction coordinate is localized in proton motions and the magnitude of the imaginary frequencies for the transition states are >1100 cm-1. Calculations on complexes of these acids with water are performed for comparison. Variations of normal vibration modes along the reaction coordinate in the complexes are described.

  8. Reaction mechanisms of riboflavin triplet state with nucleic acid bases.

    PubMed

    Lin, Weizhen; Lu, Changyuan; Du, Fuqiang; Shao, Zhiyong; Han, Zhenhui; Tu, Tiecheng; Yao, Side; Lin, Nianyun

    2006-04-01

    ESR and laser flash photolysis studies have determined a reasonable order of reactivity of nucleotides with triplet riboflavin (3Rb*) for the first time. ESR detection of triplet state reactivity of Rb with nucleoside, polynucleotide and DNA has been obtained simultaneously. In addition, ESR spin elimination measurement of the reactivity of 3Rb* with nucleotides in good accord with laser flash photolysis determination of the corresponding rate constants offers a simple and reliable method to detect the reactivities of nucleic acids and its components with photoexcited flavins. Kinetic, ESR and thermodynamic studies have demonstrated that Rb should be a strong endogenous photosensitizer capable of oxidizing all nucleic acid bases, and preferentially two purine nucleotides with high rate constants.

  9. Ultrasonic and densimetric titration applied for acid-base reactions.

    PubMed

    Burakowski, Andrzej; Gliński, Jacek

    2014-01-01

    Classical acoustic acid-base titration was monitored using sound speed and density measurements. Plots of these parameters, as well as of the adiabatic compressibility coefficient calculated from them, exhibit changes with the volume of added titrant. Compressibility changes can be explained and quantitatively predicted theoretically in terms of Pasynski theory of non-compressible hydrates combined with that of the additivity of the hydration numbers with the amount and type of ions and molecules present in solution. It also seems that this development could be applied in chemical engineering for monitoring the course of chemical processes, since the applied experimental methods can be carried out almost independently on the medium under test (harmful, aggressive, etc.).

  10. Envisioning an enzymatic Diels-Alder reaction by in situ acid-base catalyzed diene generation.

    PubMed

    Linder, Mats; Johansson, Adam Johannes; Manta, Bianca; Olsson, Philip; Brinck, Tore

    2012-06-07

    We present and evaluate a new and potentially efficient route for enzyme-mediated Diels-Alder reactions, utilizing general acid-base catalysis. The viability of employing the active site of ketosteroid isomerase is demonstrated.

  11. A Comparative Study of French and Turkish Students' Ideas on Acid-Base Reactions

    ERIC Educational Resources Information Center

    Cokelez, Aytekin

    2010-01-01

    The goal of this comparative study was to determine the knowledge that French and Turkish upper secondary-school students (grades 11 and 12) acquire on the concept of acid-base reactions. Following an examination of the relevant curricula and textbooks in the two countries, 528 students answered six written questions about the acid-base concept.…

  12. Weak Acid Ionization Constants and the Determination of Weak Acid-Weak Base Reaction Equilibrium Constants in the General Chemistry Laboratory

    ERIC Educational Resources Information Center

    Nyasulu, Frazier; McMills, Lauren; Barlag, Rebecca

    2013-01-01

    A laboratory to determine the equilibrium constants of weak acid negative weak base reactions is described. The equilibrium constants of component reactions when multiplied together equal the numerical value of the equilibrium constant of the summative reaction. The component reactions are weak acid ionization reactions, weak base hydrolysis…

  13. Acid-Base Chemistry According to Robert Boyle: Chemical Reactions in Words as well as Symbols

    ERIC Educational Resources Information Center

    Goodney, David E.

    2006-01-01

    Examples of acid-base reactions from Robert Boyle's "The Sceptical Chemist" are used to illustrate the rich information content of chemical equations. Boyle required lengthy passages of florid language to describe the same reaction that can be done quite simply with a chemical equation. Reading or hearing the words, however, enriches the student's…

  14. Bifunctional acid base catalyzed reactions in zeolites from the HSAB viewpoint

    NASA Astrophysics Data System (ADS)

    Hemelsoet, K.; Lesthaeghe, D.; Speybroeck, V. Van; Waroquier, M.

    2006-02-01

    The applicability of the hard and soft acids and bases principle is investigated for the interaction of 5T zeolite clusters with probe molecules such as chloromethane, methanol and olefins. The reactions are intermediately hard-hard and, therefore, mainly charge-controlled. This is confirmed by the success of the atomic charges and the electrostatic interaction energy at the acid site as correct descriptors of regio-selectivity and reactivity sequences. Both acid and basic reactive sites can be clearly indicated using frontier orbitals. Moreover, an excellent correlation is found between the activation hardnesses and the energy barriers at the absolute zero.

  15. Thermochemical study of the reactions of acid-base interaction in an aqueous solution of α-aminobutyric acid

    NASA Astrophysics Data System (ADS)

    Lytkin, A. I.; Chernikov, V. V.; Krutova, O. N.; Skvortsov, I. A.; Korchagina, A. S.

    2017-01-01

    The heat effects of the interaction between a solution of α-aminobutyric acid and solutions of HNO3 and KOH are measured by means of calorimetry in different ranges of pH at 298.15 K and values of ionic strength of 0.25, 0.5, and 0.75 (KNO3). The heat effects of the stepwise dissociation of the amino acid are determined. Standard thermodynamic characteristics (Δr H 0, Δr G 0, and Δr S 0) of the reactions of acid-base interaction in aqueous solutions of α-aminobutyric acid are calculated. The connection between the thermodynamic characteristics of the dissociation of the amino acid and the structure of this compound is considered.

  16. Cirrus cloud mimic surfaces in the laboratory: organic acids, bases and NOx heterogeneous reactions

    NASA Astrophysics Data System (ADS)

    Sodeau, J.; Oriordan, B.

    2003-04-01

    CIRRUS CLOUD MIMIC SURFACES IN THE LABORATORY:ORGANIC ACIDS, BASES AND NOX HETEROGENEOUS REACTIONS. B. ORiordan, J. Sodeau Department of Chemistry and Environment Research Institute, University College Cork, Ireland j.sodeau@ucc.ie /Fax: +353-21-4902680 There are a variety of biogenic and anthropogenic sources for the simple carboxylic acids to be found in the troposphere giving rise to levels as high as 45 ppb in certain urban areas. In this regard it is of note that ants of genus Formica produce some 10Tg of formic acid each year; some ten times that produced by industry. The expected sinks are those generally associated with tropospheric chemistry: the major routes studied, to date, being wet and dry deposition. No studies have been carried out hitherto on the role of water-ice surfaces in the atmospheric chemistry of carboxylic acids and the purpose of this paper is to indicate their potential function in the heterogeneous release of atmospheric species such as HONO. The deposition of formic acid on a water-ice surface was studied using FT-RAIR spectroscopy over a range of temperatures between 100 and 165K. In all cases ionization to the formate (and oxonium) ions was observed. The results were confirmed by TPD (Temperature Programmed Desorption) measurements, which indicated that two distinct surface species adsorb to the ice. Potential reactions between the formic acid/formate ion surface and nitrogen dioxide were subsequently investigated by FT-RAIRS. Co-deposition experiments showed that N2O3 and the NO+ ion (associated with water) were formed as products. A mechanism is proposed to explain these results, which involves direct reaction between the organic acid and nitrogen dioxide. Similar experiments involving acetic acid also indicate ionization on a water-ice surface. The results are put into the context of atmospheric chemistry potentially occuring on cirrus cloud surfaces.

  17. RNA internal standard synthesis by nucleic acid sequence-based amplification for competitive quantitative amplification reactions.

    PubMed

    Lo, Wan-Yu; Baeumner, Antje J

    2007-02-15

    Nucleic acid sequence-based amplification (NASBA) reactions have been demonstrated to successfully synthesize new sequences based on deletion and insertion reactions. Two RNA internal standards were synthesized for use in competitive amplification reactions in which quantitative analysis can be achieved by coamplifying the internal standard with the wild type sample. The sequences were created in two consecutive NASBA reactions using the E. coli clpB mRNA sequence as model analyte. The primer sequences of the wild type sequence were maintained, and a 20-nt-long segment inside the amplicon region was exchanged for a new segment of similar GC content and melting temperature. The new RNA sequence was thus amplifiable using the wild type primers and detectable via a new inserted sequence. In the first reaction, the forwarding primer and an additional 20-nt-long sequence was deleted and replaced by a new 20-nt-long sequence. In the second reaction, a forwarding primer containing as 5' overhang sequence the wild type primer sequence was used. The presence of pure internal standard was verified using electrochemiluminescence and RNA lateral-flow biosensor analysis. Additional sequence deletion in order to shorten the internal standard amplicons and thus generate higher detection signals was found not to be required. Finally, a competitive NASBA reaction between one internal standard and the wild type sequence was carried out proving its functionality. This new rapid construction method via NASBA provides advantages over the traditional techniques since it requires no traditional cloning procedures, no thermocyclers, and can be completed in less than 4 h.

  18. Nuclemeter: A Reaction-Diffusion Based Method for Quantifying Nucleic Acids Undergoing Enzymatic Amplification

    PubMed Central

    Liu, Changchun; Sadik, Mohamed M.; Mauk, Michael G.; Edelstein, Paul H.; Bushman, Frederic D.; Gross, Robert; Bau, Haim H.

    2014-01-01

    Real-time amplification and quantification of specific nucleic acid sequences plays a major role in medical and biotechnological applications. In the case of infectious diseases, such as HIV, quantification of the pathogen-load in patient specimens is critical to assess disease progression and effectiveness of drug therapy. Typically, nucleic acid quantification requires expensive instruments, such as real-time PCR machines, which are not appropriate for on-site use and for low-resource settings. This paper describes a simple, low-cost, reaction-diffusion based method for end-point quantification of target nucleic acids undergoing enzymatic amplification. The number of target molecules is inferred from the position of the reaction-diffusion front, analogous to reading temperature in a mercury thermometer. The method was tested for HIV viral load monitoring and performed on par with conventional benchtop methods. The proposed method is suitable for nucleic acid quantification at point of care, compatible with multiplexing and high-throughput processing, and can function instrument-free. PMID:25477046

  19. Fluorimetric determination of phytic acid in urine based on replacement reaction.

    PubMed

    Chen, Yingyu; Chen, Jingwen; Ma, Kang; Cao, Shuhong; Chen, Xiaoqing

    2007-12-19

    A sensitive fluorimetric method for determination of phytic acid in human urine samples was described. The method was based on a fluorimetric replacement reaction, in which the added phytic acid replaced the Cu2+ ion from Cu2+-gelatin complex, liberating the fluorescent gelatin molecule. The fluorescence of the solution was accordingly recovered proportionally to the amount of the foreign phytic acid. The excitation wavelength was 273.5 nm and the characteristic emission wavelength was 305.0 nm, respectively. The calibration graph was obtained by plotting the recovered fluorescent intensity at maximum 305.0 nm against the added standard phytic acid, and was divided into two sections. One section was linear over the range of 0.40-2.40 mg L(-1) with a linear regression equation of I(f) = -0.895+15.146c (R2 > 0.9993), and the other over the range of 2.40-9.20 mg L(-1) with a linear regression equation of I(f) = -29.526+26.113c (R2 > 0.9996), respectively. The relative standard deviation (R.S.D.) at 95% confidence degree for a 2.0 mg L(-1) of standard phytic acid within 1 month was less than 1.26% (n = 5), indicating the procedure is reproducible. The detection and the quantification limits of phytic acid were estimated to be 0.23 and 0.40 mg L(-1), respectively. The proposed method was applied to the determination of phytic acid in urine samples and the found concentrations of phytic acid in urine were in the range of 0.49-0.75 mg L(-1) with recoveries of 96.2-108.8%. Comparison of the obtained results with the reported HPLC was performed, indicating the proposed method was reliable.

  20. [Experimental and kinetic modeling of acid/base and redox reactions over oxide catalysts

    SciTech Connect

    Not Available

    1993-01-01

    The research has involved the characterization of catalyst acidity, [sup 2]D NMR studies of Bronsted acid sites, and kinetic, calorimetric, and spectroscopic studies of methylamine synthesis and related reactions over acid catalysts. Approach of this work was to explore quantitative correlations between factors that control the generation, type, strength, and catalytic properties of acid sites on zeolite catalysts. Microcalorimetry, thermogravimetric analysis, IR spectroscopy, and NMR spectroscopy have provided information about the nature and strength of acid sites in zeolites. This was vital in understanding the catalytic cycles involved in methylamine synthesis and related reactions over zeolite catalysts.

  1. Acid-base bifunctional catalysis of silica-alumina-supported organic amines for carbon-carbon bond-forming reactions.

    PubMed

    Motokura, Ken; Tomita, Mitsuru; Tada, Mizuki; Iwasawa, Yasuhiro

    2008-01-01

    Acid-base bifunctional heterogeneous catalysts were prepared by the reaction of an acidic silica-alumina (SA) surface with silane-coupling reagents possessing amino functional groups. The obtained SA-supported amines (SA-NR2) were characterized by solid-state 13C and 29Si NMR spectroscopy, FT-IR spectroscopy, and elemental analysis. The solid-state NMR spectra revealed that the amines were immobilized by acid-base interactions at the SA surface. The interactions between the surface acidic sites and the immobilized basic amines were weaker than the interactions between the SA and free amines. The catalytic performances of the SA-NR2 catalysts for various carbon-carbon bond-forming reactions, such as cyano-ethoxycarbonylation, the Michael reaction, and the nitro-aldol reaction, were investigated and compared with those of homogeneous and other heterogeneous catalysts. The SA-NR2 catalysts showed much higher catalytic activities for the carbon-carbon bond-forming reactions than heterogeneous amine catalysts using other supports, such as SiO2 and Al2O3. On the other hand, homogeneous amines hardly promoted these reactions under similar reaction conditions, and the catalytic behavior of SA-NR2 was also different from that of MgO, which was employed as a typical heterogeneous base. An acid-base dual-activation mechanism for the carbon-carbon bond-forming reactions is proposed.

  2. Graphene-Based Non-Noble-Metal Catalysts for Oxygen Reduction Reaction in Acid

    SciTech Connect

    H Byon; J Suntivich; Y Shao-Horn

    2011-12-31

    Non-noble-metal catalysts based on Fe-N-C moieties have shown promising oxygen reduction reaction (ORR) activity in proton exchange membrane fuel cells (PEMFCs). In this study, we report a facile method to prepare a Fe-N-C catalyst based on modified graphene (Fe-N-rGO) from heat treatment of a mixture of Fe salt, graphitic carbon nitride (g-C{sub 3}N{sub 4}), and chemically reduced graphene (rGO). The Fe-N-rGO catalyst was found to have pyridinic N-dominant heterocyclic N (40% atomic concentration among all N components) on the surface and have an average Fe coordination of {approx}3 N (Fe-N{sub 3,average}) in bulk. Rotating disk electrode measurements revealed that Fe-N-rGO had high mass activity in acid and exhibited high stability at 0.5 V at 80 C in acid over 70 h, which was correlated to low H{sub 2}O{sub 2} production shown from rotating ring disk electrode measurements.

  3. Lewis base activation of Lewis acids: catalytic, enantioselective vinylogous aldol addition reactions.

    PubMed

    Denmark, Scott E; Heemstra, John R

    2007-07-20

    The generality of Lewis base catalyzed, Lewis acid mediated, enantioselective vinylogous aldol addition reactions has been investigated. The combination of silicon tetrachloride and chiral phosphoramides is a competent catalyst for highly selective additions of a variety of alpha,beta-unsaturated ketone-, 1,3-diketone-, and alpha,beta-unsaturated amide-derived dienolates to aldehydes. These reactions provided high levels of gamma-site selectivity for a variety of substitution patterns on the dienyl unit. Both ketone- and morpholine amide-derived dienol ethers afforded high enantio- and diastereoselectivity in the addition to conjugated aldehydes. Although alpha,beta-unsaturated ketone-derived dienolate did not react with aliphatic aldehydes, alpha,beta-unsaturated amide-derived dienolates underwent addition at reasonable rates affording high yields of vinylogous aldol product. The enantioselectivities achieved with the morpholine derived-dienolate in the addition to aliphatic aldehydes was the highest afforded to date with the silicon tetrachloride-chiral phosphoramide system. Furthermore, the ability to cleanly convert the morpholine amide to a methyl ketone was demonstrated.

  4. [Reaction of bone tissue elements on synthetic bioresorbable materials based on lactic and glycolic acids].

    PubMed

    Kulakov, A A; Grigor'ian, A S

    2014-01-01

    The aim of the study was to evaluate the adverse effects of synthetic polymeric bioresorbable materials based on lactic and glycolic acids on the bone tissue. The study was carried-out on 40 Wister-line rats. Four types of bioresorbable polymeric materials were implanted: PolyLactide Glycolide Acid (PLGA), Poly-L-Lactide Acid (PLLA); Poly-96L/4D-Lactide Acid (96/4 PLDLA); Poly-70L/30D-Lactide Acid (70/30 PLDLA). The results showed connective tissue formation (fibrointegration) bordering bone adjacent to implanted materials. This proved the materials to cause pathogenic influence on the bone which mechanisms are described in the article.

  5. Gas-phase ion/ion reactions of peptides and proteins: acid/base, redox, and covalent chemistries.

    PubMed

    Prentice, Boone M; McLuckey, Scott A

    2013-02-01

    Gas-phase ion/ion reactions are emerging as useful and flexible means for the manipulation and characterization of peptide and protein biopolymers. Acid/base-like chemical reactions (i.e., proton transfer reactions) and reduction/oxidation (redox) reactions (i.e., electron transfer reactions) represent relatively mature classes of gas-phase chemical reactions. Even so, especially in regards to redox chemistry, the widespread utility of these two types of chemistries is undergoing rapid growth and development. Additionally, a relatively new class of gas-phase ion/ion transformations is emerging which involves the selective formation of functional-group-specific covalent bonds. This feature details our current work and perspective on the developments and current capabilities of these three areas of ion/ion chemistry with an eye towards possible future directions of the field.

  6. Gas-phase ion/ion reactions of peptides and proteins: acid/base, redox, and covalent chemistries

    PubMed Central

    Prentice, Boone M.

    2013-01-01

    Gas-phase ion/ion reactions are emerging as useful and flexible means for the manipulation and characterization of peptide and protein biopolymers. Acid/base-like chemical reactions (i.e., proton transfer reactions) and reduction/oxidation (redox) reactions (i.e., electron transfer reactions) represent relatively mature classes of gas-phase chemical reactions. Even so, especially in regards to redox chemistry, the widespread utility of these two types of chemistries is undergoing rapid growth and development. Additionally, a relatively new class of gas-phase ion/ion transformations is emerging which involves the selective formation of functional-group-specific covalent bonds. This feature details our current work and perspective on the developments and current capabilities of these three areas of ion/ion chemistry with an eye towards possible future directions of the field. PMID:23257901

  7. Kinetics and Mechanisms of the Acid-base Reaction Between NH3 and HCOOH in Interstellar Ice Analogs

    NASA Astrophysics Data System (ADS)

    Bergner, Jennifer B.; Öberg, Karin I.; Rajappan, Mahesh; Fayolle, Edith C.

    2016-10-01

    Interstellar complex organic molecules are commonly observed during star formation, and are proposed to form through radical chemistry in icy grain mantles. Reactions between ions and neutral molecules in ices may provide an alternative cold channel to complexity, as ion-neutral reactions are thought to have low or even no-energy barriers. Here we present a study of the kinetics and mechanisms of a potential ion-generating, acid-base reaction between NH3 and HCOOH to form the salt NH{}4+HCOO-. We observe salt growth at temperatures as low as 15 K, indicating that this reaction is feasible in cold environments. The kinetics of salt growth are best fit by a two-step model involving a slow “pre-reaction” step followed by a fast reaction step. The reaction energy barrier is determined to be 70 ± 30 K with a pre-exponential factor 1.4 ± 0.4 × 10-3 s-1. The pre-reaction rate varies under different experimental conditions and likely represents a combination of diffusion and orientation of reactant molecules. For a diffusion-limited case, the pre-reaction barrier is 770 ± 110 K with a pre-exponential factor of ˜7.6 × 10-3 s-1. Acid-base chemistry of common ice constituents is thus a potential cold pathway to generating ions in interstellar ices.

  8. How are the Concepts and Theories of Acid-Base Reactions Presented? Chemistry in Textbooks and as Presented by Teachers

    ERIC Educational Resources Information Center

    Furio-Mas, Carlos; Calatayud, Maria Luisa; Guisasola, Jenaro; Furio-Gomez, Cristina

    2005-01-01

    This paper investigates the views of science and scientific activity that can be found in chemistry textbooks and heard from teachers when acid-base reactions are introduced to grade 12 and university chemistry students. First, the main macroscopic and microscopic conceptual models are developed. Second, we attempt to show how the existence of…

  9. Tissue reactions to engineered cartilage based on poly-L-lactic acid scaffolds.

    PubMed

    Fujihara, Yuko; Asawa, Yukiyo; Takato, Tsuyoshi; Hoshi, Kazuto

    2009-07-01

    Tissue reactions against poly-L-lactic acid (PLLA) in engineered cartilage may influence the size or maturity of regenerative tissue. To understand the biological events in these reactions, we subcutaneously transplanted engineered constructs of PLLA scaffolds with or without human chondrocytes or atelocollagen in nude mice and evaluated neovascularization and macrophage activation, which can be assessed even in nude mice. Although not showing cartilage regeneration, PLLA alone demonstrated dense localization of macrophages and blood vessels, as well as a high level of interleukin-1 beta and tissue hemoglobin at 2 and 8 weeks. Otherwise, constructs with PLLA and chondrocytes with or without atelocollagen (PLLA/cell/gel or PLLA/cell) formed mature cartilage by 8 weeks, which was more prominent in PLLA/cell/gel. Although accumulation of macrophages and blood vessels in PLLA/cell/gel and PLLA/cell was comparable with that in PLLA at 2 weeks, that in PLLA/cell/gel markedly decreased by 8 weeks, with blood vessels and macrophages excluded into non-cartilage areas. Macrophage migration inhibitory factor could be involved in these suppressed tissue reactions, because it was expressed in chondrocytes of engineered cartilage. Intense tissue reactions inevitably occurred in biopolymers alone, but it is possible that maturation of engineered cartilage suppressed these reactions, which may contribute to circumventing deformity or malformation of engineered tissues.

  10. Silicon-based Lewis acid assisted cinchona alkaloid catalysis: highly enantioselective aza-Michael reaction under solvent-free conditions.

    PubMed

    Yang, Hua-Meng; Li, Li; Li, Fei; Jiang, Ke-Zhi; Shang, Jun-Yan; Lai, Guo-Qiao; Xu, Li-Wen

    2011-12-16

    The study showed that a combination of an achiral silicon-based Lewis acid and chiral Lewis base, such as iodotrimethylsilane (TMSI) and cinchonine, generated a highly enantioselective catalyst system under solvent-free conditions which gave aromatic β-amino ketones with up to >99% ee. Mechanistic studies demonstrate the enhanced asymmetric induction may be due to the combined and competitive activation of a carbonyl moiety of chalcone with cinchonine and the silicon-based Lewis acid in the aza-Michael reaction.

  11. Chemiluminescence determination of gemifloxacin based on diperiodatoargentate (III)-sulphuric acid reaction in a micellar medium.

    PubMed

    Zhao, Fang; Zhao, Wen-hui; Xiong, Wei

    2013-01-01

    A novel flow-injection chemiluminescence (FI-CL) analysis method for the determination of gemifloxacin in the presence of cetyltrimethylammonium bromide (CTAB) surfactant micelles is described. Strong CL signal was generated during the reaction of gemifloxacin with diperiodatoargentate (III) in a sulfuric acid medium sensitized by CTAB. Under optimum experimental conditions, the CL intensity was linearly related to the concentration of gemifloxacin from 1.0 × 10(-9) to 3.0 × 10(-7) g/mL and the detection limit was 7.3 × 10(-10) g/mL (3σ). The relative standard deviation (RSD) was 1.7 % for a 3.0 × 10(-8) g/mL gemifloxacin solution (11 repeated measurements). The proposed method was successfully applied to the determination of gemifloxacin in pharmaceutical preparations and biological fluids. The possible mechanism of the CL reaction is also discussed briefly.

  12. Synthesis of quaternary α-amino acid-based arginase inhibitors via the Ugi reaction.

    PubMed

    Golebiowski, Adam; Whitehouse, Darren; Beckett, R Paul; Van Zandt, Michael; Ji, Min Koo; Ryder, Todd R; Jagdmann, Erik; Andreoli, Monica; Lee, Yung; Sheeler, Ryan; Conway, Bruce; Olczak, Jacek; Mazur, Marzena; Czestkowski, Wojciech; Piotrowska, Wieslawa; Cousido-Siah, Alexandra; Ruiz, Francesc X; Mitschler, Andre; Podjarny, Alberto; Schroeter, Hagen

    2013-09-01

    The Ugi reaction has been successfully applied to the synthesis of novel arginase inhibitors. In an effort to decrease conformational flexibility of the previously reported series of 2-amino-6-boronohexanoic acid (ABH) analogs 1, we designed and synthesized a series of compounds, 2, in which a piperidine ring is linked directly to a quaternary amino acid center. Further improvement of in vitro activity was achieved by adding two carbon bridge in the piperidine ring, that is, tropane analogs 11. These improvements in activity are rationalized by X-ray crystallography analysis, which show that the tropane ring nitrogen atom moves into direct contact with Asp202 (arginase II numbering). The synthetic routes described here enabled the design of novel arginase inhibitors with improved potency and markedly different physico-chemical properties compared to ABH. Compound 11c represents the most in vitro active arginase inhibitor reported to date.

  13. Studies on Pre-Ignition Reactions of Hydrocarbon-Based Rocket Fuels Hypergolic with Red Fuming Nitric Acid as Oxidizer

    NASA Astrophysics Data System (ADS)

    Kulkarni, Suresh G.; Bagalkote, Vrushali S.

    2010-06-01

    Carene, norbornadiene, ethylidene norbornene, and furfuryl alcohol exhibit hypergolic ignition with red fuming nitric acid as oxidizer. Carene, when blended with norbornadiene, ethylidene norbornene, and furfuryl alcohol in appropriate proportions, exhibits synergistic hypergolic ignition with further decrease in ignition delay. In order to understand the probable mechanism of hypergolic ignition and synergy in ignition, various pre-ignition reactions have been studied by quenching the reactions and analyzing the intermediate products by Fourier transform infrared (FTIR) and gas chromatography-mass spectrometry (GC-MS) techniques. Based on the product analysis, the probable schemes of reactions have been proposed. Oxidation, nitration, and cationic polymerization appear to be the important pre-ignition reactions taking place simultaneously that are responsible for hypergolic ignition.

  14. Amplified detection of nucleic acid by G-quadruplex based hybridization chain reaction.

    PubMed

    Dong, Juan; Cui, Xin; Deng, Yun; Tang, Zhuo

    2012-01-01

    A protein-free, isothermal, self-amplified nucleic acid sensing system which was a G-quadruplex integrated hybridization chain reaction (GQ-HCR) system was developed. The G-quadruplex was closed two-thirds in the loop and one-third in the stem of one of the GQ-HCR hairpin probes. In the absence of the target molecule, the GQ-HCR probes stayed as inactive meta-stable hairpin structures and the G-quadruplex was inert. Reversely, the GQ-HCR probes could be cross-opened to start a hybridization chain reaction and the closed G-quadruplex could be released to be free when the GQ-HCR probes came across the target molecule. The GQ-HCR nucleic acid sensing system could detect as low as 7.5 nM ssDNA or RNA by the colorimetric method and 4 nM ssDNA by the fluorometric method. Less than 10 copies of dsDNA template could also be detected when PCR was combined with the GQ-HCR system (PCR+GQ-HCR). Because of these advantages, the GQ-HCR system was also studied for application in visual chip detection to obtain a satisfactory repeatable and specific result.

  15. A review of proton transfer reactions between various carbon-acids and amine bases in aprotic solvents

    NASA Astrophysics Data System (ADS)

    Jarczewski, Arnold; Hubbard, Colin D.

    2003-04-01

    The subject of proton transfer between carbon acids and nitrogen bases in aprotic solvents is reviewed. Equilibrium and rate constants that characterize such reactions are most often determined utilizing UV-visible spectrophotometry. At ambient temperature reaction rates are sufficiently rapid that fast reaction methods, for example, the stopped-flow and temperature-jump techniques are required in many cases. Variation of the properties of the donor and acceptor reaction pairs enables electronic and steric effects upon thermodynamic and kinetic parameters of proton transfer to be assessed. Determination of the kinetic isotope effect (KIE), i.e. k(protium)/ k(deuterium) led to the conclusion that, under certain circumstances and when the KIE is greater than seven, the proton undergoes reaction with a significant degree of quantum mechanical tunneling, consistent with a theoretical prediction advanced several decades earlier. In fact this aspect may be one of the most significant outgrowths of these studies. Many reactions have been characterized (by tunneling) but rarely are the reacting systems experimentally amenable to obtaining all the experimental criteria that support tunneling. Controversy that has arisen regarding treatment of experimental data and resulting conclusions from them is visited in this review. The structural nature of the product state of reaction is formulated based on spectroscopic evidence, in favorable cases, and probable structures of the transition state can be inferred.

  16. Visual detection of nucleic acids based on lateral flow biosensor and hybridization chain reaction amplification.

    PubMed

    Ying, Na; Ju, Chuanjing; Li, Zhongyi; Liu, Wensen; Wan, Jiayu

    2017-03-01

    In this study, a new lateral flow nucleic acid biosensor (LFNAB) using hybridization chain reaction (HCR) for signal amplification was developed for visual detection of nucleic acids with high sensitivity and low cost. A "sandwich-type" detection strategy was employed in our design. The sandwich system of capture probe (CP)/target DNA/reporter probe (RP)-HCR complexes was fabricated as the sensing platform. As the initiator strand, reporter probe propagated a chain reaction of hybridization events between the two hairpin probes modified with biotin, and determined whether long nicked DNA polymers were formed. The biotin-labeled double-strand DNA polymers then introduced numerous Streptavidin (SA)-labeled gold nanoparticles (AuNPs) on the lateral flow device. The CP/target DNA/RP-HCR complexes were captured on the test zone by the specific reaction between anti-Fam monoclonal antibody (anti-Fam mAb) on the test zone and Fam of the complexes. The accumulation of AuNPs on the test zone of the biosensor enabled the visual detection of specific sequences. The detection limit of specific DNA was as low as 1.76pM, which was about 2 orders lower than that of the LFNAB without HCR amplification. And the detection limit of Salmonella was 3×10(3)cfumL(-1). In conclusion, this visual detection system, HCR-LFNAB, is suitable for non-specialist personnel and point-of-care (POC) diagnosis in low-resource settings.

  17. Contributions of separate reactions to the acid-base buffering of soils in brook floodplains (Central Forest State Reserve)

    NASA Astrophysics Data System (ADS)

    Sokolova, T. A.; Tolpeshta, I. I.; Rusakova, E. S.

    2016-04-01

    The acid-base buffering of gleyic gray-humus soils developed in brook floodplains and undisturbed southern-taiga landscapes has been characterized by the continuous potentiometric titration of soil water suspensions. During the interaction with an acid, the major amount of protons (>80%) is consumed for the displacement of exchangeable bases and the dissolution of Ca oxalates. In the O and AY horizons, Mn compounds make the major contribution (2-15%) to the acid buffering. The buffer reactions with the participation of Al compounds make up from 0.5 to 1-2% of the total buffering capacity, and the protonation of the surface OH groups of kaolinite consumes 2-3% of the total buffering capacity. The deprotonation of OH groups on the surface of Fe hydroxides (9-43%), the deprotonation of OH groups on the surface of illite crystals (3-19%), and the dissolution of unidentified aluminosilicates (9-14%) are the most significant buffer reactions whose contributions have been quantified during the interaction with a base. The contribution of the deprotonation of OH groups on the surface of kaolinite particles is lower (1-5%) because of the small specific surface area of this mineral, and that of the dissolution of Fe compounds is insignificant. In the AY horizon, the acid and base buffering of soil in the rhizosphere is higher than beyond the rhizosphere because of the higher contents of organic matter and nonsilicate Fe and Al compounds.

  18. Reaction Mechanism for Direct Proton Transfer from Carbonic Acid to a Strong Base in Aqueous Solution II: Solvent Coordinate-Dependent Reaction Path.

    PubMed

    Daschakraborty, Snehasis; Kiefer, Philip M; Miller, Yifat; Motro, Yair; Pines, Dina; Pines, Ehud; Hynes, James T

    2016-03-10

    The protonation of methylamine base CH3NH2 by carbonic acid H2CO3 within a hydrogen (H)-bonded complex in aqueous solution was studied via Car-Parrinello dynamics in the preceding paper (Daschakraborty, S.; Kiefer, P. M.; Miller, Y.; Motro, Y.; Pines, D.; Pines, E.; Hynes, J. T. J. Phys. Chem. B 2016, DOI: 10.1021/acs.jpcb.5b12742). Here some important further details of the reaction path are presented, with specific emphasis on the water solvent's role. The overall reaction is barrierless and very rapid, on an ∼100 fs time scale, with the proton transfer (PT) event itself being very sudden (<10 fs). This transfer is preceded by the acid-base H-bond's compression, while the water solvent changes little until the actual PT occurrence; this results from the very strong driving force for the reaction, as indicated by the very favorable acid-protonated base ΔpKa difference. Further solvent rearrangement follows immediately the sudden PT's production of an incipient contact ion pair, stabilizing it by establishment of equilibrium solvation. The solvent water's short time scale ∼120 fs response to the incipient ion pair formation is primarily associated with librational modes and H-bond compression of water molecules around the carboxylate anion and the protonated base. This is consistent with this stabilization involving significant increase in H-bonding of hydration shell waters to the negatively charged carboxylate group oxygens' (especially the former H2CO3 donor oxygen) and the nitrogen of the positively charged protonated base's NH3(+).

  19. The chlorate-iodine-nitrous acid clock reaction.

    PubMed

    Sant'Anna, Rafaela T P; Faria, Roberto B

    2014-01-01

    A new clock reaction based on chlorate, iodine and nitrous acid is presented. The induction period of this new clock reaction decreases when the initial concentrations of chlorate, nitrous acid and perchloric acid increase, but it is independent on the initial iodine concentration. The proposed mechanism is based on the LLKE autocatalytic mechanism for the chlorite-iodide reaction and the initial reaction between chlorate and nitrous acid to produce nitrate and chlorite. This new clock reaction opens the possibility for a new family of oscillating reactions containing chlorate or nitrous acid, which in both cases has not been observed until now.

  20. The Chlorate-Iodine-Nitrous Acid Clock Reaction

    PubMed Central

    Sant'Anna, Rafaela T. P.; Faria, Roberto B.

    2014-01-01

    A new clock reaction based on chlorate, iodine and nitrous acid is presented. The induction period of this new clock reaction decreases when the initial concentrations of chlorate, nitrous acid and perchloric acid increase, but it is independent on the initial iodine concentration. The proposed mechanism is based on the LLKE autocatalytic mechanism for the chlorite-iodide reaction and the initial reaction between chlorate and nitrous acid to produce nitrate and chlorite. This new clock reaction opens the possibility for a new family of oscillating reactions containing chlorate or nitrous acid, which in both cases has not been observed until now. PMID:25313803

  1. [Experimental and kinetic modeling of acid/base and redox reactions over oxide catalysts]. Technical progress report

    SciTech Connect

    Not Available

    1993-07-01

    The research has involved the characterization of catalyst acidity, {sup 2}D NMR studies of Bronsted acid sites, and kinetic, calorimetric, and spectroscopic studies of methylamine synthesis and related reactions over acid catalysts. Approach of this work was to explore quantitative correlations between factors that control the generation, type, strength, and catalytic properties of acid sites on zeolite catalysts. Microcalorimetry, thermogravimetric analysis, IR spectroscopy, and NMR spectroscopy have provided information about the nature and strength of acid sites in zeolites. This was vital in understanding the catalytic cycles involved in methylamine synthesis and related reactions over zeolite catalysts.

  2. Continuous monitoring of the zinc-phosphate acid-base cement setting reaction by proton nuclear magnetic relaxation

    NASA Astrophysics Data System (ADS)

    Apih, T.; Lebar, A.; Pawlig, O.; Trettin, R.

    2001-06-01

    Proton nuclear magnetic relaxation is a well-established technique for continuous and non destructive monitoring of hydration of conventional Portland building cements. Here, we demonstrate the feasibility of nuclear magnetic resonance (NMR) monitoring of the setting reaction of zinc-phosphate acid-base dental cements, which harden in minutes as compared to days, as in the case of Portland cements. We compare the setting of cement powder (mainly, zinc oxide) prepared with clinically used aluminum-modified orthophosphoric acid solution with the setting of a model system where cement powder is mixed with pure orthophosphoric acid solution. In contrast to previously published NMR studies of setting Portland cements, where a decrease of spin-lattice relaxation time is attributed to enhanced relaxation at the growing internal surface, spin-lattice relaxation time T1 increases during the set of clinically used zinc-phosphate cement. Comparison of these results with a detailed study of diffusion, viscosity, and magnetic-field dispersion of T1 in pure and aluminum-modified orthophosphoric acid demonstrates that the increase of T1 in the setting cement is connected with the increase of molecular mobility in the residual phosphoric acid solution. Although not taken into account so far, such effects may also significantly influence the relaxation times in setting Portland cements, particularly when admixtures with an effect on water viscosity are used.

  3. The hydrothermal reaction kinetics of aspartic acid

    NASA Astrophysics Data System (ADS)

    Cox, Jenny S.; Seward, Terry M.

    2007-02-01

    Experimental data on the hydrothermal reaction kinetics of aspartic acid were acquired using a custom-built spectrophotometric reaction cell which permits in situ observation under hydrothermal conditions. The results of this study indicate that the reaction kinetics of dilute aspartic acid solutions are significantly different depending on the presence or absence of catalytic surfaces such as standard metal alloys. The spectroscopic data presented here represent the first direct observations, in situ and in real time, of an amino acid reacting in a hydrothermal solution. Quantitative kinetic information, including rate constants, concentration versus time profiles, and calculations of the individual component spectra, was obtained from the data using a chemometric approach based on factor analysis/principle component analysis which treats the rate expressions simultaneously as a system of differential algebraic equations (DAE) of index 1. Identification of the products was confirmed where possible by high pressure anion exchange chromatography with pulsed amperometric detection (HPAEC-PAD). The reaction kinetics of aspartic acid under hydrothermal conditions was observed to be highly complex, in contrast to previous studies which indicated almost exclusively deamination. At lower temperatures (120-170 °C), several different reaction pathways were observed, including decarboxylation and polymerization, and the catalytic effects of reactor surfaces on the aspartic acid system were clearly demonstrated. At higher temperatures (above 170 °C), aspartic acid exhibited highly complex behaviour, with evidence indicating that it can simultaneously dimerize and cyclize, deaminate (by up to two pathways), and decarboxylate (by up to two pathways). These higher temperature kinetics were not fully resolvable in a quantitative manner due to the complexity of the system and the constraints of UV spectroscopy. The results of this study provide strong evidence that the reaction

  4. Lewis acid-base 1,2-addition reactions: synthesis of pyrylium borates from en-ynoate precursors.

    PubMed

    Wilkins, Lewis C; Hamilton, Hugh B; Kariuki, Benson M; Hashmi, A Stephen K; Hansmann, Max M; Melen, Rebecca L

    2016-04-14

    Treatment of methyl (Z)-2-alken-4-ynoates with the strong Lewis acid tris(pentafluorophenyl) borane, B(C6F5)3, yield substituted zwitterionic pyrylium borate species via an intramolecular 6-endo-dig cyclisation reaction.

  5. A simple ligation-based method to increase the information density in sequencing reactions used to deconvolute nucleic acid selections

    PubMed Central

    Childs-Disney, Jessica L.; Disney, Matthew D.

    2008-01-01

    Herein, a method is described to increase the information density of sequencing experiments used to deconvolute nucleic acid selections. The method is facile and should be applicable to any selection experiment. A critical feature of this method is the use of biotinylated primers to amplify and encode a BamHI restriction site on both ends of a PCR product. After amplification, the PCR reaction is captured onto streptavidin resin, washed, and digested directly on the resin. Resin-based digestion affords clean product that is devoid of partially digested products and unincorporated PCR primers. The product's complementary ends are annealed and ligated together with T4 DNA ligase. Analysis of ligation products shows formation of concatemers of different length and little detectable monomer. Sequencing results produced data that routinely contained three to four copies of the library. This method allows for more efficient formulation of structure-activity relationships since multiple active sequences are identified from a single clone. PMID:18065718

  6. Visual detection of trace copper ions based on copper-catalyzed reaction of ascorbic acid with oxygen

    NASA Astrophysics Data System (ADS)

    Hou, Xin Yan; Chen, Shu; Shun, Lian Ju; Zhao, Yi Ni; Zhang, Zhi Wu; Long, Yun Fei; Zhu, Li

    2015-10-01

    A visual detection method for trace Cu2+ in aqueous solutions using triangular silver nanoplates (abbreviated as TAgNPs) as the probe was developed. The method is based on that TAgNPs could be corroded in sodium thiosulfate (Na2S2O3) solutions. The absorption spectrum of TAgNPs solution changed when it is corroded by Na2S2O3. The reaction of oxygen with ascorbic acid (Vc) in the presence of a low concentration of Cu2+ generates hydrogen peroxide that reacts with Na2S2O3, which leads the concentration of Na2S2O3 in the solution to be decreased. Therefore, the reaction between TAgNPs and the reacted mixture of Na2S2O3/Vc/Cu2+ was prevented efficiently. When the Na2S2O3 concentration and reaction time are constant, the decrease in the concentration of Na2S2O3 is directly proportional to the Cu2+ concentration. Thus, morphology, color, and maximum absorption wavelength of TAgNPs changed with the change of Cu2+ concentration. The changed maximum absorption wavelength of TAgNPs (Δλ) is proportional to Cu2+ concentration in the range from 7.5 × 10-9 to 5.0 × 10-7 M with a correlation coefficient of r = 0.9956. Moreover, color change of TAgNP solution was observed clearly over a Cu2+ concentration range from 7.5 × 10-8 to 5.0 × 10-7 M. This method has been used to detect the Cu2+ content of a human hair sample, and the result is in agreement with that obtained by the atomic absorption spectroscopy (AAS) method.

  7. Gas-phase enthalpies of formation and enthalpies of sublimation of amino acids based on isodesmic reaction calculations.

    PubMed

    Dorofeeva, Olga V; Ryzhova, Oxana N

    2014-05-15

    Accurate gas-phase enthalpies of formation (ΔfH298°) of 20 common α-amino acids, seven uncommon amino acids, and three small peptides were calculated by combining G4 theory calculations with an isodesmic reaction approach. The internal consistency over a set of ΔfH298°(g) values was achieved by sequential adjustment of their values through the isodesmic reactions. Four amino acids, alanine, β-alanine, sarcosine, and glycine, with reliable internally self-consistent experimental data, were chosen as the key reference compounds. These amino acids together with about 100 compounds with reliable experimental data (their accuracy was supported by G4 calculations) were used to estimate the enthalpies of formation of remaining amino acids. All of the amino acids with the previously established enthalpies of formation were later used as the reference species in the isodesmic reactions for the other amino acids. A systematic comparison was made of 14 experimentally determined enthalpies of formation with the results of calculations. The experimental enthalpies of formation for 10 amino acids were reproduced with good accuracy, but the experimental and calculated values for 4 compounds differed by 11–21 kJ/mol. For these species, the theoretical ΔfH298°(g) values were suggested as more reliable than the experimental values. On the basis of theoretical results, the recommended values for the gas-phase enthalpies of formation were also provided for amino acids for which the experimental ΔfH298°(g) were not available. The enthalpies of sublimation were evaluated for all compounds by taking into account the literature data on the solid-phase enthalpies of formation and the ΔfH298°(g) values recommended in our work. A special attention was paid to the accurate prediction of enthalpies of formation of amino acids from the atomization reactions. The problems associated with conformational flexibility of these compounds and harmonic treatment of low frequency torsional

  8. Acid and base catalyzed Davis-Beirut reaction: experimental and theoretical mechanistic studies and synthesis of novel 3-amino-2H-indazoles.

    PubMed

    Avila, Belem; El-Dakdouki, Mohammad H; Nazer, Musa Z; Harrison, Jason G; Tantillo, Dean J; Haddadin, Makhluf J; Kurth, Mark J

    2012-11-28

    The Davis-Beirut reaction, which provides an efficient synthesis of 2H-indazoles and, subsequently, indazolones, is shown to proceed rapidly from o-nitrosobenzaldehyde and primary amines under both acid or base catalysis. Experimental and theoretical evidence in support of a reaction mechanism is provided in which o-nitrosobenzylidine imine is a pivotal intermediate in this N,N-bond forming heterocyclization reaction. The Davis-Beirut reaction is also shown to effectively synthesize a number of novel 3-amino-2H-indazole derivatives.

  9. Photoinduced strong acid-weak base reactions in a polar aprotic solvent

    NASA Astrophysics Data System (ADS)

    Lee, Young Min; Park, Sun-Young; Kim, Heesu; Gyum Kim, Taeg; Kwon, Oh-Hoon

    2016-06-01

    The excited-state proton transfer (ESPT) of the strong photoacid, N-methyl-7-hydroxyquinolinium, was studied in the presence of different weak bases such as methanol, ethanol, and dimethyl sulfoxide in an aprotic solvent of acetonitrile. Here, we present chemical kinetics analysis of the ESPT mechanism to explain biphasic fluorescence decay of the parent photoacid and the sign reversal of the rise and decay of the resulting conjugate-base fluorescence. The ESPT of the free photoacid showed a molecularity of 2 with reacting alcohol molecules. In the ground state, it was found that a fraction of the photoacid formed 1 : 2 hydrogen-bonded complexes with the residual water present in the aprotic solvent or 1 : 1 complexes with the additive alcohols. In the excited state, these adducts underwent proton transfer when complexed further with diffusing alcohol molecules.

  10. Mechanochemical solid-state synthesis of 2-aminothiazoles, quinoxalines and benzoylbenzofurans from ketones by one-pot sequential acid- and base-mediated reactions.

    PubMed

    Nagarajaiah, Honnappa; Mishra, Abhaya Kumar; Moorthy, Jarugu Narasimha

    2016-04-26

    α-Chloroketones - obtained by the atom-economical chlorination of ketones with trichloroisocyanuric acid (TCCA) in the presence of p-TSA under ball-milling conditions - were set up for a sequential base-mediated condensation reaction with thiourea/thiosemicarbazides, o-phenylenediamine and salicylaldehyde to afford 2-aminothiazoles, 2-hydrazinylthiazoles, quinoxalines and benzoylbenzofurans, respectively, in respectable yields. The viability of one-pot sequential acid- and base-mediated reactions in the solid state under ball-milling conditions is thus demonstrated.

  11. Nonstoichiometric acid-base reaction as reliable synthetic route to highly stable CH3NH3PbI3 perovskite film

    NASA Astrophysics Data System (ADS)

    Long, Mingzhu; Zhang, Tiankai; Chai, Yang; Ng, Chun-Fai; Mak, Thomas C. W.; Xu, Jianbin; Yan, Keyou

    2016-11-01

    Perovskite solar cells have received worldwide interests due to swiftly improved efficiency but the poor stability of the perovskite component hampers the device fabrication under normal condition. Herein, we develop a reliable nonstoichiometric acid-base reaction route to stable perovskite films by intermediate chemistry and technology. Perovskite thin-film prepared by nonstoichiometric acid-base reaction route is stable for two months with negligible PbI2-impurity under ~65% humidity, whereas other perovskites prepared by traditional methods degrade distinctly after 2 weeks. Route optimization involves the reaction of PbI2 with excess HI to generate HPbI3, which subsequently undergoes reaction with excess CH3NH2 to deliver CH3NH3PbI3 thin films. High quality of intermediate HPbI3 and CH3NH2 abundance are two important factors to stable CH3NH3PbI3 perovskite. Excess volatile acid/base not only affords full conversion in nonstoichiometric acid-base reaction route but also permits its facile removal for stoichiometric purification, resulting in average efficiency of 16.1% in forward/reverse scans.

  12. Bifunctional heterogeneous catalysis of silica-alumina-supported tertiary amines with controlled acid-base interactions for efficient 1,4-addition reactions.

    PubMed

    Motokura, Ken; Tanaka, Satoka; Tada, Mizuki; Iwasawa, Yasuhiro

    2009-10-19

    We report the first tunable bifunctional surface of silica-alumina-supported tertiary amines (SA-NEt(2)) active for catalytic 1,4-addition reactions of nitroalkanes and thiols to electron-deficient alkenes. The 1,4-addition reaction of nitroalkanes to electron-deficient alkenes is one of the most useful carbon-carbon bond-forming reactions and applicable toward a wide range of organic syntheses. The reaction between nitroethane and methyl vinyl ketone scarcely proceeded with either SA or homogeneous amines, and a mixture of SA and amines showed very low catalytic activity. In addition, undesirable side reactions occurred in the case of a strong base like sodium ethoxide employed as a catalytic reagent. Only the present SA-supported amine (SA-NEt(2)) catalyst enabled selective formation of a double-alkylated product without promotions of side reactions such as an intramolecular cyclization reaction. The heterogeneous SA-NEt(2) catalyst was easily recovered from the reaction mixture by simple filtration and reusable with retention of its catalytic activity and selectivity. Furthermore, the SA-NEt(2) catalyst system was applicable to the addition reaction of other nitroalkanes and thiols to various electron-deficient alkenes. The solid-state magic-angle spinning (MAS) NMR spectroscopic analyses, including variable-contact-time (13)C cross-polarization (CP)/MAS NMR spectroscopy, revealed that acid-base interactions between surface acid sites and immobilized amines can be controlled by pretreatment of SA at different temperatures. The catalytic activities for these addition reactions were strongly affected by the surface acid-base interactions.

  13. Further links between the maximum hardness principle and the hard/soft acid/base principle: insights from hard/soft exchange reactions.

    PubMed

    Chattaraj, Pratim K; Ayers, Paul W; Melin, Junia

    2007-08-07

    Ayers, Parr, and Pearson recently showed that insight into the hard/soft acid/base (HSAB) principle could be obtained by analyzing the energy of reactions in hard/soft exchange reactions, i.e., reactions in which a soft acid replaces a hard acid or a soft base replaces a hard base [J. Chem. Phys., 2006, 124, 194107]. We show, in accord with the maximum hardness principle, that the hardness increases for favorable hard/soft exchange reactions and decreases when the HSAB principle indicates that hard/soft exchange reactions are unfavorable. This extends the previous work of the authors, which treated only the "double hard/soft exchange" reaction [P. K. Chattaraj and P. W. Ayers, J. Chem. Phys., 2005, 123, 086101]. We also discuss two different approaches to computing the hardness of molecules from the hardness of the composing fragments, and explain how the results differ. In the present context, it seems that the arithmetic mean of fragment softnesses is the preferable definition.

  14. Asymmetric synthesis of α-amino acids via homologation of Ni(II) complexes of glycine Schiff bases. Part 2: aldol, Mannich addition reactions, deracemization and (S) to (R) interconversion of α-amino acids.

    PubMed

    Sorochinsky, Alexander E; Aceña, José Luis; Moriwaki, Hiroki; Sato, Tatsunori; Soloshonok, Vadim

    2013-11-01

    This review provides a comprehensive treatment of literature data dealing with asymmetric synthesis of α-amino-β-hydroxy and α,β-diamino acids via homologation of chiral Ni(II) complexes of glycine Schiff bases using aldol and Mannich-type reactions. These reactions proceed with synthetically useful chemical yields and thermodynamically controlled stereoselectivity and allow direct introduction of two stereogenic centers in a single operation with predictable stereochemical outcome. Furthermore, new application of Ni(II) complexes of α-amino acids Schiff bases for deracemization of racemic α-amino acids and (S) to (R) interconversion providing additional synthetic opportunities for preparation of enantiomerically pure α-amino acids, is also reviewed. Origin of observed diastereo-/enantioselectivity in the aldol, Mannich-type and deracemization reactions, generality and limitations of these methodologies are critically discussed.

  15. Preparation of acid-base bifunctional mesoporous KIT-6 (KIT: Korea Advanced Institute of Science and Technology) and its catalytic performance in Knoevenagel reaction

    SciTech Connect

    Xu, Ling; Wang, Chunhua; Guan, Jingqi

    2014-05-01

    Acid-base bifunctional mesoporous catalysts Al-KIT-6-NH{sub 2} containing different aluminum content have been synthesized through post synthetic grafting method. The materials were characterized by X-ray diffraction (XRD), scanning electron micrographs (SEM), transmission electron micrographs (TEM), Fourier-transform infrared spectroscopy (FTIR), IR spectra of pyridine adsorption, NH{sub 3}-TPD and TG analysis. The characterization results indicated that the pore structure of KIT-6 was well kept after the addition of aluminum and grafting of aminopropyl groups. The acid amount of Al-KIT-6 increased with enhancing aluminum content. Catalytic results showed that weak acid and weak base favor the Knoevenagel reaction, while catalysts with strong acid and weak base exhibited worse catalytic behavior. - Graphical abstract: The postulated steps of mechanism for the acid-base catalyzed process are as follows: (1) the aldehyde gets activated by the surface acidic sites which allow the amine undergoes nucleophilic to attack the carbonyl carbon of benzaldehyde. (2) Water is released in the formation of imine intermediate. (3) The ethyl cyanoacetate reacts with the intermediate. (4) The benzylidene ethyl cyanoacetate is formed and the amine is regenerated. - Highlights: • KIT-6 and Al-KIT-6-NH{sub 2} with different Si/Al ratios has been successfully prepared. • 79.4% Yield was obtained over 46-Al-KIT-6-NH{sub 2} within 20 min in Knoevenagel reaction. • Low Al-content Al-KIT-6-NH{sub 2} shows better catalytic stability than high Al-content catalysts. • There is acid-base synergistic effect in Knoevenagel reaction.

  16. The strong reactions of Lewis-base noble-metals with vanadium and other acidic transition metals

    SciTech Connect

    Ebbinghaus, B.B.

    1991-05-01

    The noble metals often thought of as unreactive solids,react strongly with nearly 40% of the elements in the periodictable: group IIIB-VB transition metals, lanthanides, theactinides, and group IIIA-IVA non-transition metals. These strong reactions arise from increased bonding/electron transfer fromnonbonding electrons d electron pairs on the noble metal tovacant orbitals on V, etc. This effect is a generalized Lewis acid-base interaction. The partial Gibbs energy of V in the noblemetals has been measured as a function of concentration at a temperature near 1000C. Thermodynamics of the intermetallics are determined by ternary oxide equilibria, ternary carbide equilibria, and the high-temperature galvanic cell technique. These experimental methods use equilibrated solid composite mixtures in which grains of V oxides or of V carbides are interspersed with grains of V-NM(noble-metal) alloys. In equilibrium the activity of V in the oxide or the carbide equals the activity in the alloy. Consequently, the thermodynamics available in the literature for the V oxides and V carbides are reviewed. Test runs on the galvanic cell were attempted. The V oxide electrode reacts with CaF{sub 2}, ThO{sub 2}, YDT(0.85ThO{sub 2}-0.15YO{sub 1.5}), and LDT(0.85ThO{sub 2}- 0.15LaO{sub 1.5}) to interfere with the measured data observed toward the beginning of a galvanic cell experiment are the most accurate. The interaction of vanadium at infinite dilution in the noble-metals was determined.

  17. The strong reactions of Lewis-base noble-metals with vanadium and other acidic transition metals

    SciTech Connect

    Ebbinghaus, B.B.

    1991-05-01

    The noble metals often thought of as unreactive solids,react strongly with nearly 40% of the elements in the periodictable: group IIIB-VB transition metals, lanthanides, theactinides, and group IIIA-IVA non-transition metals. These strong reactions arise from increased bonding/electron transfer fromnonbonding electrons d electron pairs on the noble metal tovacant orbitals on V, etc. This effect is a generalized Lewis acid-base interaction. The partial Gibbs energy of V in the noblemetals has been measured as a function of concentration at a temperature near 1000C. Thermodynamics of the intermetallics are determined by ternary oxide equilibria, ternary carbide equilibria, and the high-temperature galvanic cell technique. These experimental methods use equilibrated solid composite mixtures in which grains of V oxides or of V carbides are interspersed with grains of V-NM(noble-metal) alloys. In equilibrium the activity of V in the oxide or the carbide equals the activity in the alloy. Consequently, the thermodynamics available in the literature for the V oxides and V carbides are reviewed. Test runs on the galvanic cell were attempted. The V oxide electrode reacts with CaF[sub 2], ThO[sub 2], YDT(0.85ThO[sub 2]-0.15YO[sub 1.5]), and LDT(0.85ThO[sub 2]- 0.15LaO[sub 1.5]) to interfere with the measured data observed toward the beginning of a galvanic cell experiment are the most accurate. The interaction of vanadium at infinite dilution in the noble-metals was determined.

  18. Model Experiment of Thermal Runaway Reactions Using the Aluminum-Hydrochloric Acid Reaction

    ERIC Educational Resources Information Center

    Kitabayashi, Suguru; Nakano, Masayoshi; Nishikawa, Kazuyuki; Koga, Nobuyoshi

    2016-01-01

    A laboratory exercise for the education of students about thermal runaway reactions based on the reaction between aluminum and hydrochloric acid as a model reaction is proposed. In the introductory part of the exercise, the induction period and subsequent thermal runaway behavior are evaluated via a simple observation of hydrogen gas evolution and…

  19. Effect of inclusion complex on nitrous acid reaction with flavonoids

    NASA Astrophysics Data System (ADS)

    Khalafi, Lida; Rafiee, Mohammad; Sedaghat, Sajjad

    2011-10-01

    The kinetic of the nitrous acid reactions with quercetin and catechin has been studied using spectrophotometric method in aqueous solution. The results show that these antioxidants participate in oxidation reactions with nitrous acid which is derived from protonation of nitrite ion in mild acidic conditions. Corresponding o-quinones as relatively stable products were detected by spectrophotometric techniques. pH dependence of the reactions has been examined and the rate constants of reactions were obtained by non-linear fitting of kinetic profiles. The effect of β-cyclodextrin on the oxidation pathway was another object of this study. It is shown that β-cyclodextrin has an inhibitory effect on the oxidation reaction. The rate constants of oxidation reactions for complexed forms and their stability constants were obtained based on changes in the reaction rates as a function of β-cyclodextrin concentration.

  20. Investigation of acid-base catalysis in the extradiol and intradiol catechol dioxygenase reactions using a broad specificity mutant enzyme and model chemistry.

    PubMed

    Brivio, Michela; Schlosrich, Janne; Ahmad, Mark; Tolond, Caroline; Bugg, Timothy D H

    2009-04-07

    The extradiol and intradiol catechol dioxygenase reaction mechanisms proceed via a common proximal hydroperoxide intermediate, which is processed via different Criegee 1,2-rearrangements. An R215W mutant of extradiol dioxygenase MhpB, able to produce a mixture of extradiol and intradiol cleavage products, was analysed at pH 5.2-8.6, and the yield of extradiol product was found to be highly pH-dependent, whereas the yield of intradiol product was pH-independent. The acid-base chemistry of a biomimetic reaction for extradiol oxidative catechol cleavage was also investigated, using 1,4,7-triazacyclononane, FeCl(2), and pyridine in methanol, in which pyridine is proposed to act as both a general base and (in protonated form) a general acid. Kinetic experiments using a range of meta- and para-substituted pyridines gave a Brønsted plot of log(v) vs. pK(a) showing a bell-shaped plot. Oxidative catechol cleavage by a pyridine-monosubstituted beta-cyclodextrin in the presence of TACN and FeCl(2) in methanol yielded only intradiol cleavage products. It is therefore proposed that bifunctional acid-base catalysis is required for iron (ii)-dependent extradiol catechol cleavage, whereas the rate-determining step for intradiol catechol cleavage does not involve acid-base catalysis.

