Showing papers on "Acetic acid published in 1989"
TL;DR: The internal pH of Saccharomyces cerevisiae IGC 3507 III (a respiratory-deficient mutant) was measured by the distribution of [14C]propionic acid, when the yeast was fermenting glucose at pH 3.5, 4.5 and 5 in the presence of several concentrations of acetic acid and ethanol.
Abstract: The internal pH of Saccharomyces cerevisiae IGC 3507 III (a respiratory-deficient mutant) was measured by the distribution of [14C]propionic acid, when the yeast was fermenting glucose at pH 3.5, 4.5 and 5.5 in the presence of several concentrations of acetic acid and ethanol. Good correlation was obtained between fermentation rates and internal pH. For all external pH values tested, the internal pH was 7.0–7.2 in the absence of inhibitors. The addition of acetic acid and/or ethanol resulted in a decrease of fermentation rate together with a drop in internal pH. Internal pH did not depend on the concentration of total external acetic acid but only on the concentration of the undissociated form of the acid. Ethanol potentiated the effect of acetic acid both with respect to inhibition of fermentation and internal acidification.
296 citations
TL;DR: Sodium perborate in acetic acid is an effective reagent for the oxidation of aromatic aldehydes to carboxylic acids, iodoarenes to (diacetoxyiodo)arenes, azines to N -oxides, and various types of sulphur heterocycles to S, S -dioxides.
183 citations
TL;DR: Inhibition of Listeria monocytogenes CA and V7 by of acetic, citric, and lactic acids at 7, 13, 21, and 35°C was investigated.
149 citations
TL;DR: It is suggested that 3HP is an intermediate in a pathway for acetate assimilation and in a new reductive carboxylic acid cycle for autotrophic CO2 fixation.
Abstract: Chloroflexus aurantiacus OK-70 fl secreted 3-hydroxypropionate (3HP) during phototrophic growth. The greatest amounts were secreted by cells grown on propionate (0.35 mM 3HP) while the lowest levels were found in autotrophically grown cultures (1.5 μM). Large amounts of 2-fluoro,3-hydroxypropionate were formed by autotrophically grown cells exposed to fluoroacetate (FAc). Increased levels of 3HP were observed in these cultures when incubated with acctate. The secretion of 3HP was further stimulated by 0.2 mM KCN, an inhibitor of CO2 fixation, but only in the presence of acetate. The pathway of 3HP formation was studied by using 13C-labelled substrates and NMR. The 3HP formed in the presence of C1-labelled acetate and FAc was labelled at C3 and somewhat less at C2 while with C2-labelled acetate as the tracer 3HP was labelled predominantly at C2. The carboxyl group was derived from CO2. The 3HP formed by cells grown on propionate and 13CO2 was labelled at all carbon atoms, the label content of C2 and C3 was about 25 and 65% of that of C1 respectively. It is suggested that 3HP is an intermediate in a pathway for acetate assimilation and in a new reductive carboxylic acid cycle for autotrophic CO2 fixation.
141 citations
TL;DR: In this paper, the electrooxidation pathways of ethanol and acetaldehyde in 0.1M HClO4 on ordered Pt (111) surfaces were examined by means of FTIR spectra obtained in real time during slow (2-10 mV s−1) thin-layer voltametric sweeps.
141 citations
TL;DR: In this article, a gas-phase Fourier transform infrared spectrometer was used to determine volatile products from pyrolysis of wood, coupled with a thermal balance, and the influence of the removal of inorganic salts and of ion-exchanged cations on these yields was studied.
119 citations
TL;DR: In this article, enzymatic hydrolysates of hemicellulose from steam-pretreated aspenwood were more fermentable than the acid hydrolysate after rotoevaporation or ethyl acetate extraction treatments to remove acetic acid and sugar-and lignin-degradation products prior to fermentation by Pichia stipitis CBS 5776.
Abstract: Enzymatic hydrolysates of hemicellulose from steam-pretreated aspenwood were more fermentable than the acid hydrolysate after rotoevaporation or ethyl acetate extraction treatments to remove acetic acid and sugar- and lignin-degradation products prior to fermentation by Pichia stipitis CBS 5776. Total xylose and xylobiose utilization from 5.0% (w/v) ethyl acetate extracted enzymatic hydrolysate was observed with an ethanol yield of 0.47 g ethanol/g total available substrate and an ethanol production rate of 0.20 g·l-1 per hour in 72 h batch fermentation.
108 citations
Patent•
BP1
TL;DR: In this paper, a carboxylic acid ester is produced at a selectivity of greater than 50% whilst producing the corresponding alcohol at the selectivity less than 10% from an acid or anhydride thereof.
Abstract: A carboxylic acid ester is produced at a selectivity of greater than 50% whilst producing the corresponding alcohol at a selectivity less than 10% from a carboxylic acid or anhydride thereof by reacting the acid or anhydride with hydrogen at elevated temperature in the presence as catalyst of a composition comprising a component (i) comprising at least one of Group VIII noble metal and/or a component (ii) comprising at least one of molybdenum, tungsten and rhenium and a component (iii) comprising an oxide of a Group IVb element. The process is particularly applicable to the hydrogenation of acetic acid to ethyl acetate.
97 citations
TL;DR: This article corrects the article on p. 514 in vol.
Abstract: Marked differences were found for minimum threshold concentrations of acetate catabolism by Methanosarcina barkeri 227 (1.180 mM), Methanosarcina mazei S-6 (0.396 mM), and a Methanothrix sp. (0.069 mM). This indicates that the aceticlastic methanogens responsible for the conversion of acetate to methane in various ecosystems might be different, depending on the prevailing in situ acetate concentrations.
96 citations
TL;DR: The kinetics of acetate utilization were examined for washed concentrated cell suspensions of two thermophilic acetotrophic methanogens isolated from a 58 degrees C anaerobic digestor and results are in agreement with a general model in which high acetate concentrations favor Methanosarcina spp.
Abstract: The kinetics of acetate utilization were examined for washed concentrated cell suspensions of two thermophilic acetotrophic methanogens isolated from a 58°C anaerobic digestor. Progress curves for acetate utilization by cells of Methanosarcina sp. strain CALS-1 showed that the utilization rate was concentration independent (zero order) above concentrations near 3 mM and that acetate utilization ceased when a threshold concentration near 1 mM was reached. Acetate utilization by cells of Methanothrix sp. strain CALS-1 was concentration independent down to 0.1 to 0.2 mM, and threshold values of 12 to 21 μM were observed. Typical utilization rates in the concentration-independent stage were 210 and 130 nmol min−1 mg of protein−1 for the methanosarcina and the methanothrix, respectively. These results are in agreement with a general model in which high acetate concentrations favor Methanosarcina spp., while low concentrations favor Methanothrix spp. However, acetate utilization by these two strains did not follow simple Michaelis-Menton kinetics.
94 citations
TL;DR: Dietary reduction of the intake of tyrosine and phenylalanine substantially reduced the excretion of homogentisic acid, presumably through an effect on the immature p-hydroxyphenylpyruvic acid oxidase.
Abstract: The effects of ascorbic acid on the excretion of homogentisic acid and its derivative benzoquinone acetic acid were studied in two adults and three infants. The administration of relatively large amounts of ascorbic acid to the adults was followed by a disappearance of benzoquinone acetic acid from the urine, whereas the level of excretion of homogentisic acid did not change. This could have relevance to the pathogenesis of ochronotic arthritis. In the 4-mo-old infant and the 5-mo-old infant ascorbic acid in the urine may have doubled the amount of homogentisic acid, presumably through an effect on the immature p-hydroxyphenylpyruvic acid oxidase. Dietary reduction of the intake of tyrosine and phenylalanine substantially reduced the excretion of homogentisic acid.
TL;DR: Cell extracts of acetonitrile-grown cells contained activities corresponding to nitrile hydratase and amidase, which mediate the breakdown of actonitrile into acetic acid and ammonia.
Abstract: A bacterium capable of utilizing high concentrations of acetonitrile as the sole source of carbon and nitrogen was isolated from soil and identified as Pseudomonas putida. This bacterium could also utilize butyronitrile, glutaronitrile, isobutyronitrile, methacrylonitrile, propionitrile, succinonitrile, valeronitrile, and some of their corresponding amides, such as acetamide, butyramide, isobutyramide, methacrylamide, propionamide, and succinamide as growth substrates. Acetonitrile-grown cells oxidized acetonitrile with a Km of 40.61 mM. Mass balance studies with [14C]acetonitrile indicated that nearly 66% of carbon of acetonitrile was released as 14CO2 and 14% was associated with the biomass. Metabolites of acetonitrile in the culture medium were acetic acid and ammonia. The acetate formed in the early stages of growth completely disappeared in the later stages. Cell extracts of acetonitrile-grown cells contained activities corresponding to nitrile hydratase and amidase, which mediate the breakdown of actonitrile into acetic acid and ammonia. Both enzymes were intracellular and inducible and hydrolyzed a wide range of substrates. The specific activity of amidase was at least 150-fold higher than the activity of the enzyme nitrile hydratase.