  1. Stratospheric Reactions of Peroxynitric Acid.

    DTIC Science & Technology

    1981-04-23

    was always at least 10 times greater than the HOONO2 concentration at the time of the 03 addition. Because of the small absorption coefficient [ Herzberg ...and J. N. Pitts, Jr., Pressure and temperature dependence of the unimolecular decomposition of HO2N02, J. Chem. Phys., 68, 4505, 1978. Herzberg ... Gerhard , Infrared and Raman Spectra, Vol. II, van Nostrand Reinhold Company, 1945, p. 286. Howard, C. J., Kinetics of the reaction of HO2 with NO2, J. Chem

  2. Acid-, base-, and lewis-acid-catalyzed heterolysis of methoxide from an alpha-hydroxy-beta-methoxy radical: models for reactions catalyzed by coenzyme B12-dependent diol dehydratase.

    PubMed

    Xu, Libin; Newcomb, Martin

    2005-11-11

    [Reaction: see text].A model for glycol radicals was employed in laser flash photolysis kinetic studies of catalysis of the fragmentation of a methoxy group adjacent to an alpha-hydroxy radical center. Photolysis of a phenylselenylmethylcyclopropane precursor gave a cyclopropylcarbinyl radical that rapidly ring opened to the target alpha-hydroxy-beta-methoxy radical (3). Heterolysis of the methoxy group in 3 gave an enolyl radical (4a) or an enol ether radical cation (4b), depending upon pH. Radicals 4 contain a 2,2-diphenylcyclopropane reporter group, and they rapidly opened to give UV-observable diphenylalkyl radicals as the final products. No heterolysis was observed for radical 3 under neutral conditions. In basic aqueous acetonitrile solutions, specific base catalysis of the heterolysis was observed; the pK(a) of radical 3 was determined to be 12.5 from kinetic titration plots, and the ketyl radical formed by deprotonation of 3 eliminated methoxide with a rate constant of 5 x 10(7) s(-1). In the presence of carboxylic acids in acetonitrile solutions, radical 3 eliminated methanol in a general acid-catalyzed reaction, and rate constants for protonation of the methoxy group in 3 by several acids were measured. Radical 3 also reacted by fragmentation of methoxide in Lewis-acid-catalyzed heterolysis reactions; ZnBr2, Sc(OTf)3, and BF3 were found to be efficient catalysts. Catalytic rate constants for the heterolysis reactions were in the range of 3 x 10(4) to 2 x 10(6) s(-1). The Lewis-acid-catalyzed heterolysis reactions are fast enough for kinetic competence in coenzyme B12 dependent enzyme-catalyzed reactions of glycols, and Lewis-acid-catalyzed cleavages of beta-ethers in radicals might be applied in synthetic reactions.

  3. 40 CFR 721.10679 - Carboxylic acid, substituted alkylstannylene ester, reaction products with inorganic acid tetra...

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... alkylstannylene ester, reaction products with inorganic acid tetra alkyl ester (generic). 721.10679 Section 721... Carboxylic acid, substituted alkylstannylene ester, reaction products with inorganic acid tetra alkyl ester... identified generically as carboxylic acid, substituted alkylstannylene ester, reaction products...

  4. Formose reaction controlled by boronic acid compounds

    PubMed Central

    Imai, Toru; Michitaka, Tomohiro

    2016-01-01

    Formose reactions were carried out in the presence of low molecular weight and macromolecular boronic acid compounds, i.e., sodium phenylboronate (SPB) and a copolymer of sodium 4-vinylphenylboronate with sodium 4-styrenesulfonate (pVPB/NaSS), respectively. The boronic acid compounds provided different selectivities; sugars of a small carbon number were formed favorably in the presence of SPB, whereas sugar alcohols of a larger carbon number were formed preferably in the presence of pVPB/NaSS. PMID:28144337

  5. Marangoni instability in the iodate–arsenous acid reaction front

    SciTech Connect

    Pópity-Tóth, Éva; Pótári, Gábor; Erdős, István; Tóth, Ágota; Horváth, Dezső

    2014-07-28

    Horizontally propagating chemical fronts leading to the formation of a single stable convection roll are investigated in the iodate–arsenous acid reaction with arsenous acid stoichiometrically limiting, leaving the surface active iodine present in the product mixture. In sufficiently thin solution layers with open upper surface, the contribution of Marangoni instability is significantly enhanced. Acting in the same direction as buoyancy driven instability, it distorts the entire tilted reaction front that becomes 50% more elongated. The corresponding three-dimensional calculations based on the empirical rate-law of the reaction corroborate the experimental findings.

  6. Development of an Intermittent-Flow Enantioselective Aza-Henry Reaction Using an Arylnitromethane and Homogeneous Brønsted Acid-Base Catalyst with Recycle.

    PubMed

    Tsukanov, Sergey V; Johnson, Martin D; May, Scott A; Rosemeyer, Morgan; Watkins, Michael A; Kolis, Stanley P; Yates, Matthew H; Johnston, Jeffrey N

    2016-02-19

    A stereoselective aza-Henry reaction between an arylnitromethane and Boc-protected aryl aldimine using a homogeneous Brønsted acid-base catalyst was translated from batch format to an automated intermittent-flow process. This work demonstrates the advantages of a novel intermittent-flow setup with product crystallization and slow reagent addition which is not amenable to the standard continuous equipment: plug flow tube reactor (PFR) or continuous stirred tank reactor (CSTR). A significant benefit of this strategy was the integration of an organocatalytic enantioselective reaction with straightforward product separation, including recycle of the catalyst, resulting in increased intensity of the process by maintaining high catalyst concentration in the reactor. A continuous campaign confirmed that these conditions could effectively provide high throughput of material using an automated system while maintaining high selectivity, thereby addressing nitroalkane safety and minimizing catalyst usage.

  7. Asymmetric synthesis of α-amino acids via homologation of Ni(II) complexes of glycine Schiff bases. Part 3: Michael addition reactions and miscellaneous transformations.

    PubMed

    Aceña, José Luis; Sorochinsky, Alexander E; Soloshonok, Vadim

    2014-09-01

    The major goal of this review is a critical discussion of the literature data on asymmetric synthesis of α-amino acids via Michael addition reactions involving Ni(II)-complexes of amino acids. The material covered is divided into two conceptually different groups dealing with applications of: (a) Ni(II)-complexes of glycine as C-nucleophiles and (b) Ni(II)-complexes of dehydroalanine as Michael acceptors. The first group is significantly larger and consequently subdivided into four chapters based on the source of stereocontrolling element. Thus, a chiral auxiliary can be used as a part of nucleophilic glycine Ni(II) complex, Michael acceptor or both, leading to the conditions of matching vs. mismatching stereochemical preferences. The particular focus of the review is made on the practical aspects of the methodology under discussion and mechanistic considerations.

  8. Gallic Acid, Ellagic Acid and Pyrogallol Reaction with Metallic Iron

    NASA Astrophysics Data System (ADS)

    Jaén, J. A.; González, L.; Vargas, A.; Olave, G.

    2003-06-01

    The reaction between gallic acid, ellagic acid and pyrogallol with metallic iron was studied using infrared and Mössbauer spectroscopy. Most hydrolysable tannins with interesting anticorrosive or inhibition properties are structurally related to these compounds, thus they may be used as models for the study of hydrolysable tannins and related polyphenols. The interaction was followed up to 3 months. Results indicated two different behaviors. At polyphenol concentrations higher than 1% iron converts to sparingly soluble and amorphous ferric (and ferrous) polyphenolate complexes. At lower concentrations (0.1%), the hydrolysis reactions are dominant, resulting in the formation of oxyhydroxides, which can be further reduced to compounds like magnetite by the polyphenols.

  9. CHLORINATION OF AMINO ACIDS: REACTION PATHWAYS AND REACTION RATES.

    PubMed

    How, Zuo Tong; Linge, Kathryn; Busetti, Francesco; Joll, Cynthia A

    2017-03-15

    Chlorination of amino acids can result in the formation of organic monochloramines or organic dichloramines, depending on the chlorine to amino acid ratio (Cl:AA). After formation, organic chloramines degrade into aldehydes, nitriles and N-chloraldimines. In this paper, the formation of organic chloramines from chlorination of lysine, tyrosine and valine were investigated. Chlorination of tyrosine and lysine demonstrated that the presence of a reactive secondary group can increase the Cl:AA ratio required for the formation of N,N-dichloramines, and potentially alter the reaction pathways between chlorine and amino acids, resulting in the formation of unexpected by-products. In a detailed investigation, we report rate constants for all reactions in the chlorination of valine, for the first time, using experimental results and modelling. At Cl:AA = 2.8, the chlorine was found to first react quickly with valine (5.4x104 M-1 s-1) to form N-monochlorovaline, with a slower subsequent reaction with N-monochlorovaline to form N,N-dichlorovaline (4.9x102 M-1 s-1), although some N-monochlorovaline degraded into isobutyraldehyde (1.0x10-4 s-1). The N,N-dichlorovaline then competitively degraded into isobutyronitrile (1.3x10-4 s-1) and N-chloroisobutyraldimine (1.2x10-4 s-1). In conventional drinking water disinfection, N-chloroisobutyraldimine can potentially be formed in concentrations higher than its odour threshold concentration, resulting in aesthetic challenges and an unknown health risk.

  10. Reaction of 3-Amino-1,2,4-Triazole with Diethyl Phosphite and Triethyl Orthoformate: Acid-Base Properties and Antiosteoporotic Activities of the Products.

    PubMed

    Miszczyk, Patrycja; Wieczorek, Dorota; Gałęzowska, Joanna; Dziuk, Błażej; Wietrzyk, Joanna; Chmielewska, Ewa

    2017-02-08

    The reaction of diethyl phosphite with triethyl orthoformate and a primary amine followed by hydrolysis is presented, and the reaction was suitable for the preparation of (aminomethylene)bisphosphonates. 3-Amino-1,2,4-triazole was chosen as an interesting substrate for this reaction because it possesses multiple groups that can serve as the amino component in the reaction-namely, the side-chain and triazole amines. This substrate readily forms 1,2,4-triazolyl-3-yl-aminomethylenebisphosphonic acid (compound 1) as a major product, along with N-ethylated bisphosphonates as side products. The in vitro antiproliferative effects of the synthesized aminomethylenebisphosphonic acids against J774E macrophages were determined. These compounds exhibit similar activity to zoledronic acid and higher activity than incadronic acid.

  11. Kinetic-spectrophotometric determination of ascorbic acid by inhibition of the hydrochloric acid-bromate reaction

    NASA Astrophysics Data System (ADS)

    Ensafi, Ali A.; Rezaei, B.; Movahedinia, H.

    2002-10-01

    A new analytical method was developed for the determination of ascorbic acid in fruit juice and pharmaceuticals. The method is based on its inhibition effect on the reaction between hydrochloric acid and bromate. The decolourisation of Methyl Orange by the reaction products was used to monitor the reaction spectrophotometrically at 510 nm. The linearity range of the calibration graph depends on bromate concentration. The variable affecting the rate of the reaction was investigated. The method is simple, rapid, relatively sensitive and precise. The limit of detection is 7.6×10 -6 M and calibration rang is 8×10 -6-1.2×10 -3 M ascorbic acid. The relative standard deviation of seven replication determinations of 8×10 -6 and 2×10 -5 M ascorbic acid was 2.8 and 1.7%, respectively. The influence of potential interfering substance was studied. The method was successfully applied for the determination of ascorbic acid in pharmaceuticals.

  12. Niflumic acid and cutaneous reactions in children

    PubMed Central

    Menniti-Ippolito, F; Sagliocca, L; Da Cas, R; Saggiomo, G; Di, N; Traversa, G; the, S

    2001-01-01

    In a case control study of adverse drug reactions in children, the odds ratio of developing a serious mucocutaneous event among users of niflumic acid, adjusted for concomitant use of all other drugs, was 4.9 (95% CI 1.9 to 12.8). Given the availability of safer analgesics and antipyretics, there is no indication, in our opinion, that requires the prescription of substances which bear an increased risk.

 PMID:11316692

  13. Niflumic acid and cutaneous reactions in children.

    PubMed

    Menniti-Ippolito, F; Sagliocca, L; Da Cas, R; Saggiomo, G; Di Nardo, R; Traversa, G

    2001-05-01

    In a case control study of adverse drug reactions in children, the odds ratio of developing a serious mucocutaneous event among users of niflumic acid, adjusted for concomitant use of all other drugs, was 4.9 (95% CI 1.9 to 12.8). Given the availability of safer analgesics and antipyretics, there is no indication, in our opinion, that requires the prescription of substances which bear an increased risk.

  14. Surface modification of biomaterials based on high-molecular polylactic acid and their effect on inflammatory reactions of primary human monocyte-derived macrophages: perspective for personalized therapy.

    PubMed

    Stankevich, Ksenia S; Gudima, Alexandru; Filimonov, Victor D; Klüter, Harald; Mamontova, Evgeniya M; Tverdokhlebov, Sergei I; Kzhyshkowska, Julia

    2015-06-01

    Polylactic acid (PLA) based implants can cause inflammatory complications. Macrophages are key innate immune cells that control inflammation. To provide higher biocompatibility of PLA-based implants with local innate immune cells their surface properties have to be improved. In our study surface modification technique for high-molecular PLA (MW=1,646,600g/mol) based biomaterials was originally developed and successfully applied. Optimal modification conditions were determined. Treatment of PLA films with toluene/ethanol=3/7 mixture for 10min with subsequent exposure in 0.001M brilliant green dye (BGD) solution allows to entrap approximately 10(-9)mol/cm(2) model biomolecules. The modified PLA film surface was characterized by optical microscopy, SERS, FT-IR, UV and TG/DTA/DSC analysis. Tensile strain of modified films was determined as well. The effect of PLA films modified with BGD on the inflammatory reactions of primary human monocyte-derived macrophages was investigated. We developed in vitro test-system by differentiating primary monocyte-derived macrophages on a coating material. Type 1 and type 2 inflammatory cytokines (TNFα, CCL18) secretion and histological biomarkers (CD206, stabilin-1) expression were analyzed by ELISA and confocal microscopy respectively. BGD-modified materials have improved thermal stability and good mechanical properties. However, BGD modifications induced additional donor-specific inflammatory reactions and suppressed tolerogenic phenotype of macrophages. Therefore, our test-system successfully demonstrated specific immunomodulatory effects of original and modified PLA-based biomaterials, and can be further applied for the examination of improved coatings for implants and identification of patient-specific reactions to implants.

  15. Design of a highly efficient and water-tolerant sulfonic acid nanoreactor based on tunable ordered porous silica for the von Pechmann reaction.

    PubMed

    Karimi, Babak; Zareyee, Daryoush

    2008-09-18

    Among a number of different sulfonic acid nanoreactors prepared, 5 having both acidic sites and phenyl groups located inside the mesochannels of SBA-15 was shown to be the most active and reusable catalyst in the von Pechmann reaction. The mesochannels, and covalently anchored organic groups, provide a synergistic means of an efficient approach of the reactants to acidic sites, enough space for the subsequent cyclization, and suitable hydrophobicity to drive out the water byproduct.

  16. Layered materials with coexisting acidic and basic sites for catalytic one-pot reaction sequences.

    PubMed

    Motokura, Ken; Tada, Mizuki; Iwasawa, Yasuhiro

    2009-06-17

    Acidic montmorillonite-immobilized primary amines (H-mont-NH(2)) were found to be excellent acid-base bifunctional catalysts for one-pot reaction sequences, which are the first materials with coexisting acid and base sites active for acid-base tamdem reactions. For example, tandem deacetalization-Knoevenagel condensation proceeded successfully with the H-mont-NH(2), affording the corresponding condensation product in a quantitative yield. The acidity of the H-mont-NH(2) was strongly influenced by the preparation solvent, and the base-catalyzed reactions were enhanced by interlayer acid sites.

  17. Impact of immobilizing of low molecular weight hyaluronic acid within gelatin-based hydrogel through enzymatic reaction on behavior of enclosed endothelial cells.

    PubMed

    Khanmohammadi, Mehdi; Sakai, Shinji; Taya, Masahito

    2017-04-01

    The hydrogels having the ability to promote migration and morphogenesis of endothelial cells (ECs) are useful for fabricating vascularized dense tissues in vitro. The present study explores the immobilization of low molecular weight hyaluronic acid (LMWHA) derivative within gelatin-based hydrogel to stimulate migration of ECs. The LMWHA derivative possessing phenolic hydroxyl moieties (LMWHA-Ph) was bound to gelatin-based derivative hydrogel through the horseradish peroxidase-catalyzed reaction. The motility of ECs was analyzed by scratch migration assay and microparticle-based cell migration assay. The incorporated LMWHA-Ph molecules within hydrogel was found to be preserved stably through covalent bonds during incubation. The free and immobilized LMWHA-Ph did not lose an inherent stimulatory effect on human umbilical vein endothelial cells (HUVECs). The immobilized LMWHA-Ph within gelatin-based hydrogel induced the high motility of HUVECs, accompanied by robust cytoskeleton extension, and cell subpopulation expressing CD44 cell receptor. In the presence of immobilized LMWHA-Ph, the migration distance and the number of existing HUVECs were demonstrated to be encouraged in dose-dependent and time-dependent manners. Based on the results obtained in this work, it was concluded that the enzymatic immobilization of LMWHA-Ph within gelatin-based hydrogel represents a promising approach to promote ECs' motility and further exploitation for vascular tissue engineering applications.

  18. Facile "one-pot" synthesis of poly(methacrylic acid)-based hybrid monolith via thiol-ene click reaction for hydrophilic interaction chromatography.

    PubMed

    Lv, Xumei; Tan, Wangming; Chen, Ye; Chen, Yingzhuang; Ma, Ming; Chen, Bo; Yao, Shouzhuo

    2016-07-08

    A novel sol-gel "one-pot" approach in tandem with a radical-mediated thiol-ene reaction for the synthesis of a methacrylic acid-based hybrid monolith was developed. The polymerization monomers, tetramethoxysilane (TMOS) and 3-mercaptopropyl trimethoxysilane (MPTS), were hydrolyzed in high-concentration methacrylic acid solution that also served as a hydrophilic functional monomer. The resulting solution was then mixed with initiator (2, 2'-azobis (2-methylpropionamide) dihydrochloride) and porogen (urea, polyethylene glycol 20,000) in a capillary column and polymerized in water bath. The column had a uniform porous structure and a good permeability. The evaluation of the monolith was performed by separation of small molecules including nucleosides, phenols, amides, bases and Triton X-100. The calibration curves for uridine, inosine, adenosine and cytidine were determined. All the calibration curves exhibited good linear regressions (R(2)≥0.995) within the test ranges of 0.5-40μg/mL for four nucleosides. Additionaliy, atypical hydrophilic mechanism was proved by elution order from low to high according to polarity retention time increased with increases in the content of the organic solvent in the mobile phase. Further studies indicated that hydrogen bond and electrostatic interactions existed between the polar analytes and the stationary phase. This was the mechanism of retention. The excellent separation of the BSA digest showed good hydrophility of the column and indicated the potential in separation of complex biological samples.

  19. Design optimization of tall tubular lead/acid cells based on an analysis of the reaction distribution

    NASA Astrophysics Data System (ADS)

    Asai, Kenji; Hatanaka, Teruhiro; Tsubota, Masaharu; Yonezu, Kunio; Ando, Koji

    In order to estimate the discharge performance of tall lead/acid cells (with tubular positives), changes in current and potential distributions with discharge progress were calculated with a computer on the basis of plate resistance and the current—potential—time relationship between small facing parts of positive and negative plates. The taller the cell, the larger the voltage drop along the plates. Thus, the discharge time became shorter despite a large amount of available active mass remaining in the bottom part of the plates. Various current-collector designs were evaluated, e.g., one with varying resistance at each height; a side conductor placed along the plates and connected to them at the top, centre and bottom, etc. Results revealed an optimum collector design with which the maximum discharge capacity could be obtained. Furthermore, it was shown that the side conductor markedly improved the discharge performance because the active mass near the connecting parts was appreciably used.

  20. Selective recognition of sulfate anions in a 95% ethanol solvent with a simple neutral salicylaldehyde dansyl hydrazine Schiff base tuned by Brønsted-Lowry acid-base reaction.

    PubMed

    Wei, Gao-Ning; Zhang, Jing-Li; Jia, Cang; Fan, Wei-Zhen; Lin, Li-Rong

    2014-07-15

    A new Schiff base compound, 5-(dimethylamino)-N'-(2-hydroxybenzylidene)naphthalene-1-sulfonohydrazide (R), has been synthesized, characterized, and employed as a selective fluorescence receptor for the recognition of sulfate anions. UV-vis absorption, fluorescence emission, (1)H NMR spectra and DFT calculation studies on the system have been carried out to determine the nature of the interactions between R and anions. The results reveal that the deprotonation of the phenol without the need of a strong base leads to the formation of a hydrogen-bonding complex with a -SO2-NH- group, which is responsible for the spectra changes. The deprotonation process for the selectivity recognition of sulfate can be tuned by the Brønsted-Lowry acid-base reaction in nonaqueous solutions, revealing that suitable phenolic hydroxyl acidity is the key factor for anion recognition selectivity.

  1. Selective recognition of sulfate anions in a 95% ethanol solvent with a simple neutral salicylaldehyde dansyl hydrazine Schiff base tuned by Brønsted-Lowry acid-base reaction

    NASA Astrophysics Data System (ADS)

    Wei, Gao-Ning; Zhang, Jing-Li; Jia, Cang; Fan, Wei-Zhen; Lin, Li-Rong

    2014-07-01

    A new Schiff base compound, 5-(dimethylamino)-N‧-(2-hydroxybenzylidene)naphthalene-1-sulfonohydrazide (R), has been synthesized, characterized, and employed as a selective fluorescence receptor for the recognition of sulfate anions. UV-vis absorption, fluorescence emission, 1H NMR spectra and DFT calculation studies on the system have been carried out to determine the nature of the interactions between R and anions. The results reveal that the deprotonation of the phenol without the need of a strong base leads to the formation of a hydrogen-bonding complex with a sbnd SO2sbnd NHsbnd group, which is responsible for the spectra changes. The deprotonation process for the selectivity recognition of sulfate can be tuned by the Brønsted-Lowry acid-base reaction in nonaqueous solutions, revealing that suitable phenolic hydroxyl acidity is the key factor for anion recognition selectivity.

  2. Effect of metal ions on the reactions of the cumyloxyl radical with hydrogen atom donors. Fine control on hydrogen abstraction reactivity determined by Lewis acid-base interactions.

    PubMed

    Salamone, Michela; Mangiacapra, Livia; DiLabio, Gino A; Bietti, Massimo

    2013-01-09

    A time-resolved kinetic study on the effect of metal ions (M(n+)) on hydrogen abstraction reactions from C-H donor substrates by the cumyloxyl radical (CumO(•)) was carried out in acetonitrile. Metal salt addition was observed to increase the CumO(•) β-scission rate constant in the order Li(+) > Mg(2+) > Na(+). These effects were explained in terms of the stabilization of the β-scission transition state determined by Lewis acid-base interactions between M(n+) and the radical. When hydrogen abstraction from 1,4-cyclohexadiene was studied in the presence of LiClO(4) and Mg(ClO(4))(2), a slight increase in rate constant (k(H)) was observed indicating that interaction between M(n+) and CumO(•) can also influence, although to a limited extent, the hydrogen abstraction reactivity of alkoxyl radicals. With Lewis basic C-H donors such as THF and tertiary amines, a decrease in k(H) with increasing Lewis acidity of M(n+) was observed (k(H)(MeCN) > k(H)(Li(+)) > k(H)(Mg(2+))). This behavior was explained in terms of the stronger Lewis acid-base interaction of M(n+) with the substrate as compared to the radical. This interaction reduces the degree of overlap between the α-C-H σ* orbital and a heteroatom lone-pair, increasing the C-H BDE and destabilizing the carbon centered radical formed after abstraction. With tertiary amines, a >2-order of magnitude decrease in k(H) was measured after Mg(ClO(4))(2) addition up to a 1.5:1 amine/Mg(ClO(4))(2) ratio. At higher amine concentrations, very similar k(H) values were measured with and without Mg(ClO(4))(2). These results clearly show that with strong Lewis basic substrates variations in the nature and concentration of M(n+) can dramatically influence k(H), allowing for a fine control of the substrate hydrogen atom donor ability, thus providing a convenient method for C-H deactivation. The implications and generality of these findings are discussed.

  3. Direct RNA detection without nucleic acid purification and PCR: Combining sandwich hybridization with signal amplification based on branched hybridization chain reaction.

    PubMed

    Xu, Yao; Zheng, Zhi

    2016-05-15

    We have developed a convenient, robust and low-cost RNA detection system suitable for high-throughput applications. This system uses a highly specific sandwich hybridization to capture target RNA directly onto solid support, followed by on-site signal amplification via 2-dimensional, branched hybridizing chain polymerization through toehold-mediated strand displacement reaction. The assay uses SYBR Green to detect targets at concentrations as low as 1 pM, without involving nucleic acid purification or any enzymatic reaction, using ordinary oligonucleotides without modification or labeling. The system was demonstrated in the detection of malaria RNA in blood and GAPDH gene expression in cell lysate.

  4. Kinetics of an acid-base catalyzed reaction (aspartame degradation) as affected by polyol-induced changes in buffer pH and pK values.

    PubMed

    Chuy, S; Bell, L N

    2009-01-01

    The kinetics of an acid-base catalyzed reaction, aspartame degradation, were examined as affected by the changes in pH and pK(a) values caused by adding polyols (sucrose, glycerol) to phosphate buffer. Sucrose-containing phosphate buffer solutions had a lower pH than that of phosphate buffer alone, which contributed, in part, to reduced aspartame reactivity. A kinetic model was introduced for aspartame degradation that encompassed pH and buffer salt concentrations, both of which change with a shift in the apparent pK(a) value. Aspartame degradation rate constants in sucrose-containing solutions were successfully predicted using this model when corrections (that is, lower pH, lower apparent pK(a) value, buffer dilution from the polyol) were applied. The change in buffer properties (pH, pK(a)) from adding sucrose to phosphate buffer does impact food chemical stability. These effects can be successfully incorporated into predictive kinetic models. Therefore, pH and pK(a) changes from adding polyols to buffer should be considered during food product development.

  5. Multicomponent cascade reactions of unprotected carbohydrates and amino acids.

    PubMed

    Voigt, Benjamin; Linke, Michael; Mahrwald, Rainer

    2015-06-05

    Herein an operationally simple multicomponent reaction of unprotected carbohydrates with amino acids and isonitriles is presented. By the extension of this Ugi-type reaction to an unprotected disaccharide a novel glycopeptide structure was accessible.

  6. Incorporation of Alkylamine into Metal-Organic Frameworks through a Brønsted Acid-Base Reaction for CO2 Capture.

    PubMed

    Li, Hao; Wang, Kecheng; Feng, Dawei; Chen, Ying-Pin; Verdegaal, Wolfgang; Zhou, Hong-Cai

    2016-10-06

    The escalating atmospheric CO2 concentration is one of the most urgent environmental concerns of our age. To effectively capture CO2 , various materials have been studied. Among them, alkylamine-modified metal-organic frameworks (MOFs) are considered to be promising candidates. In most cases, alkylamine molecules are integrated into MOFs through the coordination bonds formed between open metal sites (OMSs) and amine groups. Thus, the alkylamine density, as well as the corresponding CO2 uptake in MOFs, are severely restricted by the density of OMSs. To overcome this limit, other approaches to incorporating alkylamine into MOFs are highly desired. We have developed a new method based on Brønsted acid-base reaction to tether alkylamines into Cr-MIL-101-SO3 H for CO2 capture. A systematic optimization of the amine tethering process was also conducted to maximize the CO2 uptake of the modified MOF. Under the optimal amine tethering condition, the obtained tris(2-aminoethyl)amine-functionalized Cr-MIL-101-SO3 H (Cr-MIL-101-SO3 H-TAEA) has a cyclic CO2 uptake of 2.28 mmol g(-1) at 150 mbar and 40 °C, and 1.12 mmol g(-1) at 0.4 mbar and 20 °C. The low-cost starting materials and simple synthetic procedure for the preparation of Cr-MIL-101-SO3 H-TAEA suggest that it has the potential for large-scale production and practical applications.

  7. Development of a Lewis Base Catalyzed Selenocyclization Reaction

    ERIC Educational Resources Information Center

    Collins, William

    2009-01-01

    The concept of Lewis base activation of selenium Lewis acids has been effectively reduced to practice in the Lewis base catalyzed selenofunctionalization of unactivated olefins. In this reaction, the weakly acidic species, "N"-phenylselenyl succinimide, is cooperatively activated by the addition of a "soft" Lewis base donor (phosphine sulfides,…

  8. Magnetite-supported sulfonic acid: a retrievable nanocatalyst for the Ritter reaction and multicomponent reactions

    EPA Science Inventory

    Magnetite-sulfonic acid (NanocatFe-OSO3H), prepared by wet-impregnation method, serves as a magnetically retrievable sustainable catalyst for the Ritter reaction which can be used in several reaction cycles without any loss of activity.

  9. Kinetics of haloacetic acid reactions with Fe(0).

    PubMed

    Zhang, Li; Arnold, William A; Hozalski, Raymond M

    2004-12-15

    Detailed kinetic studies of the reactions of haloacetic acids (HAAs) with Fe(0) were performed in longitudinally mixed batch reactors. The reactions of tribromoacetic acid (TBAA), bromodichloroacetic acid, and chlorodibromoacetic acid were mass transfer limited, with corrected mass transfer coefficients of 3.7-3.9 x 10(-4) m/s. The reactions of trichloroacetic acid (TCAA), dichloroacetic acid (DCAA), chloroacetic acid (CAA), and bromoacetic acid (BAA) were reaction limited. Bromochloroacetic acid (BCAA) and dibromoacetic acid (DBAA) were partially reaction limited. For the reaction limited species and partially reaction limited species, intra- and interspecies competition effects were observed. A Langmuir-Hinshelwood-Hougen-Watson kinetic model incorporating a mass transfer term was adopted to account for these effects. The lumped kinetic parameters for the HAAs ranged from 0.04 to 248 microM min(-1) for an iron loading of 0.3 g of Fe/125 mL and followed the trend DBAA > BCAA > TCAA > BAA > DCAA. The adsorption parameters ranged from 0.0007 to 0.0065 microM(-1). The effect of dissolved oxygen (DO) on the reaction of TBAA or BAA with Fe(0) was also investigated. No significant effect of DO on the reaction rate of TBAA, which is a mass transfer limited species, was observed. A lag phase, however, was observed for the reaction of BAA, which is a reaction limited species, until the DO was depleted. Simulations were performed to investigate the potential significance of the reactions of HAAs with Fe(0) in water distribution systems.

  10. Effect of Bronsted Acids and Bases, and Lewis Acid (Sn(2+)) on the Regiochemistry of the Reaction of Amines with Trifluoromethyl-β-diketones: Reaction of 3-Aminopyrrole to Selectively Produce Regioisomeric 1H-Pyrrolo[3,2-b]pyridines.

    PubMed

    De Rosa, Michael; Arnold, David; Hartline, Douglas; Truong, Linda; Verner, Roman; Wang, Tianwei; Westin, Christian

    2015-12-18

    Reaction of 3-aminopyrrole (as its salt) with trifluoromethyl-β-diketones gave γ-1H-pyrrolo[3,2-b]pyridines via reaction at the less reactive carbonyl group. The trifluoromethyl group increased the electrophilicity of the adjacent carbonyl group and decreased the basicity of the hydroxyl group of the CF3 amino alcohol formed. This amino alcohol was formed faster, but its subsequent dehydration to the β-enaminone was slow resulting in the preferential formation of the γ-regioisomer. Reaction of 4,4,4-trifluoro-1-phenyl-1,3-butadione with 3-aminopyrrole was carried out using a series of 6 amine buffers. Yields of the α-1H-pyrrolo[3,2-b]pyridine increased as the pKa of the amine buffer decreased. Surprisingly the yield went down at higher pKas. There was a change in mechanism as the reaction mixture became more basic. With strong amines trifluoromethyl-β-diketones were present mainly or completely as the enolate. Under reductive conditions (3-nitropyrrole/Sn/AcOH/trifluoromethyl-β-diketone) the α-1H-pyrrolo[3,2-b]pyridine was the major product as a result of Lewis acid catalysis by Sn(2+). Similar α-regiochemistry was observed when the reaction of the 3-aminopyrrole salt with trifluoromethyl-β-diketones was carried out in the presence of base and tin(II) acetate.

  11. Flow injection determination of diclofenac sodium based on its sensitizing effect on the chemiluminescent reaction of acidic potassium permanganate-formaldehyde.

    PubMed

    Song, Jingjing; Sun, Pulv; Ji, Zhongling; Li, Jianguo

    2015-02-01

    A sensitive and simple chemiluminescent (CL) method for the determination of diclofenac sodium has been developed by combining the flow injection technique and its sensitizing effect on the weak CL reaction between formaldehyde and acidic potassium permanganate. A calibration curve is constructed for diclofenac sodium under optimized experimental parameters over the range 0.040-5.0 µg/mL and the limit of detection is 0.020 µg/mL (3σ). The inter-assay relative standard deviation for 0.040 µg/mL diclofenac sodium (n = 11) is 2.0%. This method is rapid, sensitive, simple, and shows good selectivity and reproducibility. The proposed method has been successfully applied to the determination of the studied diclofenac sodium in pharmaceutical preparations with satisfactory results. Furthermore, the possible mechanism for the CL reaction has been discussed in detail on the basis of UV and CL spectra.

  12. Production of L-malic acid with fixation of HCO3(-) by malic enzyme-catalyzed reaction based on regeneration of coenzyme on electrode modified by layer-by-layer self-assembly method.

    PubMed

    Zheng, Haitao; Ohno, Yoko; Nakamori, Toshihiko; Suye, Shin-Ichiro

    2009-01-01

    Malic enzyme prepared and purified from Brevundimonas diminuta IFO13182 catalyzed the decarboxylation reaction of malate to pyruvate and CO2 using NAD+ as the coenzyme, and the reverse reaction was used in the present study for L-malic acid production with fixation of HCO3(-) as a model compound for carbon source. The L-malic acid production was based on electrochemical regeneration of NADH on a carbon plate electrode modified by layer-by-layer adsorption of polymer-bound mediator (Alginic acid bound viologen derivative, Alg-V), polymer-bound coenzyme (Alginic acid bound NAD+, Alg-NAD+), and lipoamide dehydrogenase (LipDH). Electrochemical reduction of immobilized NAD+ catalyzed by LipDH in a multilayer film was achieved, and the L-malic acid production with HCO3(-) fixation system with layer-by-layer immobilization of Alg-V/LipDH/Alg-NAD+/malic enzyme multilayer film on the electrode gave an L-malic acid production of nearly 11.9 mmol and an HCO3(-) fixation rate of nearly 47.4% in a buffer containing only KHCO3 and pyruvic acid potassium salt, using a cation exchange membrane. The total turnover number of NADH within 48 h was about 19,000, which suggests that efficient NADH regeneration and fast electron transfer were achieved within the multilayer film, and that the modified electrode is a potential method for the fixation of HCO3(-) without addition of free coenzyme.

  13. Carbogenic molecular sieves for reaction and separation by design: A novel approach to shape selective super base, super acid and catalytic membranes. Final report

    SciTech Connect

    Foley, Henry C.

    2002-03-18

    This report details the findings of three years of research plus one year of a no-cost extension. Primary results are the work with supported nanoporous carbon membranes for separation and reaction as well as with cesium-nanoporous carbon catalysts. The work resulted in 17 plus 2 papers (2 are in progress) and partial or full support for five Ph.D. students. Two patents were filed based on this research.

  14. 40 CFR 721.10125 - Alkenedioic acid, dialkyl ester, reaction products with polyaminocarbomonocycle and alkenoic acid...

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Alkenedioic acid, dialkyl ester, reaction products with polyaminocarbomonocycle and alkenoic acid alkyl ester (generic). 721.10125 Section... Substances § 721.10125 Alkenedioic acid, dialkyl ester, reaction products with polyaminocarbomonocycle...

  15. 40 CFR 721.10125 - Alkenedioic acid, dialkyl ester, reaction products with polyaminocarbomonocycle and alkenoic acid...

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Alkenedioic acid, dialkyl ester, reaction products with polyaminocarbomonocycle and alkenoic acid alkyl ester (generic). 721.10125 Section... Substances § 721.10125 Alkenedioic acid, dialkyl ester, reaction products with polyaminocarbomonocycle...

  16. 40 CFR 721.10125 - Alkenedioic acid, dialkyl ester, reaction products with polyaminocarbomonocycle and alkenoic acid...

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Alkenedioic acid, dialkyl ester, reaction products with polyaminocarbomonocycle and alkenoic acid alkyl ester (generic). 721.10125 Section... Substances § 721.10125 Alkenedioic acid, dialkyl ester, reaction products with polyaminocarbomonocycle...

  17. 40 CFR 721.10125 - Alkenedioic acid, dialkyl ester, reaction products with polyaminocarbomonocycle and alkenoic acid...

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Alkenedioic acid, dialkyl ester, reaction products with polyaminocarbomonocycle and alkenoic acid alkyl ester (generic). 721.10125 Section... Substances § 721.10125 Alkenedioic acid, dialkyl ester, reaction products with polyaminocarbomonocycle...

  18. 40 CFR 721.10125 - Alkenedioic acid, dialkyl ester, reaction products with polyaminocarbomonocycle and alkenoic acid...

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Alkenedioic acid, dialkyl ester, reaction products with polyaminocarbomonocycle and alkenoic acid alkyl ester (generic). 721.10125 Section... Substances § 721.10125 Alkenedioic acid, dialkyl ester, reaction products with polyaminocarbomonocycle...

  19. Fragmentation reactions of deprotonated peptides containing aspartic acid

    NASA Astrophysics Data System (ADS)

    Harrison, Alex G.; Young, Alex B.

    2006-09-01

    The fragmentation reactions of deprotonated peptides containing aspartic acid have been elucidated using MS2 and MS3 experiments and accurate mass measurements where necessary. The disposition of labile (N and O bonded) hydrogens in the fragmentation products has been studied by exchanging the labile hydrogens for deuterium whereby the [MD]- ion is formed on electrospray ionization. [alpha]-Aspartyl and [beta]-aspartyl dipeptides give very similar fragment ion spectra on collisional activation, involving for both species primarily formation of the y1 ion and loss of H2O from [MH]- followed by further fragmentation, thus precluding the distinction of the isomeric species by negative ion tandem mass spectrometry. Dipeptides of sequence HXxxAspOH give characteristic spectra different from the [alpha]- and [beta]-isomers. For larger peptides containing aspartic acid a common fragmentation reaction involves nominal cleavage of the NC bond N-terminal to the aspartic acid residue to form a c ion (deprotonated amino acid amide (c1) or peptide amide (cn)) and the complimentary product involving elimination of a neutral amino acid amide or peptide amide. When aspartic acid is in the C-terminal position this fragmentation reaction occurs from the [MH]- ion while when the aspartic acid is not in the C-terminal position the fragmentation reaction occurs mainly from the [MHH2O]- ion. The products of this NC bond cleavage reaction serve to identify the position of the aspartic acid residue in the peptide.

  20. Iminodicarboxylic acids in the Murchison meteorite: Evidence of Strecker reactions

    NASA Astrophysics Data System (ADS)

    Lerner, Narcinda R.; Cooper, George W.

    2005-06-01

    α-Amino acids and α-hydroxy acids are well known constituents of several carbonaceous meteorites. One proposed mechanism of their formation is the reactions of CN -, NH 3, aldehydes and ketones in aqueous solution, a Strecker-like synthesis. Iminodicarboxylic acids, relatively unusual in molecular structure, are significant by-products of laboratory Strecker syntheses of α-amino acids. It is therefore notable that an analogous suite of imino acids has not been reported in CM2 chondrites where amino and hydroxy acids are abundant. In this work, aqueous extracts of the Murchison meteorite were examined for the presence of imino acids; GC-MS and HPLC molecular analyses revealed a complex suite of such acids. With the exception of one of the seven-carbon members, all of the C4 through C7 imino acids were observed in Murchison. These observations suggest that the Strecker synthesis made, at least, some contribution to the formation of extraterrestrial amino acids.

  1. Nucleic acid amplification: Alternative methods of polymerase chain reaction

    PubMed Central

    Fakruddin, Md; Mannan, Khanjada Shahnewaj Bin; Chowdhury, Abhijit; Mazumdar, Reaz Mohammad; Hossain, Md. Nur; Islam, Sumaiya; Chowdhury, Md. Alimuddin

    2013-01-01

    Nucleic acid amplification is a valuable molecular tool not only in basic research but also in application oriented fields, such as clinical medicine development, infectious diseases diagnosis, gene cloning and industrial quality control. A comperehensive review of the literature on the principles, applications, challenges and prospects of different alternative methods of polymerase chain reaction (PCR) was performed. PCR was the first nucleic acid amplification method. With the advancement of research, a no of alternative nucleic acid amplification methods has been developed such as loop mediated isothermal amplification, nucleic acid sequence based amplification, strand displacement amplification, multiple displacement amplification. Most of the alternative methods are isothermal obviating the need for thermal cyclers. Though principles of most of the alternate methods are relatively complex than that of PCR, they offer better applicability and sensitivity in cases where PCR has limitations. Most of the alternate methods still have to prove themselves through extensive validation studies and are not available in commercial form; they pose the potentiality to be used as replacements of PCR. Continuous research is going on in different parts of the world to make these methods viable technically and economically. PMID:24302831

  2. Nucleic acid amplification: Alternative methods of polymerase chain reaction.

    PubMed

    Fakruddin, Md; Mannan, Khanjada Shahnewaj Bin; Chowdhury, Abhijit; Mazumdar, Reaz Mohammad; Hossain, Md Nur; Islam, Sumaiya; Chowdhury, Md Alimuddin

    2013-10-01

    Nucleic acid amplification is a valuable molecular tool not only in basic research but also in application oriented fields, such as clinical medicine development, infectious diseases diagnosis, gene cloning and industrial quality control. A comperehensive review of the literature on the principles, applications, challenges and prospects of different alternative methods of polymerase chain reaction (PCR) was performed. PCR was the first nucleic acid amplification method. With the advancement of research, a no of alternative nucleic acid amplification methods has been developed such as loop mediated isothermal amplification, nucleic acid sequence based amplification, strand displacement amplification, multiple displacement amplification. Most of the alternative methods are isothermal obviating the need for thermal cyclers. Though principles of most of the alternate methods are relatively complex than that of PCR, they offer better applicability and sensitivity in cases where PCR has limitations. Most of the alternate methods still have to prove themselves through extensive validation studies and are not available in commercial form; they pose the potentiality to be used as replacements of PCR. Continuous research is going on in different parts of the world to make these methods viable technically and economically.

  3. Acid-functionalized polyolefin materials and their use in acid-promoted chemical reactions

    DOEpatents

    Oyola, Yatsandra; Tian, Chengcheng; Bauer, John Christopher; Dai, Sheng

    2016-06-07

    An acid-functionalized polyolefin material that can be used as an acid catalyst in a wide range of acid-promoted chemical reactions, wherein the acid-functionalized polyolefin material includes a polyolefin backbone on which acid groups are appended. Also described is a method for the preparation of the acid catalyst in which a precursor polyolefin is subjected to ionizing radiation (e.g., electron beam irradiation) of sufficient power and the irradiated precursor polyolefin reacted with at least one vinyl monomer having an acid group thereon. Further described is a method for conducting an acid-promoted chemical reaction, wherein an acid-reactive organic precursor is contacted in liquid form with a solid heterogeneous acid catalyst comprising a polyolefin backbone of at least 1 micron in one dimension and having carboxylic acid groups and either sulfonic acid or phosphoric acid groups appended thereto.

  4. Imino Acids in the Murchison Meteorite: Evidence of Strecker Reactions

    NASA Technical Reports Server (NTRS)

    Lerner, N. R.; Cooper, G. W.

    2003-01-01

    Both alpha-amino acids and alpha-hydroxy acids occur in aqueous extracts of the Murchison carbonaceous meteorite. The Strecker-cyanohydrin reaction, the reaction of carbonyl compounds, cyanide, and ammonia to produce amino and hydroxy acids, has been proposed as a source of such organic acids in meteorites. Such syntheses are consistent with the suggestion that interstellar precursors of meteoritic organic compounds accreted on the meteorite parent body together with other ices. Subsequent internal heating of the parent body melted these ices and led to the formation of larger compounds in synthetic reactions during aqueous alteration, which probably occurred at temperatures between 273K and 298K. In the laboratory, imino acids are observed as important by-products of the Strecker synthesis.

  5. Spectrophotometric method for determination and kinetics of amino acids through their reaction with syringaldehyde

    NASA Astrophysics Data System (ADS)

    Medien, H. A. A.

    1998-02-01

    A spectrophotometric method is described for the determination of amino acids. The method is based on the reaction between amino acids and syringaldehyde at pH 9.0, by which a color is developed with maximum absorption at 420 nm in aqueous methyl alcohol. The absorption of the product obeys Beer's law within the concentration range of 0.025-0.5 mM of original amino acid. The kinetics of the reaction follows overall second order kinetics, first order in each of the reactants. The rates of the reaction were investigated as a function of pH of the reaction medium and structure of the amino compounds. Logarithms of the second-order rate constants increased with amino acid anion concentration as the pH was increased. The mechanisms of the reaction have been discussed.

  6. Nucleic acid based logical systems.

    PubMed

    Han, Da; Kang, Huaizhi; Zhang, Tao; Wu, Cuichen; Zhou, Cuisong; You, Mingxu; Chen, Zhuo; Zhang, Xiaobing; Tan, Weihong

    2014-05-12

    Researchers increasingly visualize a significant role for artificial biochemical logical systems in biological engineering, much like digital logic circuits in electrical engineering. Those logical systems could be utilized as a type of servomechanism to control nanodevices in vitro, monitor chemical reactions in situ, or regulate gene expression in vivo. Nucleic acids (NA), as carriers of genetic information with well-regulated and predictable structures, are promising materials for the design and engineering of biochemical circuits. A number of logical devices based on nucleic acids (NA) have been designed to handle various processes for technological or biotechnological purposes. This article focuses on the most recent and important developments in NA-based logical devices and their evolution from in vitro, through cellular, even towards in vivo biological applications.

  7. Carbocations as Lewis acid catalysts in Diels-Alder and Michael addition reactions.

    PubMed

    Bah, Juho; Franzén, Johan

    2014-01-20

    In general, Lewis acid catalysts are metal-based compounds that owe their reactivity to a low-lying empty orbital. However, one potential Lewis acid that has received negligible attention as a catalyst is the carbocation. We have demonstrated the potential of the carbocation as a highly powerful Lewis acid catalyst for organic reactions. The stable and easily available triphenylmethyl (trityl) cation was found to be a highly efficient catalyst for the Diels-Alder reaction for a range of substrates. Catalyst loadings as low as 500 ppm, excellent yields, and good endo/exo selectivities were achieved. Furthermore, by changing the electronic properties of the substituents on the tritylium ion, the Lewis acidity of the catalyst could be tuned to control the outcome of the reaction. The ability of this carbocation as a Lewis acid catalyst was also further extended to the Michael reaction.

  8. Effective and site-specific phosphoramidation reaction for universally labeling nucleic acids.

    PubMed

    Su, Yu-Chih; Chen, Hsing-Yin; Ko, Ni Chien; Hwang, Chi-Ching; Wu, Min Hui; Wang, Li-Fang; Wang, Yun-Ming; Chang, Sheng-Nan; Wang, Eng-Chi; Wang, Tzu-Pin

    2014-03-15

    Here we report efficient and selective postsynthesis labeling strategies, based on an advanced phosphoramidation reaction, for nucleic acids of either synthetic or enzyme-catalyzed origin. The reactions provided phosphorimidazolide intermediates of DNA or RNA which, whether reacted in one pot (one-step) or purified (two-step), were directly or indirectly phosphoramidated with label molecules. The acquired fluorophore-labeled nucleic acids, prepared from the phosphoramidation reactions, demonstrated labeling efficacy by their F/N ratio values (number of fluorophores per molecule of nucleic acid) of 0.02-1.2 which are comparable or better than conventional postsynthesis fluorescent labeling methods for DNA and RNA. Yet, PCR and UV melting studies of the one-step phosphoramidation-prepared FITC-labeled DNA indicated that the reaction might facilitate nonspecific hybridization in nucleic acids. Intrinsic hybridization specificity of nucleic acids was, however, conserved in the two-step phosphoramidation reaction. The reaction of site-specific labeling nucleic acids at the 5'-end was supported by fluorescence quenching and UV melting studies of fluorophore-labeled DNA. The two-step phosphoramidation-based, effective, and site-specific labeling method has the potential to expedite critical research including visualization, quantification, structural determination, localization, and distribution of nucleic acids in vivo and in vitro.

  9. Brønsted acid catalyzed asymmetric aldol reaction: a complementary approach to enamine catalysis.

    PubMed

    Pousse, Guillaume; Le Cavelier, Fabien; Humphreys, Luke; Rouden, Jacques; Blanchet, Jérôme

    2010-08-20

    A syn-enantioselective aldol reaction has been developed using Brønsted acid catalysis based on H(8)-BINOL-derived phosphoric acids. This method affords an efficient synthesis of various beta-hydroxy ketones, some of which could not be synthesized using enamine organocatalysis.

  10. 40 CFR 721.10629 - Fatty acids, tall-oil, reaction products with modified fatty acids and polyalkanolamines (generic).

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Fatty acids, tall-oil, reaction... Fatty acids, tall-oil, reaction products with modified fatty acids and polyalkanolamines (generic). (a... generically as fatty acids, tall-oil, reaction products with modified fatty acids and polyalkanolamines (PMN...

  11. 40 CFR 721.10629 - Fatty acids, tall-oil, reaction products with modified fatty acids and polyalkanolamines (generic).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Fatty acids, tall-oil, reaction... Fatty acids, tall-oil, reaction products with modified fatty acids and polyalkanolamines (generic). (a... generically as fatty acids, tall-oil, reaction products with modified fatty acids and polyalkanolamines (PMN...

  12. Comparative study on sample stacking by moving reaction boundary formed with weak acid and weak or strong base in capillary electrophoresis: II. Experiments.

    PubMed

    Zhang, Wei; Fan, Liuyin; Shao, Jing; Li, Si; Li, Shan; Cao, Chengxi

    2011-04-15

    To demonstrate the theoretic method on the stacking of zwitterion with moving reaction boundary (MRB) in the accompanying paper, the relevant experiments were performed. The experimental results quantitatively show that (1) MRB velocity, including the comparisons between MRB and zwitterionic velocities, possesses key importance to the design of MRB stacking; (2) a much long front alkaline plug without sample should be injected before the sample injection for a complete stacking of zwitterion if sample buffer is prepared with strong base, conversely no such plug is needed if using a weak base as the sample buffer with proper concentration and pH value; (3) the presence of salt in MRB system holds dramatic effect on the MRB stacking if sample solution is a strong base, but has no effect if a weak alkali is used as sample solution; (4) all of the experiments of this paper, including the previous work, quantitatively manifest the theory and predictions shown in the accompanying paper. In addition, the so-called derivative MRB-induced re-stacking and transient FASI-induced re-stacking were also observed during the experiments, and the relevant mechanisms were briefly demonstrated with the results. The theory and its calculation procedures developed in the accompanying paper can be well used for the predictions to the MRB stacking of zwitterion in CE.

  13. Kinetic study of free fatty acid esterification reaction catalyzed by recoverable and reusable hydrochloric acid.

    PubMed

    Su, Chia-Hung

    2013-02-01

    The catalytic performance and recoverability of several homogeneous acid catalysts (hydrochloric, sulfuric, and nitric acids) for the esterification of enzyme-hydrolyzed free fatty acid (FFA) and methanol were studied. Although all tested catalysts drove the reaction to a high yield, hydrochloric acid was the only catalyst that could be considerably recovered and reused. The kinetics of the esterification reaction catalyzed by hydrochloric acid was investigated under varying catalyst loading (0.1-1M), reaction temperature (303-343K), and methanol/FFA molar ratio (1:1-20:1). In addition, a pseudo-homogeneous kinetic model incorporating the above factors was developed. A good agreement (r(2)=0.98) between the experimental and calculated data was obtained, thus proving the reliability of the model. Furthermore, the reusability of hydrochloric acid in FFA esterification can be predicted by the developed model. The recoverable hydrochloric acid achieved high yields of FFA esterification within five times of reuse.

  14. Liquid chromatography coupled to quadrupole-time of flight tandem mass spectrometry based quantitative structure-retention relationships of amino acid analogues derivatized via n-propyl chloroformate mediated reaction.

    PubMed

    Kritikos, Nikolaos; Tsantili-Kakoulidou, Anna; Loukas, Yannis L; Dotsikas, Yannis

    2015-07-17

    In the current study, quantitative structure-retention relationships (QSRR) were constructed based on data obtained by a LC-(ESI)-QTOF-MS/MS method for the determination of amino acid analogues, following their derivatization via chloroformate esters. Molecules were derivatized via n-propyl chloroformate/n-propanol mediated reaction. Derivatives were acquired through a liquid-liquid extraction procedure. Chromatographic separation is based on gradient elution using methanol/water mixtures from a 70/30% composition to an 85/15% final one, maintaining a constant rate of change. The group of examined molecules was diverse, including mainly α-amino acids, yet also β- and γ-amino acids, γ-amino acid analogues, decarboxylated and phosphorylated analogues and dipeptides. Projection to latent structures (PLS) method was selected for the formation of QSRRs, resulting in a total of three PLS models with high cross-validated coefficients of determination Q(2)Y. For this reason, molecular structures were previously described through the use of descriptors. Through stratified random sampling procedures, 57 compounds were split to a training set and a test set. Model creation was based on multiple criteria including principal component significance and eigenvalue, variable importance, form of residuals, etc. Validation was based on statistical metrics Rpred(2),QextF2(2),QextF3(2) for the test set and Roy's metrics rm(Av)(2) and rm(δ)(2), assessing both predictive stability and internal validity. Based on aforementioned models, simplified equivalent were then created using a multi-linear regression (MLR) method. MLR models were also validated with the same metrics. The suggested models are considered useful for the estimation of retention times of amino acid analogues for a series of applications.

  15. Dissolution, speciation, and reaction of acetaldehyde in cold sulfuric acid

    NASA Astrophysics Data System (ADS)

    Michelsen, Rebecca R.; Ashbourn, Samantha F. M.; Iraci, Laura T.

    2004-12-01

    The uptake of gas-phase acetaldehyde [CH3CHO, ethanal] by aqueous sulfuric acid solutions was studied under upper tropospheric/lower stratospheric (UT/LS) conditions. The solubility of acetaldehyde was found to be low, between 2 × 102 M atm-1 and 1.5 × 105 M atm-1 under the ranges of temperature (211-241 K) and acid composition (39-76 weight percent, wt%, H2SO4) studied. Under most conditions, acetaldehyde showed simple solubility behavior when exposed to sulfuric acid. Under moderately acidic conditions (usually 47 wt% H2SO4), evidence of reaction was observed. Enhancement of uptake at long times was occasionally detected in conjunction with reaction. The source of these behaviors and the effect of acetaldehyde speciation on solubility are discussed. Implications for the uptake of oxygenated organic compounds by tropospheric aerosols are considered.

  16. A computational study of ultrafast acid dissociation and acid-base neutralization reactions. II. The relationship between the coordination state of solvent molecules and concerted versus sequential acid dissociation.

    PubMed

    Maurer, Patrick; Thomas, Vibin; Iftimie, Radu

    2011-03-07

    We investigate the role played by the coordination state of pre-existing water wires during the dissociation of moderately strong acids by means of first-principles molecular dynamics calculations. By preparing 2,4,6-tricyanophenol (calc. pKa∼0.5) in two different initial states, we are able to observe sequential as well as concerted trajectories of dissociation: On one hand, equilibrium dissociation takes place on a ∼50 ps timescale; proton conduction occurs through three-coordinated water wires in this case, by means of sequential Grotthus hopping. On the other hand, by preparing 2,4,6-tricyanophenol in a hydration state inherited from that of equilibrated phenol (calc. pKa=7.6), the moderately strong acid finds itself in a presolvated state from which dissociation can take place on a ∼1 ps timescale. In this case, concerted dissociation trajectories are observed, which consist of proton translocation through two intervening, four-coordinated, water molecules in 0.1-1.0 ps. The present results suggest that, in general, the mechanism of proton translocation depends on how the excess proton is injected into a hydrogen bond network. In particular, if the initial conditions favour proton release to a fourfold H-bonded water molecule, proton translocation by as much as 6-8 Å can take place on a sub-picosecond timescale.

  17. Deoxyribonucleic Acid Polymerase of Rous Sarcoma Virus: Reaction Conditions and Analysis of the Reaction Product Nucleic Acids

    PubMed Central

    Bishop, D. H. L.; Ruprecht, Ruth; Simpson, R. W.; Spiegelman, S.

    1971-01-01

    Reaction conditions for Rous sarcoma virus ribonucleic acid (RNA)-instructed deoxyribonucleic acid (DNA) polymerase activity are described whereby the viral RNA is relatively protected from endogenous or added nuclease activity. Three analyses of reaction product nucleic acids (3H-RNA, 32P-DNA) were compared, namely, gel electrophoresis, Cs2SO4 gradient centrifugation, and hydroxyapatite column chromatography. It was found that hydroxyapatite analysis could be misleading unless the state of the template RNA was monitored concomitantly with the DNA analysis. Gel electrophoresis and Cs2SO4 gradient centrifugation gave comparable results. It was concluded that analyses of the product of reverse transcriptase reactions should not only refer to the template RNA and product DNA species, but also be performed with virus or viral RNA which do not have or obtain nicks in the 60S RNA. Otherwise, interpretation of the results would have the ambiguity of potential artifacts caused by those degraded RNA molecules. PMID:4332143

  18. Dissociative attachment reactions of electrons with strong acid molecules

    SciTech Connect

    Adams, N.G.; Smith, D.; Viggiano, A.A.; Paulson, J.F.; Henchman, M.J.

    1986-06-15

    Using the flowing afterglow/Langmuir probe (FALP) technique, we have determined (at variously 300 and 570 K) the dissociative attachment coefficients ..beta.. for the reactions of electrons with the common acids HNO/sub 3/ (producing NO/sup -//sub 2/) and H/sub 2/SO/sub 4/ (HSO/sup -//sub 4/), the superacids FSO/sub 3/H (FSO/sup -//sub 3/), CF/sub 3/SO/sub 3/H (CF/sub 3/SO/sup -//sub 3/), ClSO/sub 3/H (ClSO/sup -//sub 3/,Cl/sup -/), the acid anhydride (CF/sub 3/SO/sub 2/)/sub 2/O (CF/sub 3/SO/sup -//sub 3/), and the halogen halides HBr (Br/sup -/) and HI (I/sup -/). The anions formed in the reactions are those given in the parentheses. The reactions with HF and HCl were investigated, but did not occur at a measurable rate since they are very endothermic. Dissociative attachment is rapid for the common acids, the superacids, and the anhydride, the measured ..beta.. being appreciable fractions of the theoretical maximum ..beta.. for such reactions, ..beta../sub max/. The HI reaction is very fast ( ..beta..approx...beta../sub max/) but the HBr reaction occurs much more slowly because it is significantly endothermic. The data indicate that the extreme acidity of the (Bronsted-type) superacids has its equivalence in the very efficient gas-phase dissociative attachment which these species undergo when reacting with free electrons. The anions of the superacids generated in these reactions, notably FSO/sup -//sub 3/ and CF/sub 3/SO/sup -//sub 3/, are very stable (unreactive) implying exceptionally large electron affinities for the FSO/sub 3/ and CF/sub 3/SO/sub 3/ radicals.

  19. The Roles of Acids and Bases in Enzyme Catalysis

    ERIC Educational Resources Information Center

    Weiss, Hilton M.

    2007-01-01

    Many organic reactions are catalyzed by strong acids or bases that protonate or deprotonate neutral reactants leading to reactive cations or anions that proceed to products. In enzyme reactions, only weak acids and bases are available to hydrogen bond to reactants and to transfer protons in response to developing charges. Understanding this…

  20. An acidic layered clay is combined with a basic layered clay for one-pot sequential reactions.

    PubMed

    Motokura, Ken; Fujita, Noriaki; Mori, Kohsuke; Mizugaki, Tomoo; Ebitani, Kohki; Kaneda, Kiyotomi

    2005-07-13

    A Ti4+-exchanged montmorillonite (Ti4+-mont) and a hydrotalcite (HT) are strong solid Brønsted acid and base, and these two clay catalysts could be used in a single reactor without neutralization of active sites. Because the Ti4+-mont have active acid site in the narrow interlayers, the base sites of large HT particles show no interaction with the acid sites. A variety of acid and base reactions, such as esterification, acetalization, deacetalization, aldol reaction, Michael reaction, and epoxidation, proceeded using both the Ti4+-mont and the HT in a single reactor.

  1. The role of surface oxygenated-species and adsorbed hydrogen in the oxygen reduction reaction (ORR) mechanism and product selectivity on Pd-based catalysts in acid media.

    PubMed

    Rahul, R; Singh, R K; Bera, B; Devivaraprasad, R; Neergat, M

    2015-06-21

    Oxygen reduction reaction (ORR) is investigated on bulk PdO-based catalysts (oxides of Pd and Pd3Co) in oxygen-saturated 0.1 M HClO4 to establish the role of surface oxides and adsorbed hydrogen in the activity and product selectivity (H2O/H2O2). The initial voltammetric features suggest that the oxides are inactive toward ORR. The evolution of the ORR voltammograms and potential-dependent H2O2 generation features on the PdO catalyst suggest gradual and parallel in situ reduction of the bulk PdO phase below ∼0.4 V in the hydrogen underpotential deposition (Hupd) region; the reduction of the bulk PdO catalyst is confirmed from the X-ray photoelectron spectra (XPS) and X-ray diffraction (XRD) patterns. The potential-dependent H2O2 generation features originate due to the presence of surface oxides and adsorbed hydrogen; this is further confirmed using halide ions (Cl(-) and Br(-)) and peroxide as the external impurities.

  2. [Stewart's acid-base approach].

    PubMed

    Funk, Georg-Christian

    2007-01-01

    In addition to paCO(2), Stewart's acid base model takes into account the influence of albumin, inorganic phosphate, electrolytes and lactate on acid-base equilibrium. It allows a comprehensive and quantitative analysis of acid-base disorders. Particularly simultaneous and mixed metabolic acid-base disorders, which are common in critically ill patients, can be assessed. Stewart's approach is therefore a valuable tool in addition to the customary acid-base approach based on bicarbonate or base excess. However, some chemical aspects of Stewart's approach remain controversial.

  3. Reactions of Thiocyanate Ions with Acid: A Laboratory Experiment.

    ERIC Educational Resources Information Center

    Glidewell, Christopher; And Others

    1984-01-01

    Background information, procedures, and typical results are provided for a three-part experiment involving reactions of potassium thiocynate (KNCS) with sulfuric acid. The experiment represents the final stage of structured work prior to students' research projects during their final year. (JM)

  4. 40 CFR 721.10448 - Acetic acid, hydroxy- methoxy-, methyl ester, reaction products with substituted alkylamine...

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... ester, reaction products with substituted alkylamine (generic). 721.10448 Section 721.10448 Protection... Acetic acid, hydroxy- methoxy-, methyl ester, reaction products with substituted alkylamine (generic). (a... generically as acetic acid, hydroxymethoxy-, methyl ester, reaction products with substituted alkylamine...

  5. 40 CFR 721.10448 - Acetic acid, hydroxy- methoxy-, methylester, reaction products with substituted alkylamine...

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ...-, methylester, reaction products with substituted alkylamine (generic). 721.10448 Section 721.10448 Protection... Acetic acid, hydroxy- methoxy-, methylester, reaction products with substituted alkylamine (generic). (a... generically as acetic acid, hydroxymethoxy-, methyl ester, reaction products with substituted alkylamine...

  6. Development of a Simple Adjustable Zinc Acid/Base Hybrid Catalyst for C-C and C-O Bond-Forming and C-C Bond-Cleavage Reactions.

    PubMed

    Yamashita, Yasuhiro; Minami, Kodai; Saito, Yuki; Kobayashi, Shū

    2016-09-06

    A newly designed zinc Lewis acid/base hybrid catalyst was developed. By adjusting the Lewis acidity of the zinc center, aldol-type additions of 2-picolylamine Schiff base to aldehydes proceeded smoothly to afford syn-aldol adduct equivalents, trans-N,O-acetal adducts, in high yields with high selectivities. NMR experiments, including microchanneled cell for synthesis monitoring (MICCS) NMR analysis, revealed that anti-aldol adducts were formed at the initial stage of the reactions under kinetic control, but the final products were the trans-(syn)-N,O-acetal adducts that were produced through a retro-aldol process under thermodynamic control. In the whole reaction process, the zinc catalyst played three important roles: i) promotion of the aldol process (C-C bond formation), ii) cyclization process to the N,O-acetal product (C-O bond formation), and iii) retro-aldol process from the anti-aldol adduct to the syn-aldol adduct (C-C bond cleavage and C-C bond formation).

  7. Amplification-Free Detection of Circulating microRNA Biomarkers from Body Fluids Based on Fluorogenic Oligonucleotide-Templated Reaction between Engineered Peptide Nucleic Acid Probes: Application to Prostate Cancer Diagnosis.

    PubMed

    Metcalf, Gavin A D; Shibakawa, Akifumi; Patel, Hinesh; Sita-Lumsden, Ailsa; Zivi, Andrea; Rama, Nona; Bevan, Charlotte L; Ladame, Sylvain

    2016-08-16

    Highly abundant in cells, microRNAs (or miRs) play a key role as regulators of gene expression. A proportion of them are also detectable in biofluids making them ideal noninvasive biomarkers for pathologies in which miR levels are aberrantly expressed, such as cancer. Peptide nucleic acids (PNAs) are engineered uncharged oligonucleotide analogues capable of hybridizing to complementary nucleic acids with high affinity and high specificity. Herein, novel PNA-based fluorogenic biosensors have been designed and synthesized that target miR biomarkers for prostate cancer (PCa). The sensing strategy is based on oligonucleotide-templated reactions where the only miR of interest serves as a matrix to catalyze an otherwise highly unfavorable fluorogenic reaction. Validated in vitro using synthetic RNAs, these newly developed biosensors were then shown to detect endogenous concentrations of miR in human blood samples without the need for any amplification step and with minimal sample processing. This low-cost, quantitative, and versatile sensing technology has been technically validated using gold-standard RT-qPCR. Compared to RT-qPCR however, this enzyme-free, isothermal blood test is amenable to incorporation into low-cost portable devices and could therefore be suitable for widespread public screening.

  8. Change of monochloroacetic acid to biodegradable organic acids by hydrothermal reaction.

    PubMed

    Kim, Kyoungrean; Fujita, Masafumi; Daimon, Hiroyuki; Fujie, Koichi

    2004-04-30

    The feasibility of biodegradability improvement induced from the structural conversion of refractory pollutants by hydrothermal reaction was investigated. Monochloroacetic acid (MCAA) was selected as a preliminary material represented for linear hydrocarbon structured refractory pollutants. Under the tested conditions, MCAA was partially destructed and then converted to biodegradable reaction products by hydrolysis, dehydration and thermal decomposition. The identified products were glycolic acid, citric acid and formic acid. Total organic carbon (TOC) reduction during the structural conversion did not exceed 24%, except the results at the reaction conditions of 350 degrees C and 17 MPa. However, Produced biodegradable organic acids were reduced by thermal decomposition with increasing reaction temperature and time. At the reaction temperature of 250 and 300 degrees C, biodegradability (BOD/COD(Cr)) was reached at 0.51 in 6.9 min and 0.52 in 7.4 min despite the presence of dissociated chlorine ions. The detachment of recalcitrant chlorine ion from MCAA and the production of biodegradable organic acids by hydrothermal reaction were directly related to the biodegradability improvement of reaction products.

  9. Template directed reactions of 2-aminoadenylic acid derivatives

    NASA Technical Reports Server (NTRS)

    Webb, T. R.; Orgel, L. E.

    1982-01-01

    The template-directed oligomerization of activated derivatives of 2-aminoadenylic acid (paA) on polyuridylic acid (poly(U)) in aqueous buffers was studied. The reaction differs from that of adenylic acid (pA) under identical conditions, in that only di- and tri-nucleotides are observed as substantial products rather than a longer sequence of oligomers. The reaction of paA also differs from that of pA in that it does not require Mg (2+), and is less susceptible to increased temperature. The relevance of these observations to the chemical evolution of polynucleotide replication is discussed. Improved syntheses of paA and its diphosphate are reported.

  10. Sequential injection redox or acid-base titration for determination of ascorbic acid or acetic acid.

    PubMed

    Lenghor, Narong; Jakmunee, Jaroon; Vilen, Michael; Sara, Rolf; Christian, Gary D; Grudpan, Kate

    2002-12-06

    Two sequential injection titration systems with spectrophotometric detection have been developed. The first system for determination of ascorbic acid was based on redox reaction between ascorbic acid and permanganate in an acidic medium and lead to a decrease in color intensity of permanganate, monitored at 525 nm. A linear dependence of peak area obtained with ascorbic acid concentration up to 1200 mg l(-1) was achieved. The relative standard deviation for 11 replicate determinations of 400 mg l(-1) ascorbic acid was 2.9%. The second system, for acetic acid determination, was based on acid-base titration of acetic acid with sodium hydroxide using phenolphthalein as an indicator. The decrease in color intensity of the indicator was proportional to the acid content. A linear calibration graph in the range of 2-8% w v(-1) of acetic acid with a relative standard deviation of 4.8% (5.0% w v(-1) acetic acid, n=11) was obtained. Sample throughputs of 60 h(-1) were achieved for both systems. The systems were successfully applied for the assays of ascorbic acid in vitamin C tablets and acetic acid content in vinegars, respectively.

  11. Tuning Lipase Reaction for Production of Fatty Acids from Oil.

    PubMed

    Odaneth, Annamma A; Vadgama, Rajeshkumar N; Bhat, Anuradha D; Lali, Arvind M

    2016-10-01

    Fats or oils are split partially or completely to obtain fatty acids that find wide applications in oleo-chemical industries. Lipase-mediated complete splitting (hydrolysis) of oils is a green process having great potential to replace the traditional methods of oil splitting. However, cost of lipases, mechanistic kinetic equilibrium and associated operational limitations prove to be deterrents for scale up of the enzymatic oil splitting process. In the present study, we demonstrate the use of immobilised 1,3-regioselective lipase (HyLIP) for complete hydrolysis of oil in monophasic reaction medium. Incorporation of a polar organic solvent (tert-butanol, 1:5, v/v) homogenises the oil-water mixture and contributes positively towards complete hydrolysis. The monophasic oil hydrolysis reaction with optimised water concentration (0.05 %, v/v) gave Free Fatty Acid (FFA) yield of 88 % (HyLIP and Novozym-435) and 66 % (TLIM and RMIM). Smart reaction engineering and modification of the reaction intermediates to favourable substrate lead to ∼99 % degree of hydrolysis of triglycerides with ∼90 % FFA yield using 1,3-regioselective lipase. The present work becomes basic platform for developing technologies for synthesis of fatty acids, monoglycerides, diglycerides and glycerol.

  12. Thermochemistry for silicic acid formation reaction: Prediction of new reaction pathway

    NASA Astrophysics Data System (ADS)

    Mondal, Bhaskar; Ghosh, Deepanwita; Das, Abhijit K.

    2009-08-01

    Reaction between SiO 2 and water has been studied extensively using ab initio methods. The mechanism for formation of metasilicic acid SiO(OH) 2 and orthosilicic acid Si(OH) 4 has been explored and a new pathway for formation of Si(OH) 4 is predicted. Heats of reaction ( ΔrH298∘) and heats of formation ( ΔfH298∘) at 298 K for the related reactions and species calculated at two different theoretical levels G3B3 and G3MP2B3 agree well with the literature values. It is found that when SiO 2 reacts simultaneously with two water molecules, the thermodynamic as well as kinetic feasibility of the process is much greater than that when SiO 2 reacts with one molecule of water.

  13. Phosphoric Acid-Mediated Synthesis of Vinyl Sulfones through Decarboxylative Coupling Reactions of Sodium Sulfinates with Phenylpropiolic Acids.

    PubMed

    Rong, Guangwei; Mao, Jincheng; Yan, Hong; Zheng, Yang; Zhang, Guoqi

    2015-08-07

    A novel phosphoric acid -mediated synthesis of vinyl sulfones through decarboxylative coupling reactions of sodium sulfinates with phenylpropiolic acids is described. This transformation is efficient and environmentally friendly.

  14. Heterogeneous atmospheric reactions - Sulfuric acid aerosols as tropospheric sinks

    NASA Technical Reports Server (NTRS)

    Baldwin, A. C.; Golden, D. M.

    1979-01-01

    The reaction probabilities of various atmospheric species incident on a bulk sulfuric acid surface are measured in order to determine the role of sulfuric acid aerosols as pollutant sinks. Reaction products and unreacted starting materials leaving a Knudsen cell flow reactor after collision at 300 K with a H2SO4 surface or a soot surface were detected by mass spectrometry. Significant collision reaction probabilities are observed on a H2SO4 surface for H2O2, HNO3, HO2NO2, ClONO2, N2O5, H2O and NH3, and on soot for NH3. Estimates of the contribution of heterogeneous reactions to pollutant removal under atmospheric conditions indicate that while aerosol removal in the stratosphere is insignificant (loss rate constants approximately 10 to the -10th/sec), heterogeneous reactions may be the dominant loss process for several tropospheric species (loss rate constant approximately 10 to the -5th/sec, comparable to photolysis rate constants).

  15. Kinetics of the reaction between ozone and phenolic acids present in agro-industrial wastewaters.

    PubMed

    Beltran-Heredia, J; Torregrosa, J; Dominguez, J R; Peres, J A

    2001-03-01

    The kinetics of the ozonation of three phenolic acids is investigated from ozone absorption experiments in a semi-continuous reactor. After the evaluation of stoichiometric ratios for the individual reactions between ozone and each phenolic acid, the oxidation of p-hydroxybenzoic acid by ozone is performed in a first stage. The influence of the operating variables on the degradation process is established, and the application of a mass transfer with chemical reaction model based on the film theory leads to the determination of the reaction orders and kinetic rate constants. The experimental absorption rates obtained agree well with those calculated theoretically. In the second stage, a mixture of ferulic acid (4-hydroxy-3-methoxycinnamic acid), beta-resorcylic acid (2,4-dihydroxybenzoic acid) and p-hydroxybenzoic acid is ozonated under different experimental conditions. The kinetic study is performed by means of a competitive method that takes p-hydroxybenzoic acid as reference compound. The application of this model allows to determine the kinetic rate constants for each compound, which are correlated as a function of pH and temperature. The results obtained support that the kinetic regime of absorption is fast and pseudo-first order with respect to ozone, a condition required by the competitive method used.

  16. Reaction of acetaldehyde with 5-aminolevulinic acid via dihydropyrazine derivative.

    PubMed

    Suzuki, Toshinori; Yasuhara, Naoki; Ueda, Takashi; Inukai, Michiyo; Mio, Mitsunobu

    2015-01-01

    When a solution of 5-aminolevulinic acid (ALA) was incubated with acetaldehyde at neutral pH, a product was generated. This product was identified as 3-ethylpyrazine-2,5-dipropanoic acid (ETPY). ETPY was stable at neutral pH. It has been reported that ALA dimerizes at neutral pH generating 3,6-dihydropyrazine-2,5-dipropanoic acid (DHPY), and subsequently resulting in pyrazine-2,5-dipropanoic acid (PY) by autoxidation. In the present reaction, DHPY generated from ALA reacted with acetaldehyde, resulting in ETPY. Preadministration of ALA 3 min prior to acetaldehyde injection supressed the toxicity of acetaldehyde in male mice. These results suggest that ALA may be useful as a scavenger for acetaldehyde.

  17. Signal enhancement for gene detection based on a redox reaction of [Fe(CN)(6)](4-) mediated by ferrocene at the terminal of a peptide nucleic acid as a probe with hybridization-amenable conformational flexibility.

    PubMed

    Aoki, Hiroshi; Tao, Hiroaki

    2008-07-01

    Electrochemically enhanced DNA detection was demonstrated by utilizing the couple of a synthesized ferrocene-terminated peptide nucleic acid (PNA) with a cysteine anchor and a sacrificial electron donor [Fe(CN)(6)](4-). DNA detection sensors were prepared by modifying a gold electrode surface with a mixed monolayer of the probe PNA and 11-hydroxy-1-undecanethiol (11-HUT), protecting [Fe(CN)(6)](4-) from any unexpected redox reaction. Before hybridization, the terminal ferrocene moiety of the probe was subject to a redox reaction due to the flexible probe structure and, in the presence of [Fe(CN)(6)](4-), the observed current was amplified based on regeneration of the ferrocene moiety. Hybridization decreased the redox current of the ferrocene. This occurred because hybridization rigidified the probe structure: the ferrocene moiety was then removed from the electrode surface, and the redox reaction of [Fe(CN)(6)](4-) was again prevented. The change in the anodic current before and after hybridization was enhanced 1.75-fold by using the electron donor [Fe(CN)(6)](4-). Sequence-specific detection of the complementary target DNA was also demonstrated.

  18. Organocatalytic Enantioselective Aza-Friedel-Crafts Reaction of Cyclic Ketimines with Pyrroles using Imidazolinephosphoric Acid Catalysts.

    PubMed

    Nakamura, Shuichi; Matsuda, Nazumi; Ohara, Mutsuyo

    2016-07-04

    Organocatalytic enantioselective aza-Friedel-Crafts reactions of cyclic ketimines with pyrroles or indoles were catalyzed by imidazoline/phosphoric acid catalysts. The reaction was applied to various 3H-indol-3-ones to afford products in excellent yields and enantioselectivities. The chiral catalysts can be recovered by a single separation step using column chromatography and are reusable without further purification. Based on the experimental investigations, a possible transition state has been proposed to explain the origin of the asymmetric induction.

  19. A generic reaction-based biogeochemical simulator

    SciTech Connect

    Fang, Yilin; Yabusaki, Steven B.; Yeh, Gour T.; C.T. Miller, M.W. Farthing, W.G. Gray, and G.F. Pinder

    2004-06-17

    This paper presents a generic biogeochemical simulator, BIOGEOCHEM. The simulator can read a thermodynamic database based on the EQ3/EQ6 database. It can also read user-specified equilibrium and kinetic reactions (reactions not defined in the format of that in EQ3/EQ6 database) symbolically. BIOGEOCHEM is developed with a general paradigm. It overcomes the requirement in most available reaction-based models that reactions and rate laws be specified in a limited number of canonical forms. The simulator interprets the reactions, and rate laws of virtually any type for input to the MAPLE symbolic mathematical software package. MAPLE then generates Fortran code for the analytical Jacobian matrix used in the Newton-Raphson technique, which are compiled and linked into the BIOGEOCHEM executable. With this feature, the users are exempted from recoding the simulator to accept new equilibrium expressions or kinetic rate laws. Two examples are used to demonstrate the new features of the simulator.

  20. Reaction kinetics of free fatty acids esterification in palm fatty acid distillate using coconut shell biochar sulfonated catalyst

    NASA Astrophysics Data System (ADS)

    Hidayat, Arif; Rochmadi, Wijaya, Karna; Budiman, Arief

    2015-12-01

    Recently, a new strategy of preparing novel carbon-based solid acids has been developed. In this research, the esterification reactions of Palm Fatty Acid Distillate (PFAD) with methanol, using coconut shell biochar sulfonated catalyst from biomass wastes as catalyst, were studied. In this study, the coconut shell biochar sulfonated catalysts were synthesized by sulfonating the coconut shell biochar using concentrated H2SO4. The kinetics of free fatty acid (FFA) esterification in PFAD using a coconut shell biochar sulfonated catalyst was also studied. The effects of the mass ratio of catalyst to oil (1-10%), the molar ratio of methanol to oil (6:1-12:1), and the reaction temperature (40-60°C) were studied for the conversion of PFAD to optimize the reaction conditions. The results showed that the optimal conditions were an methanol to PFAD molar ratio of 12:1, the amount of catalyst of 10%w, and reaction temperature of 60°C. The proposed kinetic model shows a reversible second order reaction and represents all the experimental data satisfactorily, providing deeper insight into the kinetics of the reaction.

  1. Mechanism of arylboronic acid-catalyzed amidation reaction between carboxylic acids and amines.

    PubMed

    Wang, Chen; Yu, Hai-Zhu; Fu, Yao; Guo, Qing-Xiang

    2013-04-07

    Arylboronic acids were found to be efficient catalysts for the amidation reactions between carboxylic acids and amines. Theoretical calculations have been carried out to investigate the mechanism of this catalytic process. It is found that the formation of the acyloxyboronic acid intermediates from the carboxylic acid and the arylboronic acid is kinetically facile but thermodynamically unfavorable. Removal of water (as experimentally accomplished by using molecular sieves) is therefore essential for overall transformation. Subsequently C-N bond formation between the acyloxyboronic acid intermediates and the amine occurs readily to generate the desired amide product. The cleavage of the C-O bond of the tetracoordinate acyl boronate intermediates is the rate-determining step in this process. Our analysis indicates that the mono(acyloxy)boronic acid is the key intermediate. The high catalytic activity of ortho-iodophenylboronic acid is attributed to the steric effect as well as the orbital interaction between the iodine atom and the boron atom.

  2. Serum uric acid levels during leprosy reaction episodes

    PubMed Central

    Alves-Junior, Eduardo R.; Arruda, Talita A.; Lopes, Jose C.; Fontes, Cor J.F.

    2016-01-01

    Background. Leprosy reactions are acute inflammatory episodes that occur mainly in the multibacillary forms of the disease. The reactions are classified as type 1 (reverse reaction) or type 2 (erythema nodosum leprosum). Leprosy-associated oxidative stress has been widely demonstrated. Several recent studies have shown uric acid (UA) to have antioxidative effects under pathologic conditions. The objective of this study was to assess serum levels of UA in patients with leprosy reactions, with the aim of monitoring their levels before and after treatment, compared with levels in leprosy patients without reactions. Methods. The study included patients aged 18–69 years assisted at a leprosy treatment reference center in the Central Region of Brazil. Patients who were pregnant; were using immunosuppressant drugs or immunobiologicals; or had an autoimmune disease, human immunodeficiency virus infection, acquired immune deficiency syndrome, or tuberculosis were excluded. Upon recruitment, all individuals were clinically assessed for skin lesions and neural or systemic impairment. Some patients had already completed treatment for leprosy, while others were still undergoing treatment or had initiated treatment after being admitted. The treatment of the reactional episode was started only after the initial evaluation. Laboratory assessments were performed upon admission (baseline) and at approximately 30 and 60 days (time points 1 and 2, respectively). Results. A total of 123 leprosy patients were recruited between June 2012 and June 2015; among them, 56, 42, and 25 presented with type 1, type 2, and no reactions, respectively. Serum UA levels were significantly reduced in patients with type 2 leprosy reactions compared with patients in the control group and remained lower in the two subsequent assessments, after initiation of anti-reaction treatments, with similar values to those recorded before the treatment. Discussion. The decreased serum UA levels in patients with

  3. Heterogeneous Reaction of HO2 Radical with Dicarboxylic Acid Particles

    NASA Astrophysics Data System (ADS)

    Taketani, F.; Kanaya, Y.

    2010-12-01

    HOx(OH+ HO2) radical plays a central role in the tropospheric chemistry. Recently, the heterogeneous loss of HO2 by aerosol particles is a potentially important HOx sink in the troposphere suggested from observation study. However, there have been few studies for loss of HO2 by aerosols. In this study, we measured the HO2 uptake coefficients for four dicarboxylic acids (succinic acid, glutaric acid, adipic acid, and pimelic acid) aerosol particles under ambient conditions (760Torr and 296K) using an aerosol flow tube(AFT) coupled with a chemical conversion /laser-induced fluorescence(CC/LIF) technique. The CC/LIF technique enabled experiments to be performed at almost the same HO2 radical concentration as that in the atmosphere(-10^8 molecules/cm^3). In this system, the effect of the self-reaction of HO2 in the gas phase can be neglected. HO2 radicals were injected into the AFT through a vertically movable Pyrex tube. Injector position dependent profiles of LIF intensity were measured as a function of aerosol concentration at 30% and 70% of relative humilities (RH). Determined HO2 uptake coefficients by succinic acid, glutaric acid, adipic acid, and pimelic acid aerosol particles at 30% RH were 0.05 +/- 0.02, 0.07 +/- 0.03, 0.02 +/- 0.01, and 0.06 +/- 0.03, respectively, while the uptake coefficients by those particles at 70% RH were 0.13 +/- 0.05, 0.13 +/- 0.03, 0.06 +/- 0.01, and 0.11 +/- 0.03, respectively. These results suggest that compositions and relative humidity are significant to the HO2 uptake. We will discuss the potential HO2 loss processes.

  4. Polymerase chain reaction system using magnetic beads for analyzing a sample that includes nucleic acid

    DOEpatents

    Nasarabadi, Shanavaz [Livermore, CA

    2011-01-11

    A polymerase chain reaction system for analyzing a sample containing nucleic acid includes providing magnetic beads; providing a flow channel having a polymerase chain reaction chamber, a pre polymerase chain reaction magnet position adjacent the polymerase chain reaction chamber, and a post pre polymerase magnet position adjacent the polymerase chain reaction chamber. The nucleic acid is bound to the magnetic beads. The magnetic beads with the nucleic acid flow to the pre polymerase chain reaction magnet position in the flow channel. The magnetic beads and the nucleic acid are washed with ethanol. The nucleic acid in the polymerase chain reaction chamber is amplified. The magnetic beads and the nucleic acid are separated into a waste stream containing the magnetic beads and a post polymerase chain reaction mix containing the nucleic acid. The reaction mix containing the nucleic acid flows to an analysis unit in the channel for analysis.

  5. New method for spectrophotometric determination of quinones and barbituric acid through their reaction. A kinetic study

    NASA Astrophysics Data System (ADS)

    Medien, H. A. A.

    1996-11-01

    A new and sensitive spectrophotometric method is described for the determination of p-benzoquinone, p-chloranil and 1.4-naphthoquinone. The method is based on the reaction between quinones and barbituric acid, by which a color is developed with maximum absorption between 485 and 555 nm in 50% methyl alcohol-water mixture. The absorption of the product obeys Beer's law within the concentration range 0.025-05 mM of orginal quinone. The kinetics of the reaction between p-benzoquinone and barbituric acid was studied in a range of methyl alcohol-water mixtures. The reaction follows overall second order kinetics, first order in each of the reactants. The rate increases with increasing dielectric constant. The method was applied for determination of barbituric acid with p-benzoquinone in the concentration range of 0.025-0.345 mM. Other barbiturates do not interfere.

  6. REACTION OF AMINO-ACIDS AND PEPTIDE BONDS WITH FORMALDEHYDE AS MEASURED BY CHANGES IN THE ULTRA-VIOLET SPECTRA,

    DTIC Science & Technology

    AMINO ACIDS , CHEMICAL REACTIONS), (*PEPTIDES, CHEMICAL REACTIONS), (*FORMALDEHYDE, CHEMICAL REACTIONS), (*ULTRAVIOLET SPECTROSCOPY, PROTEINS), ABSORPTION SPECTRA, CHEMICAL BONDS, AMIDES, CHEMICAL EQUILIBRIUM, REACTION KINETICS

  7. 40 CFR 721.10664 - Alkenedioic acid dialkyl ester, reaction products with alkenoic acid alkyl esters and diamine...

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Alkenedioic acid dialkyl ester, reaction products with alkenoic acid alkyl esters and diamine (generic). 721.10664 Section 721.10664... Alkenedioic acid dialkyl ester, reaction products with alkenoic acid alkyl esters and diamine (generic)....

  8. 40 CFR 721.10664 - Alkenedioic acid dialkyl ester, reaction products with alkenoic acid alkyl esters and diamine...

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Alkenedioic acid dialkyl ester, reaction products with alkenoic acid alkyl esters and diamine (generic). 721.10664 Section 721.10664... Alkenedioic acid dialkyl ester, reaction products with alkenoic acid alkyl esters and diamine (generic)....

  9. Influences of acidic reaction and hydrolytic conditions on monosaccharide composition analysis of acidic, neutral and basic polysaccharides.

    PubMed

    Wang, Qing-Chi; Zhao, Xia; Pu, Jiang-Hua; Luan, Xiao-Hong

    2016-06-05

    Monosaccharide composition analysis is important for structural characterization of polysaccharides. To investigate the influences of acidic reaction and hydrolytic conditions on monosaccharide composition analysis of polysaccharides, we chose alginate, starch, chitosan and chondroitin sulfate as representative of acidic, neutral, basic and complex polysaccharides to compare the release degree of monosaccharides under different hydrolytic conditions. The hydrolysis stability of 10 monosaccharide standards was also explored. Results showed that the basic sugars were hard to release but stable, the acidic sugars (uronic acids) were easy to release but unstable, and the release and stability of neutral sugars were in between acidic and basic sugars. In addition, the hydrolysis process was applied to monosaccharide composition analysis of Hippocampus trimaculatus polysaccharide and the appropriate hydrolytic condition was accorded with that of the above four polysaccharides. Thus, different hydrolytic conditions should be used for the monosaccharide composition analysis of polysaccharides based on their structural characteristics.

  10. Enantioconvergent Nucleophilic Substitution Reaction of Racemic Alkyne-Dicobalt Complex (Nicholas Reaction) Catalyzed by Chiral Brønsted Acid.

    PubMed

    Terada, Masahiro; Ota, Yusuke; Li, Feng; Toda, Yasunori; Kondoh, Azusa

    2016-08-31

    Catalytic enantioselective syntheses enable a practical approach to enantioenriched molecules. While most of these syntheses have been accomplished by reaction at the prochiral sp(2)-hybridized carbon atom, little attention has been paid to enantioselective nucleophilic substitution at the sp(3)-hybridized carbon atom. In particular, substitution at the chiral sp(3)-hybridized carbon atom of racemic electrophiles has been rarely exploited. To establish an unprecedented enantioselective substitution reaction of racemic electrophiles, enantioconvergent Nicholas reaction of an alkyne-dicobalt complex derived from racemic propargylic alcohol was developed using a chiral phosphoric acid catalyst. In the present enantioconvergent process, both enantiomers of the racemic alcohol were transformed efficiently to a variety of thioethers with high enantioselectivity. The key to achieving success is dynamic kinetic asymmetric transformation (DYKAT) of enantiomeric cationic intermediates generated via dehydroxylation of the starting racemic alcohol under the influence of the chiral phosphoric acid catalyst. The present fascinating DYKAT involves the efficient racemization of these enantiomeric intermediates and effective resolution of these enantiomers through utilization of the chiral conjugate base of the phosphoric acid.

  11. Laboratory measurements of heterogeneous reactions on sulfuric acid surfaces

    NASA Technical Reports Server (NTRS)

    Williams, Leah R.; Manion, Jeffrey A.; Golden, David M.; Tolbert, Margaret A.

    1994-01-01

    Increasing evidence from field, modeling, and laboratory studies suggests that heterogeneous reactions on stratospheric sulfate aerosol particles may contribute to global ozone depletion. Using a Knudsen cell reactor technique, the authors have studied the uptake, reactivity, and solubility of several trace atmospheric species on cold sulfuric acid surfaces representative of stratospheric aerosol particles. The results suggest that the heterogeneous conversion of N2O5 to HNO3 is fast enough to significantly affect the partitioning of nitrogen species in the global stratosphere and thus contribute to global ozone depletion. The hydrolysis of ClONO2 is slower and unlikely to be important under normal conditions at midlatitudes. The solubilities of HCl and HNO3 in sulfuric acid down to 200 K were found to be quite low. For HCl, this means that little HCl is available for reaction on the surfaces of stratospheric sulfate aerosol particles. The low solubility of HNO3 means that this product of heterogeneous reactions will enter the gas phase, and the denitrification observed in polar regions is unlikely to occur in the global stratosphere.

  12. 40 CFR 721.10126 - Alkyl amino substituted triazine amino substituted benezenesulfonic acid reaction product with...

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... substituted triazine amino substituted benezenesulfonic acid reaction product with naphthalenesulfonato azo... substituted triazine amino substituted benezenesulfonic acid reaction product with naphthalenesulfonato azo... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Alkyl amino substituted triazine...

  13. 40 CFR 721.10126 - Alkyl amino substituted triazine amino substituted benezenesulfonic acid reaction product with...

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... substituted triazine amino substituted benezenesulfonic acid reaction product with naphthalenesulfonato azo... substituted triazine amino substituted benezenesulfonic acid reaction product with naphthalenesulfonato azo... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Alkyl amino substituted triazine...

  14. 40 CFR 721.10126 - Alkyl amino substituted triazine amino substituted benezenesulfonic acid reaction product with...

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... substituted triazine amino substituted benezenesulfonic acid reaction product with naphthalenesulfonato azo... substituted triazine amino substituted benezenesulfonic acid reaction product with naphthalenesulfonato azo... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Alkyl amino substituted triazine...

  15. 40 CFR 721.10126 - Alkyl amino substituted triazine amino substituted benezenesulfonic acid reaction product with...

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... substituted triazine amino substituted benezenesulfonic acid reaction product with naphthalenesulfonato azo... substituted triazine amino substituted benezenesulfonic acid reaction product with naphthalenesulfonato azo... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Alkyl amino substituted triazine...

  16. 40 CFR 721.10126 - Alkyl amino substituted triazine amino substituted benezenesulfonic acid reaction product with...

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... substituted triazine amino substituted benezenesulfonic acid reaction product with naphthalenesulfonato azo... substituted triazine amino substituted benezenesulfonic acid reaction product with naphthalenesulfonato azo... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Alkyl amino substituted triazine...

  17. Coupling of hydrologic transport and chemical reactions in a stream affected by acid mine drainage

    USGS Publications Warehouse

    Kimball, B.A.; Broshears, R.E.; Bencala, K.E.; McKnight, Diane M.

    1994-01-01

    Experiments in St. Kevin Gulch, an acid mine drainage stream, examined the coupling of hydrologic transport to chemical reactions affecting metal concentrations. Injection of LiCl as a conservative tracer was used to determine discharge and residence time along a 1497-m reach. Transport of metals downstream from inflows of acidic, metal-rich water was evaluated based on synoptic samples of metal concentrations and the hydrologic characteristics of the stream. Transport of SO4 and Mn was generally conservative, but in the subreaches most affected by acidic inflows, transport was reactive. Both 0.1-??m filtered and particulate Fe were reactive over most of the stream reach. Filtered Al partitioned to the particulate phase in response to high instream concentrations. Simulations that accounted for the removal of SO4, Mn, Fe, and Al with first-order reactions reproduced the steady-state profiles. The calculated rate constants for net removal used in the simulations embody several processes that occur on a stream-reach scale. The comparison between rates of hydrologie transport and chemical reactions indicates that reactions are only important over short distances in the stream near the acidic inflows, where reactions occur on a comparable time scale with hydrologic transport and thus affect metal concentrations.

  18. 40 CFR 721.4461 - Hydrofluoric acid, reaction products with octane (generic).

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Hydrofluoric acid, reaction products... New Uses for Specific Chemical Substances § 721.4461 Hydrofluoric acid, reaction products with octane... identified generically as a hydrofluoric acid, reaction products with octane (PMN P-99-0052) is subject...

  19. 40 CFR 721.9460 - Tall oil fatty acids, reaction products with polyamines, alkyl substituted.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Tall oil fatty acids, reaction... SUBSTANCES Significant New Uses for Specific Chemical Substances § 721.9460 Tall oil fatty acids, reaction... reporting. (1) The chemical substance identified generically as tall oil fatty acids, reaction products...

  20. 40 CFR 721.4385 - Hydrofluoric acid, reaction products with heptane.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Hydrofluoric acid, reaction products... Specific Chemical Substances § 721.4385 Hydrofluoric acid, reaction products with heptane. (a) Chemical... hydrofluoric acid, reaction products with heptane (PMN P-98-1036; CAS No. 207409-71-0) is subject to...

  1. 40 CFR 721.9460 - Tall oil fatty acids, reaction products with polyamines, alkyl substituted.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Tall oil fatty acids, reaction... SUBSTANCES Significant New Uses for Specific Chemical Substances § 721.9460 Tall oil fatty acids, reaction... reporting. (1) The chemical substance identified generically as tall oil fatty acids, reaction products...

  2. 40 CFR 721.10251 - Fatty acids, reaction products with alkanolamine (generic).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Fatty acids, reaction products with... Specific Chemical Substances § 721.10251 Fatty acids, reaction products with alkanolamine (generic). (a... generically as fatty acids, reaction products with alkanolamine (PMN P-09-366) is subject to reporting...

  3. 40 CFR 721.4461 - Hydrofluoric acid, reaction products with octane (generic).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Hydrofluoric acid, reaction products... New Uses for Specific Chemical Substances § 721.4461 Hydrofluoric acid, reaction products with octane... identified generically as a hydrofluoric acid, reaction products with octane (PMN P-99-0052) is subject...

  4. 40 CFR 721.9484 - Dimer acid/rosin amidoamine reaction product (generic).

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Dimer acid/rosin amidoamine reaction... Specific Chemical Substances § 721.9484 Dimer acid/rosin amidoamine reaction product (generic). (a... generically as Dimer acid/rosin amidoamine reaction product (PMN P-99-0143) is subject to reporting under...

  5. 40 CFR 721.10211 - Octadecanoic acid, reaction products with diethylenetriamine and urea, acetates.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Octadecanoic acid, reaction products... SUBSTANCES Significant New Uses for Specific Chemical Substances § 721.10211 Octadecanoic acid, reaction... subject to reporting. (1) The chemical substance identified as octadecanoic acid, reaction products...

  6. 40 CFR 721.9484 - Dimer acid/rosin amidoamine reaction product (generic).

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Dimer acid/rosin amidoamine reaction... Specific Chemical Substances § 721.9484 Dimer acid/rosin amidoamine reaction product (generic). (a... generically as Dimer acid/rosin amidoamine reaction product (PMN P-99-0143) is subject to reporting under...

  7. 40 CFR 721.10464 - Fatty acid, reaction products with alkanolamine (generic).

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Fatty acid, reaction products with... Specific Chemical Substances § 721.10464 Fatty acid, reaction products with alkanolamine (generic). (a... generically as fatty acid, reaction products with alkanolamine (PMN P-03-461) is subject to reporting...

  8. 40 CFR 721.4461 - Hydrofluoric acid, reaction products with octane (generic).

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Hydrofluoric acid, reaction products... New Uses for Specific Chemical Substances § 721.4461 Hydrofluoric acid, reaction products with octane... identified generically as a hydrofluoric acid, reaction products with octane (PMN P-99-0052) is subject...

  9. 40 CFR 721.9460 - Tall oil fatty acids, reaction products with polyamines, alkyl substituted.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Tall oil fatty acids, reaction... SUBSTANCES Significant New Uses for Specific Chemical Substances § 721.9460 Tall oil fatty acids, reaction... reporting. (1) The chemical substance identified generically as tall oil fatty acids, reaction products...

  10. 40 CFR 721.10251 - Fatty acids, reaction products with alkanolamine (generic).

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Fatty acids, reaction products with... Specific Chemical Substances § 721.10251 Fatty acids, reaction products with alkanolamine (generic). (a... generically as fatty acids, reaction products with alkanolamine (PMN P-09-366) is subject to reporting...

  11. 40 CFR 721.9484 - Dimer acid/rosin amidoamine reaction product (generic).

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Dimer acid/rosin amidoamine reaction... Specific Chemical Substances § 721.9484 Dimer acid/rosin amidoamine reaction product (generic). (a... generically as Dimer acid/rosin amidoamine reaction product (PMN P-99-0143) is subject to reporting under...

  12. 40 CFR 721.9484 - Dimer acid/rosin amidoamine reaction product (generic).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Dimer acid/rosin amidoamine reaction... Specific Chemical Substances § 721.9484 Dimer acid/rosin amidoamine reaction product (generic). (a... generically as Dimer acid/rosin amidoamine reaction product (PMN P-99-0143) is subject to reporting under...

  13. 40 CFR 721.4385 - Hydrofluoric acid, reaction products with heptane.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Hydrofluoric acid, reaction products... Specific Chemical Substances § 721.4385 Hydrofluoric acid, reaction products with heptane. (a) Chemical... hydrofluoric acid, reaction products with heptane (PMN P-98-1036; CAS No. 207409-71-0) is subject to...

  14. 40 CFR 721.9484 - Dimer acid/rosin amidoamine reaction product (generic).

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Dimer acid/rosin amidoamine reaction... Specific Chemical Substances § 721.9484 Dimer acid/rosin amidoamine reaction product (generic). (a... generically as Dimer acid/rosin amidoamine reaction product (PMN P-99-0143) is subject to reporting under...

  15. 40 CFR 721.9460 - Tall oil fatty acids, reaction products with polyamines, alkyl substituted.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Tall oil fatty acids, reaction... SUBSTANCES Significant New Uses for Specific Chemical Substances § 721.9460 Tall oil fatty acids, reaction... reporting. (1) The chemical substance identified generically as tall oil fatty acids, reaction products...

  16. 40 CFR 721.10211 - Octadecanoic acid, reaction products with diethylenetriamine and urea, acetates.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Octadecanoic acid, reaction products... SUBSTANCES Significant New Uses for Specific Chemical Substances § 721.10211 Octadecanoic acid, reaction... subject to reporting. (1) The chemical substance identified as octadecanoic acid, reaction products...

  17. 40 CFR 721.10211 - Octadecanoic acid, reaction products with diethylenetriamine and urea, acetates.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Octadecanoic acid, reaction products... SUBSTANCES Significant New Uses for Specific Chemical Substances § 721.10211 Octadecanoic acid, reaction... subject to reporting. (1) The chemical substance identified as octadecanoic acid, reaction products...

  18. 40 CFR 721.10251 - Fatty acids, reaction products with alkanolamine (generic).

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Fatty acids, reaction products with... Specific Chemical Substances § 721.10251 Fatty acids, reaction products with alkanolamine (generic). (a... generically as fatty acids, reaction products with alkanolamine (PMN P-09-366) is subject to reporting...

  19. 40 CFR 721.9460 - Tall oil fatty acids, reaction products with polyamines, alkyl substituted.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Tall oil fatty acids, reaction... SUBSTANCES Significant New Uses for Specific Chemical Substances § 721.9460 Tall oil fatty acids, reaction... reporting. (1) The chemical substance identified generically as tall oil fatty acids, reaction products...

  20. 40 CFR 721.4385 - Hydrofluoric acid, reaction products with heptane.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Hydrofluoric acid, reaction products... Specific Chemical Substances § 721.4385 Hydrofluoric acid, reaction products with heptane. (a) Chemical... hydrofluoric acid, reaction products with heptane (PMN P-98-1036; CAS No. 207409-71-0) is subject to...

  1. 40 CFR 721.10464 - Fatty acid, reaction products with alkanolamine (generic).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Fatty acid, reaction products with... Specific Chemical Substances § 721.10464 Fatty acid, reaction products with alkanolamine (generic). (a... generically as fatty acid, reaction products with alkanolamine (PMN P-03-461) is subject to reporting...

  2. 40 CFR 721.4461 - Hydrofluoric acid, reaction products with octane (generic).

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Hydrofluoric acid, reaction products... New Uses for Specific Chemical Substances § 721.4461 Hydrofluoric acid, reaction products with octane... identified generically as a hydrofluoric acid, reaction products with octane (PMN P-99-0052) is subject...

  3. 40 CFR 721.4385 - Hydrofluoric acid, reaction products with heptane.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Hydrofluoric acid, reaction products... Specific Chemical Substances § 721.4385 Hydrofluoric acid, reaction products with heptane. (a) Chemical... hydrofluoric acid, reaction products with heptane (PMN P-98-1036; CAS No. 207409-71-0) is subject to...

  4. 40 CFR 721.4461 - Hydrofluoric acid, reaction products with octane (generic).

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Hydrofluoric acid, reaction products... New Uses for Specific Chemical Substances § 721.4461 Hydrofluoric acid, reaction products with octane... identified generically as a hydrofluoric acid, reaction products with octane (PMN P-99-0052) is subject...

  5. 40 CFR 721.10211 - Octadecanoic acid, reaction products with diethylenetriamine and urea, acetates.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Octadecanoic acid, reaction products... SUBSTANCES Significant New Uses for Specific Chemical Substances § 721.10211 Octadecanoic acid, reaction... subject to reporting. (1) The chemical substance identified as octadecanoic acid, reaction products...

  6. 40 CFR 721.4385 - Hydrofluoric acid, reaction products with heptane.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Hydrofluoric acid, reaction products... Specific Chemical Substances § 721.4385 Hydrofluoric acid, reaction products with heptane. (a) Chemical... hydrofluoric acid, reaction products with heptane (PMN P-98-1036; CAS No. 207409-71-0) is subject to...

  7. Kinetics of the reactions of hypochlorous acid and amino acid chloramines with thiols, methionine, and ascorbate.

    PubMed

    Peskin, A V; Winterbourn, C C

    2001-03-01

    Thiol oxidation by hypochlorous acid and chloramines is a favorable reaction and may be responsible for alterations in regulatory or signaling pathways in cells exposed to neutrophil oxidants. In order to establish the mechanism for such changes, it is necessary to appreciate whether these oxidants are selective for different thiols as compared with other scavengers. We have measured rate constants for reactions of amino acid chloramines with a range of thiols, methionine, and ascorbate, using a combination of stopped-flow and competitive kinetics. For HOCl, rate constants are too fast to measure directly by our system and values relative to reduced glutathione were determined by competition with methionine. For taurine chloramine, the rate constants for reaction with 5-thio-2-nitrobenzoic acid, GSH, methionine, and ascorbate at pH 7.4 were 970, 115, 39, and 13 M(-1) s(-1), respectively. Values for 10 thiols varied by a factor of 20 and showed an inverse relationship to the pK(a) of the thiol group. Rate constants for chloramines of glycine and N-alpha-acetyl-lysine also showed these relationships. Rates increased with decreasing pH, suggesting a mechanism involving acid catalysis. For hypochlorous acid, rates of reaction with 5-thio-2-nitrobenzoic acid, GSH, cysteine, and most of the other thiols were very similar. Relative reactivities varied by less than 5 and there was no dependence on thiol pK(a). Chloramines have the potential to be selective for different cellular thiols depending on their pK(a). For HOCl to be selective, other factors must be important, or its reactions could be secondary to chloramine formation.

  8. Contribution to the chemistry of the Belousov-Zhabotinsky reaction. Products of the Ferriin-Bromomalonic acid and the Ferriin-Malonic acid reactions.

    PubMed

    Hegedüs, Laszló; Försterling, Horst-Dieter; Onel, Lavinia; Wittmann, Maria; Noszticzius, Zoltan

    2006-11-30

    In the present mechanistic schemes of the ferroin-catalyzed oscillatory Belousov-Zhabotinsky (BZ) reaction the oxidation of the organic substrates (bromomalonic or malonic acid) by ferriin (the oxidized form of the catalyst) plays an important role. As the organic products of these reactions were not yet identified experimentally, they were studied here by an HPLC technique. It was found that the main organic oxidation product of bromomalonic acid is bromo-ethene-tricarboxylic acid (BrEETRA), the same compound that is formed when bromomalonic acid is oxidized by Ce4+ (another catalyst of the BZ reaction). Formation of BrEETRA is explained here by a new mechanism that is more realistic than the one suggested earlier. To find any oxidation product of malonic acid in the ferriin-malonic acid reaction was not successful, however. Neither ethane-tetracarboxylic acid (ETA) nor malonyl malonate (MAMA), the usual products of the Ce4+- malonic acid reaction, nor any other organic acid, not even CO2, was found as a product of the reaction. We propose that malonic acid is not oxidized in the ferriin-malonic acid reaction, and it plays only the role of a complex forming catalyst in a process where Fe3+ oxidizes mostly its phenantroline ligand.

  9. Rapid generation of molecular complexity in the Lewis or Brønsted acid-mediated reactions of methylenecyclopropanes.

    PubMed

    Shi, Min; Lu, Jian-Mei; Wei, Yin; Shao, Li-Xiong

    2012-04-17

    Although they are highly strained, methylenecyclopropanes (MCPs) are readily accessible molecules that have served as useful building blocks in organic synthesis. MCPs can undergo a variety of ring-opening reactions because the release of cyclopropyl ring strain (40 kcal/mol) can provide a thermodynamic driving force for reactions and the π-character of the bonds within the cyclopropane can afford the kinetic opportunity to initiate the ring-opening. Since the 1970s, the chemistry of MCPs has been widely explored in the presence of transition metal catalysts, but less attention had been paid to the Lewis or Brønsted acid mediated chemistry of MCPs. During the past decade, significant developments have also been made in the Lewis or Brønsted acid mediated reactions of MCPs. This Account describes chemistry developed in our laboratory and by other researchers. Lewis and Brønsted acids can be used as catalysts or reagents in the reactions of MCPs with a variety of substrates, and substituents on the terminal methylene or on the cyclopropyl ring of MCPs significantly affect the reaction pathways. During the past decade, we and other researchers have found interesting transformations based on this chemistry. These new reactions include the ring expansion of MCPs, cycloaddition reactions of MCPs with aldehydes and imines, cycloaddition reactions of MCPs with nitriles in the presence of strong Brønsted acid, radical reactions of MCPs with 1,3-dicarbonyl compounds, intramolecular Friedel-Crafts reactions of MCPs with arenes, acylation reactions of MCPs, and the reaction of MCPs with 1,1,3-triarylprop-2-yn-1-ols or their methyl ethers. These Lewis or Brønsted acid mediated reactions of MCPs can produce a variety of new compounds such as cyclobutanones, indenes, tetrahydrofurans, and tetrahydroquinolines. Finally, we have also carried out computational studies to explain the mechanism of the Brønsted acid mediated reactions of MCPs with acetonitrile.

  10. Geminal Brønsted Acid Ionic Liquids as Catalysts for the Mannich Reaction in Water

    PubMed Central

    He, Leqin; Qin, Shenjun; Chang, Tao; Sun, Yuzhuang; Zhao, Jiquan

    2014-01-01

    Quaternary ammonium geminal Brønsted acid ionic liquids (GBAILs) based on zwitterionic 1,2-bis[N-methyl-N-(3-sulfopropyl)-alkylammonium]ethane (where the carbon number of the alkyl chain is 4, 8, 10, 12, 14, 16, or 18) and p-toluenesulfonic acid monohydrate were synthesized. The catalytic ionic liquids were applied in three-component Mannich reactions with an aldehyde, ketone, and amine at 25 °C in water. The effects of the type and amount of catalyst and reaction time as well as the scope of the reaction were investigated. Results showed that GBAIL-C14 has excellent catalytic activity and fair reusability. The catalytic procedure was simple, and the catalyst could be recycled seven times via a simple separation process without noticeable decreases in catalytic activity. PMID:24837832

  11. Chemoselective Boron-Catalyzed Nucleophilic Activation of Carboxylic Acids for Mannich-Type Reactions.

    PubMed

    Morita, Yuya; Yamamoto, Tomohiro; Nagai, Hideoki; Shimizu, Yohei; Kanai, Motomu

    2015-06-10

    The carboxyl group (COOH) is an omnipresent functional group in organic molecules, and its direct catalytic activation represents an attractive synthetic method. Herein, we describe the first example of a direct catalytic nucleophilic activation of carboxylic acids with BH3·SMe2, after which the acids are able to act as carbon nucleophiles, i.e. enolates, in Mannich-type reactions. This reaction proceeds with a mild organic base (DBU) and exhibits high levels of functional group tolerance. The boron catalyst is highly chemoselective toward the COOH group, even in the presence of other carbonyl moieties, such as amides, esters, or ketones. Furthermore, this catalytic method can be extended to highly enantioselective Mannich-type reactions by using a (R)-3,3'-I2-BINOL-substituted boron catalyst.

  12. The Effect of Hetrogeneous Reactions on Model Performance for Nitrous Acid

    EPA Science Inventory

    Recent studies suggest that emissions, heterogeneous reactions, and surface photolysis of adsorbed nitric acid may produce additional nitrous acid in the atmosphere. The effects of these sources on nitrous acid formation are evaluated using the Community Multiscale Air Quality m...

  13. Absolute quantification of the alleles in somatic point mutations by bioluminometric methods based on competitive polymerase chain reaction in the presence of a locked nucleic acid blocker or an allele-specific primer.

    PubMed

    Iliadi, Alexandra; Petropoulou, Margarita; Ioannou, Penelope C; Christopoulos, Theodore K; Anagnostopoulos, Nikolaos I; Kanavakis, Emmanuel; Traeger-Synodinos, Jan

    2011-09-01

    In somatic (acquired) point mutations, the challenge is to quantify minute amounts of the mutant allele in the presence of a large excess of the normal allele that differs only in a single base pair. We report two bioluminometric methods that enable absolute quantification of the alleles. The first method exploits the ability of a locked nucleic acid (LNA) oligonucleotide to bind to and inhibit effectively the polymerase chain reaction (PCR) amplification of the normal allele while the amplification of the mutant allele remains unaffected. The second method employs allele-specific PCR primers, thereby allowing the amplification of the corresponding allele only. DNA internal standards (competitors) are added to the PCR mixture to compensate for any sample-to-sample variation in the amplification efficiency. The amplification products from the two alleles and the internal standards are quantified by a microtiter well-based bioluminometric hybridization assay using the photoprotein aequorin as a reporter. The methods allow absolute quantification of less than 300 copies of the mutant allele even in samples containing less than 1% of the mutant allele.

  14. Acid activated montmorillonite as catalysts in methyl esterification reactions of lauric acid.

    PubMed

    Zatta, Leandro; Ramos, Luiz Pereira; Wypych, Fernando

    2012-01-01

    The catalytic activity of acid activated montmorillonite in the esterification of free fatty acids (FFA) is reported. Standard Montmorillonite (MMT) type STx-1 provided by the Clay Mineral Society repository was activated using phosphoric, nitric and sulphuric acids under different conditions and the resulting materials were characterized and evaluated as catalysts in the methyl esterification of lauric acid. Blank reactions carried out in the absence of any added catalyst presented conversions of 32.64, 69.79 and 79.23%, for alcohol:lauric acid molar ratios of 60:1, 12:1 and 6:1, respectively. In the presence of the untreated clay and using molar ratios of 12:1 and 6:1 with 12% of catalyst, conversions of 70.92 and 82.30% were obtained, respectively. For the acid activated clays, conversions up to 93.08% of lauric acid to methyl laurate were obtained, much higher than those observed for the thermal conversion or using untreated montmorillonite. Relative good correlations were observed between the catalytic activity and the development of acid sites and textural properties of the resulting materials. Therefore, a simple acid activation was able to improve the catalytic activity and produce clay catalysts that are environmental friendly, cost effective, noncorrosive and reusable.

  15. Kinetics of liquid-solid reactions in naphthenic acid conversion and Kraft pulping

    NASA Astrophysics Data System (ADS)

    Yang, Ling

    Two liquid-solid reactions, in which the morphology of the solid changes as the reactions proceeds, were examined. One is the NA conversion in oil by decarboxylation on metal oxides and carbonates, and the other is the Kraft pulping in which lignin removal by delignification reaction. In the study of the NA conversion, CaO was chosen as the catalyst for the kinetic study from the tested catalysts based on NA conversion. Two reaction mixtures, carrier oil plus commercial naphthenic acids and heavy vacuum gas oil (HVGO) from Athabasca bitumen, were applied in the kinetic study. The influence of TAN, temperature, and catalyst loading on the NA conversion and decarboxylation were studied systematically. The results showed that the removal rate of TAN and the decarboxylation of NA were both independent of the concentration of NA over the range studied, and significantly dependent on reaction temperature. The data from analyzing the spent catalyst demonstrated that calcium naphthenate was an intermediate of the decarboxylation reaction of NA, and the decomposition of calcium naphthenate was a rate-determining step. In the study on the delignification of the Kraft pulping, a new mechanism was proposed for the heterogeneous delignification reaction during the Kraft pulping process. In particular, the chemical reaction mechanism took into account the heterogeneous nature of Kraft pulping. Lignin reacted in parallel with sodium hydroxide and sodium sulfide. The mechanism consists of three key kinetic steps: (1) adsorption of hydroxide and hydrosulfide ions on lignin; (2) surface reaction on the solid surface to produce degraded lignin products; and (3) desorption of degradation products from the solid surface. The most important step for the delignification process is the surface reaction, rather than the reactions occurring in the liquid phase. A kinetic model has, thus, been developed based on the proposed mechanism. The derived kinetic model showed that the mechanism

  16. Conversion of waste cellulose to ethanol. Phase II. Reaction kinetics with phosphoric acid

    SciTech Connect

    Moeller, M.B.; Isbell, R.E.

    1982-05-01

    Waste cellulosic material can be hydrolyzed in dilute acid solution to produce fermentable sugars which can then be converted into ethanol. A laboratory investigation was made of the feasibility of using phosphoric acid as the hydrolysis catalyst. The hydrolysis reaction with phosphoric acid solutions was compared with the reaction employing the more conventional dilute sulfuric acid catalyst. The purpose of this research was to examine the hydrolysis step in a proposed process for the conversion of cellulose (from wood, newspapers, municipal solid waste, or other sources) into ethanol - by which a potentially valuable co-product, DICAL (dicalcium phosphate), might be made and sold with or without the lignin content as a fertilizer. The pertinent reaction kinetics for the acid catalyzed production of glucose from cellulose consists of consecutive, pseudo-first order reactions. The first reaction forms glucose by hydrolyzing the cellulose polymer and a subsequent reaction decomposes the glucose. The maximum theoretical yield depends on the ratio of the rate constants for these two reactions. The rate constants of both reactions were measured in a series of experiments studying temperature and concentration effects. The results suggest that the glucose decomposition reaction is similar with the two acids but that the cellulose hydrolysis reaction mechanism with phosphoric acid may be different than with sulfuric acid. The studies show phosphoric acid is unpromising and much inferior to sulfuric acid as the catalytic agent. Under the conditions studied, 0.8 wt % sulfuric acid gives a greater yield of glucose than 8.0 wt % phosphoric acid.

  17. An Investigation of the Complexity of Maillard Reaction Product Profiles from the Thermal Reaction of Amino Acids with Sucrose Using High Resolution Mass Spectrometry

    PubMed Central

    Golon, Agnieszka; Kropf, Christian; Vockenroth, Inga; Kuhnert, Nikolai

    2014-01-01

    Thermal treatment of food changes its chemical composition drastically with the formation of “so-called” Maillard reaction products, being responsible for the sensory properties of food, along with detrimental and beneficial health effects. In this contribution, we will describe the reactivity of several amino acids, including arginine, lysine, aspartic acid, tyrosine, serine and cysteine, with carbohydrates. The analytical strategy employed involves high and ultra-high resolution mass spectrometry followed by chemometric-type data analysis. The different reactivity of amino acids towards carbohydrates has been observed with cysteine and serine, resulting in complex MS spectra with thousands of detectable reaction products. Several compounds have been tentatively identified, including caramelization reaction products, adducts of amino acids with carbohydrates, their dehydration and hydration products, disproportionation products and aromatic compounds based on molecular formula considerations. PMID:28234331

  18. Destruction of microcystins (cyanotoxins) by UV-254 nm-based direct photolysis and advanced oxidation processes (AOPs): influence of variable amino acids on the degradation kinetics and reaction mechanisms.

    PubMed

    He, Xuexiang; de la Cruz, Armah A; Hiskia, Anastasia; Kaloudis, Triantafyllos; O'Shea, Kevin; Dionysiou, Dionysios D

    2015-05-01

    Hepatotoxic microcystins (MCs) are the most frequently detected group of cyanobacterial toxins. This study investigated the degradation of common MC variants in water, MC-LR, MC-RR, MC-YR and MC-LA, by UV-254 nm-based processes, UV only, UV/H2O2, UV/S2O8(2-) and UV/HSO5(-). Limited direct photolysis of MCs was observed, while the addition of an oxidant significantly improved the degradation efficiency with an order of UV/S2O8(2-) > UV/HSO5(-) > UV/H2O2 at the same initial molar concentration of the oxidant. The removal of MC-LR by UV/H2O2 appeared to be faster than another cyanotoxin, cylindrospermopsin, at either the same initial molar concentration or the same initial organic carbon concentration of the toxin. It suggested a faster reaction of MC-LR with hydroxyl radical, which was further supported by the determined second-order rate constant of MCs with hydroxyl radical. Both isomerization and photohydration byproducts were observed in UV only process for all four MCs; while in UV/H2O2, hydroxylation and diene-Adda double bond cleavage byproducts were detected. The presence of a tyrosine in the structure of MC-YR significantly promoted the formation of monohydroxylation byproduct m/z 1061; while the presence of a second arginine in MC-RR led to the elimination of a guanidine group and the absence of double bond cleavage byproducts. It was therefore demonstrated in this study that the variable amino acids in the structure of MCs influenced not only the degradation kinetics but also the preferable reaction mechanisms.

  19. Surface reactions of iron - enriched smectites: adsorption and transformation of hydroxy fatty acids and phenolic acids

    NASA Astrophysics Data System (ADS)

    Polubesova, Tamara; Olshansky, Yaniv; Eldad, Shay; Chefetz, Benny

    2014-05-01

    Iron-enriched smectites play an important role in adsorption and transformation of soil organic components. Soil organo-clay complexes, and in particular humin contain hydroxy fatty acids, which are derived from plant biopolymer cutin. Phenolic acids belong to another major group of organic acids detected in soil. They participate in various soil processes, and are of concern due to their allelopathic activity. We studied the reactivity of iron-enriched smectites (Fe(III)-montmorillonite and nontronite) toward both groups of acids. We used fatty acids- 9(10),16-dihydroxypalmitic acid (diHPA), isolated from curtin, and 9,10,16-trihydroxypalmitic acid (triHPA); the following phenolic acids were used: ferulic, p-coumaric, syringic, and vanillic. Adsorption of both groups of acids was measured. The FTIR spectra of fatty acid-mineral complexes indicated inner-sphere complexation of fatty acids with iron-enriched smectites (versus outer-sphere complexation with Ca(II)-montmorillonite). The LC-MS results demonstrated enhanced esterification of fatty acids on the iron-enriched smectite surfaces (as compared to Ca(II)-montmorillonite). This study suggests that fatty acids can be esterified on the iron-enriched smectite surfaces, which results in the formation of stable organo-mineral complexes. These complexes may serve as a model for the study of natural soil organo-clay complexes and humin. The reaction of phenolic acids with Fe(III)-montmorillonite demonstrated their oxidative transformation by the mineral surfaces, which was affected by molecular structure of acids. The following order of their transformation was obtained: ferulic >syringic >p-coumaric >vanillic. The LC-MS analysis demonstrated the presence of dimers, trimers, and tetramers of ferulic acid on the surface of Fe(III)-montmorillonite. Oxidation and transformation of ferulic acid were more intense on the surface of Fe(III)-montmorillonite as compared to Fe(III) in solution due to stronger complexation on

  20. Pitchfork and winged-cusp singularities in iodate-arsenous acid reaction

    NASA Astrophysics Data System (ADS)

    Li, Ru-Sheng

    1994-09-01

    The iodate-arsenous acid reaction was reported to be able to exhibit hysteresis bistability, including mushrooms and isolas, in a continuous flow stirred tank reactor (CSTR) when an additional flow of solvent is introduced [N. Ganapathisubramanian and K. Showalter, J. Chem. Phys. 80, 4177 (1984)]. Based on their kinetic data and the empirical rate law, it is shown that the reaction may also exhibit pitchfork-type and winged cusp-type singularities if additional flows of the reactants are introduced to the CSTR.

  1. Reaction of Thymidine with Hypobromous Acid in Phosphate Buffer.

    PubMed

    Suzuki, Toshinori; Kitabatake, Akihiko; Koide, Yuki

    2016-01-01

    When thymidine was treated with hypobromous acid (HOBr) in 100 mM phosphate buffer at pH 7.2, two major product peaks appeared in the HPLC chromatogram. The products in each peak were identified by NMR and MS as two isomers of 5-hydroxy-5,6-dihydrothymidine-6-phosphate (a novel compound) and two isomers of 5,6-dihydroxy-5,6-dihydrothymidine (thymidine glycol) with comparable yields. 5-Hydroxy-5,6-dihydrothymidine-6-phosphate was relatively stable, and decomposed with a half-life of 32 h at pH 7.2 and 37°C generating thymidine glycol. The results suggest that 5-hydroxy-5,6-dihydrothymidine-6-phosphate in addition to thymidine glycol may have importance for mutagenesis by the reaction of HOBr with thymine residues in nucleotides and DNA.

  2. Structural and medium effects on the reactions of the cumyloxyl radical with intramolecular hydrogen bonded phenols. The interplay between hydrogen-bonding and acid-base interactions on the hydrogen atom transfer reactivity and selectivity.

    PubMed

    Salamone, Michela; Amorati, Riccardo; Menichetti, Stefano; Viglianisi, Caterina; Bietti, Massimo

    2014-07-03

    A time-resolved kinetic study on the reactions of the cumyloxyl radical (CumO(•)) with intramolecularly hydrogen bonded 2-(1-piperidinylmethyl)phenol (1) and 4-methoxy-2-(1-piperidinylmethyl)phenol (2) and with 4-methoxy-3-(1-piperidinylmethyl)phenol (3) has been carried out. In acetonitrile, intramolecular hydrogen bonding protects the phenolic O-H of 1 and 2 from attack by CumO(•) and hydrogen atom transfer (HAT) exclusively occurs from the C-H bonds that are α to the piperidine nitrogen (α-C-H bonds). With 3 HAT from both the phenolic O-H and the α-C-H bonds is observed. In the presence of TFA or Mg(ClO4)2, protonation or Mg(2+) complexation of the piperidine nitrogen removes the intramolecular hydrogen bond in 1 and 2 and strongly deactivates the α-C-H bonds of the three substrates. Under these conditions, HAT to CumO(•) exclusively occurs from the phenolic O-H group of 1-3. These results clearly show that in these systems the interplay between intramolecular hydrogen bonding and Brønsted and Lewis acid-base interactions can drastically influence both the HAT reactivity and selectivity. The possible implications of these findings are discussed in the framework of the important role played by tyrosyl radicals in biological systems.

  3. Polymeric electrolytes based on hydrosilyation reactions

    DOEpatents

    Kerr, John Borland; Wang, Shanger; Hou, Jun; Sloop, Steven Edward; Han, Yong Bong; Liu, Gao

    2006-09-05

    New polymer electrolytes were prepared by in situ cross-linking of allyl functional polymers based on hydrosilation reaction using a multifunctional silane cross-linker and an organoplatinum catalyst. The new cross-linked electrolytes are insoluble in organic solvent and show much better mechanical strength. In addition, the processability of the polymer electrolyte is maintained since the casting is finished well before the gel formation.

  4. Functionalization of Carbon Nanotubes via Electrophilic Substitution Reaction in Polyphosphoric Acid

    DTIC Science & Technology

    2006-07-26

    1 Title of proposed research: Functionalization of Carbon Nanotubes via Electrophilic Substitution Reaction in Polyphosphoric Acid Proposer: Jong...Choi, J.-Y.; Tan, L.-S.; Baek, J.-B. “Functionalization of carbon nanotubes via electrophilic substitution reaction in polyphosphoric acid” AFOSR...2006 4. TITLE AND SUBTITLE Functionalization of carbon nanotubes via electrophilic substitution reaction in polyphosphoric acid 5a. CONTRACT

  5. Advances in nucleic acid-based detection methods.

    PubMed Central

    Wolcott, M J

    1992-01-01

    Laboratory techniques based on nucleic acid methods have increased in popularity over the last decade with clinical microbiologists and other laboratory scientists who are concerned with the diagnosis of infectious agents. This increase in popularity is a result primarily of advances made in nucleic acid amplification and detection techniques. Polymerase chain reaction, the original nucleic acid amplification technique, changed the way many people viewed and used nucleic acid techniques in clinical settings. After the potential of polymerase chain reaction became apparent, other methods of nucleic acid amplification and detection were developed. These alternative nucleic acid amplification methods may become serious contenders for application to routine laboratory analyses. This review presents some background information on nucleic acid analyses that might be used in clinical and anatomical laboratories and describes some recent advances in the amplification and detection of nucleic acids. PMID:1423216

  6. The first proton sponge-based amino acids: synthesis, acid-base properties and some reactivity.

    PubMed

    Ozeryanskii, Valery A; Gorbacheva, Anastasia Yu; Pozharskii, Alexander F; Vlasenko, Marina P; Tereznikov, Alexander Yu; Chernov'yants, Margarita S

    2015-08-21

    The first hybrid base constructed from 1,8-bis(dimethylamino)naphthalene (proton sponge or DMAN) and glycine, N-methyl-N-(8-dimethylamino-1-naphthyl)aminoacetic acid, was synthesised in high yield and its hydrobromide was structurally characterised and used to determine the acid-base properties via potentiometric titration. It was found that the basic strength of the DMAN-glycine base (pKa = 11.57, H2O) is on the level of amidine amino acids like arginine and creatine and its structure, zwitterionic vs. neutral, based on the spectroscopic (IR, NMR, mass) and theoretical (DFT) approaches has a strong preference to the zwitterionic form. Unlike glycine, the DMAN-glycine zwitterion is N-chiral and is hydrolytically cleaved with the loss of glycolic acid on heating in DMSO. This reaction together with the mild decarboxylative conversion of proton sponge-based amino acids into 2,3-dihydroperimidinium salts under air-oxygen was monitored with the help of the DMAN-alanine amino acid. The newly devised amino acids are unique as they combine fluorescence, strongly basic and redox-active properties.

  7. Nitro-fatty acid reaction with glutathione and cysteine. Kinetic analysis of thiol alkylation by a Michael addition reaction.

    PubMed

    Baker, Laura M S; Baker, Paul R S; Golin-Bisello, Franca; Schopfer, Francisco J; Fink, Mitchell; Woodcock, Steven R; Branchaud, Bruce P; Radi, Rafael; Freeman, Bruce A

    2007-10-19

    Fatty acid nitration by nitric oxide-derived species yields electrophilic products that adduct protein thiols, inducing changes in protein function and distribution. Nitro-fatty acid adducts of protein and reduced glutathione (GSH) are detected in healthy human blood. Kinetic and mass spectrometric analyses reveal that nitroalkene derivatives of oleic acid (OA-NO2) and linoleic acid (LNO2) rapidly react with GSH and Cys via Michael addition reaction. Rates of OA-NO2 and LNO2 reaction with GSH, determined via stopped flow spectrophotometry, displayed second-order rate constants of 183 M(-1)S(-1) and 355 M(-1)S(-1), respectively, at pH 7.4 and 37 degrees C. These reaction rates are significantly greater than those for GSH reaction with hydrogen peroxide and non-nitrated electrophilic fatty acids including 8-iso-prostaglandin A2 and 15-deoxy-Delta(12,14)-prostaglandin J2. Increasing reaction pH from 7.4 to 8.9 enhanced apparent second-order rate constants for the thiol reaction with OA-NO2 and LNO2, showing dependence on the thiolate anion of GSH for reactivity. Rates of nitroalkene reaction with thiols decreased as the pKa of target thiols increased. Increasing concentrations of the detergent octyl-beta-d-glucopyranoside decreased rates of nitroalkene reaction with GSH, indicating that the organization of nitro-fatty acids into micellar or membrane structures can limit Michael reactivity with more polar nucleophilic targets. In aggregate, these results reveal that the reversible adduction of thiols by nitro-fatty acids is a mechanism for reversible post-translational regulation of protein function by nitro-fatty acids.

  8. Solid Acid Based Fuel Cells

    DTIC Science & Technology

    2007-11-02

    superprotonic solid acids with elements such as P, As, Si and Ge, which have greater affinities to oxygen , we anticipate that the reduction reaction will be...bulk material consisted of an apatite phase (hexagonal symmetry) of variable composition, LixLa10-x(SiO4)6O3-x, with excess lithium residing in the...in Tables 1 and 2, indicate that this compound is a rather conventional apatite with fixed stoichiometry, LiLa9(SiO4)6O2 (x = 1). Such a result is

  9. High School Forum: "Invitations to Enquiry": The Calcite/Acid Reaction.

    ERIC Educational Resources Information Center

    Herron, J. Dudley, Ed.; Driscoll, D. R.

    1979-01-01

    Describes a high school chemistry experiment which involves the reaction between calcite and hydrochloric and sulfuric acids. This reaction can be carried out as a projected demonstration and on an individual basis. (HM)

  10. Phytosphingosine degradation pathway includes fatty acid α-oxidation reactions in the endoplasmic reticulum.

    PubMed

    Kitamura, Takuya; Seki, Naoya; Kihara, Akio

    2017-03-28

    Although normal fatty acids (FAs) are degraded via β-oxidation, unusual FAs such as 2-hydroxy (2-OH) FAs and 3-methyl-branched FAs are degraded via α-oxidation. Phytosphingosine (PHS) is one of the long-chain bases (the sphingolipid components) and exists in specific tissues, including the epidermis and small intestine in mammals. In the degradation pathway, PHS is converted to 2-OH palmitic acid and then to pentadecanoic acid (C15:0-COOH) via FA α-oxidation. However, the detailed reactions and genes involved in the α-oxidation reactions of the PHS degradation pathway have yet to be determined. In the present study, we reveal the entire PHS degradation pathway: PHS is converted to C15:0-COOH via six reactions [phosphorylation, cleavage, oxidation, CoA addition, cleavage (C1 removal), and oxidation], in which the last three reactions correspond to the α-oxidation. The aldehyde dehydrogenase ALDH3A2 catalyzes both the first and second oxidation reactions (fatty aldehydes to FAs). In Aldh3a2-deficient cells, the unmetabolized fatty aldehydes are reduced to fatty alcohols and are incorporated into ether-linked glycerolipids. We also identify HACL2 (2-hydroxyacyl-CoA lyase 2) [previous name, ILVBL; ilvB (bacterial acetolactate synthase)-like] as the major 2-OH acyl-CoA lyase involved in the cleavage (C1 removal) reaction in the FA α-oxidation of the PHS degradation pathway. HACL2 is localized in the endoplasmic reticulum. Thus, in addition to the already-known FA α-oxidation in the peroxisomes, we have revealed the existence of FA α-oxidation in the endoplasmic reticulum in mammals.

  11. Silicon-based sleeve devices for chemical reactions

    DOEpatents

    Northrup, M. Allen; Mariella, Jr., Raymond P.; Carrano, Anthony V.; Balch, Joseph W.

    1996-01-01

    A silicon-based sleeve type chemical reaction chamber that combines heaters, such as doped polysilicon for heating, and bulk silicon for convection cooling. The reaction chamber combines a critical ratio of silicon and silicon nitride to the volume of material to be heated (e.g., a liquid) in order to provide uniform heating, yet low power requirements. The reaction chamber will also allow the introduction of a secondary tube (e.g., plastic) into the reaction sleeve that contains the reaction mixture thereby alleviating any potential materials incompatibility issues. The reaction chamber may be utilized in any chemical reaction system for synthesis or processing of organic, inorganic, or biochemical reactions, such as the polymerase chain reaction (PCR) and/or other DNA reactions, such as the ligase chain reaction, which are examples of a synthetic, thermal-cycling-based reaction. The reaction chamber may also be used in synthesis instruments, particularly those for DNA amplification and synthesis.

  12. Silicon-based sleeve devices for chemical reactions

    DOEpatents

    Northrup, M.A.; Mariella, R.P. Jr.; Carrano, A.V.; Balch, J.W.

    1996-12-31

    A silicon-based sleeve type chemical reaction chamber is described that combines heaters, such as doped polysilicon for heating, and bulk silicon for convection cooling. The reaction chamber combines a critical ratio of silicon and silicon nitride to the volume of material to be heated (e.g., a liquid) in order to provide uniform heating, yet low power requirements. The reaction chamber will also allow the introduction of a secondary tube (e.g., plastic) into the reaction sleeve that contains the reaction mixture thereby alleviating any potential materials incompatibility issues. The reaction chamber may be utilized in any chemical reaction system for synthesis or processing of organic, inorganic, or biochemical reactions, such as the polymerase chain reaction (PCR) and/or other DNA reactions, such as the ligase chain reaction, which are examples of a synthetic, thermal-cycling-based reaction. The reaction chamber may also be used in synthesis instruments, particularly those for DNA amplification and synthesis. 32 figs.

  13. Understanding Nitrilotris(methylenephosphonic acid) reactions with ferric hydroxide.

    PubMed

    Martínez, Rodrigo Javier; Farrell, James

    2017-05-01

    Phosphonate compounds are used in a wide variety of industrial and agricultural applications, and are commonly found in surface and ground waters. Adsorption to ferric hydroxide can have a significant effect on the transport and fate of phosphonate compounds in the environment. This research used density functional theory modeling to investigate the adsorption mechanisms of nitrilotris(methylenephosphonic acid) (NTMP) on ferric hydroxide. Standard Gibbs free energies of reaction (ΔGr(o)) and reaction activation barriers (Ea) were calculated for different possible adsorption mechanisms. Physical adsorption of NTMP to ferric hydroxide was promoted by negative charge assisted hydrogen bonding, and had ΔGr(o) ranging from -2.7 to -7.4 kcal/mol. NTMP was found to form three different types of inner sphere complexes, monodentate, bidentate mononuclear and bidentate binuclear. For the monodentate complexes, ΔGr(o) ranged from -8.0 to -13.7 kcal/mol, for the bidentate complexes ΔGr(o) ranged from -15.3 to -28.9 kcal/mol. Complexation with Ca(2+) decreased the energy for physical adsorption but increased the binding energies for mono- and bidentate complexes. Complexation with Ca(2+) also allowed formation of a tridentate ternary surface complex, whereby the Ca(2+) ion formed a bridge between three FeO(-) and three PO(-) groups. Physical adsorption had Ea = 0, but mono- and bidentate complex formation had Ea values ranging from 36 to 53 kcal/mol. Formation of tridentate ternary surface complexes involving Ca(2+) had the lowest activation barriers of 8 and 10 kcal/mol. The different activation barriers for different modes of adsorption may explain previous experimental observations of unusual kinetic behavior for adsorption and desorption of NTMP.

  14. Reversion and dehydration reactions of glucose during the dilute sulfuric acid hydrolysis of cellulose

    SciTech Connect

    Helm, R.F.

    1987-01-01

    The inaccessibility of all glycosidic bonds necessitates industrial conversion schemes which employ a dilute acid catalyst at high temperatures. Process conditions also promote further reactions of glucose via the reversion and dehydration pathways. Quantitative determination of the yields of the major reversion and dehydration products is important for understanding and predicting the amounts of these materials expected under envisioned industrial operating conditions. Microcrystalline cellulose (Avicel) was hydrolyzed with sulfuric acid (0.0-1.25 wt.%), at high temperatures (160-250/sup 0/C), and at a 3:1 liquid-to-solid ratio. The hydrolysis was monitored by evaluating the amount of cellulose remaining and the yields of glucose, solid humin, levulinic acid, formic acid, hydroxymethylfurfural (HMF), and reversion products as a function of the aforementioned reaction conditions. Analysis of the reversion products required the development of a technique for the quantitation of trace carbohydrates in complex mixtures and led to the development of a reduction/permethylation gas chromatographic procedure. Cellulose hydrolysis followed pseudo-homogeneous first-order kinetics. Glucose yield was adequately described as consecutive first-order reactions. Anhydrosugars formed via reversion followed equilibrium reaction kinetics whereas the disaccharides did not. Total reversion product yields approached 10% at 250/sup 0/C. Quantitative determination of the major dehydration products provided important information concerning the destruction of glucose. HMF was produced in up to 12% yields based on the theoretical amount of glucose available, and furfural was detected in up to 5% yields. A carbon mass balance based on the determined product yields revealed that approximately 90% of all carbon was accounted for at maximum glucose yields.

  15. Library of Antifouling Surfaces Derived From Natural Amino Acids by Click Reaction.

    PubMed

    Xu, Chen; Hu, Xin; Wang, Jie; Zhang, Ye-Min; Liu, Xiao-Jiu; Xie, Bin-Bin; Yao, Chen; Li, Yi; Li, Xin-Song

    2015-08-12

    Biofouling is of great concern in numerous applications ranging from ophthalmological implants to catheters, and from bioseparation to biosensors. In this report, a general and facile strategy to combat surface fouling is developed by grafting of amino acids onto polymer substrates to form zwitterionic structure through amino groups induced epoxy ring opening click reaction. First of all, a library of poly(2-hydroxyethyl methacrylate-co-glycidyl methacrylate) hydrogels with zwitterionic surfaces were prepared, resulting in the formation of pairs of carboxyl anions and protonated secondary amino cations. The analysis of attenuated total reflectance Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy confirmed the successful immobilization of amino acids on the hydrogel surfaces. After that, the contact angle and equilibrium water content of the modified hydrogels showed that the hydrogels exhibited improved hydrophilicity compared with the parent hydrogel. Furthermore, the protein deposition was evaluated by bicinchoninic acid assay using bovine serum albumin (BSA) and lysozyme as models. The results indicated that the performance of the hydrogels was determined by the nature of incorporated amino acid: the hydrogels incorporated with neutral amino acids had nonspecific antiadsorption capability to both BSA and lysozyme; the hydrogels incorporated with charged amino acids showed antiadsorption behaviors against protein with same charge and enhanced adsorption to the protein with opposite charge; the optimal antiadsorption performance was observed on the hydrogels incorporated with polar amino acids with a hydroxyl residual. The improvement of antiprotein fouling of the neutral amino acids grafted hydrogels can be ascribed to the formation of zwitterionic surfaces. Finally, a couple of soft contact lenses grafted with amino acids were fabricated having improved antifouling property and hydrophilicity. The result demonstrated the success of

  16. Laser Spot Detection Based on Reaction Diffusion

    PubMed Central

    Vázquez-Otero, Alejandro; Khikhlukha, Danila; Solano-Altamirano, J. M.; Dormido, Raquel; Duro, Natividad

    2016-01-01

    Center-location of a laser spot is a problem of interest when the laser is used for processing and performing measurements. Measurement quality depends on correctly determining the location of the laser spot. Hence, improving and proposing algorithms for the correct location of the spots are fundamental issues in laser-based measurements. In this paper we introduce a Reaction Diffusion (RD) system as the main computational framework for robustly finding laser spot centers. The method presented is compared with a conventional approach for locating laser spots, and the experimental results indicate that RD-based computation generates reliable and precise solutions. These results confirm the flexibility of the new computational paradigm based on RD systems for addressing problems that can be reduced to a set of geometric operations. PMID:26938537

  17. Laser Spot Detection Based on Reaction Diffusion.

    PubMed

    Vázquez-Otero, Alejandro; Khikhlukha, Danila; Solano-Altamirano, J M; Dormido, Raquel; Duro, Natividad

    2016-03-01

    Center-location of a laser spot is a problem of interest when the laser is used for processing and performing measurements. Measurement quality depends on correctly determining the location of the laser spot. Hence, improving and proposing algorithms for the correct location of the spots are fundamental issues in laser-based measurements. In this paper we introduce a Reaction Diffusion (RD) system as the main computational framework for robustly finding laser spot centers. The method presented is compared with a conventional approach for locating laser spots, and the experimental results indicate that RD-based computation generates reliable and precise solutions. These results confirm the flexibility of the new computational paradigm based on RD systems for addressing problems that can be reduced to a set of geometric operations.

  18. Kinetic Studies on the Reaction between Dicyanocobinamide and Hypochlorous Acid

    PubMed Central

    Maitra, Dhiman; Ali, Iyad; Abdulridha, Rasha M.; Shaeib, Faten; Khan, Sana N.; Saed, Ghassan M.; Pennathur, Subramaniam; Abu-Soud, Husam M.

    2014-01-01

    Hypochlorous acid (HOCl) is a potent oxidant generated by myeloperoxidase (MPO), which is an abundant enzyme used for defense against microbes. We examined the potential role of HOCl in corrin ring destruction and subsequent formation of cyanogen chloride (CNCl) from dicyanocobinamide ((CN)2-Cbi). Stopped-flow analysis revealed that the reaction consists of at least three observable steps, including at least two sequential transient intermediates prior to corrin ring destruction. The first two steps were attributed to sequential replacement of the two cyanide ligands with hypochlorite, while the third step was the destruction of the corrin ring. The formation of (OCl)(CN)-Cbi and its conversion to (OCl)2-Cbi was fitted to a first order rate equation with second order rate constants of 0.002 and 0.0002 µM−1s−1, respectively. The significantly lower rate of the second step compared to the first suggests that the replacement of the first cyanide molecule by hypochlorite causes an alteration in the ligand trans effects changing the affinity and/or accessibility of Co toward hypochlorite. Plots of the apparent rate constants as a function of HOCl concentration for all the three steps were linear with Y-intercepts close to zero, indicating that HOCl binds in an irreversible one-step mechanism. Collectively, these results illustrate functional differences in the corrin ring environments toward binding of diatomic ligands. PMID:25375773

  19. [Influencing factors and reaction mechanism of chloroacetic acid reduction by cast iron].

    PubMed

    Tang, Shun; Yang, Hong-Wei; Wang, Xiao-Mao; Xie, Yue-Feng

    2014-03-01

    The chloroacetic acids are ubiquitous present as a class of trace chlorinated organic pollutants in surface and drinking water. Most of chloroacetic acids are known or suspected carcinogens and, when at high concentrations, are of great concern to human health. In order to economically remove chloroacetic acids, the degradation of chloroacetic acids by cast iron was investigated. Moreover, the effect of iron style, pretreatment process, shocking mode and dissolved oxygen on chloroacetic acids reduced by cast iron was discussed. Compared to iron source and acid pretreatment, mass transfer was more important to chloroacetic acid removal. Dichloroacetic acid (DCAA) and monochloroacetic acid (MCAA) were the main products of anoxic and oxic degradation of trichloroacetic acid (TCAA) by cast iron during the researched reaction time, respectively. With longtitudinal shock, the reaction kinetics of chloroaectic acid removal by cast iron conformed well to the pseudo first order reaction. The anoxic reaction constants of TCAA, DCAA and MCAA were 0.46 h(-1), 0.03 h(-1) and 0, and their oxic constants were 1.24 h(-1), 0.79 h(-1) and 0.28 h(-1), respectively. The removal mechanisms of chloroacetic acids were different under various oxygen concentrations, including sequential hydrogenolysis for anoxic reaction and sequential hydrogenolysis and direct transformation possible for oxic reaction, respectively.

  20. Lewis Acid and Substituent Effects on the Molecular Mechanism for the Nazarov Reaction of Penta-1,4-dien-3-one and Derivatives. A Topological Analysis Based on the Combined Use of Electron Localization Function and Catastrophe Theory.

    PubMed

    Polo, Victor; Andrés, Juan

    2007-05-01

    The joint use of the topological analysis provided by the electron localization function (ELF) and catastrophe theory (CT), at the B3LYP/6-31G(d) calculation level, allows us to examine the Lewis acid (protonation H(+) and presence of BH3) and the role of an electron donor substituent (-OCH3) at α and β positions along the course of the molecular mechanism for the Nazarov rearrangement of penta-1,4-dien-3-one and eight derivatives. The progress of the reaction is monitored by the changes of the ELF structural stability domains (SSDs), each change being controlled by a turning point derived from CT. These SSDs and the corresponding turning points are associated with a sequence of elementary chemical steps. Along the cyclization path of penta-1,4-diene-3-one, four SSDs as well as three turning points (cusp1-fold1-cusp2) have been characterized. The first and second SSDs correspond to a polarization of the C-O bond and electronic redistribution among the C-C bonds, respectively, and they can be associated with the formation of an oxyallyl structure. The third and fourth SSDs can be assigned to the ring closure process. Protonation of the oxygen atom shifts the reactive directly into the second SSD, greatly reducing the activation and reaction energies. The electronic effects due to Lewis acids and electron donor substituents have been rationalized in terms of calculations of mesomeric structures from ELF basin populations. The combination of Lewis acids together with α and β -OCH3 substitutions renders a cooperative and competitive effect on activation and reaction free energies, respectively.

  1. Nonenzymatic oligomerization reactions on templates containing inosinic acid or diaminopurine nucleotide residues

    NASA Technical Reports Server (NTRS)

    Kozlov, I. A.; Orgel, L. E.; Bada, J. L. (Principal Investigator)

    1999-01-01

    The template-directed oligomerization of nucleoside-5'-phosphoro-2-methyl imidazolides on standard oligonucleotide templates has been studied extensively. Here, we describe experiments with templates in which inosinic acid (I) is substituted for guanylic acid, or 2,6-diaminopurine nucleotide (D) for adenylic acid. We find that the substitution of I for G in a template is strongly inhibitory and prevents any incorporation of C into internal positions in the oligomeric products of the reaction. The substitution of D for A, on the contrary, leads to increased incorporation of U into the products. We found no evidence for the template-directed facilitation of oligomerization of A or I through A-I base pairing. The significance of these results for prebiotic chemistry is discussed.

  2. Graphene oxide for acid catalyzed-reactions: Effect of drying process

    NASA Astrophysics Data System (ADS)

    Gong, H. P.; Hua, W. M.; Yue, Y. H.; Gao, Z.

    2017-03-01

    Graphene oxides (GOs) were prepared by Hummers method through various drying processes, and characterized by XRD, SEM, FTIR, XPS and N2 adsorption. Their acidities were measured using potentiometric titration and acid-base titration. The catalytic properties were investigated in the alkylation of anisole with benzyl alcohol and transesterification of triacetin with methanol. GOs are active catalysts for both reaction, whose activity is greatly affected by their drying processes. Vacuum drying GO exhibits the best performance in transesterification while freezing drying GO is most active for alkylation. The excellent catalytic behavior comes from abundant surface acid sites as well as proper surface functional groups, which can be obtained by selecting appropriate drying process.

  3. Acid-free aza Diels-Alder reaction of Danishefsky's diene with imines.

    PubMed

    Yuan, Yu; Li, Xin; Ding, Kuiling

    2002-09-19

    [reaction: see text] A highly efficient aza Diels-Alder reaction of Danishefsky's diene with imines was found to occur in methanol in the absence of any acids at room temperature to give corresponding 2-substituted dihydro-4-pyridone derivatives in high yields. This reaction can be also carried out in a three-component one-pot reaction manner. The reaction was found to proceed through a Mannich-type condensation mechanism.

  4. Activation of stratospheric chlorine by reactions in liquid sulphuric acid

    SciTech Connect

    Cox, R.A.; MacKenzie, A.R. ); Mueller, R.H.; Peter, Th.; Crutzen, P.J. )

    1994-06-22

    The authors discuss activation mechanisms for chlorine compounds in the stratosphere, based on laboratory measurements for the solubility and reaction rates of HOCl and HCl in H[sub 2]SO[sub 4] solutions, as found on aerosols in the stratosphere. Their interest is in the impact of the large increase in aerosol loading in the stratosphere in the winter on 1991-92 due to the Mt. Pinatubo eruption. While laboratory data is not available for the temperature range close to 190 K, they argue that should the solubility and hydrolysis rates be high enough, this excess aerosol density could have contributed a significant additional amount of reactive chlorine to the stratosphere.

  5. Lewis base activation of Lewis acids: development of a Lewis base catalyzed selenolactonization.

    PubMed

    Denmark, Scott E; Collins, William R

    2007-09-13

    The concept of Lewis base activation of Lewis acids has been applied to the selenolactonization reaction. Through the use of substoichiometric amounts of Lewis bases with "soft" donor atoms (S, Se, P) significant rate enhancements over the background reaction are seen. Preliminary mechanistic investigations have revealed the resting state of the catalyst as well as the significance of a weak Brønsted acid promoter.

  6. Synthesis of cyclopropyl-substituted furans by brønsted Acid promoted cascade reactions.

    PubMed

    Clark, J Stephen; Romiti, Filippo; Hogg, Kirsten F; Hamid, Malai Haniti S A; Richter, Sven C; Boyer, Alistair; Redman, Joanna C; Farrugia, Louis J

    2015-05-04

    Chloroacetic acid promotes an efficient and diastereoselective intramolecular cascade reaction of electron-deficient ynenones to deliver products featuring a 2,3,5-trisubstituted furan bearing a fused cyclopropyl substituent at the 5-position. Synthetically relevant polycyclic building blocks featuring rings of various sizes and heteroatoms have been synthesized in high yield using this mild acid-catalyzed reaction.

  7. 40 CFR 721.9485 - Dimer acid/polymerized rosin amidoamine reaction product (generic).

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... amidoamine reaction product (generic). 721.9485 Section 721.9485 Protection of Environment ENVIRONMENTAL... reaction product (generic). (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as Dimer acid/polymerized rosin amidoamine reaction product...

  8. 40 CFR 721.9485 - Dimer acid/polymerized rosin amidoamine reaction product (generic).

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... amidoamine reaction product (generic). 721.9485 Section 721.9485 Protection of Environment ENVIRONMENTAL... reaction product (generic). (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as Dimer acid/polymerized rosin amidoamine reaction product...

  9. 40 CFR 721.10428 - Fatty acids, C18-unsatd., dimers, reaction products with 1-piperazineethanamine.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ..., reaction products with 1-piperazineethanamine. 721.10428 Section 721.10428 Protection of Environment..., reaction products with 1-piperazineethanamine. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified as fatty acids, C18-unsatd., dimers, reaction products...

  10. 40 CFR 721.10428 - Fatty acids, C18-unsatd., dimers, reaction products with 1-piperazineethanamine.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ..., reaction products with 1-piperazineethanamine. 721.10428 Section 721.10428 Protection of Environment..., reaction products with 1-piperazineethanamine. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified as fatty acids, C18-unsatd., dimers, reaction products...

  11. 40 CFR 721.9485 - Dimer acid/polymerized rosin amidoamine reaction product (generic).

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... amidoamine reaction product (generic). 721.9485 Section 721.9485 Protection of Environment ENVIRONMENTAL... reaction product (generic). (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as Dimer acid/polymerized rosin amidoamine reaction product...

  12. 40 CFR 721.9485 - Dimer acid/polymerized rosin amidoamine reaction product (generic).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... amidoamine reaction product (generic). 721.9485 Section 721.9485 Protection of Environment ENVIRONMENTAL... reaction product (generic). (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as Dimer acid/polymerized rosin amidoamine reaction product...

  13. 40 CFR 721.9485 - Dimer acid/polymerized rosin amidoamine reaction product (generic).

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... amidoamine reaction product (generic). 721.9485 Section 721.9485 Protection of Environment ENVIRONMENTAL... reaction product (generic). (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as Dimer acid/polymerized rosin amidoamine reaction product...

  14. Reaction of folic acid with single-walled carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Ellison, Mark D.; Chorney, Matthew

    2016-10-01

    The oxygen-containing functional groups on oxidized single-walled carbon nanotubes (SWNTs) are used to covalently bond folic acid molecules to the SWNTs. Infrared spectroscopy confirms intact molecular binding to the SWNTs through the formation of an amide bond between a carboxylic acid group on an SWNT and the primary amine group of folic acid. The folic acid-functionalized SWNTs are readily dispersible in water and phosphate-buffered saline, and the dispersions are stable for a period of two weeks or longer. These folic acid-functionalized SWNTs offer potential for use as biocompatible SWNTs.

  15. Organo-niobate Ionic Liquids: Synthesis, Characterization and Application as Acid Catalyst in Pechmann Reactions

    PubMed Central

    Soares, Valerio C. D.; Alves, Melquizedeque B.; Souza, Ernesto R.; Pinto, Ivana O.; Rubim, Joel C.; Andrade, Carlos Kleber Z.; Suarez, Paulo A. Z.

    2007-01-01

    The combinations of 1-butyl-3-methylimidazolium chloride with NbCl5 yielded ionic mixtures with different melting point temperatures and acidity depending on the niobium molar fraction. The mixtures were characterized by thermal (DSC) and spectroscopic (FT-IR and 1H NMR) analysis. The Pechmann reactions of different phenols with ethylacetoacetate, producing coumarins, was used as model to evaluate the catalytic behavior of these mixtures as acid Lewis catalyst. These reactions were carried out using acidic mixtures of 60 mol%.

  16. 40 CFR 721.10429 - Fatty acids, C18-unsatd., dimers, reaction products with 1-piperazineethanamine and tall-oil...

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ..., reaction products with 1-piperazineethanamine and tall-oil fatty acids. 721.10429 Section 721.10429... Fatty acids, C18-unsatd., dimers, reaction products with 1-piperazineethanamine and tall-oil fatty acids... identified as fatty acids, C18-unsatd., dimers, reaction products with 1-piperazineethanamine and...

  17. 40 CFR 721.10429 - Fatty acids, C18-unsatd., dimers, reaction products with 1-piperazineethanamine and tall-oil...

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ..., reaction products with 1-piperazineethanamine and tall-oil fatty acids. 721.10429 Section 721.10429... Fatty acids, C18-unsatd., dimers, reaction products with 1-piperazineethanamine and tall-oil fatty acids... identified as fatty acids, C18-unsatd., dimers, reaction products with 1-piperazineethanamine and...

  18. Origin of asymmetric induction in bicyclic guanidine-catalyzed thio-Michael reaction: a bifunctional mode of Lewis acid-Brønsted acid activation.

    PubMed

    Cho, Bokun; Tan, Choon-Hong; Wong, Ming Wah

    2012-08-03

    In addition to a bifunctional Brønsted acid activation mode, an unconventional bifunctional mode of Lewis and Brønsted acid activations was revealed in a DFT study of bicyclic guanidine-catalyzed thio-Michael reaction. This activation mode provides an alternate reaction pathway for the C-S bond forming step and influences the final stereochemical outcome. The calculated turnover frequencies of the R- and S-products, based on the energetic span model, are in good accord with the observed high stereoselectivity toward the S-product.

  19. Isocyanide-based multicomponent reactions towards cyclic constrained peptidomimetics

    PubMed Central

    Koopmanschap, Gijs; Ruijter, Eelco

    2014-01-01

    Summary In the recent past, the design and synthesis of peptide mimics (peptidomimetics) has received much attention. This because they have shown in many cases enhanced pharmacological properties over their natural peptide analogues. In particular, the incorporation of cyclic constructs into peptides is of high interest as they reduce the flexibility of the peptide enhancing often affinity for a certain receptor. Moreover, these cyclic mimics force the molecule into a well-defined secondary structure. Constraint structural and conformational features are often found in biological active peptides. For the synthesis of cyclic constrained peptidomimetics usually a sequence of multiple reactions has been applied, which makes it difficult to easily introduce structural diversity necessary for fine tuning the biological activity. A promising approach to tackle this problem is the use of multicomponent reactions (MCRs), because they can introduce both structural diversity and molecular complexity in only one step. Among the MCRs, the isocyanide-based multicomponent reactions (IMCRs) are most relevant for the synthesis of peptidomimetics because they provide peptide-like products. However, these IMCRs usually give linear products and in order to obtain cyclic constrained peptidomimetics, the acyclic products have to be cyclized via additional cyclization strategies. This is possible via incorporation of bifunctional substrates into the initial IMCR. Examples of such bifunctional groups are N-protected amino acids, convertible isocyanides or MCR-components that bear an additional alkene, alkyne or azide moiety and can be cyclized via either a deprotection–cyclization strategy, a ring-closing metathesis, a 1,3-dipolar cycloaddition or even via a sequence of multiple multicomponent reactions. The sequential IMCR-cyclization reactions can afford small cyclic peptide mimics (ranging from four- to seven-membered rings), medium-sized cyclic constructs or peptidic macrocycles

  20. Isotope Effects and Mechanism of the Asymmetric BOROX Brønsted Acid Catalyzed Aziridination Reaction

    PubMed Central

    Vetticatt, Mathew J.; Desai, Aman A.; Wulff, William D.

    2013-01-01

    The mechanism of the chiral VANOL-BOROX Brønsted acid catalyzed aziridination reaction of imines and ethyldiazoacetate has been studied using a combination of experimental kinetic isotope effects and theoretical calculations. A stepwise mechanism where reversible formation of a diazonium ion intermediate precedes rate-limiting ring-closure to form the cis-aziridine is implicated. A revised model for the origin of enantio- and diastereoselectivity is proposed based on relative energies of the ring closing transition structures. PMID:23687986

  1. Chiral BINOL-derived phosphoric acids: privileged Brønsted acid organocatalysts for C-C bond formation reactions.

    PubMed

    Zamfir, Alexandru; Schenker, Sebastian; Freund, Matthias; Tsogoeva, Svetlana B

    2010-12-07

    BINOL-derived phosphoric acids have emerged during the last five years as powerful chiral Brønsted acid catalysts in many enantioselective processes. The most successful transformations carried out with chiral BINOL phosphates include C-C bond formation reactions. The recent advances have been reviewed in this article with a focus being placed on hydrocyanations, aldol-type, Mannich, Friedel-Crafts, aza-ene-type, Diels-Alder, as well as cascade and multi-component reactions.

  2. Aqueous Phase Photo-Oxidation of Succinic Acid: Changes in Hygroscopic Properties and Reaction Products

    NASA Astrophysics Data System (ADS)

    Hudson, P. K.; Ninokawa, A.; Hofstra, J.; de Lijser, P.

    2013-12-01

    Atmospheric aerosol particles have been identified as important factors in understanding climate change. The extent to which aerosols affect climate is determined, in part, by hygroscopic properties which can change as a result of atmospheric processing. Dicarboxylic acids, components of atmospheric aerosol, have a wide range of hygroscopic properties and can undergo oxidation and photolysis reactions in the atmosphere. In this study, the hygroscopic properties of succinic acid aerosol, a non-hygroscopic four carbon dicarboxylic acid, were measured with a humidified tandem differential mobility analyzer (HTDMA) and compared to reaction products resulting from the aqueous phase photo-oxidation reaction of hydrogen peroxide and succinic acid. Reaction products were determined and quantified using gas chromatography-flame ionization detection (GC-FID) and GC-mass spectrometry (GC-MS) as a function of hydrogen peroxide:succinic acid concentration ratio and photolysis time. Although reaction products include larger non-hygroscopic dicarboxylic acids (e.g. adipic acid) and smaller hygroscopic dicarboxylic acids (e.g. malonic and oxalic acids), comparison of hygroscopic growth curves to Zdanovskii-Stokes-Robinson (ZSR) predictions suggests that the hygroscopic properties of many of the product mixtures are largely independent of the hygroscopicity of the individual components. This study provides a framework for future investigations to fully understand and predict the role of chemical reactions in altering atmospheric conditions that affect climate.

  3. A clock reaction based on molybdenum blue.

    PubMed

    Neuenschwander, Ulrich; Negron, Arnaldo; Jensen, Klavs F

    2013-05-30

    Clock reactions are rare kinetic phenomena, so far limited mostly to systems with ionic oxoacids and oxoanions in water. We report a new clock reaction in cyclohexanol that forms molybdenum blue from a noncharged, yellow molybdenum complex as precursor, in the presence of hydrogen peroxide. Interestingly, the concomitant color change is reversible, enabling multiple clock cycles to be executed consecutively. The kinetics of the clock reaction were experimentally characterized, and by adding insights from quantum chemical calculations, a plausible reaction mechanism was postulated. Key elementary reaction steps comprise sigmatropic rearrangements with five-membered or bicyclo[3.1.0] transition states. Importantly, numerical kinetic modeling demonstrated the mechanism's ability to reproduce the experimental findings. It also revealed that clock behavior is intimately connected to the sudden exhaustion of hydrogen peroxide. Due to the stoichiometric coproduction of ketone, the reaction bears potential for application in alcohol oxidation catalysis.

  4. Field and Laboratory Studies of Reactions between Atmospheric Water Soluble Organic Acids and Inorganic Particles

    SciTech Connect

    Wang, Bingbing; Kelly, Stephen T.; Sellon, Rachel E.; Shilling, John E.; Tivanski, Alexei V.; Moffet, Ryan C.; Gilles, Mary K.; Laskin, Alexander

    2013-06-25

    Atmospheric inorganic particles undergo complex heterogeneous reactions that change their physicochemical properties. Depletion of chloride in sea salt particles was reported in previous field studies and was attributed to the acid displacement of chlorides with inorganic acids, such as nitric and sulfuric acids [1-2]. Recently, we showed that NaCl can react with water soluble organic acids (WSOA) and release gaseous hydrochloric acid (HCl) resulting in formation of organic salts [3]. A similar mechanism is also applicable to mixed WSOA/nitrate particles where multi-phase reactions are driven by the volatility of nitric acid. Furthermore, secondary organic material, which is a complex mixture of carboxylic acids, exhibits the same reactivity towards chlorides and nitrates. Here, we present a systematic study of reactions between atmospheric relevant WSOA, SOM, and inorganic salts including NaCl, NaNO3, and Ca(NO3)2 using complementary micro-spectroscopy analysis.

  5. Process for chemical reaction of amino acids and amides yielding selective conversion products

    DOEpatents

    Holladay, Jonathan E.

    2006-05-23

    The invention relates to processes for converting amino acids and amides to desirable conversion products including pyrrolidines, pyrrolidinones, and other N-substituted products. L-glutamic acid and L-pyroglutamic acid provide general reaction pathways to numerous and valuable selective conversion products with varied potential industrial uses.

  6. Uptake of Hypobromous Acid (HOBr) by Aqueous Sulfuric Acid Solutions: Low-Temperature Solubility and Reaction

    NASA Technical Reports Server (NTRS)

    Iraci, Laura T.; Michelsen, Rebecca R.; Ashbourn, Samatha F. M.; Rammer, Thomas A.; Golden, David M.

    2005-01-01

    Hypobromous acid (HOBr) is a key species linking inorganic bromine to the chlorine and odd hydrogen chemical families. We have measured the solubility of HOBr in 45 - 70 wt% sulfuric acid solutions representative of upper tropospheric and lower stratospheric aerosol composition. Over the temperature range 201 - 252 K, HOBr is quite soluble in sulfuric acid, with an effective Henry's law coefficient, H* = 10(exp 4) - 10(exp 7) mol/L/atm. H* is inversely dependent on temperature, with Delta H = -46.2 kJ/mol and Delta S = -106.2 J/mol/K for 55 - 70 wt% H2SO4 solutions. Our study includes temperatures which overlap both previous measurements of HOBr solubility. For uptake into aqueous 45 wt% H2SO4, the solubility can be described by log H* = 3665/T - 10.63. For 55 - 70 wt% H2SO4, log H* = 2412/T - 5.55. At temperatures colder than approx. 213 K, the solubility of HOBr in 45 wt% H2SO4 is noticeably larger than in 70 wt% H2SO4. The solubility of HOBr is comparable to that of HBr, indicating that upper tropospheric and lower stratospheric aerosols should contain equilibrium concentrations of HOBr which equal or exceed those of HBr. Our measurements indicate chemical reaction of HOBr upon uptake into aqueous sulfuric acid in the presence of other brominated gases followed by evolution of gaseous products including Br2O and Br2, particularly at 70 wt% H2SO4.

  7. Initiation Temperature for Runaway Tri-n-Butyl Phosphate/Nitric Acid Reaction

    SciTech Connect

    Rudisill, T.S.

    2001-09-14

    In a review of the safety basis for solvent extraction processes at the Department of Energy's Savannah River Site, a question was raised concerning the safety margin associated with a postulated accident involving a runaway tri-n-butyl phosphate (TBP)/nitric acid reaction due to the inadvertent heating of a tank. The safety margin was based on studies which showed the maximum temperature would not exceed 128 degrees Celsius compared to 130 degrees Celsius, the minimum initiation temperature for runaway reaction established in the 1950's following damaging incidents at the Savannah River and Hanford Sites. The reviewers were concerned the minimum temperature was not conservative since data for solutions containing 20 wt percent dissolved solids showed initiation temperatures at or below 130 degrees Celsius and process solutions normally contain some dissolved solids.

  8. The effects of phytic acid on the Maillard reaction and the formation of acrylamide.

    PubMed

    Wang, Huan; Zhou, Yamin; Ma, Jimei; Zhou, Yuanyuan; Jiang, Hong

    2013-11-01

    Phytic acid, myo-inositol hexaphosphoric acid, exists in substantial (1-5%) amounts in edible plant seeds. In this study the effects of phytic acid on the Maillard reaction and the formation of acrylamide were investigated. Both phytic acid and phosphate enhanced browning in glucose/β-alanine system, but phytic acid was less effective than phosphate. Higher pH favoured the catalytic activities for both of them. The influence of the types of sugar and amino acid on the reaction was also examined. Browning was suppressed by the addition of calcium and magnesium ions, but an additive effect was observed for ferrous ions and phytic acid in glucose/β-alanine solution at pH 8.0. Both phytic acid and phosphate promoted the polymerisation of the reaction intermediates. The kinetics of Maillard reaction was first-ordered reaction in the presence of phytic acid. Phytic acid was less effective than phosphate in the formation of acrylamide. When potato slices were treated with sodium phytate and calcium chloride successively, the formation of acrylamide was greatly suppressed.

  9. Nucleic acid duplexes incorporating a dissociable covalent base pair

    NASA Technical Reports Server (NTRS)

    Gao, K.; Orgel, L. E.; Bada, J. L. (Principal Investigator)

    1999-01-01

    We have used molecular modeling techniques to design a dissociable covalently bonded base pair that can replace a Watson-Crick base pair in a nucleic acid with minimal distortion of the structure of the double helix. We introduced this base pair into a potential precursor of a nucleic acid double helix by chemical synthesis and have demonstrated efficient nonenzymatic template-directed ligation of the free hydroxyl groups of the base pair with appropriate short oligonucleotides. The nonenzymatic ligation reactions, which are characteristic of base paired nucleic acid structures, are abolished when the covalent base pair is reduced and becomes noncoplanar. This suggests that the covalent base pair linking the two strands in the duplex is compatible with a minimally distorted nucleic acid double-helical structure.

  10. Nucleic Acid Duplexes Incorporating a Dissociable Covalent Base Pair

    NASA Astrophysics Data System (ADS)

    Gao, Kui; Orgel, Leslie E.

    1999-12-01

    We have used molecular modeling techniques to design a dissociable covalently bonded base pair that can replace a Watson-Crick base pair in a nucleic acid with minimal distortion of the structure of the double helix. We introduced this base pair into a potential precursor of a nucleic acid double helix by chemical synthesis and have demonstrated efficient nonenzymatic template-directed ligation of the free hydroxyl groups of the base pair with appropriate short oligonucleotides. The nonenzymatic ligation reactions, which are characteristic of base paired nucleic acid structures, are abolished when the covalent base pair is reduced and becomes noncoplanar. This suggests that the covalent base pair linking the two strands in the duplex is compatible with a minimally distorted nucleic acid double-helical structure.

  11. Initiation Temperature for Runaway Tri-n-Butyl Phosphate/Nitric Acid Reaction

    SciTech Connect

    Rudisill, T.S.

    2000-11-28

    During a review of the H-Canyon authorization basis, Defense Nuclear Facility Safety Board (DNFSB) staff members questioned the margin of safety associated with a postulated tri-n-butyl phosphate (TBP)/nitric acid runaway reaction due to the inadvertent heating of a canyon tank containing greater than 3000 lbs (1362 kg) of TBP. The margin of safety was partially based on experiments and calculations performed by the Actinide Technology Section (ATS) to support deletion of indication of tank agitation as a Safety Class System. In the technical basis for deletion of this system, ATS personnel conservatively calculated the equilibrium temperature distribution of a canyon tank containing TBP and nitric acid layers which were inadvertently heated by a steam jet left on following a transfer. The maximum calculated temperature (128 degrees C) was compared to the minimum initiation temperature for a runaway reaction (greater than 130 degrees C) documented by experimental work in the mid 195 0s. In this work, the initiation temperature as a function of nitric acid concentration was measured for 0 and 20 wt percent dissolved solids. The DNFSB staff members were concerned that data for 0 wt percent dissolved solids were not conservative given the facts that data for 20 wt percent dissolved solids show initiation temperatures at or below 130 degrees C and H-Canyon solutions normally contained a small amount of dissolved solids.

  12. Thermochemical comparisons of homogeneous and heterogeneous acids and bases. 1. Sulfonic acid solutions and resins as prototype Broensted acids

    SciTech Connect

    Arnett, E.M.; Haaksma, R.A.; Chawla, B.; Healy, M.H.

    1986-08-06

    Heats of ionization by thermometric titration for a series of bases (or acids) can be used to compare solid acids (or bases) with liquid analogues bearing the same functionalities in homogeneous solutions. The method is demonstrated for Broensted acids by reacting a series of substituted nitrogen bases with solutions of p-toluenesulfonic acid (PTSA) in acetonitrile and with suspensions of the microporous polymeric arylsulfonic acid resin-Dowex 50W-X8 in the same solvent. Under well-controlled anhydrous conditions there is a good correlation (r = 0.992) between the heats of reaction of the bases with the homogeneous and heterogeneous acid systems, but the homogeneous system gives a more exothermic interaction by 3-4 kcal mol/sup -1/ for a series of 29 substituted pyrimidines, anilines, and some other amines. This difference may be attributed to homohydrogen bonding interactions between excess acid and sulfonate anion sites which are more restricted geometrically in the resin than in solution. Other factors which affect the enthalpy change for the acid-base interaction are the acid/base ratio, the water content of the sulfonic acid, the solvent, and the resin structure (e.g., microporous vs. macroporous). Steric hindrance in the base does not differentiate solid from homogeneous acid. In addition to the use of titration calorimetry, heats of immersion are reported for the Dowex-arylsulfonic acid resins and the Nafion-perfluorinated sulfonic acid resin in a series of basic liquids. The results are compared with each other and with those from a previous study of several varieties of coal.

  13. Investigation of heat induced reactions between lipid oxidation products and amino acids in lipid rich model systems and hazelnuts.

    PubMed

    Karademir, Yeşim; Göncüoğlu, Neslihan; Gökmen, Vural

    2013-07-01

    This study aimed to investigate the contribution of lipid oxidation to non-enzymatic browning reactions in lipid rich model and actual food systems. Hazelnut oil and model reaction mixtures consisting of different amino acids were heated under certain conditions to determine possible lipid oxidation and non-enzymatic browning reaction products. In model systems, the Schiff base of 2,4-decadienal, its decarboxylated form, and reaction products formed after hydrolytic cleavage of the Schiff base or decarboxylated form were identified by high resolution mass spectrometry. No furosine was detected in hazelnuts after roasting at 160 °C while the concentration of free amino acids significantly decreased. 2,4-Decadienal reacted effectively with all amino acids studied through a Maillard type carbonyl-amine condensation pathway. (2E,4E)-Deca-2,4-dien-1-amine was identified as a typical reaction product in model systems and roasted hazelnuts. In lipid-rich foods like hazelnuts, lipid-derived carbonyls might be responsible for potential modifications of free and protein bound amino acids during heating.

  14. Acid- and base-catalysis in the mononuclear rearrangement of some (Z)-arylhydrazones of 5-amino-3-benzoyl-1,2,4-oxadiazole in toluene: effect of substituents on the course of reaction.

    PubMed

    D'Anna, Francesca; Frenna, Vincenzo; Ghelfi, Franco; Marullo, Salvatore; Spinelli, Domenico

    2011-04-15

    The reaction rates for the rearrangement of eleven (Z)-arylhydrazones of 5-amino-3-benzoyl-1,2,4-oxadiazole 3a-k into the relevant (2-aryl-5-phenyl-2H-1,2,3-triazol-4-yl)ureas 4a-k in the presence of trichloroacetic acid or of piperidine have been determined in toluene at 313.1 K. The results have been related to the effect of the aryl substituent by using Hammett and/or Ingold-Yukawa-Tsuno correlations and have been compared with those previously collected in a protic polar solvent (dioxane/water) as well as with those on the analogous rearrangement of the corresponding (Z)-arylhydrazones of 3-benzoyl-5-phenyl-1,2,4-oxadiazole 1a-k in benzene. Some light can thus be shed on the general differences of chemical reactivity between protic polar (or dipolar aprotic) and apolar solvents.

  15. Geochemical Modeling of Reactions and Partitioning of Trace Metals and Radionuclides during Titration of Contaminated Acidic Sediments

    SciTech Connect

    Zhang, Fan; Parker, Jack C.; Luo, Wensui; Spalding, Brian Patrick; Brooks, Scott C; Watson, David B; Jardine, Philip M; Gu, Baohua

    2008-01-01

    Many geochemical reactions that control aqueous metal concentrations are directly affected by solution pH. However, changes in solution pH are strongly buffered by various aqueous phase and solid phase precipitation/dissolution and adsorption/desorption reactions. The ability to predict acid-base behavior of the soil-solution system is thus critical to predict metal transport under variable pH conditions. This study was undertaken to develop a practical generic geochemical modeling approach to predict aqueous and solid phase concentrations of metals and anions during conditions of acid or base additions. The method of Spalding and Spalding was utilized to model soil buffer capacity and pH-dependent cation exchange capacity by treating aquifer solids as a polyprotic acid. To simulate the dynamic and pH-dependent anion exchange capacity, the aquifer solids were simultaneously treated as a polyprotic base controlled by mineral precipitation/dissolution reactions. An equilibrium reaction model that describes aqueous complexation, precipitation, sorption and soil buffering with pH-dependent ion exchange was developed using HydroGeoChem v5.0 (HGC5). Comparison of model results with experimental titration data of pH, Al, Ca, Mg, Sr, Mn, Ni, Co, and SO{sub 4}{sup 2-} for contaminated sediments indicated close agreement, suggesting that the model could potentially be used to predict the acid-base behavior of the sediment-solution system under variable pH conditions.

  16. Geochemical modeling of reactions and partitioning of trace metals and radionuclides during titration of contaminated acidic sediments.

    PubMed

    Zhang, Fan; Luo, Wensui; Parker, Jack C; Spalding, Brian P; Brooks, Scott C; Watson, David B; Jardine, Philip M; Gu, Baohua

    2008-11-01

    Many geochemical reactions that control aqueous metal concentrations are directly affected by solution pH. However, changes in solution pH are strongly buffered by various aqueous phase and solid phase precipitation/dissolution and adsorption/desorption reactions. The ability to predict acid-base behavior of the soil-solution system is thus critical to predict metal transport under variable pH conditions. This studywas undertaken to develop a practical generic geochemical modeling approach to predict aqueous and solid phase concentrations of metals and anions during conditions of acid or base additions. The method of Spalding and Spalding was utilized to model soil buffer capacity and pH-dependent cation exchange capacity by treating aquifer solids as a polyprotic acid. To simulate the dynamic and pH-dependent anion exchange capacity, the aquifer solids were simultaneously treated as a polyprotic base controlled by mineral precipitation/ dissolution reactions. An equilibrium reaction model that describes aqueous complexation, precipitation, sorption and soil buffering with pH-dependent ion exchange was developed using HydroGeoChem v5.0 (HGC5). Comparison of model results with experimental titration data of pH, Al, Ca, Mg, Sr, Mn, Ni, Co, and SO4(2-) for contaminated sediments indicated close agreement suggesting that the model could potentially be used to predictthe acid-base behavior of the sediment-solution system under variable pH conditions.

  17. Conversion of waste cellulose to ethanol. Phase 2: Reaction kinetics with phosphoric acid

    NASA Astrophysics Data System (ADS)

    Moeller, M. B.; Isbell, R. E.

    1982-05-01

    Waste cellulosic material can be hydrolyzed in dilute acid solution to produce fermentable sugars which can then be converted into ethanol. A laboratory investigation was made of the feasibility of using phosphoric acid as the hydrolysis catalyst. The hydrolysis reaction with phosphoric acid solutions was compared with the reaction employing the more conventional dilute sulfuric acid catalyst. The purpose of this research was to examine the hydrolysis step in a proposed process for the conversion of cellulose (from wood, newspapers, municipal solid waste, or other sources) into ethanol - by which a potentially valuable co-product, DICAL (dicalcium phosphate), might be made and sold with or without the lignin content as a fertilizer. The pertinent reaction kinetics for the acid catalyzed production of glucose from cellulose consists of consecutive, pseudo-first order reactions.

  18. Material balance studies on animal cell metabolism using a stoichiometrically based reaction network.

    PubMed

    Xie, L; Wang, D I

    1996-12-05

    A detailed reaction network of mammalian cell metabolism contains hundreds of enzymatic reactions. By grouping serial reactions into single overall reactions and separating overlapped pathways into independent reactions, the total number of reactions of the network is significantly reduced. This strategy of manipulating the reaction network avoids the manipulations of a large number of reactions otherwise needed to determine the reaction extents. A stoichiometric material balance model is developed based on the stoichiometry of the simplified reaction network. Closures of material balances on glucose and each of the 20 amino acids are achieved using experimental data from three controlled fed-batch and one-batch hybridoma cultures. Results show that the critical role of essential amino acids, except glutamine, is to provide precursors for protein synthesis. The catabolism of some of the essential amino acids, particularly isoleucine and leucine, is observed when an excess amount of these amino acids is available in the culture medium. It was found that the reduction of glutamine utilization (for reducing ammonia production) is accompanied by an increase in the uptake of nonessential amino acids (NAAs) from the culture medium. This suggests that NAAs are necessary even though they are not essential for cell growth. A glutamine balance shows that less than 20% of the glutamine nitrogen is utilized for essential roles, such as protein and nucleotide syntheses. A relatively constant percentage (about 45%) of the glutamine nitrogen is utilized for NAA biosynthesis, despite the fact that the absolute amount varies among the four experiments. As to the carbon skeleton of glutamine, a significant portion enters the tricarboxylic acid (TCA) cycle. A material balance on glucose shows that most of the glucose (81%) is converted into lactate when glucose is in excess. On the other hand, when glucose is limited, lactate production is considerably reduced, while a major portion

  19. Reaction-contingency based bipartite Boolean modelling

    PubMed Central

    2013-01-01

    Background Intracellular signalling systems are highly complex, rendering mathematical modelling of large signalling networks infeasible or impractical. Boolean modelling provides one feasible approach to whole-network modelling, but at the cost of dequantification and decontextualisation of activation. That is, these models cannot distinguish between different downstream roles played by the same component activated in different contexts. Results Here, we address this with a bipartite Boolean modelling approach. Briefly, we use a state oriented approach with separate update rules based on reactions and contingencies. This approach retains contextual activation information and distinguishes distinct signals passing through a single component. Furthermore, we integrate this approach in the rxncon framework to support automatic model generation and iterative model definition and validation. We benchmark this method with the previously mapped MAP kinase network in yeast, showing that minor adjustments suffice to produce a functional network description. Conclusions Taken together, we (i) present a bipartite Boolean modelling approach that retains contextual activation information, (ii) provide software support for automatic model generation, visualisation and simulation, and (iii) demonstrate its use for iterative model generation and validation. PMID:23835289

  20. Reactivity and reaction intermediates for acetic acid adsorbed on CeO2(111)

    SciTech Connect

    Calaza, Florencia C.; Chen, Tsung -Liang; Mullins, David R.; Xu, Ye; Steven H. Overbury

    2015-05-02

    Adsorption and reaction of acetic acid on a CeO2(1 1 1) surface was studied by a combination of ultra-highvacuum based methods including temperature desorption spectroscopy (TPD), soft X-ray photoelectronspectroscopy (sXPS), near edge X-ray absorption spectroscopy (NEXAFS) and reflection absorption IRspectroscopy (RAIRS), together with density functional theory (DFT) calculations. TPD shows that thedesorption products are strongly dependent upon the initial oxidation state of the CeO2 surface, includingselectivity between acetone and acetaldehyde products. The combination of sXPS and NEXAFS demon-strate that acetate forms upon adsorption at low temperature and is stable to above 500 K, above whichpoint ketene, acetone and acetic acid desorb. Furthermore, DFT and RAIRS show that below 500 K, bridge bondedacetate coexists with a moiety formed by adsorption of an acetate at an oxygen vacancy, formed bywater desorption.

  1. Molybdenum phosphosulfide: an active, acid-stable, earth-abundant catalyst for the hydrogen evolution reaction.

    PubMed

    Kibsgaard, Jakob; Jaramillo, Thomas F

    2014-12-22

    Introducing sulfur into the surface of molybdenum phosphide (MoP) produces a molybdenum phosphosulfide (MoP|S) catalyst with superb activity and stability for the hydrogen evolution reaction (HER) in acidic environments. The MoP|S catalyst reported herein exhibits one of the highest HER activities of any non-noble-metal electrocatalyst investigated in strong acid, while remaining perfectly stable in accelerated durability testing. Whereas mixed-metal alloy catalysts are well-known, MoP|S represents a more uncommon mixed-anion catalyst where synergistic effects between sulfur and phosphorus produce a high-surface-area electrode that is more active than those based on either the pure sulfide or the pure phosphide. The extraordinarily high activity and stability of this catalyst open up avenues to replace platinum in technologies relevant to renewable energies, such as proton exchange membrane (PEM) electrolyzers and solar photoelectrochemical (PEC) water-splitting cells.

  2. Asymmetric Lewis acid organocatalysis of the Diels-Alder reaction by a silylated C-H acid.

    PubMed

    Gatzenmeier, Tim; van Gemmeren, Manuel; Xie, Youwei; Höfler, Denis; Leutzsch, Markus; List, Benjamin

    2016-02-26

    Silylium ion equivalents have shown promise as Lewis acid catalysts for a range of important C-C bond-forming reactions. Here we describe chiral C-H acids that upon in situ silylation, generate silylium-carbanion pairs, which are extremely active Lewis acid catalysts for enantioselective Diels-Alder reactions of cinnamates with cyclopentadiene. Enantiomeric ratios of up to 97:3 and diastereomeric ratios of more than 20:1 are observed across a diverse set of substitution patterns with 1 mole percent (mol %) of C-H acid catalyst and 10 mol % of a silylating reagent. The results show promise for broad applications of such C-H acid-derived silylium ion equivalents in asymmetric Lewis acid catalysis.

  3. Lipoic acid suppresses compound 48/80-induced anaphylaxis-like reaction

    PubMed Central

    Choi, Yun Ho; Chai, Ok Hee; Han, Eui-Hyeog; Choi, Su-Young; Kim, Hyoung Tae

    2010-01-01

    Alpha-lipoic acid (LA), a naturally occurring dithiol compound, is an essential cofactor in metabolic reactions involved in energy utilization. LA improves glycemic control, reduces diabetic polyneuropathies, atherosclerosis, and allergic inflammation. The effects of LA on mast cell-mediated anaphylactic reactions, however, are unknown. LA dose-dependently inhibited systemic and passive cutaneous anaphylaxis-like reactions in mice induced by compound 48/80, a condensation product of N-methyl-p-methoxyphenethylamine and formaldehyde. Pretreatment with LA, prior to induction of the systemic anaphylaxis-like reaction with compound 48/80, reduced plasma histamine levels in a dose-dependent manner. In our in vitro study, LA decreased histamine release from rat peritoneal mast cells (RPMCs) triggered by compound 48/80. Moreover, an increase in calcium uptake activated by compound 48/80 was inhibited by LA. LA also significantly elevated intracellular cyclic adenosine-3',5' monophosphate (cAMP) levels in RPMCs. This inhibition of mediator release from RPMCs may be due to inhibition of calcium uptake and augmentation of intracellular cAMP levels. Based on these results, we suggest that LA may be a potential remedy for allergy-related diseases. PMID:21267406

  4. The Acid-Base Titration of a Very Weak Acid: Boric Acid

    ERIC Educational Resources Information Center

    Celeste, M.; Azevedo, C.; Cavaleiro, Ana M. V.

    2012-01-01

    A laboratory experiment based on the titration of boric acid with strong base in the presence of d-mannitol is described. Boric acid is a very weak acid and direct titration with NaOH is not possible. An auxiliary reagent that contributes to the release of protons in a known stoichiometry facilitates the acid-base titration. Students obtain the…

  5. FDI report on adverse reactions to resin-based materials.

    PubMed

    Fan, P L; Meyer, D M

    2007-02-01

    Resin-based restorative materials are considered safe for the vast majority of dental patients. Although constituent chemicals such as monomers, accelerators and initiators can potentially leach out of cured resin-based materials after placement, adverse reactions to these chemicals are rare and reaction symptoms commonly subside after removal of the materials. Dentists should be aware of the rare possibility that patients could have adverse reactions to constituents of resin-based materials and be vigilant in observing any adverse reactions after restoration placement. Dentists should also be cognisant of patient complaints about adverse reactions that may result from components of resin-based materials. To minimise monomer leaching and any potential risk of dermatological reactions, resin-based materials should be adequately cured. Dental health care workers should avoid direct skin contact with uncured resin-based materials. Latex and vinyl gloves do not provide adequate barrier protection to the monomers in resin-based materials.

  6. Nuclear reaction inputs based on effective interactions

    NASA Astrophysics Data System (ADS)

    Hilaire, S.; Goriely, S.; Péru, S.; Dubray, N.; Dupuis, M.; Bauge, E.

    2016-11-01

    Extensive nuclear structure studies have been performed for decades using effective interactions as sole input. They have shown a remarkable ability to describe rather accurately many types of nuclear properties. In the early 2000s, a major effort has been engaged to produce nuclear reaction input data out of the Gogny interaction, in order to challenge its quality also with respect to nuclear reaction observables. The status of this project, well advanced today thanks to the use of modern computers as well as modern nuclear reaction codes, is reviewed and future developments are discussed.

  7. Acid Base Titrations in Nonaqueous Solvents and Solvent Mixtures

    NASA Astrophysics Data System (ADS)

    Barcza, Lajos; Buvári-Barcza, Ágnes

    2003-07-01

    The acid base determination of different substances by nonaqueous titrations is highly preferred in pharmaceutical analyses since the method is quantitative, exact, and reproducible. The modern interpretation of the reactions in nonaqueous solvents started in the last century, but several inconsistencies and unsolved problems can be found in the literature. The acid base theories of Brønsted Lowry and Lewis as well as the so-called solvent theory are outlined first, then the promoting (and leveling) and the differentiating effects are discussed on the basis of the hydrogen-bond concept. Emphasis is put on the properties of formic acid and acetic anhydride since their importance is increasing.

  8. Bipolar Membranes for Acid Base Flow Batteries

    NASA Astrophysics Data System (ADS)

    Anthamatten, Mitchell; Roddecha, Supacharee; Jorne, Jacob; Coughlan, Anna

    2011-03-01

    Rechargeable batteries can provide grid-scale electricity storage to match power generation with consumption and promote renewable energy sources. Flow batteries offer modular and flexible design, low cost per kWh and high efficiencies. A novel flow battery concept will be presented based on acid-base neutralization where protons (H+) and hydroxyl (OH-) ions react electrochemically to produce water. The large free energy of this highly reversible reaction can be stored chemically, and, upon discharge, can be harvested as usable electricity. The acid-base flow battery concept avoids the use of a sluggish oxygen electrode and utilizes the highly reversible hydrogen electrode, thus eliminating the need for expensive noble metal catalysts. The proposed flow battery is a hybrid of a battery and a fuel cell---hydrogen gas storing chemical energy is produced at one electrode and is immediately consumed at the other electrode. The two electrodes are exposed to low and high pH solutions, and these solutions are separated by a hybrid membrane containing a hybrid cation and anion exchange membrane (CEM/AEM). Membrane design will be discussed, along with ion-transport data for synthesized membranes.

  9. 40 CFR 721.6477 - Alkyl polycarboxylic acids, esters with ethoxylated fatty alcohols, reaction products with maleic...

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... with ethoxylated fatty alcohols, reaction products with maleic anhydride. 721.6477 Section 721.6477... Alkyl polycarboxylic acids, esters with ethoxylated fatty alcohols, reaction products with maleic... identified generically as alkyl polycarboxylic acids, esters with ethoxylated fatty alcohols,...

  10. 40 CFR 721.6477 - Alkyl polycarboxylic acids, esters with ethoxylated fatty alcohols, reaction products with maleic...

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... with ethoxylated fatty alcohols, reaction products with maleic anhydride. 721.6477 Section 721.6477... Alkyl polycarboxylic acids, esters with ethoxylated fatty alcohols, reaction products with maleic... identified generically as alkyl polycarboxylic acids, esters with ethoxylated fatty alcohols,...

  11. 40 CFR 721.6477 - Alkyl polycarboxylic acids, esters with ethoxylated fatty alcohols, reaction products with maleic...

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... with ethoxylated fatty alcohols, reaction products with maleic anhydride. 721.6477 Section 721.6477... Alkyl polycarboxylic acids, esters with ethoxylated fatty alcohols, reaction products with maleic... identified generically as alkyl polycarboxylic acids, esters with ethoxylated fatty alcohols,...

  12. 40 CFR 721.6477 - Alkyl polycarboxylic acids, esters with ethoxylated fatty alcohols, reaction products with maleic...

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... with ethoxylated fatty alcohols, reaction products with maleic anhydride. 721.6477 Section 721.6477... Alkyl polycarboxylic acids, esters with ethoxylated fatty alcohols, reaction products with maleic... identified generically as alkyl polycarboxylic acids, esters with ethoxylated fatty alcohols,...

  13. 40 CFR 721.6477 - Alkyl polycarboxylic acids, esters with ethoxylated fatty alcohols, reaction products with maleic...

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... with ethoxylated fatty alcohols, reaction products with maleic anhydride. 721.6477 Section 721.6477... Alkyl polycarboxylic acids, esters with ethoxylated fatty alcohols, reaction products with maleic... identified generically as alkyl polycarboxylic acids, esters with ethoxylated fatty alcohols,...

  14. Photocurable bioadhesive based on lactic acid.

    PubMed

    Marques, D S; Santos, J M C; Ferreira, P; Correia, T R; Correia, I J; Gil, M H; Baptista, C M S G

    2016-01-01

    Novel photocurable and low molecular weight oligomers based on l-lactic acid with proven interest to be used as bioadhesive were successfully manufactured. Preparation of lactic acid oligomers with methacrylic end functionalizations was carried out in the absence of catalyst or solvents by self-esterification in two reaction steps: telechelic lactic acid oligomerization with OH end groups and further functionalization with methacrylic anhydride. The final adhesive composition was achieved by the addition of a reported biocompatible photoinitiator (Irgacure® 2959). Preliminary in vitro biodegradability was investigated by hydrolytic degradation in PBS (pH=7.4) at 37 °C. The adhesion performance was evaluated using glued aminated substrates (gelatine pieces) subjected to pull-to-break test. Surface energy measured by contact angles is lower than the reported values of the skin and blood. The absence of cytoxicity was evaluated using human fibroblasts. A notable antimicrobial behaviour was observed using two bacterial models (Staphylococcus aureus and Escherichia coli). The cured material exhibited a strong thrombogenic character when placed in contact with blood, which can be predicted as a haemostatic effect for bleeding control. This novel material was subjected to an extensive characterization showing great potential for bioadhesive or other biomedical applications where biodegradable and biocompatible photocurable materials are required.

  15. N-doped carbon nanomaterials are durable catalysts for oxygen reduction reaction in acidic fuel cells

    PubMed Central

    Shui, Jianglan; Wang, Min; Du, Feng; Dai, Liming

    2015-01-01

    The availability of low-cost, efficient, and durable catalysts for oxygen reduction reaction (ORR) is a prerequisite for commercialization of the fuel cell technology. Along with intensive research efforts of more than half a century in developing nonprecious metal catalysts (NPMCs) to replace the expensive and scarce platinum-based catalysts, a new class of carbon-based, low-cost, metal-free ORR catalysts was demonstrated to show superior ORR performance to commercial platinum catalysts, particularly in alkaline electrolytes. However, their large-scale practical application in more popular acidic polymer electrolyte membrane (PEM) fuel cells remained elusive because they are often found to be less effective in acidic electrolytes, and no attempt has been made for a single PEM cell test. We demonstrated that rationally designed, metal-free, nitrogen-doped carbon nanotubes and their graphene composites exhibited significantly better long-term operational stabilities and comparable gravimetric power densities with respect to the best NPMC in acidic PEM cells. This work represents a major breakthrough in removing the bottlenecks to translate low-cost, metal-free, carbon-based ORR catalysts to commercial reality, and opens avenues for clean energy generation from affordable and durable fuel cells. PMID:26601132

  16. N-doped carbon nanomaterials are durable catalysts for oxygen reduction reaction in acidic fuel cells.

    PubMed

    Shui, Jianglan; Wang, Min; Du, Feng; Dai, Liming

    2015-02-01

    The availability of low-cost, efficient, and durable catalysts for oxygen reduction reaction (ORR) is a prerequisite for commercialization of the fuel cell technology. Along with intensive research efforts of more than half a century in developing nonprecious metal catalysts (NPMCs) to replace the expensive and scarce platinum-based catalysts, a new class of carbon-based, low-cost, metal-free ORR catalysts was demonstrated to show superior ORR performance to commercial platinum catalysts, particularly in alkaline electrolytes. However, their large-scale practical application in more popular acidic polymer electrolyte membrane (PEM) fuel cells remained elusive because they are often found to be less effective in acidic electrolytes, and no attempt has been made for a single PEM cell test. We demonstrated that rationally designed, metal-free, nitrogen-doped carbon nanotubes and their graphene composites exhibited significantly better long-term operational stabilities and comparable gravimetric power densities with respect to the best NPMC in acidic PEM cells. This work represents a major breakthrough in removing the bottlenecks to translate low-cost, metal-free, carbon-based ORR catalysts to commercial reality, and opens avenues for clean energy generation from affordable and durable fuel cells.

  17. Topological analysis of the electronic charge density in the ethene protonation reaction catalyzed by acidic zeolite.

    PubMed

    Zalazar, M Fernanda; Peruchena, Nélida M

    2007-08-16

    In the present work, the distribution of the electronic charge density in the ethene protonation reaction by a zeolite acid site is studied within the framework of the density functional theory and the atoms in molecules (AIM) theory. The key electronic effects such as topological distribution of the charge density involved in the reaction are presented and discussed. The results are obtained at B3LYP/6-31G(**) level theory. Attention is focused on topological parameters such as electron density, its Laplacian, kinetic energy density, potential energy density, and electronic energy density at the bond critical points (BCP) in all bonds involved in the interaction zone, in the reactants, pi-complex, transition state, and alkoxy product. In addition, the topological atomic properties are determined on the selected atoms in the course of the reaction (average electron population, N(Omega), atomic net charge, q(Omega), atomic energy, E(Omega), atomic volume, v(Omega), and first moment of the atomic charge distribution, M(Omega)) and their changes are analyzed exhaustively. The topological study clearly shows that the ethene interaction with the acid site of the zeolite cluster, T5-OH, in the ethene adsorbed, is dominated by a strong O-H...pi interaction with some degree of covalence. AIM analysis based on DFT calculation for the transition state (TS) shows that the hydrogen atom from the acid site in the zeolitic fragment is connected to the carbon atom by a covalent bond with some contribution of electrostatic interaction and to the oxygen atom by closed shell interaction with some contribution of covalent character. The C-O bond formed in the alkoxy product can be defined as a weaker shared interaction. Our results show that in the transition state, the dominant interactions are partially electrostatic and partially covalent in nature, in which the covalent contribution increases as the concentration and accumulation of the charge density along the bond path between

  18. Phosphoric acid impurities in phosphoric acid fuel cell electrolytes. 2: Effects on the oxygen reduction reaction at platinum electrodes

    SciTech Connect

    Sugishima, Noboru; Hinatsu, J.T.; Foulkes, F.R. . Dept. of Chemical Engineering and Applied Chemistry)

    1994-12-01

    The effects of phosphorus acid additions on the oxygen reduction reaction at platinum electrodes in concentrated phosphoric acid were studied. The oxygen reduction currents decreased, and the Tafel slopes became more negative upon the addition of small concentrations of phosphorus acid. In addition,the phosphorus acid oxidation current tended to complete with the oxygen reduction current. These effects became more pronounced at higher phosphorus acid concentrations and at higher temperatures. Upon the addition of phosphorus acid the number of electrons involved in the oxygen reduction reaction decreased from a value close to four to a value approaching two, suggesting promotion of a two-electron reduction to peroxide. Therefore, in studies of the electrochemical reduction of oxygen in hot concentrated phosphoric acid or in fuel cell systems using hot concentrated phosphoric acid as electrolyte, it is recommended that precautions be taken against the inadvertent formation of the phosphorus acid. The removal of phosphorus acid from concentrated phosphoric acid by repeated potential cycling at 100 mV/s between + 0.5 and +1.50 V (vs. dynamic hydrogen electrode) was demonstrated.

  19. Microwave-assisted reaction of glycosylamine with aspartic acid.

    PubMed

    Real-Fernández, Feliciana; Nuti, Francesca; Bonache, M Angeles; Boccalini, Marco; Chimichi, Stefano; Chelli, Mario; Papini, Anna Maria

    2010-07-01

    The synthesis of N-protected glycosyl amino acids from amines has been investigated and it was found that, under microwave conditions, glycosylamines could be hydrolyzed leading to new products containing a glycosyl ester linkage. The efficiency of the microwave-induced glycosylation of aspartic acid was studied comparing the microwave activity between amide and ester bond formation. Different sugar moieties have been employed to demonstrate the simple and reproducible coupling methodology. New glycosyl ester compounds were further characterized by NMR spectroscopy.

  20. Ionic liquid supported acid/base-catalyzed production of biodiesel.

    PubMed

    Lapis, Alexandre A M; de Oliveira, Luciane F; Neto, Brenno A D; Dupont, Jairton

    2008-01-01

    The transesterification (alcoholysis) reaction was successfully applied to synthesize biodiesel from vegetable oils using imidazolium-based ionic liquids under multiphase acidic and basic conditions. Under basic conditions, the combination of the ionic liquid 1-n-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (BMINTf2), alcohols, and K2CO3 (40 mol %) results in the production of biodiesel from soybean oil in high yields (>98%) and purity. H2SO4 immobilized in BMINTf2 efficiently promotes the transesterification reaction of soybean oil and various primary and secondary alcohols. In this multiphase process the acid is almost completely retained in the ionic liquid phase, while the biodiesel forms a separate phase. The recovered ionic liquid containing the acid could be reused at least six times without any significant loss in the biodiesel yield or selectivity. In both catalytic processes (acid and base), the reactions proceed as typical multiphasic systems in which the formed biodiesel accumulates as the upper phase and the glycerol by-product is selectively captured by the alcohol-ionic liquid-acid/base phase. Classical ionic liquids such as 1-n-butyl-3-methylimidazolium tetrafluoroborate and hexafluorophosphate are not stable under these acidic or basic conditions and decompose.

  1. Nuclemeter: A Reaction-Diffusion Column for Quantifying Nucleic Acids Undergoing Enzymatic Amplification

    NASA Astrophysics Data System (ADS)

    Bau, Haim; Liu, Changchun; Killawala, Chitvan; Sadik, Mohamed; Mauk, Michael

    2014-11-01

    Real-time amplification and quantification of specific nucleic acid sequences plays a major role in many medical and biotechnological applications. In the case of infectious diseases, quantification of the pathogen-load in patient specimens is critical to assessing disease progression, effectiveness of drug therapy, and emergence of drug-resistance. Typically, nucleic acid quantification requires sophisticated and expensive instruments, such as real-time PCR machines, which are not appropriate for on-site use and for low resource settings. We describe a simple, low-cost, reactiondiffusion based method for end-point quantification of target nucleic acids undergoing enzymatic amplification. The number of target molecules is inferred from the position of the reaction-diffusion front, analogous to reading temperature in a mercury thermometer. We model the process with the Fisher Kolmogoroff Petrovskii Piscounoff (FKPP) Equation and compare theoretical predictions with experimental observations. The proposed method is suitable for nucleic acid quantification at the point of care, compatible with multiplexing and high-throughput processing, and can function instrument-free. C.L. was supported by NIH/NIAID K25AI099160; M.S. was supported by the Pennsylvania Ben Franklin Technology Development Authority; C.K. and H.B. were funded, in part, by NIH/NIAID 1R41AI104418-01A1.

  2. Cascade dearomatization of N-substituted tryptophols via Lewis acid-catalyzed Michael reactions.

    PubMed

    Liu, Chuan; Zhang, Wei; Dai, Li-Xin; You, Shu-Li

    2012-09-21

    Lewis acid-catalyzed cascade dearomatization of N-substituted tryptophols via Michael addition reaction was developed. The generality of the method has been demonstrated by the synthesis of versatile furoindoline derivatives with a quaternary carbon center in good yields.

  3. A Mini-Review on Solid Acid Catalysts for Esterification Reactions

    NASA Astrophysics Data System (ADS)

    Sirsam, Rajkumar; Hansora, Dharmesh; Usmani, Ghayas A.

    2016-10-01

    This paper presents an overview of research pertaining to solid acid catalysts for esterification reactions. Prominence has been given to the literatures that have been appeared during the last two decades. A variety of reactions catalyzed by solid acid catalysts have been tabulated according to their broad classification; industrially important reactions have been outlined. Examples, where the use of various solid acid catalysts have led to an improvement in the selectivity of the desired products, have also been discussed. Various catalyzed esterification reactions using different approaches and previous kinetic studies have been reviewed. Types, preparation and synthesis of various solid acid catalysts have been reviewed and discussed. Suggestions have been summarized for their implementation in future work.

  4. Examination of Organic Reactions in UT/LS Aerosols: Temperature Dependence in Sulfuric Acid Solution

    NASA Astrophysics Data System (ADS)

    Iraci, L. T.; Michelsen, R. R.

    2004-12-01

    Sulfuric acid has been used for decades as an industrial catalyst for organic reactions, but its parallel role in atmospheric aerosols is relatively unexplored, despite identification of a wide array of organic compounds in particles. Several recent studies have demonstrated possible reactions in acidic particles, generally involving carbonyl groups (C=O) and leading to the formation of larger molecules. Reactions of oxygenated organic compounds in acidic solution are most often studied near room temperature, while the sulfate particles of the upper troposphere and lower stratosphere are significantly colder. Our studies of ethanal (acetaldehyde) suggest that reactivity in ~50 wt% H2SO4 solutions may be enhanced at lower temperatures, contrary to expectations. We will present temperature-dependent results of acid catalyzed condensation reactions, leading to formation of higher molecular weight products. Implications for aerosol composition and reactivity will be discussed.

  5. Kinetics of Acid Reactions: Making Sense of Associated Concepts

    ERIC Educational Resources Information Center

    Tan, Kim Chwee Daniel; Treagust, David F.; Chandrasegaran, A. L.; Mocerino, Mauro

    2010-01-01

    In chemical kinetics, in addition to the concepts related to kinetics, stoichiometry, chemical equilibrium and the characteristics of the reactants are often involved when comparing the rates of different reactions, making such comparisons very challenging for students at all levels, as well as for pre-service science teachers. Consequently, four…

  6. 40 CFR 721.10188 - Fatty acids, tall-oil, reaction products with 4-methyl-2-pentanone and aliphatic polyamine...

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Fatty acids, tall-oil, reaction... Fatty acids, tall-oil, reaction products with 4-methyl-2-pentanone and aliphatic polyamine (generic). (a... generically as fatty acids, tall-oil, reaction products with 4-methyl-2-pentanone and aliphatic polyamine...

  7. 40 CFR 721.10188 - Fatty acids, tall-oil, reaction products with 4-methyl-2-pentanone and aliphatic polyamine...

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Fatty acids, tall-oil, reaction... Fatty acids, tall-oil, reaction products with 4-methyl-2-pentanone and aliphatic polyamine (generic). (a... generically as fatty acids, tall-oil, reaction products with 4-methyl-2-pentanone and aliphatic polyamine...

  8. 40 CFR 721.6181 - Fatty acid, reaction product with substituted oxirane, formaldehyde-phenol polymer glycidyl ether...

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Fatty acid, reaction product with... Specific Chemical Substances § 721.6181 Fatty acid, reaction product with substituted oxirane, formaldehyde... as fatty acid, reaction product with substituted oxirane, formaldehyde-phenol polymer glycidyl...

  9. 40 CFR 721.6181 - Fatty acid, reaction product with substituted oxirane, formaldehyde-phenol polymer glycidyl ether...

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Fatty acid, reaction product with... Specific Chemical Substances § 721.6181 Fatty acid, reaction product with substituted oxirane, formaldehyde... as fatty acid, reaction product with substituted oxirane, formaldehyde-phenol polymer glycidyl...

  10. 40 CFR 721.10188 - Fatty acids, tall-oil, reaction products with 4-methyl-2-pentanone and aliphatic polyamine...

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Fatty acids, tall-oil, reaction... Fatty acids, tall-oil, reaction products with 4-methyl-2-pentanone and aliphatic polyamine (generic). (a... generically as fatty acids, tall-oil, reaction products with 4-methyl-2-pentanone and aliphatic polyamine...

  11. 40 CFR 721.10188 - Fatty acids, tall-oil, reaction products with 4-methyl-2-pentanone and aliphatic polyamine...

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Fatty acids, tall-oil, reaction... Fatty acids, tall-oil, reaction products with 4-methyl-2-pentanone and aliphatic polyamine (generic). (a... generically as fatty acids, tall-oil, reaction products with 4-methyl-2-pentanone and aliphatic polyamine...

  12. 40 CFR 721.10188 - Fatty acids, tall-oil, reaction products with 4-methyl-2-pentanone and aliphatic polyamine...

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Fatty acids, tall-oil, reaction... Fatty acids, tall-oil, reaction products with 4-methyl-2-pentanone and aliphatic polyamine (generic). (a... generically as fatty acids, tall-oil, reaction products with 4-methyl-2-pentanone and aliphatic polyamine...

  13. 40 CFR 721.6181 - Fatty acid, reaction product with substituted oxirane, formaldehyde-phenol polymer glycidyl ether...

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Fatty acid, reaction product with... Specific Chemical Substances § 721.6181 Fatty acid, reaction product with substituted oxirane, formaldehyde... as fatty acid, reaction product with substituted oxirane, formaldehyde-phenol polymer glycidyl...

  14. Synthesis of bio-based methacrylic acid by decarboxylation of itaconic acid and citric acid catalyzed by solid transition-metal catalysts.

    PubMed

    Le Nôtre, Jérôme; Witte-van Dijk, Susan C M; van Haveren, Jacco; Scott, Elinor L; Sanders, Johan P M

    2014-09-01

    Methacrylic acid, an important monomer for the plastics industry, was obtained in high selectivity (up to 84%) by the decarboxylation of itaconic acid using heterogeneous catalysts based on Pd, Pt and Ru. The reaction takes place in water at 200-250 °C without any external added pressure, conditions significantly milder than those described previously for the same conversion with better yield and selectivity. A comprehensive study of the reaction parameters has been performed, and the isolation of methacrylic acid was achieved in 50% yield. The decarboxylation procedure is also applicable to citric acid, a more widely available bio-based feedstock, and leads to the production of methacrylic acid in one pot in 41% selectivity. Aconitic acid, the intermediate compound in the pathway from citric acid to itaconic acid was also used successfully as a substrate.

  15. Citric Acid-Modified Fenton's Reaction for the Oxidation of Chlorinated Ethylenes in Soil Solution Systems

    SciTech Connect

    Seol, Yongkoo; Javandel, Iraj

    2008-03-15

    Fenton's reagent, a solution of hydrogen peroxide and ferrous iron catalyst, is used for an in-situ chemical oxidation of organic contaminants. Sulfuric acid is commonly used to create an acidic condition needed for catalytic oxidation. Fenton's reaction often involves pressure buildup and precipitation of reaction products, which can cause safety hazards and diminish efficiency. We selected citric acid, a food-grade substance, as an acidifying agent to evaluate its efficiencies for organic contaminant removal in Fenton's reaction, and examined the impacts of using citric acid on the unwanted reaction products. A series of batch and column experiments were performed with varying H{sub 2}O{sub 2} concentrations to decompose selected chlorinated ethylenes. Either dissolved iron from soil or iron sulfate salt was added to provide the iron catalyst in the batch tests. Batch experiments revealed that both citric and sulfuric acid systems achieved over 90% contaminant removal rates, and the presence of iron catalyst was essential for effective decontamination. Batch tests with citric acid showed no signs of pressure accumulation and solid precipitations, however the results suggested that an excessive usage of H{sub 2}O{sub 2} relative to iron catalysts (Fe{sup 2+}/H{sub 2}O{sub 2} < 1/330) would result in lowering the efficiency of contaminant removal by iron chelations in the citric acid system. Column tests confirmed that citric acid could provide suitable acidic conditions to achieve higher than 55% contaminant removal rates.

  16. Mathematical modeling of acid-base physiology

    PubMed Central

    Occhipinti, Rossana; Boron, Walter F.

    2015-01-01

    pH is one of the most important parameters in life, influencing virtually every biological process at the cellular, tissue, and whole-body level. Thus, for cells, it is critical to regulate intracellular pH (pHi) and, for multicellular organisms, to regulate extracellular pH (pHo). pHi regulation depends on the opposing actions of plasma-membrane transporters that tend to increase pHi, and others that tend to decrease pHi. In addition, passive fluxes of uncharged species (e.g., CO2, NH3) and charged species (e.g., HCO3− , NH4+) perturb pHi. These movements not only influence one another, but also perturb the equilibria of a multitude of intracellular and extracellular buffers. Thus, even at the level of a single cell, perturbations in acid-base reactions, diffusion, and transport are so complex that it is impossible to understand them without a quantitative model. Here we summarize some mathematical models developed to shed light onto the complex interconnected events triggered by acids-base movements. We then describe a mathematical model of a spherical cell–which to our knowledge is the first one capable of handling a multitude of buffer reaction–that our team has recently developed to simulate changes in pHi and pHo caused by movements of acid-base equivalents across the plasma membrane of a Xenopus oocyte. Finally, we extend our work to a consideration of the effects of simultaneous CO2 and HCO3− influx into a cell, and envision how future models might extend to other cell types (e.g., erythrocytes) or tissues (e.g., renal proximal-tubule epithelium) important for whole-body pH homeostasis. PMID:25617697

  17. Proton transfer reactions between nitric acid and acetone, hydroxyacetone, acetaldehyde and benzaldehyde in the solid phase.

    PubMed

    Lasne, Jérôme; Laffon, Carine; Parent, Philippe

    2012-12-05

    The heterogeneous and homogeneous reactions of acetone, hydroxyacetone, acetaldehyde and benzaldehyde with solid nitric acid (HNO(3)) films have been studied with Reflection-Absorption Infrared Spectroscopy (RAIRS) under Ultra-High Vacuum (UHV) conditions in the 90-170 K temperature range. In the bulk or at the surface of the films, nitric acid transfers its proton to the carbonyl function of the organic molecules, producing protonated acetone-H(+), hydroxyacetone-H(+), acetaldehyde-H(+) and benzaldehyde-H(+), and nitrate anions NO(3)(-), a reaction not observed when nitric acid is previously hydrated [J. Lasne, C. Laffon and Ph. Parent, Phys. Chem. Chem. Phys., 2012, 14, 697]. This provides a molecular-scale description of the carbonyl protonation reaction in an acid medium, the first step of the acid-catalyzed condensation of carbonyl compounds, fuelling the growth of secondary organic aerosols (SOA) in the atmosphere.

  18. Soot Reaction Properties (Ground-Based Study)

    NASA Technical Reports Server (NTRS)

    Dai, Z.; El-Leathy, A. M.; Lin, K.-C.; Sunderland, P. B.; Xu, F.; Faeth, G. M.; Urban, D. L. (Technical Monitor); Yuan, Z.-G. (Technical Monitor)

    2000-01-01

    Three major soot reaction processes are needed to predict soot properties in flame environments: soot growth, or the formation of soot on soot nuclei and soot particles; soot oxidation, or the reaction of soot with oxidizing species to yield the combustion products of soot oxidation; and soot nucleation, or the formation of soot nuclei from soot precursors having large molecular weights (generally thought to be large and particularly stable PAH molecules in flame environments, called stabilomers). These processes are addressed in the following, considering soot growth, oxidation and nucleation, in turn, by exploiting the soot and flame structure results for premixed and diffusion flames already discussed in Section 2.

  19. Atmospheric chemistry of hydrazoic acid (HN3): UV absorption spectrum, HO reaction rate, and reactions of the N3 radical.

    PubMed

    Orlando, John J; Tyndall, Geoffrey S; Betterton, Eric A; Lowry, Joe; Stegall, Steve T

    2005-03-15

    Processes related to the tropospheric lifetime and fate of hydrazoic acid, HN3, have been studied. The ultraviolet absorption spectrum of HN3 is shown to possess a maximum near 262 nm with a tail extending to at least 360 nm. The photolysis quantum yield for HN3 is shown to be approximately 1 at 351 nm. Using the measured spectrum and assuming unity quantum yield throughout the actinic region, a diurnally averaged photolysis lifetime near the earth's surface of 2-3 days is estimated. Using a relative rate method, the rate coefficient for reaction of HO with HN3 was found to be (3.9 +/-0.8) x 10(-12) cm3 molecule(-1) s(-1), substantially larger than the only previous measurement. The atmospheric HN3 lifetime with respect to HO oxidation is thus about 2-3 days, assuming a diurnally averaged [HO] of 10(6) molecule cm(-3). Reactions of N3, the product of the reaction of HO with HN3, were studied in an environmental chamber using an FTIR spectrometer for end-product analysis. The N3 radical reacts efficiently with NO, producing N2O with 100% yield. Reaction of N3 with NO2 appears to generate both NO and N2O, although the rate coefficient for this reaction is slower than that for reaction with NO. No evidence for reaction of N3 with CO was observed, in contrast to previous literature data. Reaction of N3 with O2 was found to be extremely slow, k < 6 x 10(-20) cm3 molecule(-1) s(-1), although this upper limit does not necessarily rule out its occurrence in the atmosphere. Finally, the rate coefficient for reaction of Cl with HN3 was measured using a relative rate method, k = (1.0+/-0.2) x 10(-12) cm3 molecule(-1) s(-1).

  20. CHROMATOGRAPHIC SEPARATION AND IDENTIFICATION OF PRODUCTS FROM THE REACTION OF DIMETHYLARSINIC ACID WITH HYDROGEN SULFIDE

    EPA Science Inventory

    The reaction of dimethylarsinic acid (DMAV) with hydrogen sulfide (H2S) is of biological significance and may be implicated in the overall toxicity and carcinogenicity of arsenic. The course of the reaction in aqueous phase was monitored and an initial product, dimethylthioarsin...

  1. The Modification of Cellulosic Surface with Fatty Acids via Plasma Mediated Reactions

    NASA Astrophysics Data System (ADS)

    Nada, Ahmed Ali Ahmed

    Much attention has been paid recently to understand the healing process made by the human body, in order to develop new approaches for promoting healing. The wound healing process includes four main phases, namely, hemostatic, inflammatory, proliferation, and remodeling, which take place successively. The human body can provide all the requirements of the healing process in normal wounds, unless there is a kind of deficiency of the skin function or massive fluid losses of vast wounds. Therefore, wound care of non-healing wounds has recently been the growing concern of many applications. The goal of this work is to explore the development of a new cellulose-based wound dressing composite that contain or release wound healing agents attained via dry textile chemical finishing techniques (thermal curing-plasma treatment). The synthesis of different wound healing agents derived from fatty acids and attached chemically to cellulose or even delivered through cyclodextrine modified cellulose are reported in this work. First, free fatty acids, which are obtained from commercial vegetable oils, were identified as wound healing agents. Many of these free acids are known to bind with and deactivate the proteases associated with inflammation at a wound site. Linoleic acid is extracted from commercial products of safflower seed oil while ricinoleic acid is obtained from castor oil. Conjugated linoleic acid was synthesized. Un-conjugated linoleic acid was used to prepare two derivatives namely linoleic azide and allylic ketone of linoleic acid. Different cellulose derivatives such as cellulose peroxide, iododeoxycellulose and cellulose diazonium salt in different degree of substitutions were synthesized in order to facilitate the free radical reaction with the fatty acid derivatives. New modified cellulosic products were synthesized by reacting the cellulosic and the linoleic acid derivatives via thermal or plasma technique and characterized by FT-IR ATR, the wettability test

  2. The temperature dependence of the rate constant for the reaction of hydroxyl radicals with nitric acid

    NASA Technical Reports Server (NTRS)

    Kurylo, M. J.; Cornett, K. D.; Murphy, J. L.

    1982-01-01

    The rate constant for the reaction of hydroxyl radicals with nitric acid in the 225-443 K temperature range has been measured by means of the flash photolysis resonance fluorescence technique. Above 300 K, the rate constant levels off in a way that can only be explained by the occurrence of two reaction channels, of which one, operative at low temperatures, proceeds through the formation of an adduct intermediate. The implications of these rate constant values for stratospheric reaction constants is discussed.

  3. Study on the spectrophotometric detection of free fatty acids in palm oil utilizing enzymatic reactions.

    PubMed

    Azeman, Nur Hidayah; Yusof, Nor Azah; Abdullah, Jaafar; Yunus, Robiah; Hamidon, Mohd Nizar; Hajian, Reza

    2015-07-07

    In this paper, a comprehensive study has been made on the detection of free fatty acids (FFAs) in palm oil via an optical technique based on enzymatic aminolysis reactions. FFAs in crude palm oil (CPO) were converted into fatty hydroxamic acids (FHAs) in a biphasic lipid/aqueous medium in the presence of immobilized lipase. The colored compound formed after complexation between FHA and vanadium (V) ion solution was proportional to the FFA content in the CPO samples and was analyzed using a spectrophotometric method. In order to develop a rapid detection system, the parameters involved in the aminolysis process were studied. The utilization of immobilized lipase as catalyst during the aminolysis process offers simplicity in the product isolation and the possibility of conducting the process under extreme reaction conditions. A good agreement was found between the developed method using immobilized Thermomyces lanuginose lipase as catalyst for the aminolysis process and the Malaysian Palm Oil Board (MPOB) standard titration method (R2 = 0.9453).

  4. Supercritical hydrogenation and acid-catalysed reactions "without gases".

    PubMed

    Hyde, Jason R; Poliakoff, Martyn

    2004-07-07

    The high temperature catalytic decomposition of HCO2H and HCO2Et are used to generate the high pressure H2 and the supercritical fluids needed for micro-scale hydrogenation of organic compounds; our approach overcomes the problems and limitations of handling high pressure gases on a small-scale and opens the way to the widespread use of continuous supercritical reactions in the laboratory.

  5. Lewis acid-Lewis acid heterobimetallic cooperative catalysis: mechanistic studies and application in enantioselective aza-Michael reaction.

    PubMed

    Yamagiwa, Noriyuki; Qin, Hongbo; Matsunaga, Shigeki; Shibasaki, Masakatsu

    2005-09-28

    The full details of a catalytic asymmetric aza-Michael reaction of methoxylamine promoted by rare earth-alkali metal heterobimetallic complexes are described, demonstrating the effectiveness of Lewis acid-Lewis acid cooperative catalysis. First, enones were used as substrates, and the 1,4-adducts were obtained in good yield (57-98%) and high ee (81-96%). Catalyst loading was successfully reduced to 0.3-3 mol % with enones. To broaden the substrate scope of the reaction to carboxylic acid derivatives, alpha,beta-unsaturated N-acylpyrroles were used as monodentate, carboxylic acid derivatives. With beta-alkyl-substituted N-acylpyrroles, the reaction proceeded smoothly and the products were obtained in high yield and good ee. Transformation of the 1,4-adducts from enones and alpha,beta-unsaturated N-acylpyrroles afforded corresponding chiral aziridines and beta-amino acids. Detailed mechanistic studies, including kinetics, NMR analysis, nonlinear effects, and rare earth metal effects, are also described. The Lewis acid-Lewis acid cooperative mechanism, including the substrate coordination mode, is discussed in detail.

  6. Chemical Reaction between Boric Acid and Phosphine Indicates Boric Acid as an Antidote for Aluminium Phosphide Poisoning

    PubMed Central

    Soltani, Motahareh; Shetab-Boushehri, Seyed F.; Shetab-Boushehri, Seyed V.

    2016-01-01

    Objectives: Aluminium phosphide (AlP) is a fumigant pesticide which protects stored grains from insects and rodents. When it comes into contact with moisture, AlP releases phosphine (PH3), a highly toxic gas. No efficient antidote has been found for AlP poisoning so far and most people who are poisoned do not survive. Boric acid is a Lewis acid with an empty p orbital which accepts electrons. This study aimed to investigate the neutralisation of PH3 gas with boric acid. Methods: This study was carried out at the Baharlou Hospital, Tehran University of Medical Sciences, Tehran, Iran, between December 2013 and February 2014. The volume of released gas, rate of gas evolution and changes in pH were measured during reactions of AlP tablets with water, acidified water, saturated boric acid solution, acidified saturated boric acid solution, activated charcoal and acidified activated charcoal. Infrared spectroscopy was used to study the resulting probable adduct between PH3 and boric acid. Results: Activated charcoal significantly reduced the volume of released gas (P <0.01). Although boric acid did not significantly reduce the volume of released gas, it significantly reduced the rate of gas evolution (P <0.01). A gaseous adduct was formed in the reaction between pure AlP and boric acid. Conclusion: These findings indicate that boric acid may be an efficient and non-toxic antidote for PH3 poisoning. PMID:27606109

  7. Reactions in glass ionomer cements: V. Effect of incorporating tartaric acid in the cement liquid.

    PubMed

    Crisp, S; Wilson, A D

    1976-01-01

    A description is give of the effect on the ASPA cement reaction of tartaric acid incorporated in the cement liquid. Tartaric acid acts as an accelerator that aids in the extraction of ions from the aluminosilicate glass and facilitates their binding to the polyanion chains. Postgelation hardening is significantly increased. Working time is unaffected possibly because cations are initially present as complexes.

  8. 40 CFR 721.9220 - Reaction products of secondary alkyl amines with a substituted benzenesulfonic acid and sulfuric...

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... amines with a substituted benzenesulfonic acid and sulfuric acid (generic name). 721.9220 Section 721... Reaction products of secondary alkyl amines with a substituted benzenesulfonic acid and sulfuric acid... benzenesulfonic acid and sulfuric acid (PMNs P-89-703, P-89-755, and P-89-756) are subject to reporting under...

  9. 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

    ... amines with a substituted benzenesulfonic acid and sulfuric acid (generic name). 721.9220 Section 721... Reaction products of secondary alkyl amines with a substituted benzenesulfonic acid and sulfuric acid... benzenesulfonic acid and sulfuric acid (PMNs P-89-703, P-89-755, and P-89-756) are subject to reporting under...

  10. 40 CFR 721.9220 - Reaction products of secondary alkyl amines with a substituted benzenesulfonic acid and sulfuric...

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... amines with a substituted benzenesulfonic acid and sulfuric acid (generic name). 721.9220 Section 721... Reaction products of secondary alkyl amines with a substituted benzenesulfonic acid and sulfuric acid... benzenesulfonic acid and sulfuric acid (PMNs P-89-703, P-89-755, and P-89-756) are subject to reporting under...

  11. 40 CFR 721.9220 - Reaction products of secondary alkyl amines with a substituted benzenesulfonic acid and sulfuric...

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... amines with a substituted benzenesulfonic acid and sulfuric acid (generic name). 721.9220 Section 721... Reaction products of secondary alkyl amines with a substituted benzenesulfonic acid and sulfuric acid... benzenesulfonic acid and sulfuric acid (PMNs P-89-703, P-89-755, and P-89-756) are subject to reporting under...

  12. 40 CFR 721.9220 - Reaction products of secondary alkyl amines with a substituted benzenesulfonic acid and sulfuric...

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... amines with a substituted benzenesulfonic acid and sulfuric acid (generic name). 721.9220 Section 721... Reaction products of secondary alkyl amines with a substituted benzenesulfonic acid and sulfuric acid... benzenesulfonic acid and sulfuric acid (PMNs P-89-703, P-89-755, and P-89-756) are subject to reporting under...

  13. Heterogeneous kinetics, products, and mechanisms of ferulic acid particles in the reaction with NO3 radicals

    NASA Astrophysics Data System (ADS)

    Liu, Changgeng; Zhang, Peng; Wen, Xiaoying; Wu, Bin

    2017-03-01

    Methoxyphenols, as an important component of wood burning, are produced by lignin pyrolysis and considered to be the potential tracers for wood smoke emissions. In this work, the heterogeneous reaction between ferulic acid particles and NO3 radicals was investigated. Six products including oxalic acid, 4-vinylguaiacol, vanillin, 5-nitrovanillin, 5-nitroferulic acid, and caffeic acid were confirmed by gas chromatography-mass spectrometry (GC-MS). In addition, the reaction mechanisms were proposed and the main pathways were NO3 electrophilic addition to olefin and the meta-position to the hydroxyl group. The uptake coefficient of NO3 radicals on ferulic acid particles was 0.17 ± 0.02 and the effective rate constant under experimental conditions was (1.71 ± 0.08) × 10-12 cm3 molecule-1 s-1. The results indicate that ferulic acid degradation by NO3 can be an important sink at night.

  14. [Study of Reaction Dynamics between Bovine Serum Albumin and Folic Acid by Stopped-Flow/Fluorescence].

    PubMed

    Ye, San-xian; Luo, Yun-jing; Qiao, Shu-liang; Li, Li; Liu, Cai-hong; Shi, Jian-long; An, Xue-jing

    2016-01-01

    As a kind of coenzyme of one-carbon enzymes in vivo, folic acid belongs to B vitamins, which can interact with other vitamins and has great significance for converting among amino acids, dividing growth of cells and protein synthesis reactions. Half-life, concentration and reaction rate constant of drugs are important parameters in pharmacokinetic study. In this paper, by utilizing fluorescence spectrophotometer and stopped-flow spectrum analyzer, reaction kinetic parameters between bovine serum albumin(BSA) and folic acid in a bionic system have been investigated, which provide references for parameters of drug metabolism related to folic acid. By using Stern-Volmer equation dealing with fluorescence quenching experiments data, we concluded that under 25, 30, and 37 degrees C, the static quenching constants of folic acid to intrinsic fluorescence from bovine serum albumin were 2.455 x 10(10), 4.900 x 10(10) and 6.427 x 10(10) L x mol(-1) x s(-1) respectively; The results of kinetic reaction rate have shown that the reaction rate of BSA and folic acid are greater than 100 mol x L(-1) x s(-1) at different temperatures, pH and buffering media, illustrating that the quenching mechanism between BSA and folic acid is to form composite static quenching process. Reaction concentration of bovine serum albumin and its initial concentration were equal to the secondary reaction formula, and the correlation coefficient was 0.998 7, while the half-life (t1/2) was 0.059 s at physiological temperature. With the increase of folic acid concentration, the apparent rate constant of this reaction had a linear increasing trend, the BSA fluorescence quenching rate constant catalyzed by folic acid was 3.174 x 10(5) mol x L(-1) x s(-1). Furthermore, with different buffer, the apparent rate constant and reaction rate constant of BSA interacting with folic acid were detected to explore the influence on the reaction under physiological medium, which is of great significance to determine the

  15. On the reaction of iron oxides and oxyhydroxides with tannic and phosphoric acid and their mixtures

    NASA Astrophysics Data System (ADS)

    Beltrán, J. J.; Novegil, F. J.; García, K. E.; Barrero, C. A.

    2010-01-01

    The actions of tannic acid, phosphoric acid and their mixture on lepidocrocite, goethite, superparamagnetic goethite, akaganeite, magnetite, hematite and maghemite for 1 day and 1 month were explored. It was found that these acids form iron tannates and phosphates. Lepidocrocite and magnetite were the iron phases more easily transformed with the mixture of the acids after 1 month of reaction, whereas hematite was the most resistant phase. In the case of goethite, our results suggest that in order to understand properly the action of these acids, we have to take into account its stoichiometry, surface area and degree of crystallinity.

  16. The Use of Gel Electrophoresis to Study the Reactions of Activated Amino Acids with Oligonucleotides

    NASA Technical Reports Server (NTRS)

    Zieboll, Gerhard; Orgel, Leslie E.

    1994-01-01

    We have used gel electrophoresis to study the primary covalent addition of amino acids to oligonu-cleotides or their analogs and the subsequent addition of further molecules of the amino acids to generate peptides covalently linked to the oligonucleotides. We have surveyed the reactions of a variety of amino acids with the phosphoramidates derived from oligonucleotide 5 inches phosphates and ethylenediamine. We find that arginine and amino acids can interact with oligonucleotidesl through stacking interactions react most efficiently. D- and L-amino acids give indistinguishable families of products.

  17. Sub-millitesla magnetic field effects on the recombination reaction of flavin and ascorbic acid radicals

    NASA Astrophysics Data System (ADS)

    Evans, Emrys W.; Kattnig, Daniel R.; Henbest, Kevin B.; Hore, P. J.; Mackenzie, Stuart R.; Timmel, Christiane R.

    2016-08-01

    Even though the interaction of a <1 mT magnetic field with an electron spin is less than a millionth of the thermal energy at room temperature (kBT), it still can have a profound effect on the quantum yields of radical pair reactions. We present a study of the effects of sub-millitesla magnetic fields on the photoreaction of flavin mononucleotide with ascorbic acid. Direct control of the reaction pathway is achieved by varying the rate of electron transfer from ascorbic acid to the photo-excited flavin. At pH 7.0, we verify the theoretical prediction that, apart from a sign change, the form of the magnetic field effect is independent of the initial spin configuration of the radical pair. The data agree well with model calculations based on a Green's function approach that allows multinuclear spin systems to be treated including the diffusive motion of the radicals, their spin-selective recombination reactions, and the effects of the inter-radical exchange interaction. The protonation states of the radicals are uniquely determined from the form of the magnetic field-dependence. At pH 3.0, the effects of two chemically distinct radical pair complexes combine to produce a pronounced response to ˜500 μT magnetic fields. These findings are relevant to the magnetic responses of cryptochromes (flavin-containing proteins proposed as magnetoreceptors in birds) and may aid the evaluation of effects of weak magnetic fields on other biologically relevant electron transfer processes.

  18. Syntheses of Papyracillic Acids: Application of the Tandem Chain Extension-Acylation Reaction

    PubMed Central

    Mazzone, Jennifer R.; Zercher, Charles K.

    2012-01-01

    A synthetic approach to the papyracillic acid family of natural products has been developed. The spiroacetal core is rapidly assembled through an unprecedented zinc carbenoid-mediated tandem chain extension-acylation reaction. Subsequent functional group manipulation provided access to papyracillic acid B and 4-epi-papyracillic acid C. The successful preparation of these molecules resulted in the clarification of structural assignments of members of this family of natural products. PMID:23013246

  19. A Novel Two-Gene Requirement for the Octanoyltransfer Reaction of Bacillus subtilis Lipoic Acid Biosynthesis

    PubMed Central

    Martin, Natalia; Christensen, Quin H.; Mansilla, María C.; Cronan, John E.; de Mendoza, Diego

    2011-01-01

    SUMMARY The Bacillus subtilis genome encodes three apparent lipoyl ligase homologues: yhfJ, yqhM, and ywfL which we have renamed lplJ, lipM and lipL, respectively. We show that LplJ encodes the sole lipoyl ligase of this bacterium. Physiological and biochemical characterization of a ΔlipM strain showed that LipM is absolutely required for the endogenous lipoylation of all lipoate-dependent proteins, confirming its role as the B. subtilis octanoyltransferase. However, we also report that in contrast to E. coli, B. subtilis requires a third protein for lipoic acid assembly, LipL. B. subtilis ΔlipL strains are unable to synthesize lipoic acid despite the presence of LipM and the sulfur insertion enzyme, LipA, which should suffice for lipoic acid biosynthesis based on the E. coli model. LipM is only required for the endogenous lipoylation pathway, whereas LipL also plays a role in lipoic acid scavenging. Expression of E. coli lipB allows growth of B. subtilis ΔlipL or ΔlipM strains in the absence of supplements. In contrast, growth of an E. coli ΔlipB strain can be complemented with lipM, but not lipL. These data together with those of the companion paper (Christensen et al., 2011) provide evidence that LipM and LipL catalyze sequential reactions in a novel pathway for lipoic acid biosynthesis. PMID:21338420

  20. Calcium-based Lewis acid catalysts.

    PubMed

    Begouin, Jeanne-Marie; Niggemann, Meike

    2013-06-17

    Recently, Lewis acidic calcium salts bearing weakly coordinating anions such as Ca(NTf₂)₂, Ca(OTf)₂, CaF₂ and Ca[OCH(CF₃)₂]₂ have been discovered as catalysts for the transformation of alcohols, olefins and carbonyl compounds. High stability towards air and moisture, selectivity and high reactivity under mild reaction conditions render these catalysts a sustainable and mild alternative to transition metals, rare-earth metals or strong Brønsted acids.

  1. Chromotropic acid-formaldehyde reaction in strongly acidic media. The role of dissolved oxygen and replacement of concentrated sulphuric acid.

    PubMed

    Fagnani, E; Melios, C B; Pezza, L; Pezza, H R

    2003-05-28

    The procedure for formaldehyde analysis recommended by the National Institute for Occupational Safety and Health (NIOSH) is the Chromotropic acid spectrophotometric method, which is the one that uses concentrated sulphuric acid. In the present study the oxidation step associated with the aforementioned method for formaldehyde determination was investigated. Experimental evidence has been obtained indicating that when concentrated H(2)SO(4) (18 mol l(-1)) is used (as in the NIOSH procedure) that acid is the oxidizing agent. On the other hand, oxidation through dissolved oxygen takes place when concentrated H(2)SO(4) is replaced by concentrated hydrochloric (12 mol l(-1)) and phosphoric (14.7 mol l(-1)) acids as well as by diluted H(2)SO(4) (9.4 mol l(-1)). Based on investigations concerning the oxidation step, a modified procedure was devised, in which the use of the potentially hazardous and corrosive concentrated H(2)SO(4) was eliminated and advantageously replaced by a less harmful mixture of HCl and H(2)O(2).

  2. Cross-coupling reactions of aryl pivalates with boronic acids.

    PubMed

    Quasdorf, Kyle W; Tian, Xia; Garg, Neil K

    2008-11-05

    The first cross-coupling of acylated phenol derivatives has been achieved. In the presence of an air-stable Ni(II) complex, readily accessible aryl pivalates participate in the Suzuki-Miyaura coupling with arylboronic acids. The process is tolerant of considerable variation in each of the cross-coupling components. In addition, a one-pot acylation/cross-coupling sequence has been developed. The potential to utilize an aryl pivalate as a directing group has also been demonstrated, along with the ability to sequentially cross-couple an aryl bromide followed by an aryl pivalate, using palladium and nickel catalysis, respectively.

  3. Reaction of methanol with chlorate ions in acid solution containing Hg{sup +2} by NMR

    SciTech Connect

    Ernst, W.R.; Indu, B.; Crump, B.; Gelbaum, L.T.

    1996-05-01

    The reaction rate of methanol was measured in solutions of sodium chlorate and sulfuric acid at several levels of temperature and concentration, in the presence of mercuric nitrate. The progress of the reaction was monitored by proton NMR signals corresponding to methanol and formic acid. Chlorine dioxide formation was suppressed by adding mercuric nitrate, which was shown earlier to catalyze the disproportionation of the intermediate species, chlorous acid, and sequester chloride ions. The reaction is first order in methanol and chlorate concentration and in the Hammett acidity function. The reaction of formic acid, sodium chlorate and sulfuric acid was also studied using the same technique. Formic acid was stable and did not react with chlorate at a measurable rate, even at concentrations and temperatures of a commercial process. This study related to commercial processes that produce chlorine dioxide by reducing chlorate ions with methanol. Chlorine dioxide is an oxidizing chemical that is used in water purification and is replacing chlorine in many chemical bleaching processes because of environmental concerns.

  4. Universal reaction mechanism of boronic acids with diols in aqueous solution: kinetics and the basic concept of a conditional formation constant.

    PubMed

    Furikado, Yuki; Nagahata, Tomomi; Okamoto, Takuya; Sugaya, Tomoaki; Iwatsuki, Satoshi; Inamo, Masahiko; Takagi, Hideo D; Odani, Akira; Ishihara, Koji

    2014-10-06

    To establish a detailed reaction mechanism for the condensation between a boronic acid, RB(OH)2, and a diol, H2L, in aqueous solution, the acid dissociation constants (Ka(BL)) of boronic acid diol esters (HBLs) were determined based on the well-established concept of conditional formation constants of metal complexes. The pKa values of HBLs were 2.30, 2.77, and 2.00 for the reaction systems, 2,4-difluorophenylboronic acid and chromotropic acid, 3-nitrophenylboronic acid and alizarin red S, and phenylboronic acid and alizarin red S, respectively. A general and precise reaction mechanism of RB(OH)2 with H2L in aqueous solution, which can serve as a universal reaction mechanism for RB(OH)2 and H2L, was proposed on the basis of (a) the relative kinetic reactivities of the RB(OH)2 and its conjugate base, that is, the boronate ion, toward H2L, and (b) the determined pKa values of HBLs. The use of the conditional formation constant, K', based on the main reaction: RB(OH)2 + H2L (K1)⇌ RB(L)(OH)(-) + H3O(+) instead of the binding constant has been proposed for the general reaction of uncomplexed boronic acid species (B') with uncomplexed diol species (L') to form boronic acid diol complex species (esters, BL') in aqueous solution at pH 5-11: B' + L' (K')⇌ BL'. The proposed reaction mechanism explains perfectly the formation of boronic acid diol ester in aqueous solution.

  5. Hydrodynamic instability in the open system of the iodate-arsenous acid reaction.

    PubMed

    Pópity-Tóth, Éva; Pimienta, Véronique; Horváth, Dezső; Tóth, Ágota

    2013-10-28

    Hydrodynamic instability arising in horizontally propagating vertical chemical fronts leading to the formation of a single stable convection roll is investigated experimentally in the iodate-arsenous acid reaction for various stoichiometry. In the presence of a free surface, the tilted reaction front becomes more elongated due to the evaporation of the surface active iodine and the decrease in the surface tension during the reaction. The experimental conditions are then identified where Marangoni instability represents the driving force for the distortion of the reaction front at the surface.

  6. Automatic NMR-based identification of chemical reaction types in mixtures of co-occurring reactions.

    PubMed

    Latino, Diogo A R S; Aires-de-Sousa, João

    2014-01-01

    The combination of chemoinformatics approaches with NMR techniques and the increasing availability of data allow the resolution of problems far beyond the original application of NMR in structure elucidation/verification. The diversity of applications can range from process monitoring, metabolic profiling, authentication of products, to quality control. An application related to the automatic analysis of complex mixtures concerns mixtures of chemical reactions. We encoded mixtures of chemical reactions with the difference between the (1)H NMR spectra of the products and the reactants. All the signals arising from all the reactants of the co-occurring reactions were taken together (a simulated spectrum of the mixture of reactants) and the same was done for products. The difference spectrum is taken as the representation of the mixture of chemical reactions. A data set of 181 chemical reactions was used, each reaction manually assigned to one of 6 types. From this dataset, we simulated mixtures where two reactions of different types would occur simultaneously. Automatic learning methods were trained to classify the reactions occurring in a mixture from the (1)H NMR-based descriptor of the mixture. Unsupervised learning methods (self-organizing maps) produced a reasonable clustering of the mixtures by reaction type, and allowed the correct classification of 80% and 63% of the mixtures in two independent test sets of different similarity to the training set. With random forests (RF), the percentage of correct classifications was increased to 99% and 80% for the same test sets. The RF probability associated to the predictions yielded a robust indication of their reliability. This study demonstrates the possibility of applying machine learning methods to automatically identify types of co-occurring chemical reactions from NMR data. Using no explicit structural information about the reactions participants, reaction elucidation is performed without structure elucidation of

  7. Clickable Nucleic Acids: Sequence-Controlled Periodic Copolymer/Oligomer Synthesis by Orthogonal Thiol-X Reactions.

    PubMed

    Xi, Weixian; Pattanayak, Sankha; Wang, Chen; Fairbanks, Benjamin; Gong, Tao; Wagner, Justine; Kloxin, Christopher J; Bowman, Christopher N

    2015-11-23

    Synthetic polymer approaches generally lack the ability to control the primary sequence, with sequence control referred to as the holy grail. Two click chemistry reactions were now combined to form nucleobase-containing sequence-controlled polymers in simple polymerization reactions. Two distinct approaches are used to form these click nucleic acid (CNA) polymers. These approaches employ thiol-ene and thiol-Michael reactions to form homopolymers of a single nucleobase (e.g., poly(A)n ) or homopolymers of specific repeating nucleobase sequences (e.g., poly(ATC)n). Furthermore, the incorporation of monofunctional thiol-terminated polymers into the polymerization system enables the preparation of multiblock copolymers in a single reaction vessel; the length of the diblock copolymer can be tuned by the stoichiometric ratio and/or the monomer functionality. These polymers are also used for organogel formation where complementary CNA-based polymers form reversible crosslinks.

  8. The suppression of the N-nitrosating reaction by chlorogenic acid.

    PubMed Central

    Kono, Y; Shibata, H; Kodama, Y; Sawa, Y

    1995-01-01

    N-Nitrosation of a model aromatic amine (2,3-diamino-naphthalene) by the N-nitrosating agent produced by nitrite in acidic solution was inhibited by a polyphenol, chlorogenic acid, which is an ester of caffeic acid quinic acid. Caffeic acid also inhibited the N-nitrosation, but quinic acid did not. 1,2-Benzenediols and 3,4-dihydroxybenzoic acid had inhibitory activities. Chlorogenic acid, caffeic acid, 1,2-benzenediols and 3,4-dihydroxybenzoic acid were able to scavenge the stable free radical, 1,1-diphenyl-2-picrylhydrazyl. Chlorogenic acid was found to be nitrated by acidic nitrite. The kinetic studies and the nitration observed only by bubbling of nitric oxide plus nitrogen dioxide gases indicated that the nitrating agent was nitrogen sesquioxide. The observations showed that the mechanism by which chlorogenic acid inhibited N-nitrosation of 2,3-diamino-naphthalene is due to its ability to scavenge the nitrosating agent, nitrogen sesquioxide. Chlorogenic acid may be effective not only in protecting against oxidative damage but also in inhibiting potentially mutagenic and carcinogenic reactions in vivo. PMID:8554543

  9. Enhanced electrocatalysis of the oxygen reduction reaction based on pattering of platinum surfaces with cyanide.

    SciTech Connect

    Strmcnik, D.; Escudero-Escribano, M.; Kodama, K.; Stamenkovic, V. R.; Cuesta, A.; Markovic, N. M.; Materials Science Division; Inst. de Quimica Fisica; Toyota Central R&D Labs., Inc.

    2010-08-15

    The slow rate of the oxygen reduction reaction in the phosphoric acid fuel cell is the main factor limiting its wide application. Here, we present an approach that can be used for the rational design of cathode catalysts with potential use in phosphoric acid fuel cells, or in any environments containing strongly adsorbing tetrahedral anions. This approach is based on molecular patterning of platinum surfaces with cyanide adsorbates that can efficiently block the sites for adsorption of spectator anions while the oxygen reduction reaction proceeds unhindered. We also demonstrate that, depending on the supporting electrolyte anions and cations, on the same CN-covered Pt(111) surface, the oxygen reduction reaction activities can range from a 25-fold increase to a 50-fold decrease. This behaviour is discussed in the light of the role of covalent and non-covalent interactions in controlling the ensemble of platinum active sites required for high turn over rates of the oxygen reduction reaction.

  10. Enhanced electrocatalysis of the oxygen reduction reaction based on patterning of platinum surfaces with cyanide

    SciTech Connect

    Strmcnik, D.; Escudero, M.; Kodama, K.; Stamenkovic, V. R.; Cuesta, A.; Markovic, N. M.

    2010-10-01

    The slow rate of the oxygen reduction reaction in the phosphoric acid fuel cell is the main factor limiting its wide application. Here, we present an approach that can be used for the rational design of cathode catalysts with potential use in phosphoric acid fuel cells, or in any environments containing strongly adsorbing tetrahedral anions. This approach is based on molecular patterning of platinum surfaces with cyanide adsorbates that can efficiently block the sites for adsorption of spectator anions while the oxygen reduction reaction proceeds unhindered. We also demonstrate that, depending on the supporting electrolyte anions and cations, on the same CN-covered Pt(111) surface, the oxygen reduction reaction activities can range from a 25-fold increase to a 50-fold decrease. This behaviour is discussed in the light of the role of covalent and non-covalent interactions in controlling the ensemble of platinum active sites required for high turn over rates of the oxygen reduction reaction.

  11. Reactivity and reaction intermediates for acetic acid adsorbed on CeO2(111)

    DOE PAGES

    Calaza, Florencia C.; Chen, Tsung -Liang; Mullins, David R.; ...

    2015-05-02

    Adsorption and reaction of acetic acid on a CeO2(1 1 1) surface was studied by a combination of ultra-highvacuum based methods including temperature desorption spectroscopy (TPD), soft X-ray photoelectronspectroscopy (sXPS), near edge X-ray absorption spectroscopy (NEXAFS) and reflection absorption IRspectroscopy (RAIRS), together with density functional theory (DFT) calculations. TPD shows that thedesorption products are strongly dependent upon the initial oxidation state of the CeO2 surface, includingselectivity between acetone and acetaldehyde products. The combination of sXPS and NEXAFS demon-strate that acetate forms upon adsorption at low temperature and is stable to above 500 K, above whichpoint ketene, acetone and acetic acidmore » desorb. Furthermore, DFT and RAIRS show that below 500 K, bridge bondedacetate coexists with a moiety formed by adsorption of an acetate at an oxygen vacancy, formed bywater desorption.« less

  12. Polymerase chain reaction (PCR) identification of Penicillium brevicompactum, a grape contaminant and mycophenolic acid producer.

    PubMed

    Patiño, B; Medina, A; Doménech, M; González-Jaén, M T; Jiménez, M; Vázquez, C

    2007-02-01

    Penicillium brevicompactum is a ubiquitous fungal species that contaminates diverse substrates and commodities and produces an array of metabolites toxic to human and animals. The present work has obtained evidence, by liquid chromatography (LC)-ion-trap mass spectrometry, of the ability of P. brevicompactum strains isolated from grapes to produce mycophenolic acid, a potent immunosuppressor. In order to facilitate early diagnosis of this species on commodities for human and animal consumption, a rapid, sensitive and specific polymerase chain reaction (PCR) assay for P. brevicompactum was developed. The specific primers were designed based on the ITS1-5.8S-ITS2ITS (Internal Transcribed Spacers of rRNA genes) multicopy region. This method provides a useful aid to detect the presence of this fungal species in grapes and other commodities in order to prevent the toxins produced entering the food chain.

  13. Interactive effects of cadmium and acid rain on photosynthetic light reaction in soybean seedlings.

    PubMed

    Sun, Zhaoguo; Wang, Lihong; Chen, Minmin; Wang, Lei; Liang, Chanjuan; Zhou, Qing; Huang, Xiaohua

    2012-05-01

    Interactive effects of cadmium (Cd(2+)) and acid rain on photosynthetic light reaction in soybean seedlings were investigated under hydroponic conditions. Single treatment with Cd(2+) or acid rain and the combined treatment decreased the content of chlorophyll, Hill reaction rate, the activity of Mg(2+)-ATPase, maximal photochemical efficiency and maximal quantum yield, increased initial fluorescence and damaged the chloroplast structure in soybean seedlings. In the combined treatment, the change in the photosynthetic parameters and the damage of chloroplast structure were stronger than those of any single pollution. Meanwhile, Cd(2+) and acid rain had the interactive effects on the test indices in soybean seedlings. The results indicated that the combined pollution of Cd(2+) and acid rain aggravated the toxic effect of the single pollution of Cd(2+) or acid rain on the photosynthetic parameters due to the serious damage to the chloroplast structure.

  14. Reduction reaction analysis of nanoparticle copper oxide for copper direct bonding using formic acid

    NASA Astrophysics Data System (ADS)

    Fujino, Masahisa; Akaike, Masatake; Matsuoka, Naoya; Suga, Tadatomo

    2017-04-01

    Copper direct bonding is required for electronics devices, especially power devices, and copper direct bonding using formic acid is expected to lower the bonding temperature. In this research, we analyzed the reduction reaction of copper oxide using formic acid with a Pt catalyst by electron spin resonance analysis and thermal gravimetry analysis. It was found that formic acid was decomposed and radicals were generated under 200 °C. The amount of radicals generated was increased by adding the Pt catalyst. Because of these radicals, both copper(I) oxide and copper(II) oxide start to be decomposed below 200 °C, and the reduction of copper oxide is accelerated by reactants such as H2 and CO from the decomposition of formic acid above 200 °C. The Pt catalyst also accelerates the reaction of copper oxide reduction. Herewith, it is considered that the copper surface can be controlled more precisely by using formic acid to induce direct bonding.

  15. Mining electronic laboratory notebooks: analysis, retrosynthesis, and reaction based enumeration.

    PubMed

    Christ, Clara D; Zentgraf, Matthias; Kriegl, Jan M

    2012-07-23

    An approach to automatically analyze and use the knowledge contained in electronic laboratory notebooks (ELNs) has been developed. Reactions were reduced to their reactive center and converted to a string representation (SMIRKS) which formed the basis for reaction classification and in silico (retro-)synthesis. Of the SMIRKS that occurred at least five times, 98% successfully regenerated the original product. The extracted reaction rules (SMIRKS) and corresponding reactants span a virtual chemical space which showed a strong dependence on the size of the reactive center. Whereas relatively few robust reaction types were sufficient to describe a large part of all reactions, considerably more reaction rules were necessary to cover all reactions in the ELN. Furthermore, reaction sequences were extracted to identify frequent combinations and diversifying reaction steps. Based on the extracted knowledge a (retro-)synthesis tool was built allowing for de novo design of compounds which have a high chance of being synthetically accessible. In an example application of the de novo design tool, various feasible retrosynthetic routes to the query molecule were obtained. Reaction based enumeration along the top ranked route yielded a library of 29 920 compounds with diverse properties, 99.9% of which are novel in the sense that they are unknown to the public domain.

  16. Switching the BZ reaction with a strong-acid-free gel.

    PubMed

    Hara, Yusuke; Yamaguchi, Yoshinori; Mayama, Hiroyuki

    2014-01-16

    In the present study, a novel gel with a semi-interpenetrating polymer network (semi-IPN) that undergo the Belousov-Zhabotinsky (BZ) reaction without the addition of a strong acid (HNO3 or H2SO4) was developed. The required concentrations of the BZ substrates, sodium bromate (NaBrO3) and malonic acid (MA), under these conditions were higher than under the normal BZ reaction conditions, involving the addition of a strong acid. The period of the BZ reaction with the novel gel (semi-IPN BZ gel) decreased with increasing concentrations of NaBrO3 and MA. Moreover, the connection of the semi-IPN BZ gel to a conventional BZ gel facilitated the reaction in the latter through the propagation of the intermediates from the former to the latter. The BZ reaction stopped when the conventional BZ gel was disconnected from the semi-IPN BZ gel. These results demonstrate that the BZ reaction in the conventional BZ gel underwent on-off switching, controlled by its attachment to the semi-IPN BZ gel. This on-off switching mechanism would be valuable in controlling actuators and robots without strong acids.

  17. Esterification Reaction of Glycerol and Palm Oil Oleic Acid Using Methyl Ester Sulfonate Acid Catalyst as Drilling Fluid Formulation

    NASA Astrophysics Data System (ADS)

    Sari, V. I.; Hambali, E.; Suryani, A.; Permadi, P.

    2017-02-01

    Esterification reaction between glycerol with palm oil oleic acid to produce glycerol ester and one of the utilization of glycerol esters is as ingredients of drilling fluids formula for oil drilling needs. The purpose of this research is to get the best conditions of the esterification process. The esterification reaction does with the reactants is glycerol with purity of 97.6%, palm oil oleic acid with the molar ratio is 1:1, Methyl Ester Sulfonate Acid (MESA) catalyst 0.5%, and stirring speed 400 rpm. The temperature range of 180°C to 240°C and the processing time between 120 to 180 minutes. The results showed that the best conditions of the esterification reaction at the temperature 240°C and time process are 180 minute. The increasing temperature resulted that the acid number decreases and causing the conversion increased. The maximum conversion is 99.24%, density 0.93 g/cm3, flash point 241°C, pour point -3°C, the boiling point of 244 °C, the acid value of 1.90 mg KOH/g sample, kinematic viscosity 31.51 cSt (40°C), surface tension 37.0526 dyne/cm and GCMS identification, glycerol ester at 22,256 retention time (minutes) and wide area 73.75 (%). From the research results obtained glycerol ester with characteristics suitable for drilling fluid formulations.

  18. Reactions Between Water Soluble Organic Acids and Nitrates in Atmospheric Aerosols: Recycling of Nitric Acid and Formation of Organic Salts

    SciTech Connect

    Wang, Bingbing; Laskin, Alexander

    2014-03-25

    Atmospheric particles often include a complex mixture of nitrate and secondary organic materials accumulated within the same individual particles. Nitrate as an important inorganic component can be chemically formed in the atmosphere. For instance, formation of sodium nitrate (NaNO3) and calcium nitrate Ca(NO3)2 when nitrogen oxide and nitric acid (HNO3) species react with sea salt and calcite, respectively. Organic acids contribute a significant fraction of photochemically formed secondary organics that can condense on the preexisting nitrate-containing particles. Here, we present a systematic microanalysis study on chemical composition of laboratory generated particles composed of water soluble organic acids and nitrates (i.e. NaNO3 and Ca(NO3)2) investigated using computer controlled scanning electron microscopy with energy dispersive analysis of X-rays (CCSEM/EDX) and Fourier transform infrared micro-spectroscopy (micro-FTIR). The results show that water-soluble organic acids can react with nitrates releasing gaseous HNO3 during dehydration process. These reactions are attributed to acid displacement of nitrate with weak organic acids driven by the evaporation of HNO3 into gas phase due to its relatively high volatility. The reactions result in significant nitrate depletion and formation of organic salts in mixed organic acids/nitrate particles that in turn may affect their physical and chemical properties relevant to atmospheric environment and climate. Airborne nitrate concentrations are estimated by thermodynamic calculations corresponding to various nitrate depletions in selected organic acids of atmospheric relevance. The results indicate a potential mechanism of HNO3 recycling, which may further affect concentrations of gas- and aerosol-phase species in the atmosphere and the heterogeneous reaction chemistry between them.

  19. Reaction of gamma-tocopherol with hypochlorous acid.

    PubMed

    Nguyen, Quyen; Southwell-Keely, Peter T

    2007-03-01

    In addition to being a very good antioxidant, gamma-tocopherol is also an excellent electrophile trap. This is a study of the reactivity of gamma-tocopherol with hypochlorous acid/hypochlorite, a potential biological foe that is both an oxidant and an electrophile. Aqueous sodium hypochlorite (1.72 mmol; pH 7.4) was stirred with gamma-tocopherol (0.12 mmol) in hexane for 2 min at room temperature. The following products were isolated: gamma-tocopheryl quinone (0.6%), tocored (10%), 3-chloro-gamma-tocopheryl quinone (14%), an ether dimer of 3-chloro-gamma-tocopheryl quinone (0.4%), two isomers of 5-(5-gamma-tocopheryl)-gamma-tocopherol (3 and 2% respectively), 5-chloro-gamma-tocopherol (14%) and two chlorinated dimers (14 and 24% respectively) which were identified as diastereomers of (3R,10R)-11a-chloro-2,3,9,10-tetrahydro-3,5,6,10,12,13-hexamethyl-3,10-bis[(4R,8R)-4,8,12-trimethyltridecyl]-1H-pyrano(3,2a)-8H-pyrano(3,2g)-dibenzofuran-14(7aH)(14aH)-one. The chlorinated dimers, 5-chloro-gamma-tocopherol, 3-chloro-gamma-tocopheryl quinone and its ether dimer are new compounds.

  20. MULTICOMPONENT REACTIONS IN ALKALOID-BASED DRUG DISCOVERY

    PubMed Central

    Magedov, I. V.; Kornienko, A.

    2016-01-01

    Multicomponent reactions are emerging as a powerful tool in alkaloid-based drug discovery. This Highlight describes several recent (all published in 2011) examples of the employment of multicomponent reactions for the synthesis of biologically active alkaloids and their medicinally relevant analogues. PMID:27917001

  1. 40 CFR 721.10136 - 2-Propenoic acid, 2-methyl-, 2-hydroxyethyl ester, reaction products with hexakis(alkoxyalkyl...

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ...-hydroxyethyl ester, reaction products with hexakis(alkoxyalkyl)melamine (generic). 721.10136 Section 721.10136... 2-Propenoic acid, 2-methyl-, 2-hydroxyethyl ester, reaction products with hexakis(alkoxyalkyl... substance identified generically as 2-propenoic acid, 2-methyl-, 2-hydroxyethyl ester, reaction...

  2. 40 CFR 721.10136 - 2-Propenoic acid, 2-methyl-, 2-hydroxyethyl ester, reaction products with hexakis(alkoxyalkyl...

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ...-hydroxyethyl ester, reaction products with hexakis(alkoxyalkyl)melamine (generic). 721.10136 Section 721.10136... 2-Propenoic acid, 2-methyl-, 2-hydroxyethyl ester, reaction products with hexakis(alkoxyalkyl... substance identified generically as 2-propenoic acid, 2-methyl-, 2-hydroxyethyl ester, reaction...

  3. 40 CFR 721.10136 - 2-Propenoic acid, 2-methyl-, 2-hydroxyethyl ester, reaction products with hexakis(alkoxyalkyl...

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ...-hydroxyethyl ester, reaction products with hexakis(alkoxyalkyl)melamine (generic). 721.10136 Section 721.10136... 2-Propenoic acid, 2-methyl-, 2-hydroxyethyl ester, reaction products with hexakis(alkoxyalkyl... substance identified generically as 2-propenoic acid, 2-methyl-, 2-hydroxyethyl ester, reaction...

  4. 40 CFR 721.10136 - 2-Propenoic acid, 2-methyl-, 2-hydroxyethyl ester, reaction products with hexakis(alkoxyalkyl...

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ...-hydroxyethyl ester, reaction products with hexakis(alkoxyalkyl)melamine (generic). 721.10136 Section 721.10136... 2-Propenoic acid, 2-methyl-, 2-hydroxyethyl ester, reaction products with hexakis(alkoxyalkyl... substance identified generically as 2-propenoic acid, 2-methyl-, 2-hydroxyethyl ester, reaction...

  5. 40 CFR 721.10136 - 2-Propenoic acid, 2-methyl-, 2-hydroxyethyl ester, reaction products with hexakis(alkoxyalkyl...

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ...-hydroxyethyl ester, reaction products with hexakis(alkoxyalkyl)melamine (generic). 721.10136 Section 721.10136... 2-Propenoic acid, 2-methyl-, 2-hydroxyethyl ester, reaction products with hexakis(alkoxyalkyl... substance identified generically as 2-propenoic acid, 2-methyl-, 2-hydroxyethyl ester, reaction...

  6. An Investigation of Solid-State Amidization and Imidization Reactions in Vapor Deposited Poly (amic acid)

    SciTech Connect

    Anthamatten, M; Letts, S A; Day, K; Cook, R C; Gies, A P; Hamilton, T P; Nonidez, W K

    2004-06-28

    The condensation polymerization reaction of 4,4'-oxydianiline (ODA) with pyromellitic dianhydride (PMDA) to form poly(amic acid) and the subsequent imidization reaction to form polyimide were investigated for films prepared using vapor deposition polymerization techniques. Fourier-transform infrared spectroscopy (FT-IR), thermal analysis, and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) of films at different temperatures indicate that additional solid-state polymerization occurs prior to imidization reactions. Experiments reveal that, upon vapor deposition, poly(amic acid) oligomers form that have a number-average molecular weight of about 1500 Daltons. Between 100 - 130 C these chains undergo additional condensation reaction to form slightly higher molecular weight oligomers. Calorimetry measurements show that this reaction is exothermic ({Delta}H {approx} -30 J/g) with an activation energy of about 120 kJ/mol. Experimental reaction enthalpies are compared to results from ab initio molecular modeling calculations to estimate the number of amide groups formed. At higher temperatures (150 - 300 C) imidization of amide linkages occurs as an endothermic reaction ({Delta}H {approx} +120 J/g) with an activation energy of about 130 kJ/mol. Solid-state kinetics were found to depend on reaction conversion as well as the processing conditions used to deposit films.

  7. Investigation and application of multiple reactions between molybdoniobium heteropoly acid and di- or trimethylthionines

    SciTech Connect

    Mirzoyam, F.B.; Karapetyan, A.A.

    1986-03-01

    This paper presents the results of the study and use of reactions of molybdoniobic acid (MNA) with di- and trimethylthiones (DMT and TMT, respectively). It was found that light absorption of acetone solutions of the products of outer-sphere interaction between MNA and DMT or TMT enabled the determination of optimum acidity for MNA formation. Reaction between TMT and MNA gives two different compounds containing two and five associated dye cations, different in molar extinction coefficient and optimum reaction acidity (pH 0.05-0.25 and 0.35-0.90). Formation of the 6th and 8th molybdenum series with an identical composition of the outer sphere is shown. A highly sensitive photometric method for determining niobium has been developed.

  8. Characterization of the esterification reaction in high free fatty acid oils

    NASA Astrophysics Data System (ADS)

    Altic, Lucas Eli Porter

    Energy and vegetable oil prices have caused many biodiesel producers to turn to waste cooking oils as feedstocks. These oils contain high levels of free fatty acids (FFAs) which make them difficult or impossible to convert to biodiesel by conventional production methods. Esterification is required for ultra-high FFA feedstocks such as Brown Grease. In addition, ultrasonic irradiation has the potential to improve the kinetics of the esterification reaction. 2-level, multi-factor DOE experiments were conducted to characterize the esterification reaction in ultra-high FFA oils as well as determine whether ultrasonic irradiation gives any benefit besides energy input. The study determined that sulfuric acid content had the greatest effect followed by temperature and water content (inhibited reaction). Methanol content had no effect in the range studied. A small interaction term existed between sulfuric acid and temperature. The study also concluded that sonication did not give any additional benefit over energy input.

  9. Theoretical stusy of the reaction between 2,2',4' - trihydroxyazobenzene-5-sulfonic acid and zirconium

    USGS Publications Warehouse

    Fletcher, Mary H.

    1960-01-01

    Zirconium reacts with 2,2',4'-trihydroxyazobenzene-5-sulfonic acid in acid solutions to Form two complexes in which the ratios of dye to zirconium are 1 to 1 and 2 to 1. Both complexes are true chelates, with zirconium acting as a bridge between the two orthohydroxy dye groups. Apparent equilibrium constants for the reactions to form each of the complexes are determined. The reactions are used as a basis for the determination of the active component in the dye and a graphical method for the determination of reagent purity is described. Four absorption spectra covering the wave length region from 350 to 750 mu are given, which completely define the color system associated with the reactions in solutions where the hydrochloric acid concentration ranges from 0.0064N to about 7N.

  10. Phosphonic acid based exchange resins

    DOEpatents

    Horwitz, E.P.; Alexandratos, S.D.; Gatrone, R.C.; Chiarizia, R.

    1995-09-12

    An ion exchange resin is described for extracting metal ions from a liquid waste stream. An ion exchange resin is prepared by copolymerizing a vinylidene diphosphonic acid with styrene, acrylonitrile and divinylbenzene. 10 figs.

  11. Phosphonic acid based exchange resins

    DOEpatents

    Horwitz, E. Philip; Alexandratos, Spiro D.; Gatrone, Ralph C.; Chiarizia, Ronato

    1995-01-01

    An ion exchange resin for extracting metal ions from a liquid waste stream. An ion exchange resin is prepared by copolymerizing a vinylidene diphosphonic acid with styrene, acrylonitrile and divinylbenzene.

  12. Reaction of perfluoroalkyl grignard reagents with phosphorus trihalides: a new route to perfluoroalkyl-phosphonous and -phosphonic acids.

    PubMed

    Hosein, Adil I; Le Goff, Xavier F; Ricard, Louis; Caffyn, Andrew J M

    2011-02-21

    The reaction of perfluoroalkyl Grignard reagents with phosphorus(III) halides was explored. In the process a new convenient, one-pot, high yield method for the synthesis of (perfluoroalkyl)phosphonic acids has been developed. Perfluoroalkyl Grignard reagents react with phosphorus trichloride or phosphorus tribromide to form (perfluoroalkyl)phosphonous dihalides. Hydrolysis gives the corresponding (perfluoroalkyl)phosphonous acids. Oxidation of the phosphonous acids with H(2)O(2) produces (perfluoroalkyl)phosphonic acids in 60-78% overall yields, based on the corresponding perfluoroalkyl iodide. The X-ray crystal structures of the toluidinium salts, [MeC(6)H(4)NH(3)](2)[C(2)F(5)PO(3)] and [MeC(6)H(4)NH(3)][C(8)F(17)P(O)(2)OH], are reported.

  13. Oxygen dependency of one-electron reactions generating ascorbate radicals and hydrogen peroxide from ascorbic acid.

    PubMed

    Boatright, William L

    2016-04-01

    The effect of oxygen on the two separate one-electron reactions involved in the oxidation of ascorbic acid was investigated. The rate of ascorbate radical (Asc(-)) formation (and stability) was strongly dependent on the presence of oxygen. A product of ascorbic acid oxidation was measurable levels of hydrogen peroxide, as high as 32.5 μM from 100 μM ascorbic acid. Evidence for a feedback mechanism where hydrogen peroxide generated during the oxidation of ascorbic acid accelerates further oxidation of ascorbic acid is also presented. The second one-electron oxidation reaction of ascorbic acid leading to the disappearance of Asc(-) was also strongly inhibited in samples flushed with argon. In the range of 0.05-1.2 mM ascorbic acid, maximum levels of measurable hydrogen peroxide were achieved with an initial concentration of 0.2 mM ascorbic acid. Hydrogen peroxide generation was greatly diminished at ascorbic acid levels of 0.8 mM or above.

  14. Molecular Design of a Chiral Brønsted Acid with Two Different Acidic Sites: Regio-, Diastereo-, and Enantioselective Hetero-Diels-Alder Reaction of Azopyridinecarboxylate with Amidodienes Catalyzed by Chiral Carboxylic Acid-Monophosphoric Acid.

    PubMed

    Momiyama, Norie; Tabuse, Hideaki; Noda, Hirofumi; Yamanaka, Masahiro; Fujinami, Takeshi; Yamanishi, Katsunori; Izumiseki, Atsuto; Funayama, Kosuke; Egawa, Fuyuki; Okada, Shino; Adachi, Hiroaki; Terada, Masahiro

    2016-09-07

    A chiral Brønsted acid containing two different acidic sites, chiral carboxylic acid-monophosphoric acid 1a, was designed to be a new and effective concept in catalytic asymmetric hetero-Diels-Alder reactions of azopyridinecarboxylate with amidodienes. The multipoint hydrogen-bonding interactions among the carboxylic acid, monophosphoric acid, azopyridinecarboxylate, and amidodiene achieved high catalytic and chiral efficiency, producing substituted 1,2,3,6-tetrahydropyridazines with excellent stereocontrol in a single step. This constitutes the first example of regio-, diastereo-, and enantioselective azo-hetero-Diels-Alder reactions by chiral Brønsted acid catalysis.

  15. 40 CFR 721.10189 - Fatty acids, tall-oil, reaction products with (butoxymethyl) oxirane formaldehyde-phenol polymer...

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Fatty acids, tall-oil, reaction... Substances § 721.10189 Fatty acids, tall-oil, reaction products with (butoxymethyl) oxirane formaldehyde... to reporting. (1) The chemical substance identified generically as fatty acids, tall-oil,...

  16. 40 CFR 721.10189 - Fatty acids, tall-oil, reaction products with (butoxymethyl) oxirane formaldehyde-phenol polymer...

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Fatty acids, tall-oil, reaction... Substances § 721.10189 Fatty acids, tall-oil, reaction products with (butoxymethyl) oxirane formaldehyde... to reporting. (1) The chemical substance identified generically as fatty acids, tall-oil,...

  17. 40 CFR 721.10189 - Fatty acids, tall-oil, reaction products with (butoxymethyl) oxirane formaldehyde-phenol polymer...

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Fatty acids, tall-oil, reaction... Substances § 721.10189 Fatty acids, tall-oil, reaction products with (butoxymethyl) oxirane formaldehyde... to reporting. (1) The chemical substance identified generically as fatty acids, tall-oil,...

  18. 40 CFR 721.10189 - Fatty acids, tall-oil, reaction products with (butoxymethyl) oxirane formaldehyde-phenol polymer...

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Fatty acids, tall-oil, reaction... Substances § 721.10189 Fatty acids, tall-oil, reaction products with (butoxymethyl) oxirane formaldehyde... to reporting. (1) The chemical substance identified generically as fatty acids, tall-oil,...

  19. The Conjugate Acid-Base Chart.

    ERIC Educational Resources Information Center

    Treptow, Richard S.

    1986-01-01

    Discusses the difficulties that beginning chemistry students have in understanding acid-base chemistry. Describes the use of conjugate acid-base charts in helping students visualize the conjugate relationship. Addresses chart construction, metal ions, buffers and pH titrations, and the organic functional groups and nonaqueous solvents. (TW)

  20. Students' Alternate Conceptions on Acids and Bases

    ERIC Educational Resources Information Center

    Pan, Hanqing; Henriques, Laura

    2015-01-01

    Knowing what students bring to the classroom can and should influence how we teach them. This study is a review of the literature associated with secondary and postsecondary students' ideas about acids and bases. It was found that there are six types of alternate ideas about acids and bases that students hold. These are: macroscopic properties of…

  1. The Kidney and Acid-Base Regulation

    ERIC Educational Resources Information Center

    Koeppen, Bruce M.

    2009-01-01

    Since the topic of the role of the kidneys in the regulation of acid base balance was last reviewed from a teaching perspective (Koeppen BM. Renal regulation of acid-base balance. Adv Physiol Educ 20: 132-141, 1998), our understanding of the specific membrane transporters involved in H+, HCO , and NH transport, and especially how these…

  2. Acid-base catalysis of N-[(morpholine)methylene]daunorubicin.

    PubMed

    Krause, Anna; Jelińska, Anna; Cielecka-Piontek, Judyta; Klawitter, Maria; Zalewski, Przemysław; Oszczapowicz, Irena; Wąsowska, Małgorzata

    2012-08-01

    The stability of N-[(morpholine)methylene]-daunorubicin hydrochloride (MMD) was investigated in the pH range 0.44-13.54, at 313, 308, 303 and 298 K. The degradation of MMD as a result of hydrolysis is a pseudo-first-order reaction described by the following equation: ln c = ln c(0) - k(obs)• t. In the solutions of hydrochloric acid, sodium hydroxide, borate, acetate and phosphate buffers, k(obs) = k(pH) because general acid-base catalysis was not observed. Specific acid-base catalysis of MMD comprises the following reactions: hydrolysis of the protonated molecules of MMD catalyzed by hydrogen ions (k(1)) and spontaneous hydrolysis of MMD molecules other than the protonated ones (k(2)) under the influence of water. The total rate of the reaction is equal to the sum of partial reactions: k(pH) = k(1) • a(H)+ • f(1) + k(2) • f(2) where: k(1) is the second-order rate constant (mol(-1) l s(-1)) of the specific hydrogen ion-catalyzed degradation of the protonated molecules of MMD; k(2) is the pseudo-first-order rate constant (s(-1)) of the water-catalyzed degradation of MMD molecules other than the protonated ones, f(1) - f(2) are fractions of the compound. MMD is the most stable at approx. pH 2.5.

  3. Transition-metal-free cascade reaction of α-halo-N-tosylhydrazones, indoles and arylboronic acids.

    PubMed

    Wu, Guojiao; Deng, Yifan; Luo, Haiqing; Zhou, Junliang; Li, Tianjiao; Zhang, Yan; Wang, Jianbo

    2016-04-18

    α-Halo-N-tosylhydrazones are employed as reagents for the formation of multiple carbon-carbon bonds in the three-component reactions. In this transformation, a strategy has been designed to generate the diazo intermediate by using a nucleophile to react with the azoalkene intermediate generated in situ from the α-halo-N-tosylhydrazone. The diazo intermediate thus generated further undergoes transition-metal-free C-C bond forming reaction with arylboronic acids.

  4. Experimental Evidence of Localized Oscillations in the Photosensitive Chlorine Dioxide-Iodine-Malonic Acid Reaction

    NASA Astrophysics Data System (ADS)

    Míguez, David G.; Alonso, Sergio; Muñuzuri, Alberto P.; Sagués, Francesc

    2006-10-01

    The interaction between Hopf and Turing modes has been the subject of active research in recent years. We present here experimental evidence of the existence of mixed Turing-Hopf modes in a two-dimensional system. Using the photosensitive chlorine dioxide-iodine-malonic acid reaction (CDIMA) and external constant background illumination as a control parameter, standing spots oscillating in amplitude and with hexagonal ordering were observed. Numerical simulations in the Lengyel-Epstein model for the CDIMA reaction confirmed the results.

  5. Enantioselective aldol reaction between isatins and cyclohexanone catalyzed by amino acid sulphonamides.

    PubMed

    Wang, Jun; Liu, Qi; Hao, Qing; Sun, Yanhua; Luo, Yiming; Yang, Hua

    2015-04-01

    Sulphonamides derived from primary α-amino acid were successfully applied to catalyze the aldol reaction between isatin and cyclohexanone under neat conditions. More interestingly, molecular sieves, as privileged additives, were found to play a vital role in achieving high enantioselectivity. Consequently, high yields (up to 99%) along with good enantioselectivities (up to 92% ee) and diastereoselectivities (up to 95:5 dr) were obtained. In addition, this reaction was also conveniently scaled up, demonstrating the applicability of this protocol.

  6. Intramolecular Diels–Alder Reactions of Cycloalkenones: Stereoselectivity, Lewis Acid Acceleration, and Halogen Substituent Effects

    PubMed Central

    2015-01-01

    The intramolecular Diels–Alder reactions of cycloalkenones and terminal dienes occur with high endo stereoselectivity, both thermally and under Lewis-acidic conditions. Through computations, we show that steric repulsion and tether conformation govern the selectivity of the reaction, and incorporation of either BF3 or α-halogenation increases the rate of cycloaddition. With a longer tether, isomerization from a terminal diene to the more stable internal diene results in a more facile cycloaddition. PMID:24410341

  7. Nonaqueous Halide-Free Flux Reactions with Tin-Based Solders

    NASA Astrophysics Data System (ADS)

    Qu, Guoying; Weinman, Craig J.; Ghosh, Tanushree; Flake, John C.

    2015-04-01

    New halide-free fluxes are becoming more prevalent in electronic packaging; however, their efficacy and reactive behavior with conventional solders has not been well characterized. In this work, we examine nonaqueous halide-free flux reactions of tin (Sn)-based solder surfaces using electrochemical methods. Cyclic voltammetry was used to study reactions of Sn(II) and Sn(IV) species, x-ray photoelectron spectroscopy (XPS) was used to study surface chemistry, and chronopotentiometry was used to quantify equilibrium constants of Sn-carboxylic complexes. Reactions were investigated using carboxylic acid solutions such as adipic acid or maleic acid in polyethylene glycol. Carboxylic acid-based fluxes are practically inactive toward SnO2 removal at room temperature (25°C); however, some species are capable of removing the oxides at temperatures as high as 180°C and at pH as low as 0.1. XPS results suggest the H+ activity of the carboxylic acid is the key to removing SnO2 on Sn-based solder surfaces. Equilibrium coefficients and potential-pH diagrams are given to elucidate the influence of pH on Sn surfaces.

  8. Evidence that protons can be the active catalysts in Lewis acid mediated hetero-Michael addition reactions.

    PubMed

    Wabnitz, Tobias C; Yu, Jin-Quan; Spencer, Jonathan B

    2004-01-23

    The mechanism of Lewis acid catalysed hetero-Michael addition reactions of weakly basic nucleophiles to alpha,beta-unsaturated ketones was investigated. Protons, rather than metal ions, were identified as the active catalysts. Other mechanisms have been ruled out by analyses of side products and of stoichiometric enone-catalyst mixtures and by the use of radical inhibitors. No evidence for the involvement of pi-olefin-metal complexes or for carbonyl-metal-ion interactions was obtained. The reactions did not proceed in the presence of the non-coordinating base 2,6-di-tert-butylpyridine. An excellent correlation of catalytic activities with cation hydrolysis constants was obtained. Different reactivities of mono- and dicarbonyl substrates have been rationalised. A (1)H NMR probe for the assessment of proton generation was established and Lewis acids have been classified according to their propensity to hydrolyse in organic solvents. Brønsted acid-catalysed conjugate addition reactions of nitrogen, oxygen, sulfur and carbon nucleophiles are developed and implications for asymmetric Lewis acid catalysis are discussed.

  9. A general paradigm to model reaction-based biogeochemical processes in batch systems

    NASA Astrophysics Data System (ADS)

    Fang, Yilin; Yeh, Gour-Tsyh; Burgos, William D.

    2003-04-01

    This paper presents the development and illustration of a numerical model of reaction-based geochemical and biochemical processes with mixed equilibrium and kinetic reactions. The objective is to provide a general paradigm for modeling reactive chemicals in batch systems, with expectations that it is applicable to reactive chemical transport problems. The unique aspects of the paradigm are to simultaneously (1) facilitate the segregation (isolation) of linearly independent kinetic reactions and thus enable the formulation and parameterization of individual rates one reaction by one reaction when linearly dependent kinetic reactions are absent, (2) enable the inclusion of virtually any type of equilibrium expressions and kinetic rates users want to specify, (3) reduce problem stiffness by eliminating all fast reactions from the set of ordinary differential equations governing the evolution of kinetic variables, (4) perform systematic operations to remove redundant fast reactions and irrelevant kinetic reactions, (5) systematically define chemical components and explicitly enforce mass conservation, (6) accomplish automation in decoupling fast reactions from slow reactions, and (7) increase the robustness of numerical integration of the governing equations with species switching schemes. None of the existing models to our knowledge has included these scopes simultaneously. This model (BIOGEOCHEM) is a general computer code to simulate biogeochemical processes in batch systems from a reaction-based mechanistic standpoint, and is designed to be easily coupled with transport models. To make the model applicable to a wide range of problems, programmed reaction types include aqueous complexation, adsorption-desorption, ion-exchange, oxidation-reduction, precipitation-dissolution, acid-base reactions, and microbial mediated reactions. In addition, user-specified reaction types can be programmed into the model. Any reaction can be treated as fast/equilibrium or slow

  10. Kinetics and Quantitative Structure—Activity Relationship Study on the Degradation Reaction from Perfluorooctanoic Acid to Trifluoroacetic Acid

    PubMed Central

    Gong, Chen; Sun, Xiaomin; Zhang, Chenxi; Zhang, Xue; Niu, Junfeng

    2014-01-01

    Investigation of the degradation kinetics of perfluorooctanoic acid (PFOA) has been carried out to calculate rate constants of the main elementary reactions using the multichannel Rice-Ramsperger-Kassel-Marcus theory and canonical variational transition state theory with small-curvature tunneling correction over a temperature range of 200~500 K. The Arrhenius equations of rate constants of elementary reactions are fitted. The decarboxylation is role step in the degradation mechanism of PFOA. For the perfluorinated carboxylic acids from perfluorooctanoic acid to trifluoroacetic acid, the quantitative structure–activity relationship of the decarboxylation was analyzed with the genetic function approximation method and the structure–activity model was constructed. The main parameters governing rate constants of the decarboxylation reaction from the eight-carbon chain to the two-carbon chain were obtained. As the structure–activity model shows, the bond length and energy of C1–C2 (RC1–C2 and EC1–C2) are positively correlated to rate constants, while the volume (V), the energy difference between EHOMO and ELUMO (ΔE), and the net atomic charges on atom C2 (QC2) are negatively correlated. PMID:25196516

  11. Closed cycle ion exchange method for regenerating acids, bases and salts

    DOEpatents

    Dreyfuss, Robert M.

    1976-01-01

    A method for conducting a chemical reaction in acidic, basic, or neutral solution as required and then regenerating the acid, base, or salt by means of ion exchange in a closed cycle reaction sequence which comprises contacting the spent acid, base, or salt with an ion exchanger, preferably a synthetic organic ion-exchange resin, so selected that the counter ions thereof are ions also produced as a by-product in the closed reaction cycle, and then regenerating the spent ion exchanger by contact with the by-product counter ions. The method is particularly applicable to closed cycle processes for the thermochemical production of hydrogen.

  12. ortho-Lithium/magnesium carboxylate-driven aromatic nucleophilic substitution reactions on unprotected naphthoic acids.

    PubMed

    Aissaoui, Regadia; Nourry, Arnaud; Coquel, Ariane; Dao, Thi Thanh Hà; Derdour, Aicha; Helesbeux, Jean-Jacques; Duval, Olivier; Castanet, Anne-Sophie; Mortier, Jacques

    2012-01-06

    Substitution of an ortho-fluoro or methoxy group in 1- and 2-naphthoic acids furnishing substituted naphthoic acids occurs in good to excellent yields upon reaction with alkyl/vinyl/aryl organolithium and Grignard reagents, in the absence of a metal catalyst without the need to protect the carboxyl (CO(2)H) group. This novel nucleophilic aromatic substitution is presumed to proceed via a precoordination of the organometallic with the substrate, followed by an addition/elimination.

  13. Determination of free fatty acids and triglycerides by gas chromatography using selective esterification reactions.

    PubMed

    Kail, Brian W; Link, Dirk D; Morreale, Bryan D

    2012-01-01

    A method for selectively determining both free fatty acids (FFA) and triacylglycerides (TAGs) in biological oils was investigated and optimized using gas chromatography after esterification of the target species to their corresponding fatty acid methyl esters (FAMEs). The method used acid catalyzed esterification in methanolic solutions under conditions of varying severity to achieve complete conversion of more reactive FFAs while preserving the concentration of TAGs. Complete conversion of both free acids and glycerides to corresponding FAMEs was found to require more rigorous reaction conditions involving heating to 120°C for up to 2 h. Method validation was provided using gas chromatography-flame ionization detection, gas chromatography-mass spectrometry, and liquid chromatography-mass spectrometry. The method improves on existing methods because it allows the total esterified lipid to be broken down by FAMEs contributed by FFA compared to FAMEs from both FFA and TAGs. Single and mixed-component solutions of pure fatty acids and triglycerides, as well as a sesame oil sample to simulate a complex biological oil, were used to optimize the methodologies. Key parameters that were investigated included: HCl-to-oil ratio, temperature and reaction time. Pure free fatty acids were found to esterify under reasonably mild conditions (10 min at 50°C with a 2.1:1 HCl to fatty acid ratio) with 97.6 ± 2.3% recovery as FAMEs, while triglycerides were largely unaffected under these reaction conditions. The optimized protocol demonstrated that it is possible to use esterification reactions to selectively determine the free acid content, total lipid content, and hence, glyceride content in biological oils. This protocol also allows gas chromatography analysis of FAMEs as a more ideal analyte than glyceride species in their native state.

  14. Chiral phosphoric acid catalyzed enantioselective 1,3-dipolar cycloaddition reaction of azlactones.

    PubMed

    Zhang, Zhenhua; Sun, Wangsheng; Zhu, Gongming; Yang, Junxian; Zhang, Ming; Hong, Liang; Wang, Rui

    2016-01-25

    The first chiral phosphoric acid catalyzed highly diastereo- and enantioselective 1,3-dipolar cycloaddition reaction of azlactones and methyleneindolinones was disclosed. By using a BINOL-derived chiral phosphoric acid as the catalyst, azlactones were activated as chiral anti N-protonated 1,3-dipoles to react with methyleneindolinones to yield biologically important 3,3'-pyrrolidonyl spirooxindole scaffolds in high yields, with good-to-excellent diastereo- and enantioselectivity.

  15. Identification of hydroxycinnamic acid-maillard reaction products in low-moisture baking model systems.

    PubMed

    Jiang, Deshou; Chiaro, Christopher; Maddali, Pranav; Prabhu, K Sandeep; Peterson, Devin G

    2009-11-11

    The chemistry and fate of hydroxycinnamic acids (ferulic, p-coumeric, caffeic, sinapic, and cinnamic acid) in a glucose/glycine simulated baking model (10% moisture at 200 degrees C for 15 min) were investigated. Liquid chromatography-mass spectrometry analysis of glucose/glycine and glucose/glycine/hydroxycinnamic acid model systems confirmed the phenolics reacted with Maillard intermediates; two main reaction product adducts were reported. On the basis of isotopomeric analysis, LC-MS, and NMR spectroscopy, structures of two ferulic acid-Maillard reaction products were identified as 6-(4-hydroxy-3-methoxyphenyl)-5-(hydroxymethyl)-8-oxabicyclo[3.2.1]oct-3-en-2-one (adduct I) and 2-(6-(furan-2-yl)-7-(4-hydroxy-3-methoxyphenyl)-1-methyl-3-oxo-2,5-diazabicyclo[2.2.2]oct-5-en-2-yl)acetic acid (adduct II). In addition, a pyrazinone-type Maillard product, 2-(5-(furan-2-yl)-6-methyl-2-oxopyrazin-1(2H)-yl) acetic acid (IIa), was identified as an intermediate for reaction product adduct II, whereas 3-deoxy-2-hexosulose was identified as an intermediate of adduct I. Both adducts I and II were suggested to be generated by pericyclic reaction mechanisms. Quantitative gas chromatography (GC) analysis and liquid chromatography (LC) also indicated that the addition of ferulic acid to a glucose/glycine model significantly reduced the generation of select Maillard-type aroma compounds, such as furfurals, methylpyrazines, 2-acetylfuran, 2-acetylpyridine, 2-acetylpyrrole, and cyclotene as well as inhibited color development in these Maillard models. In addition, adducts I and II suppressed the bacterial lipopolysaccharide (LPS)-mediated expression of two prototypical pro-inflammatory genes, inducible nitric oxide synthase (iNOS) and cyclooxygenase (COX)-2, in an in vitro murine macrophage model; ferulic acid reported negligible activity.

  16. Determination of Free Fatty Acids and Triglycerides by Gas Chromatography Using Selective Esterification Reactions

    SciTech Connect

    Kail, Brian W; Link, Dirk D; Morreale, Bryan D

    2012-11-01

    A method for selectively determining both free fatty acids (FFA) and triacylglycerides (TAGs) in biological oils was investigated and optimized using gas chromatography after esterification of the target species to their corresponding fatty acid methyl esters (FAMEs). The method used acid catalyzed esterification in methanolic solutions under conditions of varying severity to achieve complete conversion of more reactive FFAs while preserving the concentration of TAGs. Complete conversion of both free acids and glycerides to corresponding FAMEs was found to require more rigorous reaction conditions involving heating to 120°C for up to 2 h. Method validation was provided using gas chromatography–flame ionization detection, gas chromatography–mass spectrometry, and liquid chromatography–mass spectrometry. The method improves on existing methods because it allows the total esterified lipid to be broken down by FAMEs contributed by FFA compared to FAMEs from both FFA and TAGs. Single and mixed-component solutions of pure fatty acids and triglycerides, as well as a sesame oil sample to simulate a complex biological oil, were used to optimize the methodologies. Key parameters that were investigated included: HCl-to-oil ratio, temperature and reaction time. Pure free fatty acids were found to esterify under reasonably mild conditions (10 min at 50°C with a 2.1:1 HCl to fatty acid ratio) with 97.6 ± 2.3% recovery as FAMEs, while triglycerides were largely unaffected under these reaction conditions. The optimized protocol demonstrated that it is possible to use esterification reactions to selectively determine the free acid content, total lipid content, and hence, glyceride content in biological oils. This protocol also allows gas chromatography analysis of FAMEs as a more ideal analyte than glyceride species in their native state.

  17. Influence of reaction condition on viscosity of polyurethane modified epoxy based on glycerol monooleate

    NASA Astrophysics Data System (ADS)

    Triwulandari, Evi; Ramadhan, Mohammad Kemilau; Ghozali, Muhammad

    2017-01-01

    Polyurethane modified epoxy based on glycerol monooleate (PME-GMO) was synthesized. GMO as polyol for synthesis of PME-GMO was synthesized via Fisher Esterification between oleic acid from palm oil and glycerol by using sulfuric acid as catalyst with time variation i.e. 3, 4, 5 and 6 hours at 160°C. Characterizations of GMO were carried out by analysis of acid number, hydroxyl value and FTIR. The data show that the conversion of oleic acid to ester compound is directly proportional with the increasing of reaction time but the enhancement is not significant after 3 hours. Furthermore, GMO product was used as polyol for modification of epoxy with polyurethane. Modification of epoxy with polyurethane was performed by reacted epoxy, tolonate and GMO simultaneously in one step. In this research, the reaction condition was varied i.e. time reaction (0.5; 1; 1.5; 2; 2.5 hours), composition of polyurethane used (10%, 20% toward epoxy) and rasio of tolonate and GMO (NCO/OH ratio) as component of polyurethane (1.5 and 2.5). Characterization of polyurethane modified epoxy based on glycerol (PME-GMO) was conducted by viscosity and FTIR analysis. The viscosity of PME-GMO increased with increasing of reaction time, polyurethane composition and NCO/OH ratio.

  18. Differentiation of Gram-Negative, Nonfermentative Bacteria Isolated from Biofilters on the Basis of Fatty Acid Composition, Quinone System, and Physiological Reaction Profiles

    PubMed Central

    Lipski, André; Klatte, Stefan; Bendinger, Bernd; Altendorf, Karlheinz

    1992-01-01

    Gram-negative, nonfermentative bacteria isolated from biofilters for off-gas treatment of animal-rendering-plant emissions were differentiated by whole-cell fatty acid analysis, quinone analysis, and numerical taxonomy based on their physiological reaction profiles. The last system consisted of 60 physiological tests and was arranged as a microtest system on microtitration plates. Based on fatty acid analyses, 31 isolates were separated into six clusters and five single-member clusters. The isolates of two clusters were identified as Alcaligenes faecalis and Pseudomonas diminuta. The remaining nine clusters were characterized by their fatty acid profiles, quinone systems, and physiological reaction profiles. Clusters resulting from fatty acid analyses were compared with those resulting from physiological reaction profiles. Six clusters could be confirmed this way. The efficiency of the physiological test system was increased by the prearrangement of the isolates according to their quinone type. PMID:16348724

  19. Study of the ammonia (gas)-sulfuric acid (aerosol) reaction rate

    SciTech Connect

    McMurry, P.H.; Takano, H.; Anderson, G.R.

    1983-06-01

    An experimental study of the reaction rate between monodisperse sulfuric acid aerosols and ammonia gas is described. Reactions took place in a laminar flow reactor at 24/sup 0/C and 6% relative humidity, and reaction products were sampled from the core of the flow so that reaction times were well defined. For the data reported here, the reaction time was 5.0 +/- 0.5 s, ammonia concentrations ranged from 13 to 63 ppb, and particle sizes ranged from 0.03 to 0.2 ..mu..m. The extent of reaction was determined by comparing the hygroscopic and deliquescent properties of the product aerosols with known properties of aerosols consisting of internal mixtures of sulfuric acid and ammonium sulfate. It was found that the average fraction of ammonia-aerosol collisions that resulted in chemical reaction during neutralization decreased from 0.40 +/- 0.10 for 0.058-..mu..m particles to 0.18 +/- 0.03 for 0.10-..mu..m particles. Differential mobility analyzers were used for generating the monodisperse aerosols and also for measuring the hygroscopic and deliquescent properties of the product aerosols.

  20. Reduction of carbadox mediated by reaction of Mn(III) with oxalic acid.

    PubMed

    Chen, Wan-Ru; Liu, Cun; Boyd, Stephen A; Teppen, Brian J; Li, Hui

    2013-02-05

    Manganese(III) geocomponents are commonly found in the soil environment, yet their roles in many biogeochemical processes remain unknown. In this study, we demonstrated that Mn(III) generated from the reaction of MnO(2) and oxalic acid caused rapid and extensive decompositions of a quinoxaline-di-N-oxide antibiotics, viz carbadox. The reaction occurred primarily at the quinoxaline-di-N-oxide moiety resulting in the removal of one -O from N1-oxide and formation of desoxycarbadox. The reaction rate was accelerated by increasing amounts of Mn(III), carbadox and oxalate. The critical step in the overall reaction was the formation of a quinoxaline-di-N-oxide/Mn(III)/oxalate ternary complex in which Mn(III) functioned as the central complexing cation and electron conduit in which the arrangement of ligands facilitated electron transfer from oxalate to carbadox. In the complex, the C-C bond in oxalate was cleaved to create CO(2)(-•) radicals, followed by electron transfer to carbadox through the Mn(III) center. This proposed reaction mechanism is supported by the reaction products formed, reaction kinetics, and quantum mechanical calculations. The results obtained from this study suggest that naturally occurring Mn(III)-oxalic acid complexes could reductively decompose certain organic compounds in the environment such as the antibiotic quinoxaline-di-N-oxide.

  1. Two Cases of Adverse Reactions of Hyaluronic Acid–based Filler Injections

    PubMed Central

    Fan, Xing; Dong, Ming; Li, Tong; Ma, Qiaoxin

    2016-01-01

    Hyaluronic acid (HA) is one of the natural components of the human body with high biocompatibility, biodegradability, and nonimmunogenicity, which makes it the ideal biomedical filling agent currently available. However, for many medical practitioners, HA filler injections remain a relatively new item to carry out. Learning while practicing, it is inevitable to encounter some difficulties and adverse reactions in its application. Here we report two cases of adverse reactions to HA-based filler injections, including anaphylactic reaction on the face and vascular thrombosis after augmentation rhinoplasty with HA filler. In this report, we highlight the management and prevention of the adverse reactions, especially in case 2, because vascular thrombosis is one of the severe complications and injectors should know how to avoid it and how to deal with it, thereby increasing the safety of HA-based procedures. PMID:28293495

  2. Electrosynthesis of Metal-Organic Frameworks (MOFs)Based on Nickel(II) and Benzene 1,3,5-Tri Carboxylic Acid (H3BTC): An Optimization Reaction Condition

    NASA Astrophysics Data System (ADS)

    Lestari, W. W.; Winarni, I. D.; Rahmawati, F.

    2017-02-01

    Electrosynthesis of metal-organic frameworks based on nickel(II) and benzen 1,3,5-tricarboxylic acid (H3BTC) to form [Ni3(BTC)2] has been conducted. This study aims to determine the optimum electro-synthetic conditions of [Ni3(BTC)2] by varying the solvents, electrolytes, as well as the voltages. The optimum condition was determined based on the percent yield of the product which upon washing and drying at room temperature showed pale green precipitate. The materialhas high crystallinityaccording to XRD analysis with the main peak observed at 2θ 19° and 28° and appropriate with [Ni3(BTC)2] pattern (CCDC No. 1274034). The refinement results using Le Bail methods revealed the Rp and Rwp values are 3.29% and 3.47%, respectively. The coordination between nickel(II) and carboxylate moeties of the linker has been characterized using FTIR and showed significant shift from 1723 cm-1 to 1608 cm-1. The compound has thermal stability up to 400 °C according to TG/DTA analysis. The SEM analysis confirmed that compound has morphology nanoplates shape with a thickness of 75 ± 0.023 nm. Another interesting feature of the obtained material is the occupancy of the reversible frameworks, which proved after methanol absorption. The optimum condition of the electro-synthesis of [Ni3(BTC)2] achieved in the methanol with TBATFB (0.1 M) as electrolyte, and the voltage of 15 V at room temperature with a yield of 99.99%.

  3. An elementary derivation of the hard/soft-acid/base principle.

    PubMed

    Ayers, Paul W

    2005-04-08

    The hard/soft-acid/base (HSAB) principle indicates that hard acids prefer binding to hard bases (often forming bonds with substantial ionic character) while soft acids prefer binding to soft bases (often forming bonds with substantial covalent character). Though the HSAB principle is a foundational concept of the modern theory of acids and bases, the theoretical underpinnings of the HSAB principle remain murky. This paper examines the exchange reaction, wherein two molecules, one the product of reacting a hard acid and a soft base and the other the product of reacting a soft acid with a hard base, exchange substituents to form the preferred hard-hard and soft-soft product. A simple derivation shows that this reaction is exothermic, proving the validity of the HSAB principle. The analysis leads to the simple and conceptually appealing conclusion that the HSAB principle is a driven by simple electron transfer effects.

  4. Acid-base titrations using microfluidic paper-based analytical devices.

    PubMed

    Karita, Shingo; Kaneta, Takashi

    2014-12-16

    Rapid and simple acid-base titration was accomplished using a novel microfluidic paper-based analytical device (μPAD). The μPAD was fabricated by wax printing and consisted of ten reservoirs for reaction and detection. The reaction reservoirs contained various amounts of a primary standard substance, potassium hydrogen phthalate (KHPth), whereas a constant amount of phenolphthalein was added to all the detection reservoirs. A sample solution containing NaOH was dropped onto the center of the μPAD and was allowed to spread to the reaction reservoirs where the KHPth neutralized it. When the amount of NaOH exceeded that of the KHPth in the reaction reservoirs, unneutralized hydroxide ion penetrated the detection reservoirs, resulting in a color reaction from the phenolphthalein. Therefore, the number of the detection reservoirs with no color change determined the concentration of the NaOH in the sample solution. The titration was completed within 1 min by visually determining the end point, which required neither instrumentation nor software. The volumes of the KHPth and phenolphthalein solutions added to the corresponding reservoirs were optimized to obtain reproducible and accurate results for the concentration of NaOH. The μPADs determined the concentration of NaOH at orders of magnitude ranging from 0.01 to 1 M. An acid sample, HCl, was also determined using Na2CO3 as a primary standard substance instead of KHPth. Furthermore, the μPAD was applicable to the titrations of nitric acid, sulfuric acid, acetic acid, and ammonia solutions. The μPADs were stable for more than 1 month when stored in darkness at room temperature, although this was reduced to only 5 days under daylight conditions. The analysis of acidic hot spring water was also demonstrated in the field using the μPAD, and the results agreed well with those obtained by classic acid-base titration.

  5. Kinetic resolution of acids in acylation reactions in the presence of chiral tertiary amines

    SciTech Connect

    Potapov, V.M.; Dem'yanovich, V.M.; Khlebnikov, V.A.

    1988-07-10

    Asymmetric synthesis has now become an important method for the production of optically active compounds, and its most attractive form is asymmetric catalysis. This work was devoted to an investigation into asymmetric catalysis with chiral tertiary amines in acylation reactions. During the acylation of alcohols and amines by the action of racemic 2-phenylpropionic and 2-methyl-3-phenylpropionic acids in the presence of S-nicotine the initial acids are resolved kinetically. The (R)-2-phenylpropionic acid obtained in this way had an optical purity of 0.5-1.5%.

  6. Relativistic effects on acidities and basicities of Brønsted acids and bases containing gold.

    PubMed

    Koppel, Ilmar A; Burk, Peeter; Kasemets, Kalev; Koppel, Ivar

    2013-11-07

    It is usually believed that relativistic effects as described by the Dirac-Schrödinger equation (relative to the classical or time-independent Schrödinger equation) are of little importance in chemistry. A closer look, however, reveals that some important and widely known properties (e.g., gold is yellow, mercury is liquid at room temperature) stem from relativistic effects. So far the influence of relativistic effects on the acid-base properties has been mostly ignored. Here we show that at least for compounds of gold such omission is completely erroneous and would lead to too high basicity and too low acidity values with errors in the range of 25-55 kcal mol(-1) (or 20 to 44 powers of ten in pK(a) units) in the gas-phase. These findings have important implications for the design of new superstrong acids and bases, and for the understanding of gold-catalysed reactions.

  7. Acid-Base Titration of (S)-Aspartic Acid: A Circular Dichroism Spectrophotometry Experiment

    NASA Astrophysics Data System (ADS)

    Cavaleiro, Ana M. V.; Pedrosa de Jesus, Júlio D.

    2000-09-01

    The magnitude of the circular dichroism of (S)-aspartic acid in aqueous solutions at a fixed wavelength varies with the addition of strong base. This laboratory experiment consists of the circular dichroism spectrophotometric acid-base titration of (S)-aspartic acid in dilute aqueous solutions, and the use of the resulting data to determine the ionization constant of the protonated amino group. The work familiarizes students with circular dichroism and illustrates the possibility of performing titrations using a less usual instrumental method of following the course of a reaction. It shows the use of a chiroptical property in the determination of the concentration in solution of an optically active molecule, and exemplifies the use of a spectrophotometric titration in the determination of an ionization constant.

  8. Permanganate oxidation of α-amino acids: kinetic correlations for the nonautocatalytic and autocatalytic reaction pathways.

    PubMed

    Perez-Benito, Joaquin F

    2011-09-08

    The reactions of permanganate ion with seven α-amino acids in aqueous KH(2)PO(4)/K(2)HPO(4) buffers have been followed spectrophotometrically at two different wavelengths: 526 nm (decay of MnO(4)(-)) and 418 nm (formation of colloidal MnO(2)). All of the reactions studied were autocatalyzed by colloidal MnO(2), with the contribution of the autocatalytic reaction pathway decreasing in the order glycine > l-threonine > l-alanine > l-glutamic acid > l-leucine > l-isoleucine > l-valine. The rate constants corresponding to the nonautocatalytic and autocatalytic pathways were obtained by means of either a differential rate law or an integrated one, the latter requiring the use of an iterative method for its implementation. The activation parameters for the two pathways were determined and analyzed to obtain statistically significant correlations for the series of reactions studied. The activation enthalpy of the nonautocatalytic pathway showed a strong, positive dependence on the standard Gibbs energy for the dissociation of the protonated amino group of the α-amino acid. Linear enthalpy-entropy correlations were found for both pathways, leading to isokinetic temperatures of 370 ± 21 K (nonautocatalytic) and 364 ± 28 K (autocatalytic). Mechanisms in agreement with the experimental data are proposed for the two reaction pathways.

  9. Is there a redox reaction between Cu(II) and gallic acid?

    PubMed

    Severino, Joyce Ferreira; Goodman, Bernard A; Reichenauer, Thomas G; Pirker, Katharina F

    2011-02-01

    Interactions between transition metal ions and polyphenols can result in complexation, redox or polymerization, but the relative importance of these reactions is unclear. The present paper reports results from the reaction of gallic acid (GA) with Cu(II) using electron paramagnetic resonance (EPR) and UV/visible spectroscopy for various relative concentrations and pH values. Reduction of Cu(II) by GA does not occur under strongly acidic or strongly alkaline conditions. Di- or polymerization reactions between Cu(II) and carboxylate groups of GA dominate the results at acidic pH, whereas mononuclear complexes increase in importance at higher pH and GA concentrations. There was no evidence for any redox reaction between Cu(II) and GA and free radical formation from GA at high pH was shown to be the consequence of auto-oxidation, which was inhibited by Cu(II). Serious questions are thus raised about the existence of the frequently assumed redox reactions between Cu(II) and polyphenols.

  10. Reactions on sulphuric acid aerosol and on polar stratospheric clouds in the Antarctic stratosphere

    SciTech Connect

    Wolff, E.W.; Mulvaney, R.

    1991-06-01

    Heterogeneous chemistry producing active chlorine has been identified as crucial to Antarctic ozone depletion. Most attention has focused on reactions on solid polar stratospheric cloud (PSC) particles, although there is still no satisfactory understanding of the microchemical incorporation of HCl in PSCs. The alternative mechanism involving sulphuric acid aerosol as the reaction surface has been considered at lower latitudes, but its role in the special conditions of the polar stratosphere has been largely ignored. Recent data from the Antarctic stratosphere have suggested the HCl is present in sulphuric acid aerosol that remains liquid even at the lowest stratospheric temperatures. The available laboratory data show that cold, relatively dilute, sulphuric acid is particularly able to take up HCl that is available for reaction provided the aerosol remains liquid. Fast heterogeneous reaction rates compared to those at mid-latitudes will produce active chlorine rapidly. Since the aerosol is present with significant surface area throughout the lower stratosphere, it should be very effective for heterogeneous reaction once temperatures drop. These surfaces, rather than PSCs, could host the initial conversion of Cl to its active form over the Antarctic.

  11. Determination of the Molar Volume of Hydrogen from the Metal-Acid Reaction: An Experimental Alternative.

    ERIC Educational Resources Information Center

    de Berg, Kevin; Chapman, Ken

    1996-01-01

    Describes an alternative technique for determining the molar volume of hydrogen from the metal-acid reaction in which the metal sample is encased in a specially prepared cage and a pipette filler is used to fill an inverted burette with water. Eliminates some difficulties encountered with the conventional technique. (JRH)

  12. Total synthesis of (±)-epithuriferic acid methyl ester via Diels-Alder reaction.

    PubMed

    Koprowski, Marek; Bałczewski, Piotr; Owsianik, Krzysztof; Różycka-Sokołowska, Ewa; Marciniak, Bernard

    2016-02-07

    In this paper, we have described the first total synthesis of (±)-epithuriferic acid methyl ester from non-natural sources, in four steps (20% overall yield). The key step involves the Diels-Alder reaction of isobenzofuran with methyl 3-(dimethoxyphosphoryl)acrylate which is controlled by "ortho" regio- and endo stereoselectivities due to the COOMe group.

  13. Zeolite-directed cascade reactions: cycliacyarylation versus decarboxyarylation of alpha,beta-unsaturated carboxylic acids.

    PubMed

    Chassaing, Stefan; Kumarraja, Mayilvasagam; Pale, Patrick; Sommer, Jean

    2007-09-27

    The interaction of alpha,beta-unsaturated carboxylic acids with benzene derivatives was investigated in H-zeolites and led to two distinct but competing processes, cycliacyarylation and decarboxyarylation. Interestingly, H-USY selectively induced the cycliacyarylation cascade reaction, whereas H-ZSM5 selectively promoted the decarboxyarylation cascade.

  14. Gasoline compositions containing reaction products of fatty acid esters and amines as carburetor detergents

    SciTech Connect

    Schlicht, R.C.; Herbstman, S.; Levin, M.D.; Sung, R.L.

    1988-03-08

    A motor fuel composition is described comprising (a) a major portion of a fuel consisting essentially of a hydrocarbon boiling in the gasoline boiling range; and (b) a minor effective amount of, as detergent additive, a reaction product of C/sub 6/-C/sub 20/ fatty acid and a mono- or di-(hydroxy hydrocarbyl) amine.

  15. Silylium ion-catalyzed challenging Diels-Alder reactions: the danger of hidden proton catalysis with strong Lewis acids.

    PubMed

    Schmidt, Ruth K; Müther, Kristine; Mück-Lichtenfeld, Christian; Grimme, Stefan; Oestreich, Martin

    2012-03-07

    The pronounced Lewis acidity of tricoordinate silicon cations brings about unusual reactivity in Lewis acid catalysis. The downside of catalysis with strong Lewis acids is, though, that these do have the potential to mediate the formation of protons by various mechanisms, and the thus released Brønsted acid might even outcompete the Lewis acid as the true catalyst. That is an often ignored point. One way of eliminating a hidden proton-catalyzed pathway is to add a proton scavenger. The low-temperature Diels-Alder reactions catalyzed by our ferrocene-stabilized silicon cation are such a case where the possibility of proton catalysis must be meticulously examined. Addition of the common hindered base 2,6-di-tert-butylpyridine resulted, however, in slow decomposition along with formation of the corresponding pyridinium ion. Quantitative deprotonation of the silicon cation was observed with more basic (Mes)(3)P to yield the phosphonium ion. A deuterium-labeling experiment verified that the proton is abstracted from the ferrocene backbone. A reasonable mechanism of the proton formation is proposed on the basis of quantum-chemical calculations. This is, admittedly, a particular case but suggests that the use of proton scavengers must be carefully scrutinized, as proton formation might be provoked rather than prevented. Proton-catalyzed Diels-Alder reactions are not well-documented in the literature, and a representative survey employing TfOH is included here. The outcome of these catalyses is compared with our silylium ion-catalyzed Diels-Alder reactions, thereby clearly corroborating that hidden Brønsted acid catalysis is not operating with our Lewis acid. Several simple-looking but challenging Diels-Alder reactions with exceptionally rare dienophile/enophile combinations are reported. Another indication is obtained from the chemoselectivity of the catalyses. The silylium ion-catalyzed Diels-Alder reaction is general with regard to the oxidation level of the

  16. Study of the chemical mechanisms of the reaction of neutralization of calcium hydroxide by phosphoric acid

    NASA Astrophysics Data System (ADS)

    Elgadi, M.; Mejdoubi, E.; Elansari, L. L.; Essaddek, A.; Abouricha, S.; Lamhamdi, A.

    2005-03-01

    Calcium phosphates reported in this study, are prepared following an acido-basic reaction between phosphoric acid and calcium hydroxide. These phosphates are the brushite, tricalcium phosphate, hydroxyapatite and oxygenated apatite. The follow-up of the reaction by infra-red spectroscopy of absorption showed that the alkaline pH of calcium hydroxide solution, favours the formation of carbonated apatite, at the start of the reaction. Following the addition of phosphoric acid, the pH becomes increasingly favourable to the formation of the desired phase. The insertion of molecular oxygen in the apatitic tunnel is carried out by the use of hydrogen peroxide. The molecular oxygen rate in the apatite is then determined by volumetric analysis.

  17. Chemical remodeling of cell-surface sialic acids through a palladium-triggered bioorthogonal elimination reaction.

    PubMed

    Wang, Jie; Cheng, Bo; Li, Jie; Zhang, Zhaoyue; Hong, Weiyao; Chen, Xing; Chen, Peng R

    2015-04-27

    We herein report a chemical decaging strategy for the in situ generation of neuramic acid (Neu), a unique type of sialic acid, on live cells by the use of a palladium-mediated bioorthogonal elimination reaction. Palladium nanoparticles (Pd NPs) were found to be a highly efficient and biocompatible depropargylation catalyst for the direct conversion of metabolically incorporated N-(propargyloxycarbonyl)neuramic acid (Neu5Proc) into Neu on cell-surface glycans. This conversion chemically mimics the enzymatic de-N-acetylation of N-acetylneuramic acid (Neu5Ac), a proposed mechanism for the natural occurrence of Neu on cell-surface glycans. The bioorthogonal elimination was also exploited for the manipulation of cell-surface charge by unmasking the free amine at C5 to neutralize the negatively charged carboxyl group at C1 of sialic acids.

  18. Synthesis and characterization of polyacids from palm acid oil and sunflower oil via addition reaction.

    PubMed

    Zeimaran, Ehsan; Kadir, Mohammed Rafiq Abdul; Nor, Hussin Mohd; Kamarul, Tunku; Djordjevic, Ivan

    2013-12-15

    In this study aliphatic polyacids were synthesized using palm acid oil (PAO) and sunflower oil (SFO) via addition reaction technique. The synthesized materials were characterized using Fourier-transform infra-red (FTIR) spectroscopy, nuclear magnetic resonance (NMR) spectroscopy, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-ToF-MS) and thermo-gravimetric analysis (TGA). Mixing formic acid and hydrogen peroxide with PAO or SFO at the ratio 3:10:1 produced the lowest iodine value of 10.57 and 9.24 respectively, indicating the increase in epoxidization of both oils. Adding adipic acid to the epoxidized oils at a ratio of 1:10 increases the acid values of SFO and PAO to 11.22 and 6.73 respectively. The existence of multi-acid groups present in synthesized polyacid was confirmed by MALD-ToF-MS. This feature indicates a possible value to the biomaterials development.

  19. Reaction kinetics of waste sulfuric acid using H2O2 catalytic oxidation.

    PubMed

    Wang, Jiade; Hong, Binxun; Tong, Xinyang; Qiu, Shufeng

    2016-12-01

    The process of recovering waste sulfuric acids using H2O2 catalytic oxidation is studied in this paper. Activated carbon was used as catalyst. Main operating parameters, such as temperature, feed rate of H2O2, and catalyst dosage, have effects on the removal of impurities from waste sulfuric acids. The reaction kinetics of H2O2 catalytic oxidation on impurities are discussed. At a temperature of 90°C, H2O2 feeding rate of 50 g (kg waste acid)(-1) per hour, and catalyst dosage of 0.2 wt% (waste acid weight), the removal efficiencies of COD and chrominance were both more than 99%, the recovery ratio of sulfuric acid was more than 95%, and the utilization ratio of H2O2 was 88.57%.

  20. The role of acid catalysis in the Baeyer-Villiger reaction. A theoretical study.

    PubMed

    Bach, Robert D

    2012-08-17

    Quantum mechanical calculations at the B3LYP/6-311+G(d,p) level have examined the overall mechanism of the Baeyer-Villiger (BV) reaction with peroxyacetic acid. A series of reactions that include both the addition step and the subsequent alkyl group migration step included ketones, acetone, t-butyl methyl ketone, acetophenone, cyclohexyl methyl ketone, and cyclohexyl phenyl ketone. The combined data suggested that the first step for addition of the peroxyacetic acid oxidation catalyst to the ketone carbonyl to produce the Criegee or tetrahedral intermediate is rate-limiting and has activation barriers that range from 38 to 41 kcal/mol without the aid of a catalyst. The rate of addition is markedly reduced by the catalytic action of a COOH functionality acting as a donor-acceptor group affecting both its proton transfer to the ketone C═O oxygen in concert with transfer of the OOH proton to the carboxylic acid carbonyl. The second or alkyl group migration step has a much reduced activation barrier, and its rate is not markedly influenced by acid catalysis. The rate of both steps in the BV reaction is greatly influenced by the catalytic action of very strong acids.

  1. Acid and base degraded products of ketorolac.

    PubMed

    Salaris, Margherita; Nieddu, Maria; Rubattu, Nicola; Testa, Cecilia; Luongo, Elvira; Rimoli, Maria Grazia; Boatto, Gianpiero

    2010-06-05

    The stability of ketorolac tromethamine was investigated in acid (0.5M HCl) and alkaline conditions (0.5M NaOH), using the same procedure reported by Devarajan et al. [2]. The acid and base degradation products were identified by liquid chromatography-mass spectrometry (LC-MS).

  2. Reaction of Hydrogen Sulfide with Disulfide and Sulfenic Acid to Form the Strongly Nucleophilic Persulfide.

    PubMed

    Cuevasanta, Ernesto; Lange, Mike; Bonanata, Jenner; Coitiño, E Laura; Ferrer-Sueta, Gerardo; Filipovic, Milos R; Alvarez, Beatriz

    2015-11-06

    Hydrogen sulfide (H2S) is increasingly recognized to modulate physiological processes in mammals through mechanisms that are currently under scrutiny. H2S is not able to react with reduced thiols (RSH). However, H2S, more precisely HS(-), is able to react with oxidized thiol derivatives. We performed a systematic study of the reactivity of HS(-) toward symmetric low molecular weight disulfides (RSSR) and mixed albumin (HSA) disulfides. Correlations with thiol acidity and computational modeling showed that the reaction occurs through a concerted mechanism. Comparison with analogous reactions of thiolates indicated that the intrinsic reactivity of HS(-) is 1 order of magnitude lower than that of thiolates. In addition, H2S is able to react with sulfenic acids (RSOH). The rate constant of the reaction of H2S with the sulfenic acid formed in HSA was determined. Both reactions of H2S with disulfides and sulfenic acids yield persulfides (RSSH), recently identified post-translational modifications. The formation of this derivative in HSA was determined, and the rate constants of its reactions with a reporter disulfide and with peroxynitrite revealed that persulfides are better nucleophiles than thiols, which is consistent with the α effect. Experiments with cells in culture showed that treatment with hydrogen peroxide enhanced the formation of persulfides. Biological implications are discussed. Our results give light on the mechanisms of persulfide formation and provide quantitative evidence for the high nucleophilicity of these novel derivatives, setting the stage for understanding the contribution of the reactions of H2S with oxidized thiol derivatives to H2S effector processes.

  3. Timescale analysis of rule-based biochemical reaction networks

    PubMed Central

    Klinke, David J.; Finley, Stacey D.

    2012-01-01

    The flow of information within a cell is governed by a series of protein-protein interactions that can be described as a reaction network. Mathematical models of biochemical reaction networks can be constructed by repetitively applying specific rules that define how reactants interact and what new species are formed upon reaction. To aid in understanding the underlying biochemistry, timescale analysis is one method developed to prune the size of the reaction network. In this work, we extend the methods associated with timescale analysis to reaction rules instead of the species contained within the network. To illustrate this approach, we applied timescale analysis to a simple receptor-ligand binding model and a rule-based model of Interleukin-12 (IL-12) signaling in näive CD4+ T cells. The IL-12 signaling pathway includes multiple protein-protein interactions that collectively transmit information; however, the level of mechanistic detail sufficient to capture the observed dynamics has not been justified based upon the available data. The analysis correctly predicted that reactions associated with JAK2 and TYK2 binding to their corresponding receptor exist at a pseudo-equilibrium. In contrast, reactions associated with ligand binding and receptor turnover regulate cellular response to IL-12. An empirical Bayesian approach was used to estimate the uncertainty in the timescales. This approach complements existing rank- and flux-based methods that can be used to interrogate complex reaction networks. Ultimately, timescale analysis of rule-based models is a computational tool that can be used to reveal the biochemical steps that regulate signaling dynamics. PMID:21954150

  4. High Performance Fatty Acid-Based Vinyl Ester Resin for Liquid Molding

    DTIC Science & Technology

    2007-07-01

    Diglycidyl ether of bisphenol-A ( DGEBA ) Methacrylic Acid Figure 1: The reaction of DGEBA and methacrylic acid to produce the vinyl ester 2.3...High Performance Fatty Acid -Based Vinyl Ester Resin for Liquid Molding by Xing Geng, John J. La Scala, James M. Sands, and Giuseppe R...it to the originator. Army Research Laboratory Aberdeen Proving Ground, MD 21005-5069 ARL-RP-184 July 2007 High Performance Fatty Acid

  5. Base reaction optimization of redundant manipulators for space applications

    NASA Technical Reports Server (NTRS)

    Chung, C. L.; Desa, S.; Desilva, C. W.

    1988-01-01

    One of the problems associated with redundant manipulators which were proposed for space applications is that the reactions transmitted to the base of the manipulator as a result of the motion of the manipulator will cause undesirable effects on the dynamic behavior of the supporting space structure. It is therefore necessary to minimize the magnitudes of the forces and moments transmitted to the base. It is shown that kinematic redundancy can be used to solve the dynamic problem of minimizing the magnitude of the base reactions. The methodology described is applied to a four degree-of-freedom spatial manipulator with one redundant degree-of-freedom.

  6. Heterogeneous Reactions of Acetic Acid with Oxide Surfaces: Effects of Mineralogy and Relative Humidity.

    PubMed

    Tang, Mingjin; Larish, Whitney A; Fang, Yuan; Gankanda, Aruni; Grassian, Vicki H

    2016-07-21

    We have investigated the heterogeneous uptake of gaseous acetic acid on different oxides including γ-Al2O3, SiO2, and CaO under a range of relative humidity conditions. Under dry conditions, the uptake of acetic acid leads to the formation of both acetate and molecularly adsorbed acetic acid on γ-Al2O3 and CaO and only molecularly adsorbed acetic acid on SiO2. More importantly, under the conditions of this study, dimers are the major form for molecularly adsorbed acetic acid on all three particle surfaces investigated, even at low acetic acid pressures under which monomers are the dominant species in the gas phase. We have also determined saturation surface coverages for acetic acid adsorption on these three oxides under dry conditions as well as Langmuir adsorption constants in some cases. Kinetic analysis shows that the reaction rate of acetic acid increases by a factor of 3-5 for γ-Al2O3 when relative humidity increases from 0% to 15%, whereas for SiO2 particles, acetic acid and water are found to compete for surface adsorption sites.

  7. Hypochlorous acid-mediated protein oxidation: how important are chloramine transfer reactions and protein tertiary structure?

    PubMed

    Pattison, David I; Hawkins, Clare L; Davies, Michael J

    2007-08-28

    Hypochlorous acid (HOCl) is a powerful oxidant generated from H2O2 and Cl- by the heme enzyme myeloperoxidase, which is released from activated leukocytes. HOCl possesses potent antibacterial properties, but excessive production can lead to host tissue damage that occurs in numerous human pathologies. As proteins and amino acids are highly abundant in vivo and react rapidly with HOCl, they are likely to be major targets for HOCl. In this study, two small globular proteins, lysozyme and insulin, have been oxidized with increasing excesses of HOCl to determine whether the pattern of HOCl-mediated amino acid consumption is consistent with reported kinetic data for isolated amino acids and model compounds. Identical experiments have been carried out with mixtures of N-acetyl amino acids (to prevent reaction at the alpha-amino groups) that mimic the protein composition to examine the role of protein structure on reactivity. The results indicate that tertiary structure facilitates secondary chlorine transfer reactions of chloramines formed on His and Lys side chains. In light of these data, second-order rate constants for reactions of Lys side chain and Gly chloramines with Trp side chains and disulfide bonds have been determined, together with those for further oxidation of Met sulfoxide by HOCl and His side chain chloramines. Computational kinetic models incorporating these additional rate constants closely predict the experimentally observed amino acid consumption. These studies provide insight into the roles of chloramine formation and three-dimensional structure on the reactions of HOCl with isolated proteins and demonstrate that kinetic models can predict the outcome of HOCl-mediated protein oxidation.

  8. Acid-base equilibria involved in secondary reactions following the 4-carboxybenzophenone sensitized photooxidation of methionylglycine in aqueous solution. Spectral and time resolution of the decaying (S...N){sup +} radical cation

    SciTech Connect

    Hug, G.L.; Marciniak, B. |; Bobrowski, K. ||

    1996-09-05

    A radical cation with an intramolecular sulfur-nitrogen bond was formed in the photoinitiated transfer of an electron from the sulfur atom of the dipeptide Met-Gly to 4-carboxybenzophenone in its triplet state. The sulfur-nitrogen coupling involved two-center, three-electron bonds. The kinetics of the reactions of these radical cations, which were initiated by a laser flash, were followed over time. The principal method of implementing the spectral resolutions was accomplished through a multiple linear regression technique. This spectral analysis was repeated for numerous time windows during the lifetime of the transients` decays. The resulting concentrations of the transients were consistent with an independent factor analysis. It was found that the decay of the radical cations was multiexponential and that the decay varied with pH. A simplified reaction scheme was proposed whereby the absorbing radical cations can alternatively decay by an irreversible channel or react reversibly with OH{sup -}. Rate constants for the three elementary reactions of this scheme were determined from an analysis of the decay of the concentration of the radical cations. In addition, the equilibrium constant for the reversible reaction was determined by two separate procedures. 35 refs., 7 figs., 2 tabs.

  9. Relative Reaction Rates of Sulfamic Acid and Hydroxylamine with Nitric Acid

    SciTech Connect

    Karraker, D.G.

    2001-03-28

    This report describes a study of comparative reaction rates where the reductant is in excess, as in the 1B bank in the Purex process. The results of this work apply to planned plant tests to partially substitute HAN for the ferrous sulfamate reductant in the Purex 1B bank.

  10. Water-catalyzed gas-phase reaction of formic acid with hydroxyl radical: A computational investigation

    NASA Astrophysics Data System (ADS)

    Luo, Yi; Maeda, Satoshi; Ohno, Koichi

    2009-02-01

    The reaction of formic acid with hydroxyl radical, which is considered to be relevant to atmospheric chemistry, has been extensively studied. A water-catalyzed process of this reaction is computationally studied here for the first time. The scaled hypersphere search method was used for global exploration of pre-reaction complexes. Calculations were performed at high level of theory, such as CCSD(T)/cc-pVTZ//B3LYP/6-311+G(2df, 2p) and CCSD(T)/cc-pVTZ//MP2/aug-cc-pVDZ. It is found that the water-catalyzed process of this reaction is more kinetically favorable than its non-catalytic process. Such catalytic process may also be of interest for atmospheric chemistry, like the non-catalytic one.

  11. Isocyanide based [4+1] cycloaddition reactions: an indispensable tool in multi-component reactions (MCRs).

    PubMed

    Kaur, Tanpreet; Wadhwa, Preeti; Bagchi, Sourav; Sharma, Anuj

    2016-05-19

    The advent of cycloaddition reactions in the synthesis of heterocycles and their ever burgeoning applications in the fields of material chemistry, catalysis and drugs have been a profound scientific development. In particular, isocyanide based cycloaddition reactions have been harbingers of an exciting new chapter in the realms of organic synthesis. The emergence of numerous synthetic protocols utilizing formal cycloaddition of isocyanides with conjugated heterodienes has unleashed countless opportunities to design and synthesize diverse heterocyclic scaffolds. To date, there has not been any exclusive review on a formal [4+1] cycloaddition involving isocyanides. The present review highlights the journey of formal [4+1] cycloaddition reactions of isocyanides with diverse electrophilic substrates viz. oxadienes, azadienes, thioacyl imines, alkylidene amides, alkylidene hydrazines, α,β-unsaturated nitro compounds, α-thioxothioamides, nitroso alkenes, acyl imines, vinyl ketenes, vinyl isocyanates, etc. to afford functionalized pyrroles, imidazoles, furans, oxazoles, pyrazoles, etc.

  12. Whole body acid-base modeling revisited.

    PubMed

    Ring, Troels; Nielsen, Søren

    2017-04-01

    The textbook account of whole body acid-base balance in terms of endogenous acid production, renal net acid excretion, and gastrointestinal alkali absorption, which is the only comprehensive model around, has never been applied in clinical practice or been formally validated. To improve understanding of acid-base modeling, we managed to write up this conventional model as an expression solely on urine chemistry. Renal net acid excretion and endogenous acid production were already formulated in terms of urine chemistry, and we could from the literature also see gastrointestinal alkali absorption in terms of urine excretions. With a few assumptions it was possible to see that this expression of net acid balance was arithmetically identical to minus urine charge, whereby under the development of acidosis, urine was predicted to acquire a net negative charge. The literature already mentions unexplained negative urine charges so we scrutinized a series of seminal papers and confirmed empirically the theoretical prediction that observed urine charge did acquire negative charge as acidosis developed. Hence, we can conclude that the conventional model is problematic since it predicts what is physiologically impossible. Therefore, we need a new model for whole body acid-base balance, which does not have impossible implications. Furthermore, new experimental studies are needed to account for charge imbalance in urine under development of acidosis.

  13. Synthesis of new kojic acid based unnatural α-amino acid derivatives.

    PubMed

    Balakrishna, C; Payili, Nagaraju; Yennam, Satyanarayana; Devi, P Uma; Behera, Manoranjan

    2015-11-01

    An efficient method for the preparation of kojic acid based α-amino acid derivatives by alkylation of glycinate schiff base with bromokojic acids have been described. Using this method, mono as well as di alkylated kojic acid-amino acid conjugates have been prepared. This is the first synthesis of C-linked kojic acid-amino acid conjugate where kojic acid is directly linked to amino acid through a C-C bond.

  14. Enzymatic Kolbe-Schmitt reaction to form salicylic acid from phenol: enzymatic characterization and gene identification of a novel enzyme, Trichosporon moniliiforme salicylic acid decarboxylase.

    PubMed

    Kirimura, Kohtaro; Gunji, Hiroaki; Wakayama, Rumiko; Hattori, Takasumi; Ishii, Yoshitaka

    2010-04-02

    Salicylic acid decarboxylase (Sdc) can produce salicylic acid from phenol; it was found in the yeast Trichosporon moniliiforme WU-0401 and was for the first time enzymatically characterized, with the sdc gene heterologously expressed. Sdc catalyzed both reactions: decarboxylation of salicylic acid to phenol and the carboxylation of phenol to form salicylic acid without any byproducts. Both reactions were detected without the addition of any cofactors and occurred even in the presence of oxygen, suggesting that this Sdc is reversible, nonoxidative, and oxygen insensitive. Therefore, it is readily applicable in the selective production of salicylic acid from phenol, the enzymatic Kolbe-Schmitt reaction. The deduced amino acid sequence of the gene, sdc, encoding Sdc comprises 350 amino acid residues corresponding to a 40-kDa protein. The recombinant Escherichia coli BL21(DE3) expressing sdc converted phenol to salicylic acid with a 27% (mol/mol) yield at 30 degrees C for 9h.

  15. Reaction conditions affecting the relationship between thiobarbituric acid reactivity and lipid peroxides in human plasma.

    PubMed

    Lapenna, D; Ciofani, G; Pierdomenico, S D; Giamberardino, M A; Cuccurullo, F

    2001-08-01

    The thiobarbituric acid (TBA) reactivity of human plasma was studied to evaluate its adequacy in quantifying lipid peroxidation as an index of systemic oxidative stress. Two spectrophotometric TBA tests based on the use of either phosphoric acid (pH 2.0, method A) or trichloroacetic plus hydrochloric acid (pH 0.9, method B) were employed with and without sodium sulfate (SS) to inhibit sialic acid (SA) reactivity with TBA. To correct for background absorption, the absorbance values at 572 nm were subtracted from those at 532 nm, which represent the absorption maximum of the TBA:MDA adduct. Method B gave values of TBA-reactive substances (TBARS) 2-fold higher than those detected with method A. SS lowered TBARS by about 50% with both methods, indicating a significant involvement of SA in plasma TBA reactivity. Standard SA, at a physiologically relevant concentration of 1.5 mM, reacted with TBA, creating interference problems, which were substantially eliminated by SS plus correction for background absorbance. When method B was carried out in the lipid and protein fraction of plasma, SS inhibited by 65% TBARS formation only in the latter. Protein TBARS may be largely ascribed to SA-containing glycoproteins and, to a minor extent, protein-bound MDA. Indeed, EDTA did not affect protein TBARS assessed in the presence of SS. TBA reactivity of whole plasma and of its lipid fraction was instead inhibited by EDTA, suggesting that lipoperoxides (and possibly monofunctional lipoperoxidation aldehydes) are involved as MDA precursors in the TBA test. Pretreatment of plasma with KI, a specific reductant of hydroperoxides, decreased TBARS by about 27%. Moreover, aspirin administration to humans to inhibit prostaglandin endoperoxide generation reduced plasma TBARS by 40%. In conclusion, reaction conditions affect the relationship between TBA reactivity and lipid peroxidation in human plasma. After correction for the interfering effects of SA in the TBA test, 40% of plasma TBARS

  16. Heterogeneous Reactions of ClONO2, HCl, and HOCl on Liquid Sulfuric Acid Surfaces

    NASA Technical Reports Server (NTRS)

    Zhang, Renyi; Leu, Ming-Taun; Keyser, Leon F.

    1994-01-01

    The heterogeneous reactions of ClONO2 + H2O yields HNO3 + HOCl (1), ClONO2 + HCl yields C12 + HNO3 (2), and HOCl + HCl yields Cl2 + H2O (3) on liquid sulfuric acid surfaces have been studied using a fast flow reactor coupled to a quadrupole mass spectrometer. The main objectives of the study are to investigate: (a) the temperature dependence of these reactions at a fixed H2O partial pressure typical of the lower stratosphere (that is, by changing temperature at a constant water partial pressure, the H2SO4 content of the surfaces is also changed), (b) the relative importance or competition between reactions 1 and 2, and (c) the effect of HNO3 on the reaction probabilities due to the formation of a H2SO4/HNO3/H2O ternary system. The measurements show that all the reactions depend markedly on temperature at a fixed H2O partial pressure: they proceed efficiently at temperatures near 200 K and much slower at temperatures near 220 K. The reaction probability (gamma(sub 1)) for ClONO2 hydrolysis approaches 0.01 at temperatures below 200 K, whereas the values for gamma(sub 2) and gamma(sub 3) are on the order of a few tenths at 200 K. Although detailed mechanisms for these reactions are still unknown, the present data indicate that the competition between ClONO2 hydrolysis and ClONO2 reaction with HCl may depend on temperature (or H2SO4 Wt %): in the presence of gaseous HCl at stratospheric concentrations, reaction 2 is dominant at lower temperatures (less than 200 K), but reaction 1 becomes important at temperatures above 210 K. Furthermore, reaction probability measurements performed on the H2SO4/HNO3/ H2O ternary solutions do not exhibit noticeable deviation from those performed on the H2SO4/H2O binary system, suggesting little effect of HNO3 in sulfate aerosols on the ClONO2 and HOCl reactions with HCl. The results reveal that significant reductions in the chlorine-containing reservoir species (such as ClONO2 and HCl) can take place on stratospheric sulfate aerosols at

  17. Acid-catalyzed Reactions in Model Secondary Organic Aerosol (SOA): Insights using Desorption-electrospray Ionization (DESI) Tandem Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Fiddler, M. N.; Cooks, R. G.; Shepson, P.

    2008-12-01

    Atmospheric aerosols are presently little understood in terms of their sources, formation, and effect on climate forcing, despite their significant impacts on climate change and respiratory health. Secondary organic aerosols (SOA), which were thought to arise entirely from simple gas-particle partitioning, have recently been found to contain oligomeric species which result from the condensed-phase reactions of volatile organic compounds (VOCs). The non-methane VOC with the greatest emission flux, isoprene, is known to produce aerosols through chemistry involving its oxidation products. We selected one of its major oxidation product, methacrolein, to assess its role in oligomeric SOA formation in response to the acidic conditions found in cloud water. Since it has been found that acidified aerosol produces oligomeric species with greater molecular weight and yield, acid-catalyzed oligomerization is likely a significant process in the formation of SOA. Aqueous solutions of methacrolein were acidified with sulfuric acid, and studied using linear ion trap mass spectrometry (LIT-MS) with a home-built desorption-electrospray ionization (DESI) source. An extremely heterogeneous mixture of products was produced in this system, resulting from hydrolysis, acid- catalyzed oxidation, reduction, and organosulfate formation. Evidence for disproportionation and heterocycle formation are proposed as reaction mechanisms hitherto unrecognized in the production of SOA. The proposed structure and formation mechanism for several species, based upon their MS/MS spectra, will also be presented.

  18. Drug Reaction With Eosinophilia and Systemic Symptoms Induced by Valproic Acid: A Case Report

    PubMed Central

    Darban, Mahboubeh; Bagheri, Bahador

    2016-01-01

    Introduction Drug reaction with eosinophilia and systemic symptoms (DRESS) syndrome is a rare but life-threatening reaction to drugs such as carbamazepine and allopurinol. The condition is characterized by skin rashes, fever, hematological disturbances, lymphadenopathy, and organ failure, most probably hepatic dysfunction. To date, only a few cases of valproate-induced DRESS syndrome have been reported. Case Presentation We report on the case of a 60-year-old man who had been treated with valproic acid some time before being referred to Kowsar Hospital, Semnan, Iran in December 2015. He was given valproic acid 1000 mg PO, and after 20 days, he had developed widespread rashes, fever, esophagitis, cervical lymphadenopathy, and tender hepatomegaly. Laboratory results at Kowsar showed a drop in hemoglobin, in addition to lymphocytosis, thrombocytopenia, and elevated serum transaminases. DRESS was diagnosed, and corticosteroid therapy was initiated. Administration of the culprit drug to the patient was also stopped. Intravenous immunoglobulin (IVIG) improved the general condition of the patient. Conclusions Only a small number of case reports have described valproic acid-induced DRESS syndrome; therefore, the condition is difficult to prevent. Rechallenge with valproic acid should be avoided in patients with a history of reaction to the drug. PMID:28144463

  19. Light activates the reaction of bacteriorhodopsin aspartic acid-115 with dicyclohexylcarbodiimide

    SciTech Connect

    Renthal, R.; Cothran, M.; Espinoza, B.; Wall, K.A.; Bernard, M.

    1985-07-30

    Conditions for a light-induced reaction between the carboxyl-modifying reagent N,N'-dicyclohexylcarbodiimide (DCCD) and bacteriorhodopsin in Triton X-100 micelles were previously reported. The authors have now located the DCCD site in the bacteriorhodopsin amino acid sequence. ( UC)DCCD-bacteriorhodopsin was cleaved with CNBr. The resulting peptides were purified by gel filtration and reverse-phase high-performance liquid chromatography (HPLC). One major UC peptide (50%) and two minor fractions were obtained. Amino acid analysis and sequence analysis showed that the major fraction contained residues 69-118. This region includes six carboxyl side chains. The major UC peptide was also subjected to pepsin hydrolysis. HPLC analysis of the product gave only a single major radioactive subfragment. Amino acid analysis of the peptic peptide showed that it contained residues 110-118. The only carboxyl side chain in this region is Asp-115. Thus, the authors conclude that Asp-115 is the major DCCD site. The light sensitivity of this reaction suggests that Asp-115 becomes more exposed or that its environment becomes more acidic during proton pumping. The DCCD reaction blue-shifts the retinal chromophore. Such a result would be expected if Asp-115 is the negative point charge predicted to be near the cyclohexene ring of retinal.

  20. Methanol oxidation and hydrogen reactions on NiZr in acid solution

    NASA Astrophysics Data System (ADS)

    Hays, C. C.; Manoharan, R.; Goodenough, J. B.

    The electrochemical properties of a Ni 50Zr 50 (at.%) alloy have been investigated by cyclic voltammetry and steady-state polarization measurements. The alloy forms a passivating oxyhydroxide film that makes it electrochemically stable in an acid solution. The oxyhydroxide film is shown to be an electrocatalyst for the methanol oxidation reaction (MOR). The reaction proceeds at surface O 2- ions neighboring a Ni 3+ ion of a thicker passivating film; electron transfer from the surface to the electrode occurs diffusively by the nickel atoms of the film. A reaction pathway is presented that accounts for the observation of an optimum thickness for the passivating film. The NiZr alloy was also found to catalyze both hydrogen-oxidation and proton-reduction reactions (HOR and PRR) if it has a thinner surface oxyhydroxide film. The alloy appears to form mixed NiZrH and NiZrH 3- x hydrides on cycling negative of the normal hydrogen potential. The activity of the hydrogen-oxidation reaction on a hydride surface was found to increase in the presence of streaming hydrogen gas and also with increasing negative initial potential. Although the hydride is unstable in acid, it may be an attractive candidate for use as a rechargeable negative electrode in an alkaline metal/air or nickel-metal hydride secondary battery.

  1. A Direct, Biomass-Based Synthesis of Benzoic Acid: Formic Acid-Mediated Deoxygenation of the Glucose-Derived Materials Quinic Acid and Shikimic Acid

    SciTech Connect

    Arceo, Elena; Ellman, Jonathan; Bergman, Robert

    2010-05-03

    An alternative biomass-based route to benzoic acid from the renewable starting materials quinic acid and shikimic acid is described. Benzoic acid is obtained selectively using a highly efficient, one-step formic acid-mediated deoxygenation method.

  2. Click with a boronic acid handle: a neighboring group-assisted click reaction that allows ready secondary functionalization.

    PubMed

    Draganov, Alexander B; Wang, Ke; Holmes, Jalisa; Damera, Krishna; Wang, Danzhu; Dai, Chaofeng; Wang, Binghe

    2015-10-21

    The feasibility of a neighboring boronic acid-facilitated facile condensation of an aldehyde is described. This reaction is bio-orthogonal, complete at room temperature within minutes, and suitable for bioconjugation chemistry. The boronic acid group serves the dual purpose of catalyzing the condensation reaction and being a handle for secondary functionalization.

  3. Role of Lewis acid additives in a palladium catalyzed directed C-H functionalization reaction of benzohydroxamic acid to isoxazolone.

    PubMed

    Athira, C; Sunoj, Raghavan B

    2016-12-20

    Metallic salts as well as protic additives are widely employed in transition metal catalyzed C-H bond functionalization reactions to improve the efficiency of catalytic protocols. In one such example, ZnCl2 and pivalic acid are used as additives in a palladium catalyzed synthesis of isoxazolone from a readily available benzohydroxamic acid under one pot conditions. In this article, we present some important mechanistic insights into the role of ZnCl2 and pivalic acid, gained by using density functional theory (M06) computations. Two interesting modes of action of ZnCl2 are identified in various catalytic steps involved in the formation of isoxazolone. The conventional Lewis acid coordination wherein zinc chloride (ZnCl2·(DMA)) binds to the carbonyl group is found to be more favored in the C-H activation step. However, the participation of a hetero-bimetallic Pd-Zn species is preferred in reductive elimination leading to Caryl-N bond formation. Pivalic acid helps in relay proton transfer in C-H bond activation through a cyclometallation deprotonation (CMD) process. The explicit inclusion of ZnCl2 and solvent N,N-dimethyl acetamide (DMA) stabilizes the transition state and also helps reduce the activation barrier for the C-H bond activation step. The electronic communication between the two metal species is playing a crucial role in stabilizing the Caryl-N bond formation transition state through a Pd-Zn hetero-bimetallic interaction.

  4. Chemically activated formation of organic acids in reactions of the Criegee intermediate with aldehydes and ketones.

    PubMed

    Jalan, Amrit; Allen, Joshua W; Green, William H

    2013-10-21

    Reactions of the Criegee intermediate (CI, ˙CH2OO˙) are important in atmospheric ozonolysis models. In this work, we compute the rates for reactions between ˙CH2OO˙ and HCHO, CH3CHO and CH3COCH3 leading to the formation of secondary ozonides (SOZ) and organic acids. Relative to infinitely separated reactants, the SOZ in all three cases is found to be 48-51 kcal mol(-1) lower in energy, formed via 1,3-cycloaddition of ˙CH2OO˙ across the C=O bond. The lowest energy pathway found for SOZ decomposition is intramolecular disproportionation of the singlet biradical intermediate formed from cleavage of the O-O bond to form hydroxyalkyl esters. These hydroxyalkyl esters undergo concerted decomposition providing a low energy pathway from SOZ to acids. Geometries and frequencies of all stationary points were obtained using the B3LYP/MG3S DFT model chemistry, and energies were refined using RCCSD(T)-F12a/cc-pVTZ-F12 single-point calculations. RRKM calculations were used to obtain microcanonical rate coefficients (k(E)) and the reservoir state method was used to obtain temperature and pressure dependent rate coefficients (k(T, P)) and product branching ratios. At atmospheric pressure, the yield of collisionally stabilized SOZ was found to increase in the order HCHO < CH3CHO < CH3COCH3 (the highest yield being 10(-4) times lower than the initial ˙CH2OO˙ concentration). At low pressures, chemically activated formation of organic acids (formic acid in the case of HCHO and CH3COCH3, formic and acetic acid in the case of CH3CHO) was found to be the major product channel in agreement with recent direct measurements. Collisional energy transfer parameters and the barrier heights for SOZ reactions were found to be the most sensitive parameters determining SOZ and organic acid yield.

  5. Chemically Activated Formation of Organic Acids in Reactions of the Criegee Intermediate with Aldehydes and Ketones

    SciTech Connect

    Jalan, Amrit; Allen, Joshua W.; Green, William H.

    2013-08-08

    Reactions of the Criegee intermediate (CI, .CH2OO.) are important in atmospheric ozonolysis models. In this work, we compute the rates for reactions between .CH2OO. and HCHO, CH3CHO and CH3COCH3 leading to the formation of secondary ozonides (SOZ) and organic acids. Relative to infinitely separated reactants, the SOZ in all three cases is found to be 48–51 kcal mol-1 lower in energy, formed via 1,3- cycloaddition of .CH2OO. across the CQO bond. The lowest energy pathway found for SOZ decomposition is intramolecular disproportionation of the singlet biradical intermediate formed from cleavage of the O–O bond to form hydroxyalkyl esters. These hydroxyalkyl esters undergo concerted decomposition providing a low energy pathway from SOZ to acids. Geometries and frequencies of all stationary points were obtained using the B3LYP/MG3S DFT model chemistry, and energies were refined using RCCSD(T)-F12a/cc-pVTZ-F12 single-point calculations. RRKM calculations were used to obtain microcanonical rate coefficients (k(E)) and the reservoir state method was used to obtain temperature and pressure dependent rate coefficients (k(T, P)) and product branching ratios. At atmospheric pressure, the yield of collisionally stabilized SOZ was found to increase in the order HCHO o CH3CHO o CH3COCH3 (the highest yield being 10-4 times lower than the initial .CH2OO. concentration). At low pressures, chemically activated formation of organic acids (formic acid in the case of HCHO and CH3COCH3, formic and acetic acid in the case of CH3CHO) was found to be the major product channel in agreement with recent direct measurements. Collisional energy transfer parameters and the barrier heights for SOZ reactions were found to be the most sensitive parameters determining SOZ and organic acid yield.

  6. Mechanistic insights into the dehalogenation reaction of fluoroacetate/fluoroacetic acid

    SciTech Connect

    Miranda-Rojas, Sebastián; Toro-Labbé, Alejandro

    2015-05-21

    Fluoroacetate is a toxic compound whose environmental accumulation may represent an important contamination problem, its elimination is therefore a challenging issue. Fluoroacetate dehalogenase catalyzes its degradation through a two step process initiated by an S{sub N}2 reaction in which the aspartate residue performs a nucleophilic attack on the carbon bonded to the fluorine; the second step is hydrolysis that releases the product as glycolate. In this paper, we present a study based on density functional theory calculations of the S{sub N}2 initiation reaction modeled through the interaction between the substrate and the propionate anion as the nucleophile. Results are analyzed within the framework of the reaction force and using the reaction electronic flux to identify and characterize the electronic activity that drives the reaction. Our results reveal that the selective protonation of the substrate catalyzes the reaction by decreasing the resistance of the structural and electronic reorganization needed to reach the transition state. Finally, the reaction energy is modulated by the degree of stabilization of the fluoride anion formed after the S{sub N}2 reaction. In this way, a site-induced partial protonation acts as a chemical switch in a key process that determines the output of the reaction.

  7. Mechanistic insights into the dehalogenation reaction of fluoroacetate/fluoroacetic acid

    NASA Astrophysics Data System (ADS)

    Miranda-Rojas, Sebastián; Toro-Labbé, Alejandro

    2015-05-01

    Fluoroacetate is a toxic compound whose environmental accumulation may represent an important contamination problem, its elimination is therefore a challenging issue. Fluoroacetate dehalogenase catalyzes its degradation through a two step process initiated by an SN2 reaction in which the aspartate residue performs a nucleophilic attack on the carbon bonded to the fluorine; the second step is hydrolysis that releases the product as glycolate. In this paper, we present a study based on density functional theory calculations of the SN2 initiation reaction modeled through the interaction between the substrate and the propionate anion as the nucleophile. Results are analyzed within the framework of the reaction force and using the reaction electronic flux to identify and characterize the electronic activity that drives the reaction. Our results reveal that the selective protonation of the substrate catalyzes the reaction by decreasing the resistance of the structural and electronic reorganization needed to reach the transition state. Finally, the reaction energy is modulated by the degree of stabilization of the fluoride anion formed after the SN2 reaction. In this way, a site-induced partial protonation acts as a chemical switch in a key process that determines the output of the reaction.

  8. 40 CFR 721.9400 - Reaction product of phenolic pentaerythritol tetraesters with fatty acid esters and oils, and...

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Reaction product of phenolic... Reaction product of phenolic pentaerythritol tetraesters with fatty acid esters and oils, and glyceride... substances identified generically as Reaction product of phenolic pentaerythritol tetraesters with fatty...

  9. 40 CFR 721.9400 - Reaction product of phenolic pentaerythritol tetraesters with fatty acid esters and oils, and...

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Reaction product of phenolic... Reaction product of phenolic pentaerythritol tetraesters with fatty acid esters and oils, and glyceride... substances identified generically as Reaction product of phenolic pentaerythritol tetraesters with fatty...

  10. 40 CFR 721.9400 - Reaction product of phenolic pentaerythritol tetraesters with fatty acid esters and oils, and...

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Reaction product of phenolic... Reaction product of phenolic pentaerythritol tetraesters with fatty acid esters and oils, and glyceride... substances identified generically as Reaction product of phenolic pentaerythritol tetraesters with fatty...

  11. 40 CFR 721.10363 - Alkenoic acid, 2-methyl-, 2-oxiranylmethyl ester, reaction products with 4,4′ -methylenebis...

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ...-oxiranylmethyl ester, reaction products with 4,4â² -methylenebis (cyclohexanamine) (generic). 721.10363 Section... Substances § 721.10363 Alkenoic acid, 2-methyl-, 2-oxiranylmethyl ester, reaction products with 4,4..., reaction products with 4,4′ -methylenebis (cyclohexanamine) (PMN P-10-47) is subject to reporting...

  12. 40 CFR 721.10363 - Alkenoic acid, 2-methyl-, 2-oxiranylmethyl ester, reaction products with 4,4′ -methylenebis...

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ...-oxiranylmethyl ester, reaction products with 4,4â² -methylenebis (cyclohexanamine) (generic). 721.10363 Section... Substances § 721.10363 Alkenoic acid, 2-methyl-, 2-oxiranylmethyl ester, reaction products with 4,4..., reaction products with 4,4′ -methylenebis (cyclohexanamine) (PMN P-10-47) is subject to reporting...

  13. 40 CFR 721.9400 - Reaction product of phenolic pentaerythritol tetraesters with fatty acid esters and oils, and...

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Reaction product of phenolic... Reaction product of phenolic pentaerythritol tetraesters with fatty acid esters and oils, and glyceride... substances identified generically as Reaction product of phenolic pentaerythritol tetraesters with fatty...

  14. 40 CFR 721.10363 - Alkenoic acid, 2-methyl-, 2-oxiranylmethyl ester, reaction products with 4,4′ -methylenebis...

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ...-oxiranylmethyl ester, reaction products with 4,4â² -methylenebis (cyclohexanamine) (generic). 721.10363 Section... Substances § 721.10363 Alkenoic acid, 2-methyl-, 2-oxiranylmethyl ester, reaction products with 4,4..., reaction products with 4,4′ -methylenebis (cyclohexanamine) (PMN P-10-47) is subject to reporting...

  15. Organosulfate Formation through the Heterogeneous Reaction of Sulfur Dioxide with Unsaturated Fatty Acids and Long-Chain Alkenes.

    PubMed

    Passananti, Monica; Kong, Lingdong; Shang, Jing; Dupart, Yoan; Perrier, Sébastien; Chen, Jianmin; Donaldson, D James; George, Christian

    2016-08-22

    The heterogeneous reaction between SO2 and unsaturated compounds results in the efficient production of organosulfates for several fatty acids and long-chain alkenes. The presence of an acid group, the physical state of the reactants (solid or liquid), the nature of the double bond (cis, trans, terminal), and the use of light irradiation all have an impact on the reaction rate. The reaction was investigated using different set-ups (coated flow tube, aerosol flow tube, and diffuse reflectance infrared Fourier transform cell). The reaction products were identified by high-resolution mass spectrometry and the impact of this reaction on organosulfate formation in the atmosphere is discussed.

  16. Determination of nitrite via reaction with pyridine-4-carboxylic acid hydrazide

    SciTech Connect

    Verma, K.K.; Tyagi, P.

    1985-06-01

    Nitrite is determined by its reaction with a measured but excessive amount of pyridine-4-carboxylic acid hydrazide in acid medium (when the two substances react in a 1:1 molar ratio) and evaluation of the surplus hydrazide by titration with chloramine-T in the presence of acidified potassium bromide, the end-point being shown by the decolorization of the methyl red indicator. Nitrate, copper(II), mercury(II), etc. are found not to interfere, and the determination of nitrite in the presence of diazotized aromatic amines is demonstrated. 11 references, 2 tables.

  17. Dynamic behavior of the bray-liebhafsky oscillatory reaction controlled by sulfuric acid and temperature

    NASA Astrophysics Data System (ADS)

    Pejić, N.; Vujković, M.; Maksimović, J.; Ivanović, A.; Anić, S.; Čupić, Ž.; Kolar-Anić, Lj.

    2011-12-01

    The non-periodic, periodic and chaotic regimes in the Bray-Liebhafsky (BL) oscillatory reaction observed in a continuously fed well stirred tank reactor (CSTR) under isothermal conditions at various inflow concentrations of the sulfuric acid were experimentally studied. In each series (at any fixed temperature), termination of oscillatory behavior via saddle loop infinite period bifurcation (SNIPER) as well as some kind of the Andronov-Hopf bifurcation is presented. In addition, it was found that an increase of temperature, in different series of experiments resulted in the shift of bifurcation point towards higher values of sulfuric acid concentration.

  18. Nucleic acid-based nanoengineering: novel structures for biomedical applications

    PubMed Central

    Li, Hanying; LaBean, Thomas H.; Leong, Kam W.

    2011-01-01

    Nanoengineering exploits the interactions of materials at the nanometre scale to create functional nanostructures. It relies on the precise organization of nanomaterials to achieve unique functionality. There are no interactions more elegant than those governing nucleic acids via Watson–Crick base-pairing rules. The infinite combinations of DNA/RNA base pairs and their remarkable molecular recognition capability can give rise to interesting nanostructures that are only limited by our imagination. Over the past years, creative assembly of nucleic acids has fashioned a plethora of two-dimensional and three-dimensional nanostructures with precisely controlled size, shape and spatial functionalization. These nanostructures have been precisely patterned with molecules, proteins and gold nanoparticles for the observation of chemical reactions at the single molecule level, activation of enzymatic cascade and novel modality of photonic detection, respectively. Recently, they have also been engineered to encapsulate and release bioactive agents in a stimulus-responsive manner for therapeutic applications. The future of nucleic acid-based nanoengineering is bright and exciting. In this review, we will discuss the strategies to control the assembly of nucleic acids and highlight the recent efforts to build functional nucleic acid nanodevices for nanomedicine. PMID:23050076

  19. Teaching Brønsted-Lowry Acid-Base Theory in a Direct Comprehensive Way

    NASA Astrophysics Data System (ADS)

    Adcock, Jamie L.

    2001-11-01

    A figure is presented which shows in a comprehensive way the relationships between Brønsted-Lowry acids and their conjugate bases. It shows their interactions with water and quantifies the terms strong, weak, and very weak, showing precisely how these modifiers can be effectively used to indicate the nature of the reaction between any conjugate acid/base and water. It shows that ion hydrolysis is simple acid/base behavior, and it clearly suggests the leveling effect of water on strong acids and bases.

  20. Reaction of isoprene on thin sulfuric acid films: kinetics, uptake, and product analysis.

    PubMed

    Connelly, Brandon M; Tolbert, Margaret A

    2010-06-15

    A high vacuum Knudsen flow reactor was used to determine the reactive uptake coefficient, gamma, of isoprene on sulfuric acid films as a function of sulfuric acid weight percent, temperature, and relative humidity. No discernible dependence was observed for gamma over the range of temperatures (220 - 265 K) and pressures (10(-7) Torr -10(-4) Torr) studied. However, the uptake coefficient increased with increased sulfuric acid concentration between the range of 78 wt % (gamma(i) approximately 10(-4)) and 93 wt % (gamma(i) approximately 10(-3)). In addition to the Knudsen Cell, a bulk study was conducted between 60 and 85 wt % H(2)SO(4) to quantify uptake at lower acid concentrations and to determine reaction products. After exposing sulfuric acid to gaseous isoprene the condensed phase products were extracted and analyzed using gas chromatography/mass spectrometry (GC/MS). Isoprene was observed to polymerize in the sulfuric acid and form yellow/red colored monoterpenes and cyclic sesquiterpenes. Finally, addition of water to the 85 wt % sulfuric acid/isoprene product mixture released these terpenes from the condensed phase into the gas phase. Together these experiments imply that direct isoprene uptake will not produce significant SOA; however, terpene production from the small uptake may be relevant for ultrafine particles and could affect growth and nucleation.

  1. Muonium reactions with chloroacetic acid in water: Contrasts with H atoms and hydrated electrons

    NASA Astrophysics Data System (ADS)

    Stadlbauer, John M.; Venkateswaran, Krishnan; Walker, David C.

    1997-09-01

    Muonium atoms react with chloroacetic acid and chloroacetate ions in dilute aqueous solution with rate constants of 2.3 × 10 6 and 9.1 × 10 5 dm 3 mol -1 s -1 respectively. These are compared with the reactions of 1H atoms (and e aq-) and discussed in terms of a pair of competing kinetic isotope effects. Muonium reacts at least eight times faster than H overall, and probably 28 times faster in forming Cl -. It behaves as a nucleophile, thus resembling e aq- more than H, in reacting faster with the acid than the anion. Muonium's reactions must be governed to a considerable extent by quantum-mechanical effects arising from its very small mass.

  2. Revisiting the Kinetics and Mechanism of the Tetrathionate-Hypochlorous Acid Reaction in Nearly Neutral Medium

    NASA Astrophysics Data System (ADS)

    Varga, Dénes; Horváth, Attila K.

    2009-11-01

    The tetrathionate-hypochlorous acid reaction has been investigated in nearly neutral medium at I = 0.5 M ionic strength and T = 25.0 ± 0.1 °C in dihydrogen-phosphate-hydrogen-phosphate buffer by UV-vis spectrophotometry. In excess of hypochlorous acid, the stoichiometry was found to be S4O62- + 7HOCl + 3H2O → 4SO42- + 7Cl- + 13H+, but in excess of tetrathionate colloidal sulfur precipitates. On the basis of the simultaneous evaluation of the kinetic curves, a nine-step kinetic model with four fitted and five fixed rate coefficients is proposed. Analogous oxidation reactions of tetrathionate are also compared and discussed.

  3. Origin of fatty acid synthesis - Thermodynamics and kinetics of reaction pathways

    NASA Technical Reports Server (NTRS)

    Weber, Arthur L.

    1991-01-01

    The primitiveness of contemporary fatty acid biosynthesis was evaluated by using the thermodynamics and kinetics of its component reactions to estimate the extent of its dependence on powerful and selective catalysis by enzymes. Since this analysis indicated that the modern pathway is not primitive because it requires sophisticated enzymatic catalysis, an alternative pathway of primitive fatty acid synthesis is proposed that uses glycolaldehyde as a substrate. In contrast to the modern pathway, this primitive pathway is not dependent on an exogenous source of phosphoanhydride energy. Furthermore, the chemical spontaneity of its reactions suggests that it could have been readily catalyzed by the rudimentary biocatalysts available at an early stage in the origin of life.

  4. Axially chiral imidodiphosphoric Acid catalyst for asymmetric sulfoxidation reaction: insights on asymmetric induction.

    PubMed

    Jindal, Garima; Sunoj, Raghavan B

    2014-04-22

    Insights into chiral induction for an asymmetric sulfoxidation reaction involving a single oxygen atom transfer are gained through analyzing the stereocontrolling transition states. The fitting of the substrate into the chiral cavity of a new class of imidodiphosphoric Brønsted acids, as well as weak CH⋅⋅⋅π and CH⋅⋅⋅O noncovalent interactions, are identified as responsible for the observed chiral induction.

  5. Lewis acid catalyzed cascade reaction to carbazoles and naphthalenes via dehydrative [3 + 3]-annulation.

    PubMed

    Wang, Shaoyin; Chai, Zhuo; Wei, Yun; Zhu, Xiancui; Zhou, Shuangliu; Wang, Shaowu

    2014-07-03

    A novel Lewis acid catalyzed dehydrative [3 + 3]-annulation of readily available benzylic alcohols and propargylic alcohols was developed to give polysubstituted carbazoles and naphthalenes in moderate to good yields with water as the only byproduct. The reaction was presumed to proceed via a cascade process involving Friedel-Crafts-type allenylation, 1,5-hydride shift, 6π-eletrocyclization, and Wagner-Meerwein rearrangement.

  6. Reactions to Implementing Adventure-Based Learning in Physical Education

    ERIC Educational Resources Information Center

    Sutherland, Sue; Stuhr, Paul T.

    2014-01-01

    The purpose of this qualitative study was to explore the reactions of 13 pre-service teachers (PTs) implementing an adventure-based learning (ABL) unit through the lens of occupational socialization. Data were collected through interviews, critical reflections and reflection of videotaped ABL lesson. Analysis of the data resulted in two themes:…

  7. Teachers' Reactions towards Performance-Based Language Assessment

    ERIC Educational Resources Information Center

    Chinda, Bordin

    2014-01-01

    This research aims at examining the reactions of tertiary EFL teachers towards the use of performance-based language assessment. The study employed a mixed-method research methodology. For the quantitative method, 36 teachers responded to a questionnaire survey. In addition, four teachers participated in the in-depth interviews which were…

  8. Origin of saline, neutral-pH, reduced epithermal waters by reaction of acidic magmatic gas condensates with wall rock

    SciTech Connect

    Reed, M.H. . Dept. of Geological Sciences)

    1993-04-01

    Fluid inclusions in quartz and sphalerite of epithermal veins containing galena, sphalerite and chalcopyrite with silver sulfides and electrum commonly have salinities of 2 to 10 weight percent NaCl equivalent. Examples include Bohemia, OR, Comstock, NV, and Creede, CO. Salinities in such base metal-rich systems are apparently greater than those in gold-adularia, base metal-poor systems such as Sleeper, NV, Republic, WA, and Hishikare, Kyushu. Saline epithermal fluids are commonly assumed to have been derived from saline magmatic brines, from local host formations, as has been suggested for Creede, or from evaporative concentration (boiling) of more dilute meteoric ground water. Another possibility, which may be the most common origin, is reaction of wall rocks with magmatic gas condensates rich in HCl and sulfuric acid. A mixture of one part Augustine Volcanic gas condensate in 10 parts cold ground water has a pH of 0.7 and the dominant cation is H[sup +] by a factor of 10[sup 4]. Calculated reaction of this condensate mixture with andesite at 300 C to a water/rock ratio (w/r) of 4.6 yields an NaCl-dominated fluid with a total salinity of 2.1 wt %. and pH 3.7. Further reaction, to w/r 0.14 yields a fluid salinity of 2.6 wt % and pH of 5.7; this fluid is in equilibrium with a propylitic alteration assemblage. Aqueous sulfide accumulates during the rock reaction as sulfate is reduced to sulfide when ferrous iron is oxidized to ferric iron. Sulfide concentration in the latter fluid is 32 ppm, far exceeding sulfate concentration. In the overall reaction, hydrogen ion is exchanged for base cations (including base metals) and sulfate is reduced to sulfide.

  9. Impact of Lewis acids on Diels-Alder reaction reactivity: a conceptual density functional theory study.

    PubMed

    Xia, Yue; Yin, Dulin; Rong, Chunying; Xu, Qiong; Yin, Donghong; Liu, Shubin

    2008-10-09

    Density functional theory (DFT) and conceptual/chemical DFT studies are carried out in this work for the normal electron demand Diels-Alder reaction between isoprene and acrolein to compare chemical reactivity and regioselectivity of the reactants in the absence and presence of Lewis acid (LA) catalysts. A cyclic coplanar structure of acrolein-LA complex has been observed and the natural bond orbital analysis has been employed to interpret the interaction between acrolein and LAs. Reactivity indices from frontier molecular orbital energies are proved to be adequate and efficient to evaluate the catalytic property of LAs. Linear relationships have been discovered among the bond order, bond length, catalytic activation, and chemical reactivity for the systems concerned. The validity and applicability of maximum hardness principle, minimum polarizability principle, and minimum electrophilicity principle are examined and discussed in the prediction of the major regioselective isomer and the preferred reaction pathway for the reactions in the present study.

  10. Kinetic Reaction Mechanism of Sinapic Acid Scavenging NO2 and OH Radicals: A Theoretical Study

    PubMed Central

    Lu, Yang; Wang, AiHua; Shi, Peng; Zhang, Hui; Li, ZeSheng

    2016-01-01

    The mechanism and kinetics underlying reactions between the naturally-occurring antioxidant sinapic acid (SA) and the very damaging ·NO2 and ·OH were investigated through the density functional theory (DFT). Two most possible reaction mechanisms were studied: hydrogen atom transfer (HAT) and radical adduct formation (RAF). Different reaction channels of neutral and anionic sinapic acid (SA-) scavenging radicals in both atmosphere and water medium were traced independently, and the thermodynamic and kinetic parameters were calculated. We find the most active site of SA/SA- scavenging ·NO2 and ·OH is the –OH group in benzene ring by HAT mechanism, while the RAF mechanism for SA/SA- scavenging ·NO2 seems thermodynamically unfavorable. In water phase, at 298 K, the total rate constants of SA eliminating ·NO2 and ·OH are 1.30×108 and 9.20×109 M-1 S-1 respectively, indicating that sinapic acid is an efficient scavenger for both ·NO2 and ·OH. PMID:27622460

  11. A preliminary investigation of acid-catalyzed polymerization reactions of shale oil distillates

    SciTech Connect

    Netzel, D.A.

    1991-04-01

    Sinor (1989) reported that a major specialty market may exist for shale oil as an asphalt blending material. Shale oil can be converted to an asphalt blending material by acid catalyzed condensation and polymerization reactions of the many molecular species comprising the composition of shale oil. To simplify the investigation, crude shale oil was separated by distillation into three distillates of different hydrocarbon and heteroaromatic compositions. These distillates were then treated with two different types of acids to determine the effect of acid type on the end products. Three western shale oil distillates, a naphtha, a middle distillate, and an atmospheric gas oil, were reacted with anhydrous AlCl{sub 3} and 85% H{sub 2}SO{sub 4} under low-severity conditions. At relatively low temperatures, little change in the hydrocarbon composition was noted for the AlCl{sub 3} reactions. AlCl{sub 3}{center_dot} (a polymerized product and/or complex) was formed. However, it is assumed that the sludge was mainly the result of heteroaromatic-AlCl{sub 3} reactions.

  12. A preliminary investigation of acid-catalyzed polymerization reactions of shale oil distillates

    SciTech Connect

    Netzel, D.A.

    1991-04-01

    Sinor (1989) reported that a major specialty market may exist for shale oil as an asphalt blending material. Shale oil can be converted to an asphalt blending material by acid catalyzed condensation and polymerization reactions of the many molecular species comprising the composition of shale oil. To simplify the investigation, crude shale oil was separated by distillation into three distillates of different hydrocarbon and heteroaromatic compositions. These distillates were then treated with two different types of acids to determine the effect of acid type on the end products. Three western shale oil distillates, a naphtha, a middle distillate, and an atmospheric gas oil, were reacted with anhydrous AlCl{sub 3} and 85% H{sub 2}SO{sub 4} under low-severity conditions. At relatively low temperatures, little change in the hydrocarbon composition was noted for the AlCl{sub 3} reactions. AlCl{sub 3}{center dot} (a polymerized product and/or complex) was formed. However, it is assumed that the sludge was mainly the result of heteroaromatic-AlCl{sub 3} reactions.

  13. Effects of ascorbic acid on sperm motility, viability, acrosome reaction and DNA integrity in teratozoospermic samples

    PubMed Central

    Fanaei, Hamed; Khayat, Samira; Halvaei, Iman; Ramezani, Vahid; Azizi, Yaser; Kasaeian, Amir; Mardaneh, Jalal; Parvizi, Mohammad Reza; Akrami, Maryam

    2014-01-01

    Background: Oxidative stress in teratozoospermic semen samples caused poor assisted reproductive techniques (ART) outcomes. Among antioxidants, ascorbic acid is a naturally occurring free radical scavenger and as such its presence assists various other mechanisms in decreasing numerous disruptive free radical processes. Objective: The main goal of this study was to evaluate potential protective effects of ascorbic acid supplementation during in vitro culture of teratozoospermic specimens. Materials and Methods: Teratozoospermic semen samples that collected from 15 volunteers were processed, centrifuged and incubated at 37oC until sperm swimmed-up. Supernatant was divided into four groups and incubated at 37oC for one hour under different experimental conditions: Control, 10 µm A23187, 600µm ascorbic acid and 10 µm A23187+600 µm ascorbic acid. After incubation sperm motility, viability, acrosome reaction, DNA damage and malondialdehyde levels were evaluated. Results: Our results indicated that after one hour incubation, ascorbic acid significantly reduced malondialdehyde level in ascorbic acid group (1.4±0.11 nmol/ml) compared to control group (1.58±0.13 nmol/ml) (p<0.001). At the end of incubation, progressive motility and viability in ascorbic acid group (64.5±8.8% and 80.3±6.4%, respectively) were significantly (p<0.05 and p<0.001, respectively) higher than the control group (54.5±6.8% and 70.9±7.3%, respectively). A23187 significantly (p<0.0001) increased acrosome reaction in A23187 group (37.3±5.6%) compared to control group (8.5±3.2%) and this effect of A23187 attenuated by ascorbic acid in ascorbic acid+A23187 group (17.2±4.4%). DNA fragmentation in ascorbic acid group (20±4.1%) was significantly (p<0.001) lower than controls (28.9±4.6%). Conclusion: In vitro ascorbic acid supplementation during teratozoospermic semen processing for ART could protect teratozoospermic specimens against oxidative stress, and it could improve ART outcome. PMID

  14. Formation of flavor components by the reaction of amino acid and carbonyl compounds in mild conditions.

    PubMed

    Pripis-Nicolau, L; de Revel, G; Bertrand, A; Maujean, A

    2000-09-01

    This work describe products of reactions between four alpha-dicarbonyl compounds (diacetyl, pentan-2,3-dione, glyoxal, and methylglyoxal) or two alpha-hydroxy ketones, (acetoine and acetol) and amino acids present in wines. The results shows the formation of odorous products or strong-smelling additives resulting from the Maillard and Strecker reaction in a primarily aqueous medium, at low temperature and low pH ( approximately pH 3.5) of the wine. GC/FID, GC/FPD, GC/NPD and GC/MS techniques were used. The olfactive characteristics of the products are described. In the presence of sulfur amino acids and in particular cysteine, many products were formed with a heterocycle production such as pyrazines and methylpyrazines, methylthiazoles, acetylthiazoles, acetylthiazolines, acetylthiazolidines, trimethyloxazole, and dimethylethyloxazoles. These various compounds present odors of sulfur, cornlike, pungent, nut, popcorn, roasted hazelnut, toasted, roasted, and ripe fruits. The chemical conditions of the model reactions are specified. The influence of temperature and pH on the reactions in the presence of cysteine were also studied.

  15. Polymerization of amino acids containing nucleotide bases

    NASA Technical Reports Server (NTRS)

    Ben Cheikh, Azzouz; Orgel, Leslie E.

    1990-01-01

    The nucleoamino acids 1-(3'-amino,3'-carboxypropyl)uracil (3) and 9-(3'-amino,3'-carboxypropyl)adenine (4) have been prepared as (L)-en-antiomers and as racemic mixtures. When 3 or 4 is suspended in water and treated with N,N'-carbon-yldiimidazole, peptides are formed in good yield. The products formed from the (L)-enantiomers are hydrolyzed to the monomeric amino acids by pronase. Attempts to improve the efficiency of these oligomerizations by including a polyuridylate template in the reaction mixture were not successful. Similarly, oligomers derived from the (L)-enantiomer of 3 did not act as templates to facilitate the oligomerization of 4.

  16. Reaction of primary and secondary amines to form carbamic acid glucuronides.

    PubMed

    Schaefer, William H

    2006-12-01

    Glucuronidation is an important mechanism used by mammalian systems to clear and eliminate both endogenous and foreign chemicals. Many functional groups are susceptible to conjugation with glucuronic acid, including hydroxyls, phenols, carboxyls, activated carbons, thiols, amines, and selenium. Primary and secondary amines can also react with carbon dioxide (CO(2)) via a reversible reaction to form a carbamic acid. The carbamic acid is also a substrate for glucuronidation and results in a stable carbamate glucuronide metabolite. The detection and characterization of these products has been facilitated greatly by the advent of soft ionization mass spectrometry techniques and high field NMR instrumentation. The formation of carbamate glucuronide metabolites has been described for numerous pharmaceuticals and they have been identified in all of the species commonly used in drug metabolism studies (rat, dog, mouse, rabbit, guinea pig, and human). There has been no obvious species specificity for their formation and no preference for 1 degrees or 2 degrees amines. Many biological reactions have also been described in the literature that involve the reaction of CO(2) with amino groups of biomolecules. For example, CO(2) generated from cellular respiration is expired in part through the reversible formation of a carbamate between CO(2) and the alpha-amino groups of the alpha- and beta-chains of hemoglobin. Also, carbamic acid products of several amines, such as beta-N-methylamino-L-alanine (BMAA), ethylenediamine, and L-cysteine have been implicated in toxicity. Studies suggested that a significant portion of amino-compounds in biological samples (that naturally contain CO(2)/bicarbonate) can be present as a carbamic acid.

  17. Microwave-Assisted Condensation Reactions of Acetophenone Derivatives and Activated Methylene Compounds with Aldehydes Catalyzed by Boric Acid under Solvent-Free Conditions.

    PubMed

    Brun, Elodie; Safer, Abdelmounaim; Carreaux, François; Bourahla, Khadidja; L'helgoua'ch, Jean-Martial; Bazureau, Jean-Pierre; Villalgordo, Jose Manuel

    2015-06-23

    We here disclosed a new protocol for the condensation of acetophenone derivatives and active methylene compounds with aldehydes in the presence of boric acid under microwave conditions. Implementation of the reaction is simple, healthy and environmentally friendly owing to the use of a non-toxic catalyst coupled to a solvent-free procedure. A large variety of known or novel compounds have thus been prepared, including with substrates bearing acid or base-sensitive functional groups.

  18. Studies of the Mechanism and Origins of Enantioselectivity for the Chiral Phosphoric Acid-Catalyzed Stereoselective Spiroketalization Reactions.

    PubMed

    Khomutnyk, Yaroslav Ya; Argüelles, Alonso J; Winschel, Grace A; Sun, Zhankui; Zimmerman, Paul M; Nagorny, Pavel

    2016-01-13

    Mechanistic and computational studies were conducted to elucidate the mechanism and the origins of enantiocontrol for asymmetric chiral phosphoric acid-catalyzed spiroketalization reactions. These studies were designed to differentiate between the S(N)1-like, S(N)2-like, and covalent phosphate intermediate-based mechanisms. The chiral phosphoric acid-catalyzed spiroketalization of deuterium-labeled cyclic enol ethers revealed a highly diastereoselective syn-selective protonation/nucleophile addition, thus ruling out long-lived oxocarbenium intermediates. Hammett analysis of the reaction kinetics revealed positive charge accumulation in the transition state (ρ = -2.9). A new computational reaction exploration method along with dynamics simulations supported an asynchronous concerted mechanism with a relatively short-lived polar transition state (average lifetime = 519 ± 240 fs), which is consistent with the observed inverse secondary kinetic isotope effect of 0.85. On the basis of these studies, a transition state model explaining the observed stereochemical outcome has been proposed. This model predicts the enantioselective formation of the observed enantiomer of the product with 92% ee, which matches the experimentally observed value.

  19. REACTION MECHANISMS OF 15-HYDROPEROXYEICOSATETRAENOIC ACID CATALYZED BY HUMAN PROSTACYCLIN AND THROMBOXANE SYNTHASES

    PubMed Central

    Yeh, Hui-Chun; Tsai, Ah-Lim; Wang, Lee-Ho

    2007-01-01

    Prostacyclin synthase (PGIS) and thromboxane synthase (TXAS) are atypical cytochrome P450s. They do not require NADPH or dioxygen for isomerization of prostaglandin H2 (PGH2) to produce prostacyclin (PGI2) and thromboxane A2 (TXA2). PGI2 and TXA2 have opposing actions on platelet aggregation and blood vessel tone. In this report, we use a lipid hydroperoxide, 15-hydroperoxyeicosatetraenoic acid (15-HPETE), to explore the active site characteristics of PGIS and TXAS. The two enzymes transformed 15-HPETE not only into 13-hydroxy-14,15-epoxy-5,8,11-eicosatrienoic acid (13-OH-14,15-EET), like many microsomal P450s, but also to 15-ketoeicosatetraenoic acid (15-KETE) and 15-hydroxyeicosatetraenoic acid (15-HETE). 13-OH-14,15-EET and 15-KETE result from homolytic cleavage of the O–O bond, whereas 15-HETE results from heterolytic cleavage, a common peroxidase pathway. About 80% of 15-HPETE was homolytically cleaved by PGIS and 60% was homolytically cleaved by TXAS. The Vmax of homolytic cleavage is 3.5-fold faster than heterolytic cleavage for PGIS-catalyzed reactions (1100 min−1 vs. 320 min−1) and 1.4-fold faster for TXAS (170 min−1 vs. 120 min−1). Similar KM values for homolytic and heterolytic cleavages were found for PGIS (∼60 μM 15-HPETE) and TXAS (∼80 μM 15-HPETE), making PGIS a more efficient catalyst for the 15-HPETE reaction. PMID:17459323

  20. A dual arylboronic acid--aminothiourea catalytic system for the asymmetric intramolecular hetero-Michael reaction of α,β-unsaturated carboxylic acids.

    PubMed

    Azuma, Takumi; Murata, Akihiro; Kobayashi, Yusuke; Inokuma, Tsubasa; Takemoto, Yoshiji

    2014-08-15

    A bifunctional aminoboronic acid has been used to facilitate for the first time the intramolecular aza- and oxa-Michael reactions of α,β-unsaturated carboxylic acids. The combination of an arylboronic acid with a chiral aminothiourea allowed for these reactions to proceed successfully in an enantioselective manner to afford the desired heterocycles in high yields and ee's (up to 96% ee). The overall utility of this dual catalytic system was demonstrated by a one-pot enantioselective synthesis of (+)-erythrococcamide B, which proceeded via sequential Michael and amidation reactions.

  1. Aquatic photolysis: photolytic redox reactions between goethite and adsorbed organic acids in aqueous solutions

    USGS Publications Warehouse

    Goldberg, M.C.; Cunningham, K.M.; Weiner, Eugene R.

    1993-01-01

    Photolysis of mono and di-carboxylic acids that are adsorbed onto the surface of the iron oxyhydroxide (goethite) results in an oxidation of the organic material and a reduction from Fe(III) to Fe(II) in the iron complex. There is a subsequent release of Fe2+ ions into solution. At constant light flux and constant solution light absorption, the factors responsible for the degree of photolytic reaction include: the number of lattice sites that are bonded by the organic acid; the rate of acid readsorption to the surface during photolysis; the conformation and structure of the organic acid; the degree of oxidation of the organic acid; the presence or absence of an ??-hydroxy group on the acid, the number of carbons in the di-acid chain and the conformation of the di-acid. The ability to liberate Fe(III) at pH 6.5 from the geothite lattice is described by the lyotropic series: tartrate>citrate> oxalate > glycolate > maleate > succinate > formate > fumarate > malonate > glutarate > benzoate = butanoate = control. Although a larger amount of iron is liberated, the series is almost the same at pH 5.5 except that oxalate > citrate and succinate > maleate. A set of rate equations are given that describe the release of iron from the goethite lattice. It was observed that the pH of the solution increases during photolysis if the solutions are not buffered. There is evidence to suggest the primary mechanism for all these reactions is an electron transfer from the organic ligand to the Fe(III) in the complex. Of all the iron-oxyhydroxide materials, crystalline goethite is the least soluble in water; yet, this study indicates that in an aqueous suspension, iron can be liberated from the goethite lattice. Further, it has been shown that photolysis can occur in a multiphase system at the sediment- water interface which results in an oxidation of the organic species and release of Fe2+ to solution where it becomes available for further reaction. ?? 1993.

  2. Pictet–Spengler reaction-based biosynthetic machinery in fungi

    PubMed Central

    Yan, Wei; Ge, Hui Ming; Wang, Gang; Jiang, Nan; Mei, Ya Ning; Jiang, Rong; Li, Sui Jun; Chen, Chao Jun; Jiao, Rui Hua; Xu, Qiang; Ng, Seik Weng; Tan, Ren Xiang

    2014-01-01

    The Pictet–Spengler (PS) reaction constructs plant alkaloids such as morphine and camptothecin, but it has not yet been noticed in the fungal kingdom. Here, a silent fungal Pictet–Spenglerase (FPS) gene of Chaetomium globosum 1C51 residing in Epinephelus drummondhayi guts is described and ascertained to be activable by 1-methyl-l-tryptophan (1-MT). The activated FPS expression enables the PS reaction between 1-MT and flavipin (fungal aldehyde) to form “unnatural” natural products with unprecedented skeletons, of which chaetoglines B and F are potently antibacterial with the latter inhibiting acetylcholinesterase. A gene-implied enzyme inhibition (GIEI) strategy has been introduced to address the key steps for PS product diversifications. In aggregation, the work designs and validates an innovative approach that can activate the PS reaction-based fungal biosynthetic machinery to produce unpredictable compounds of unusual and novel structure valuable for new biology and biomedicine. PMID:25425666

  3. Survivability and Abiotic Reactions of Selected Amino Acids in Different Hydrothermal System Simulators

    NASA Astrophysics Data System (ADS)

    Chandru, Kuhan; Imai, Eiichi; Kaneko, Takeo; Obayashi, Yumiko; Kobayashi, Kensei

    2013-04-01

    We tested the stability and reaction of several amino acids using hydrothermal system simulators: an autoclave and two kinds of flow reactors at 200-250 °C. This study generally showed that there is a variation in the individual amino acids survivability in the simulators. This is mainly attributed to the following factors; heat time, cold quenching exposure, metal ions and also silica. We observed that, in a rapid heating flow reactor, high aggregation and/or condensation of amino acids could occur even during a heat exposure of 2 min. We also monitored their stability in a reflow-type of simulator for 120 min at 20 min intervals. The non-hydrolyzed and hydrolyzed samples for this system showed a similar degradation only in the absence of metal ions.

  4. Uptake of Small Organic Compounds by Sulfuric Acid Aerosols: Dissolution and Reaction

    NASA Technical Reports Server (NTRS)

    Iraci, L. T.; Michelsen, R. R.; Ashbourn, S. F. M.; Staton, S. J. R.

    2003-01-01

    To assess the role of oxygenated volatile organic compounds in the upper troposphere and lower stratosphere, the interactions of a series of small organic compounds with low-temperature aqueous sulfuric acid will be evaluated. The total amount of organic material which may be taken up from the gas phase by dissolution, surface layer formation, and reaction during the particle lifetime will be quantified. Our current results for acetaldehyde uptake on 40 - 80 wt% sulfuric acid solutions will be compared to those of methanol, formaldehyde, and acetone to investigate the relationships between chemical functionality and heterogeneous activity. Where possible, equilibrium uptake will be ascribed to component pathways (hydration, protonation, etc.) to facilitate evaluation of other species not yet studied in low temperature aqueous sulfuric acid.

  5. Improvement of an acid phosphatase/DHAP-dependent aldolase cascade reaction by using directed evolution.

    PubMed

    van Herk, Teunie; Hartog, Aloysius F; Babich, Lara; Schoemaker, Hans E; Wever, Ron

    2009-09-04

    To enhance the phosphorylating activity of the bacterial nonspecific acid phosphatase from Salmonella enterica ser. typhimurium LT2 towards dihydroxyacetone (DHA), a mutant library was generated from the native enzyme. Three different variants that showed enhanced activity were identified after one round of epPCR. The single mutant V78L was the most active and showed an increase in the maximal DHAP concentration to 25 % higher than that of the wild-type enzyme at pH 6.0. This variant is 17 times more active than the wild-type acid phosphatase from Salmonella enterica ser. typhimurium LT2 in the acid phosphatase/aldolase cascade reaction at pH 6.0 and is also six times more active than the phosphatase from Shigella flexneri that we previously used.

  6. Studies on reaction runaways for Urex/Purex solvent-nitric acid and red-oil synthesis

    SciTech Connect

    Kumar, Shekhar; Kumar, Rajnish; Koganti, S.B.

    2008-07-01

    In PUREX/UREX processes for recycling of spent nuclear fuels, 30% TBP solvent is used, This solvent has a small solubility in the aqueous phase. During concentration of the process solutions by an evaporation route, a runaway reaction between TBP and nitric acid is initiated at above 130 deg. C, leading to rapid pressurization and finally containment failure if proper venting is not provided. Red oil was synthesized for the first time in India, and its physical properties as well as thermodynamic parameters for the reaction were determined. It was experimentally established that the presence of metallic nitrates was not essential for red-oil formation as thought earlier. Various experiments have been completed for single-phase as well as two-phase runs. The most important finding of this work was lowering of the limiting acid concentration from the conventional values. In fact, in these experiments, red oil could be formed even at 2 N aqueous acidity. Thus, safety guidelines based on the classical literature are obsolete. New guidelines for the red-oil-safety are required. (authors)

  7. Palladium(0)-catalyzed coupling-cyclization reaction of polymer-supported aryl iodides with 1,2-allenyl carboxylic acids. Solid-phase parallel synthesis of butenolides.

    PubMed

    Ma, Shengming; Duan, Dehui; Wang, Yizhong

    2002-01-01

    In this contribution, we constructed a library of butenolides with 77 members by parallel synthesis strategy on Merrifield resin. Sixteen 2,3-allenoic acids and 12 polymer-bound aryl iodides were combined to react with each other, and then the polymer-supported products were cleaved to release butenolide derivatives. The reactions with alkyl-substituted 2,3-allenoic acids in acetonitrile afforded the corresponding products in high yields and high purities, whereas those with aryl-substituted acids in acetonitrile failed. After some reaction conditions were screened, the solid-phase reactions with aryl-substituted 2,3-allenoic acids were realized in toluene, and the products are of good purities albeit in slightly low yields. In the benzyl ether linkage, a new cleavage model was found. By adding 6 equiv of acetyl bromide, we can get single (5-oxo-2,5-dihydrofuran-3-yl)benzyl bromide other than the corresponding benzyl acetate. To further increase the diversities, a dihydropyran (DHP) linker was introduced into our combinatorial synthesis of butenolides. By reversing the addition sequence of 2,3-allenoic acids and organic base, we realized the solid-phase cyclization reaction of polymer-bound aryl iodides with the THP linkage in moderate yields and good purities. Now the library of butenolides includes (5-oxo-2,5-dihydrofuran-3-yl)benzoic acids, -aryl acetates, -benzyl bromides, -benzyl alcohols, and -phenols, which are difficult to synthesize with conventional solution methods.

  8. First principles based mean field model for oxygen reduction reaction.

    PubMed

    Jinnouchi, Ryosuke; Kodama, Kensaku; Hatanaka, Tatsuya; Morimoto, Yu

    2011-12-21

    A first principles-based mean field model was developed for the oxygen reduction reaction (ORR) taking account of the coverage- and material-dependent reversible potentials of the elementary steps. This model was applied to the simulation of single crystal surfaces of Pt, Pt alloy and Pt core-shell catalysts under Ar and O(2) atmospheres. The results are consistent with those shown by past experimental and theoretical studies on surface coverages under Ar atmosphere, the shape of the current-voltage curve for the ORR on Pt(111) and the material-dependence of the ORR activity. This model suggests that the oxygen associative pathway including HO(2)(ads) formation is the main pathway on Pt(111), and that the rate determining step (RDS) is the removal step of O(ads) on Pt(111). This RDS is accelerated on several highly active Pt alloys and core-shell surfaces, and this acceleration decreases the reaction intermediate O(ads). The increase in the partial pressure of O(2)(g) increases the surface coverage with O(ads) and OH(ads), and this coverage increase reduces the apparent reaction order with respect to the partial pressure to less than unity. This model shows details on how the reaction pathway, RDS, surface coverages, Tafel slope, reaction order and material-dependent activity are interrelated.

  9. Synthesis of phosphatidylcholine with defined fatty acid in the sn-1 position by lipase-catalyzed esterification and transesterification reaction.

    PubMed

    Adlercreutz, Dietlind; Budde, Heike; Wehtje, Ernst

    2002-05-20

    The incorporation of caproic acid in the sn-1 position of phosphatidylcholine (PC) catalyzed by lipase from Rhizopus oryzae was investigated in a water activity-controlled organic medium. The reaction was carried out either as esterification or transesterification. A comparison between these two reaction modes was made with regard to product yield, product purity, reaction time, and byproduct formation as a consequence of acyl migration. The yield in the esterification and transesterification reaction was the same under identical conditions. The highest yield (78%) was obtained at a water activity (a(w)) of 0.11 and a caproic acid concentration of 0.8 M. The reaction time was shorter in the esterification reaction than in the transesterification reaction. The difference in reaction time was especially pronounced at low water activities and high fatty acid concentrations. The loss in yield due to acyl migration and consequent enzymatic side reactions was around 16% under a wide range of conditions. The incorporation of a fatty acid in the sn-1 position of PC proved to be thermodynamically much more favorable than the incorporation of a fatty acid in the sn-2 position.

  10. Synthesis of unnatural amino acids via microwave-assisted regio-selective one-pot multi-component reactions of sulfamidates

    EPA Science Inventory

    Synthesis of triazole-based unnatural amino acids, triazole bisaminoacids and β-amino triazole has been described via stereo and regioselective one-pot multi-component reaction of sulfamidates, sodium azide, and alkynes under MW irradiation conditions. The developed method is app...

  11. Lewis acid promoted reactions of ethenetricarboxylates with allenes: synthesis of indenes and gamma-lactones via conjugate addition/cyclization reaction.

    PubMed

    Yamazaki, Shoko; Yamamoto, Yuko; Fukushima, Yugo; Takebayashi, Masachika; Ukai, Tetsuma; Mikata, Yuji

    2010-08-06

    Indenes are important core structures in organic chemistry. Few simple arylallenes have been used to construct indene skeletons by Friedel-Crafts reaction. Lewis acid catalyzed reaction of ethenetricarboxylates 1 and arylallenes has been examined in this study. The reaction of arylallenes and ethenetricarboxylate triesters with SnCl(4) gave indene derivatives efficiently, via a conjugate addition/Friedel-Crafts cyclization reaction. On the other hand, the reactions of 1,1-diethyl 2-hydrogen ethenetricarboxylate and arylallenes or alkylallenes with SnCl(4) at -78 degrees C or room temperature and subsequent treatment with Et(3)N gave gamma-lactones. The reactions of triethyl ethenetricarboxylate and 1,1-dialkylallenes with SnCl(4) at room temperature also gave gamma-lactones.

  12. Determination of fumaric and maleic acids with stacking analytes by transient moving chemical reaction boundary method in capillary electrophoresis.

    PubMed

    He, Jian-Feng; Yang, Wei-Ying; Yao, Fu-Jun; Zhao, Hong; Li, Xiang-Jun; Yuan, Zhuo-Bin

    2011-06-17

    The paper presents an on-line transient moving chemical reaction boundary (MCRB) method for simply but efficiently stacking analytes in capillary electrophoresis (CE). The CE technique was developed for a rapid determination of fumaric and maleic acid. Based on the theory of MCRB, Effects of several important factors such as the pH and concentration of running buffer and the conditions of stacking analytes were investigated to acquire the optimum conditions. The optimized separations were carried out in a 20 mmol/L sulphate neutralized with ethylenediamine to pH 6.0 electrolytes using a capillary coated with poly (diallyldimethylammonium chloride) and direct UV detection at 214 nm. The optimized preconcentrations were carried out in 50 mmol/L borax (pH 9.0). The calibration curves were linear in the concentration range of 1.0×10⁻⁷-1.0×10⁻⁴ mol/L and 5.0×10⁻⁷-1.0×10⁻⁴ mol/L for fumaric and maleic acid with correlation coefficients higher than 0.9991. The detection limits were 5.34×10⁻⁸ mol/L for fumaric acid and 1.92×10⁻⁷ mol/L for maleic acid. This method was applied for determination of fumaric acid in apple juice and of fumaric and maleic acid in dl-malic, the recovery tests established for real samples were within the range 95-105%. This work provided a valid and simple approach to detect fumaric and maleic acid.

  13. Reaction Mechanism of N-Acetylneuraminic Acid Lyase Revealed by a Combination of Crystallography, QM/MM Simulation, and Mutagenesis

    PubMed Central

    2014-01-01

    N-Acetylneuraminic acid lyase (NAL) is a Class I aldolase that catalyzes the reversible condensation of pyruvate with N-acetyl-d-mannosamine (ManNAc) to yield the sialic acid N-acetylneuraminic acid (Neu5Ac). Aldolases are finding increasing use as biocatalysts for the stereospecific synthesis of complex molecules. Incomplete understanding of the mechanism of catalysis in aldolases, however, can hamper development of new enzyme activities and specificities, including control over newly generated stereocenters. In the case of NAL, it is clear that the enzyme catalyzes a Bi-Uni ordered condensation reaction in which pyruvate binds first to the enzyme to form a catalytically important Schiff base. The identity of the residues required for catalysis of the condensation step and the nature of the transition state for this reaction, however, have been a matter of conjecture. In order to address, this we crystallized a Y137A variant of the E. coli NAL in the presence of Neu5Ac. The three-dimensional structure shows a full length sialic acid bound in the active site of subunits A, B, and D, while in subunit C, discontinuous electron density reveals the positions of enzyme-bound pyruvate and ManNAc. These ‘snapshot’ structures, representative of intermediates in the enzyme catalytic cycle, provided an ideal starting point for QM/MM modeling of the enzymic reaction of carbon–carbon bond formation. This revealed that Tyr137 acts as the proton donor to the aldehyde oxygen of ManNAc during the reaction, the activation barrier is dominated by carbon–carbon bond formation, and proton transfer from Tyr137 is required to obtain a stable Neu5Ac-Lys165 Schiff base complex. The results also suggested that a triad of residues, Tyr137, Ser47, and Tyr110 from a neighboring subunit, are required to correctly position Tyr137 for its function, and this was confirmed by site-directed mutagenesis. This understanding of the mechanism and geometry of the transition states along the C

  14. The effects of borate minerals on the synthesis of nucleic acid bases, amino acids and biogenic carboxylic acids from formamide.

    PubMed

    Saladino, Raffaele; Barontini, Maurizio; Cossetti, Cristina; Di Mauro, Ernesto; Crestini, Claudia

    2011-08-01

    The thermal condensation of formamide in the presence of mineral borates is reported. The products afforded are precursors of nucleic acids, amino acids derivatives and carboxylic acids. The efficiency and the selectivity of the reaction was studied in relation to the elemental composition of the 18 minerals analyzed. The possibility of synthesizing at the same time building blocks of both genetic and metabolic apparatuses, along with the production of amino acids, highlights the interest of the formamide/borate system in prebiotic chemistry.

  15. Jigsaw Cooperative Learning: Acid-Base Theories

    ERIC Educational Resources Information Center

    Tarhan, Leman; Sesen, Burcin Acar

    2012-01-01

    This study focused on investigating the effectiveness of jigsaw cooperative learning instruction on first-year undergraduates' understanding of acid-base theories. Undergraduates' opinions about jigsaw cooperative learning instruction were also investigated. The participants of this study were 38 first-year undergraduates in chemistry education…

  16. Separation of Acids, Bases, and Neutral Compounds

    NASA Astrophysics Data System (ADS)

    Fujita, Megumi; Mah, Helen M.; Sgarbi, Paulo W. M.; Lall, Manjinder S.; Ly, Tai Wei; Browne, Lois M.

    2003-01-01

    Separation of Acids, Bases, and Neutral Compounds requires the following software, which is available for free download from the Internet: Netscape Navigator, version 4.75 or higher, or Microsoft Internet Explorer, version 5.0 or higher; Chime plug-in, version compatible with your OS and browser (available from MDL); and Flash player, version 5 or higher (available from Macromedia).

  17. Isocyanide-Based Multicomponent Reactions for the Synthesis of Heterocycles.

    PubMed

    Váradi, András; Palmer, Travis C; Notis Dardashti, Rebecca; Majumdar, Susruta

    2015-12-23

    Multicomponent reactions (MCRs) are extremely popular owing to their facile execution, high atom-efficiency and the high diversity of products. MCRs can be used to access various heterocycles and highly functionalized scaffolds, and thus have been invaluable tools in total synthesis, drug discovery and bioconjugation. Traditional isocyanide-based MCRs utilize an external nucleophile attacking the reactive nitrilium ion, the key intermediate formed in the reaction of the imine and the isocyanide. However, when reactants with multiple nucleophilic groups (bisfunctional reactants) are used in the MCR, the nitrilium intermediate can be trapped by an intramolecular nucleophilic attack to form various heterocycles. The implications of nitrilium trapping along with widely applied conventional isocyanide-based MCRs in drug design are discussed in this review.

  18. Isocyanide-Based Multicomponent Reactions for the Synthesis of Heterocycles

    PubMed Central

    Váradi, András; Palmer, Travis C.; Dardashti, Rebecca Notis; Majumdar, Susruta

    2016-01-01

    Multicomponent reactions (MCRs) are extremely popular owing to their facile execution, high atom-efficiency and the high diversity of products. MCRs can be used to access various heterocycles and highly functionalized scaffolds, and thus have been invaluable tools in total synthesis, drug discovery and bioconjugation. Traditional isocyanide-based MCRs utilize an external nucleophile attacking the reactive nitrilium ion, the key intermediate formed in the reaction of the imine and the isocyanide. However, when reactants with multiple nucleophilic groups (bisfunctional reactants) are used in the MCR, the nitrilium intermediate can be trapped by an intramolecular nucleophilic attack to form various heterocycles. The implications of nitrilium trapping along with widely applied conventional isocyanide-based MCRs in drug design are discussed in this review. PMID:26703561

  19. Thermal denaturation of double-stranded nucleic acids: prediction of temperatures critical for gradient gel electrophoresis and polymerase chain reaction.

    PubMed Central

    Steger, G

    1994-01-01

    A program is described which calculates the thermal stability and the denaturation behaviour of double-stranded DNAs and RNAs up to a length of 1000 base pairs. The algorithm is based on recursive generation of conditional and a priori probabilities for base stacking. Output of the program may be compared directly to experimental results; thus the program may be used to optimize the nucleic acid fragments, the primers and the experimental conditions prior to experiments like polymerase chain reactions, temperature-gradient gel electrophoresis, denaturing-gradient gel electrophoresis and hybridizations. The program is available in three versions; the first version runs interactively on VAXstations producing graphics output directly, the second is implemented as part of the HUSAR package at GENIUSnet, the third runs on any computer producing text output which serves as input to available graphics programs. Images PMID:8052531

  20. Effect of acid concentration and pulp properties on hydrolysis reactions of mercerized sisal.

    PubMed

    Lacerda, Talita M; Zambon, Márcia D; Frollini, Elisabete

    2013-03-01

    The influence of sulfuric acid concentration (H2SO4 5-25%, 100°C), crystallinity and fibers size on the hydrolysis reaction of sisal pulps were investigated, with the goal of evaluating both the liquor composition, as an important step in the production of bioethanol, and the residual non-hydrolyzed pulp, to determine its potential application as materials. Aliquots were withdrawn from the reaction media, and the liquor composition was analyzed by HPLC. The residual non-hydrolyzed pulps were characterized by SEM, their average molar mass and crystallinity index, and their size distribution was determined using a fiber analyzer. Sulfuric acid 25% led to the highest glucose content (approximately 10gL(-1)), and this acid concentration was chosen to evaluate the influence of both the fiber size and crystallinity of the starting pulp on hydrolysis. The results showed that fibers with higher length and lower crystallinity favored glucose production in approximately 12%, with respect to the highly crystalline shorter fibers.

  1. Selective Michael-aldol reaction by use of sterically hindered aluminum aryloxides as Lewis acids: an easy approach to cyclobutane amino acids.

    PubMed

    Avenoza, Alberto; Busto, Jesús H; Canal, Noelia; Peregrina, Jesús M; Pérez-Fernández, Marta

    2005-08-04

    A formal [2 + 2] cycloaddition of 2-amidoacrylates with monosubstituted donor olefins, including its asymmetric version, is described. The stereoselectivity of this reaction can be modulated by the use of sterically hindered aluminum aryloxides or methylaluminoxane as Lewis acids. The reaction was applied to the synthesis of both stereoisomers of 2-benzyloxycyclobutane-alpha-amino acid, which are protected serine analogues c(4)Ser(OBn).

  2. Development of biomimetic catalytic oxidation methods and non-salt methods using transition metal-based acid and base ambiphilic catalysts.

    PubMed

    Murahashi, Shun-Ichi

    2011-01-01

    This review focuses on the development of ruthenium and flavin catalysts for environmentally benign oxidation reactions based on mimicking the functions of cytochrome P-450 and flavoenzymes, and low valent transition-metal catalysts that replace conventional acids and bases. Several new concepts and new types of catalytic reactions based on these concepts are described. (Communicated by Ryoji Noyori, M.J.A.).

  3. Development of biomimetic catalytic oxidation methods and non-salt methods using transition metal-based acid and base ambiphilic catalysts

    PubMed Central

    MURAHASHI, Shun-Ichi

    2011-01-01

    This review focuses on the development of ruthenium and flavin catalysts for environmentally benign oxidation reactions based on mimicking the functions of cytochrome P-450 and flavoenzymes, and low valent transition-metal catalysts that replace conventional acids and bases. Several new concepts and new types of catalytic reactions based on these concepts are described. PMID:21558760

  4. Reverse reaction of malic enzyme for HCO3- fixation into pyruvic acid to synthesize L-malic acid with enzymatic coenzyme regeneration.

    PubMed

    Ohno, Yoko; Nakamori, Toshihiko; Zheng, Haitao; Suye, Shin-ichiro

    2008-05-01

    Malic enzyme [L-malate: NAD(P)(+) oxidoreductase (EC 1.1.1.39)] catalyzes the oxidative decarboxylation of L-malic acid to produce pyruvic acid using the oxidized form of NAD(P) (NAD(P)(+)). We used a reverse reaction of the malic enzyme of Pseudomonas diminuta IFO 13182 for HCO(3)(-) fixation into pyruvic acid to produce L-malic acid with coenzyme (NADH) generation. Glucose-6-phosphate dehydrogenase (EC1.1.1.49) of Leuconostoc mesenteroides was suitable for coenzyme regeneration. Optimum conditions for the carboxylation of pyruvic acid were examined, including pyruvic acid, NAD(+), and both malic enzyme and glucose-6-phosphate dehydrogenase concentrations. Under optimal conditions, the ratio of HCO(3)(-) and pyruvic acid to malic acid was about 38% after 24 h of incubation at 30 degrees C, and the concentration of the accumulated L-malic acid in the reaction mixture was 38 mM. The malic enzyme reverse reaction was also carried out by the conjugated redox enzyme reaction with water-soluble polymer-bound NAD(+).

  5. Comparison of dissolution and surface reactions between calcite and aragonite in L-glutamic and L-aspartic acid solutions.

    PubMed

    Ryu, Miyoung; Kim, Hwan; Lim, Mihee; You, Kwangsuk; Ahn, Jiwhan

    2010-01-11

    We have investigated dissolution and surface reaction of calcite and aragonite in amino acid solutions of L-glutamic (L-glu) and L-aspartic acid (L-asp) at weak acidity of above pH 3. The surface reactions of calcite and aragonite were related with the dissolution. Calcite was dissolved in both solutions but the dissolution was limited by an adsorption of Ca-carboxylate salt. Aragonite was neither dissolved nor reacted in amino acid solutions because the crystal surface consisted of a hard to dissolve structure.

  6. The role of IgE recognition in allergic reactions to amoxicillin and clavulanic acid.

    PubMed

    Torres, M J; Montañez, M I; Ariza, A; Salas, M; Fernandez, T D; Barbero, N; Mayorga, C; Blanca, M

    2016-02-01

    Betalactam (BL) antibiotics are the drugs most frequently involved in IgE-mediated reactions. The culprit BL varies according to consumption patterns, with amoxicillin (AX) more prevalent in Southern Europe and penicillin V in Scandinavian countries. Nowadays, the combination of AX and clavulanic acid (CLV) is the most highly consumed BL containing medicine worldwide. Both BLs, AX and CLV, can independently be involved in reactions, which poses a diagnostic challenge. In patients with immediate allergic reactions to AX, two patterns of responses have been described, those responding to benzylpenicillin (cross-reactors) and those selective to AX. In addition, selective reactions to CLV account for around 30% of allergic reactions to the combination AX-CLV. These patterns of IgE recognition could be related to differences in the haptenation process, in the immunological response, or in the BL involved in the first sensitization. In this regard, patients with selective responses to CLV are generally younger than those allergic to AX or benzylpenicillin. So far, no evidence of cross-reactivity between CLV and other BLs has been reported. This shows the importance of an accurate diagnosis of CLV allergy, as patients with selective reactions to CLV could take other BLs including AX. Diagnosis can be performed in vivo and in vitro, although no immunoassay currently exists. Research regarding the CLV antigenic determinants and protein conjugates is essential to improve diagnosis. BLs need to covalently bind to a carrier protein to be immunogenic. The antigenic determinant of AX is the amoxicilloyl amide, but CLV leads to unstable structures, many of which are unknown. Moreover, the nature of the BL-protein conjugates plays an important role in IgE recognition. This review aims to summarize current knowledge on the immunochemistry, diagnostic approaches as well as chemical and proteomic studies for both AX and CLV.

  7. Reaction kinetics and critical phenomena: iodination of acetone in isobutyric acid + water near the consolute point.

    PubMed

    Hu, Baichuan; Baird, James K

    2010-01-14

    The rate of iodination of acetone has been measured as a function of temperature in the binary solvent isobutyric acid (IBA) + water near the upper consolute point. The reaction mixture was prepared by the addition of acetone, iodine, and potassium iodide to IBA + water at its critical composition of 38.8 mass % IBA. The value of the critical temperature determined immediately after mixing was 25.43 degrees C. Aliquots were extracted from the mixture at regular intervals in order to follow the time course of the reaction. After dilution of the aliquot with water to quench the reaction, the concentration of triiodide ion was determined by the measurement of the optical density at a wavelength of 565 nm. These measurements showed that the kinetics were zeroth order. When at the end of 24 h the reaction had come to equilibrium, the critical temperature was determined again and found to be 24.83 degrees C. An Arrhenius plot of the temperature dependence of the observed rate constant, k(obs), was linear over the temperature range 27.00-38.00 degrees C, but between 25.43 and 27.00 degrees C, the values of k(obs) fell below the extrapolation of the Arrhenius line. This behavior is evidence in support of critical slowing down. Our experimental method and results are significant in three ways: (1) In contrast to in situ measurements of optical density, the determination of the optical density of diluted aliquots avoided any interference from critical opalescence. (2) The measured reaction rate exhibited critical slowing down. (3) The rate law was pseudo zeroth order both inside and outside the critical region, indicating that the reaction mechanism was unaffected by the presence of the critical point.

  8. Linear Titration Curves of Acids and Bases.

    PubMed

    Joseph, N R

    1959-05-29

    The Henderson-Hasselbalch equation, by a simple transformation, becomes pH - pK = pA - pB, where pA and pB are the negative logarithms of acid and base concentrations. Sigmoid titration curves then reduce to straight lines; titration curves of polyelectrolytes, to families of straight lines. The method is applied to the titration of the dipeptide glycyl aminotricarballylic acid, with four titrable groups. Results are expressed as Cartesian and d'Ocagne nomograms. The latter is of a general form applicable to polyelectrolytes of any degree of complexity.

  9. Flow reactor and triple quadrupole mass spectrometer investigations of negative ion reactions involving nitric acid - Implications for atmospheric HNO3 detection by chemical ionization mass spectrometry

    NASA Astrophysics Data System (ADS)

    Moehler, O.; Arnold, F.

    1991-07-01

    The ion-molecule reactions on which Active Chemical Ionization Mass Spectrometry (ACIMS) measurements of atmospheric nitric acid are based are presently subjected to product-ion distribution and rate coefficient measurements. The results obtained indicate that while previous stratospheric nitric acid measurements were not impared by collisional dissociation processes, these processes may have played a major role during previous tropospheric measurements: leading to an undereestimation of nitric acid concentrations. A novel ACIMS ion source has been developed in order to avoid these problems.

  10. Effect of particle size in a limestone-hydrochloric acid reaction system.

    PubMed

    Sun, Bo; Zhou, Qulan; Chen, Xi; Xu, Tongmo; Hui, Shien

    2010-07-15

    Experimental characterization of the wet flue gas desulfurization process is carried out using a model limestone-hydrochloric acid reaction system, with in-situ measurement of the dissolution rate and particle size distribution. The limestone source, initial particle size distribution, working temperature and pH value are varied in large ranges. The dissolution rate is found to be higher when the average particle size is smaller, the temperature is higher, or the pH is lower. An empirical equation is established to correlate the dissolution rate with the particle size and working conditions, which agrees well with measurements. The results may be useful for providing insights to improve the efficiency of the wet flue gas desulfurization process, as well as other solid particle-liquid solution reactions.

  11. Hydrothermal reactions of pyruvic acid: synthesis, selection, and self-assembly of amphiphilic molecules.

    PubMed

    Hazen, Robert M; Deamer, David W

    2007-04-01

    Selection and self-assembly of organic compounds in aqueous phases must have been a primary process leading to emergent molecular complexity and ultimately to the origin of life. Facile reactions of pyruvic acid under hydrothermal conditions produce a complex mixture of larger organic molecules, some of which are amphiphiles that readily self-assemble into cell-sized vesicular structures. Chemical characterization of major components of this mixture reveals similarities to the suite of organic compounds present in the Murchison carbonaceous chondrite, some of whose molecules also self-assemble into membranous vesicles. Physical properties of the products are thus relevant to understanding the prebiotic emergence of molecular complexity. These results suggest that a robust family of prebiotic reaction pathways produces similar products over a range of geochemical and astrochemical environments.

  12. Dual-frequency oscillations induced by acidity in Belousov-Zhabotinskii reactions with aldosugars as substrates

    NASA Astrophysics Data System (ADS)

    Li, Hexing; Jin, Ronghua; Dai, Weilin; Deng, Jingfa

    1997-08-01

    Depending on the initial concentration of H 2SO 4, two types of dual-frequency oscillations have been observed in Belousov-Zhabotinskii type reactions catalyzed by Mn 2+ with acetone and aldosugars (arabinose, glucose, galactose, lactose or maltose) as coupled substrates in a batch reactor. No such dual-frequency oscillations have been found when a ketosugar like fructose was used instead of an aldosugar as the substrate; or acetone was replaced by N 2 flow. No oscillations were observed when Ce 3+ was used instead of Mn 2+. The reaction products of aldosugars in different oscillating regimes have been analyzed. The dual-frequency oscillatory patterns have been discussed according to the roles of the substrates and their derivatives formed at different acidity.

  13. Simple preparation of new [(18) F]F-labeled synthetic amino acid derivatives with two click reactions in one-pot and SPE purification.

    PubMed

    Yook, Cheol-Min; Lee, Sang Ju; Oh, Seung Jun; Ha, Hyun-Joon; Lee, Jong Jin

    2015-06-30

    New [(18) F]fluorinated 1,2,3-triazolyl amino acid derivatives were efficiently prepared from Huisgen 1,3-dipolar cycloaddition reactions, well known as click reaction. We developed two simultaneous click reactions in one-pot with a simple solid-phase extraction (SPE) purification method. [(18) F]fluoro-1-propyne was obtained at a 45% non-decay corrected radiochemical yield based on the [(18) F]fluoride ion. The one-pot and simultaneous two click reactions were performed with unprotected azido-alkyl amino acid, [(18) F]fluoro-1-propyne, and lipophilic additive alkyne to produce three synthetic amino acid derivatives, AMC-101 ([(18) F]-6a), AMC-102 ([(18) F]-6b), and AMC-103 ([(18) F]-6c) with 29%, 28%, and 24% of non-decay corrected radiochemical yields, respectively. All radiotracers indicated that radiochemical purities were >95% without any residual organic solvent. Our new method involving two click reactions in one-pot showed high radiochemical and chemical purity by easy removal of the residual precursor from the simultaneous two click reactions.

  14. Effective synthesis of optically active trifluoromethyldiazirinyl homophenylalanine and aroylalanine derivatives with the Friedel-Crafts reaction in triflic acid.

    PubMed

    Murashige, Ryo; Murai, Yuta; Hatanaka, Yasumaru; Hashimoto, Makoto

    2009-06-01

    The Friedel-Crafts reaction with 3-(3-methoxyphenyl)-3-(trifluoromethyl)-3H-diazirine and optically active N-TFA-Asp(Cl)-OMe in triflic acid afforded homophenylalanine derivatives without any loss of the optical purity.

  15. 40 CFR 721.6181 - Fatty acid, reaction product with substituted oxirane, formaldehyde-phenol polymer glycidyl ether...

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... substituted oxirane, formaldehyde-phenol polymer glycidyl ether, substituted proplyamine and...-phenol polymer glycidyl ether, substituted proplyamine and polyethylenepolyamines (generic). (a) Chemical... as fatty acid, reaction product with substituted oxirane, formaldehyde-phenol polymer glycidyl...

  16. 40 CFR 721.6181 - Fatty acid, reaction product with substituted oxirane, formaldehyde-phenol polymer glycidyl ether...

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... substituted oxirane, formaldehyde-phenol polymer glycidyl ether, substituted proplyamine and...-phenol polymer glycidyl ether, substituted proplyamine and polyethylenepolyamines (generic). (a) Chemical... as fatty acid, reaction product with substituted oxirane, formaldehyde-phenol polymer glycidyl...

  17. Megranate-like nanoreactor with multiple cores and an acidic mesoporous shell for a cascade reaction

    NASA Astrophysics Data System (ADS)

    Wang, Xue; Guan, Buyuan; He, Yapeng; An, Dong; Zhang, Ye; Cao, Yu; Li, Xiang; Liu, Yunling; Huo, Qisheng

    2015-02-01

    Megranate-like nanoparticles possess a unique structure that is composed of multiple cores and shells, which is different from simple yolk-shell nanoparticles. Megranate-like nanoparticles can combine the properties of each component and be used as nanoreactors. This study describes the preparation of bifunctional megranate-like nanoreactors, consisting of multiple metal cores and thiol modified mesoporous SiO2 shells. Different metal nanoparticles (Pd, Pt, Au) can be incorporated into the structure as cores, and the thiol group in the shells can be oxidized to acidic -SO3H. The megranate-like nanoparticles show good bifunctional catalytic properties and recyclability in a cascade catalytic reaction for the desired benzimidazole derivative. Moreover, the individual components of the megranate-like nanoparticles also show good catalytic activities in the hydrogenation reduction of nitro-aromatics and the deprotection reaction of benzaldehyde dimethyl acetal.Megranate-like nanoparticles possess a unique structure that is composed of multiple cores and shells, which is different from simple yolk-shell nanoparticles. Megranate-like nanoparticles can combine the properties of each component and be used as nanoreactors. This study describes the preparation of bifunctional megranate-like nanoreactors, consisting of multiple metal cores and thiol modified mesoporous SiO2 shells. Different metal nanoparticles (Pd, Pt, Au) can be incorporated into the structure as cores, and the thiol group in the shells can be oxidized to acidic -SO3H. The megranate-like nanoparticles show good bifunctional catalytic properties and recyclability in a cascade catalytic reaction for the desired benzimidazole derivative. Moreover, the individual components of the megranate-like nanoparticles also show good catalytic activities in the hydrogenation reduction of nitro-aromatics and the deprotection reaction of benzaldehyde dimethyl acetal. Electronic supplementary information (ESI) available

  18. On the reaction of lupulones, hops β-acids, with 1-hydroxyethyl radical.

    PubMed

    de Almeida, Natália E C; do Nascimento, Eduardo S P; Cardoso, Daniel R

    2012-10-24

    Lupulones, hops β-acids, are one of the main constituents of the hops resin and have an important contribution to the overall bacteriostatic activity of hops during beer brewing. The use of lupulones as natural alternatives to antibiotics is increasing in the food industry and also in bioethanol production. However, lupulones are easy oxidizable and have been shown to be very reactive toward 1-hydroxyethyl radical with apparent bimolecular rate constants close to diffusion control k = 2.9 × 10(8) and 2.6 × 10(8) L mol(-1) s(-1) at 25.0 ± 0.2 °C in ethanol-water solution (10% of ethanol (v/v)) as probed by EPR and ESI-IT-MS/MS spin-trapping competitive kinetics, respectively. The free energy change for an electron-transfer mechanism is ΔG° = 106 kJ/mol as calculated from the oxidation peak potential experimentally determined for lupulones (1.1 V vs NHE) by cyclic voltammetry and the reported reduction potential for 1-hydroxyethyl radical. The major reaction products identified by LC-ESI-IT-MS/MS and ultrahigh-resolution accurate mass spectrometry (orbitrap FT-MS) are hydroxylated lupulone derivatives and 1-hydroxyethyl radical adducts. The lack of pH dependence for the reaction rate constant, the calculated free energy change for electron transfer, and the main reaction products strongly suggest the prenyl side chains at the hops β-acids as the reaction centers rather than the β,β'-triketone moiety.

  19. Reaction-diffusion optoelectronics based on dispersed semiconductors

    NASA Astrophysics Data System (ADS)

    Gradov, O. V.; Gradova, M. A.

    2015-11-01

    Since many dispersed semiconductors are capable of light energy conversion and possess photocatalytic and luminescent properties, and any discreet light-sensitive medium can be applied for the positional-sensitive light flux registration (similar to pixels and voxels in semiconductor-based image recording), the use of chemically active dispersed semiconductors allows to perform a direct signal / image registration based on light-sensitive reaction-diffusion redox systems without conventional CCD / CMOS devices. The image capturing in this case will correspond to the formation of the metastable dissipative structures in the active medium, with their morphological properties determined by the flux gradient and provided by the corresponding dispersed semiconductor medium sensitivity.

  20. Bifunctional Organic Polymeric Catalysts with a Tunable Acid-Base Distance and Framework Flexibility

    PubMed Central

    Chen, Huanhui; Wang, Yanan; Wang, Qunlong; Li, Junhui; Yang, Shiqi; Zhu, Zhirong

    2014-01-01

    Acid-base bifunctional organic polymeric catalysts were synthesized with tunable structures. we demonstrated two synthesis approaches for structural fine-tune. In the first case, the framework flexibility was tuned by changing the ratio of rigid blocks to flexible blocks within the polymer framework. In the second case, we precisely adjusted the acid-base distance by distributing basic monomers to be adjacent to acidic monomers, and by changing the chain length of acidic monomers. In a standard test reaction for the aldol condensation of 4-nitrobenzaldehyde with acetone, the catalysts showed good reusability upon recycling and maintained relatively high conversion percentage. PMID:25267260