TL;DR: The aerobic growth and metabolism of eleven homofermentative and three heteroferMENTative Lactobacillus strains, three Leuconostoc strains, two Brochothrix thermosphacta strains and two Carnobacterium strains were studied in batch cultures and showed a maximal oxygen consumption during the stationary growth phase and this was coupled with a low final viable count.
Abstract: The aerobic growth and metabolism of eleven homofermentative and three heterofermentative Lactobacillus strains, three Leuconostoc strains, two Brochothrix thermosphacta strains and two Carnobacterium strains were studied in batch cultures at pH 6.0 and 25°C on a complex substrate containing 10.0 g glucose per litre. All strains, except Carnobacterium divergens 69, grew well aerobically. An oxygen consumption was registered for 18 of the strains—the exceptions being Lactobacillus alimentarius DSM 20249T, Lactobacillus farciminis DSM 20284T and Lactobacillus sharpeae DSM 20505T. The homofermentative lactobacilli showed a maximal oxygen consumption during the stationary growth phase and this was coupled with a low final viable count. Leuconostoc strains, heterofermentative lactobacilli, Brochothrix thermosphacta and Carnobacterium strains showed a maximal oxygen consumption during the exponential growth phase together with a high final viable count. The maximum specific growth rate varied from 0.19 to 0.54 h-1 while the growth yield varied from 19 to 86 g dry weight per mol glucose consumed. In general, homofermentative lactobacilli produced dl-lactic acid, acetic acid and acetoin. The three heterofermentative lactobacilli produced dl-lactic acid and acetic acid, two strains also produced ethanol Leuconostoc spp. formed d-lactic acid, acetic acid, and ethanol. B. thermosphacta produced acetoin, acetic acid, formic acid, isobutyric acid and isovaleric acid but no lactic acid. Carnobacterium produced l-lactic acid, acetic acid and acetoin. All strains accumulated hydrogen peroxide except L. alimentarius DSM 20249T, Carnobacterium piscicola 3 and B. thermosphacta.
TL;DR: Acetic acid inhibited fermentation in a respiratory defficient mutant of Saccharomyces cerevisiae (IGC 3507-111) in an exponential way and Ethanol potentiated this effect in a synergistic exponential way.
Abstract: Acetic acid inhibited fermentation in a respiratory defficient mutant ofSaccharomyces cerevisiae (IGC 3507-111) in an exponential way. The undissociated form of the acid probably was the toxic agent. Ethanol potentiated this effect in a synergistic exponential way.
TL;DR: Cell extracts of acetate grown Methanosarcina barkeri indicate that the archaebacterium contains the enzyme carbonic anhydrase (EC 4.2.1).
Abstract: Cell extracts (27000xg supernatant) of acetate grown Methanosarcina barkeri were found to have carbonic anhydrase activity (0.41 U/mg protein), which was lost upon heating or incubation with proteinase K. The activity was inhibited by Diamox (apparent K
i=0.5 mM), by azide (apparent K
i=1 mM), and by cyanide (apparent K
i=0.02 mM). These and other properties indicate that the archaebacterium contains the enzyme carbonic anhydrase (EC 4.2.1.1). Evidence is presented that the protein is probably located in the cytoplasm. Methanol or H2/CO2 grown cells of M. barkeri showed no or only very little carbonic anhydrase activity. After transfer of these cells to acetate medium the activity was “induced” suggesting a function of this enzyme in acetate fermentation to CO2 and CH4. Interestingly, Desulfobacter postgatei and Desulfotomaculum acetoxidans, which oxidize acetate to 2 CO2 with sulfate as electron acceptor, were also found to exhibit carbonic anhydrase activity (0.2 U/mg protein).
TL;DR: As revealed by the GLC chromatograms, ultrafiltration appears to be as effective as steam distillation in sample clean-up and enables higher, more reproducible analytical recoveries of long-chain VFAs.
Abstract: We describe a procedure for preparing fecal samples for determination of volatile fatty acids (VFAs) by gas-liquid chromatography (GLC) and "high-performance" liquid chromatography (HPLC). The simple, one-step procedure involves only ultrafiltration through a membrane with a molecular-mass cutoff of 3000 Da. As revealed by the GLC chromatograms, ultrafiltration appears to be as effective as steam distillation in sample clean-up. It also enables higher, more reproducible analytical recoveries of long-chain VFAs. The VFA content of the filtrate can also be measured by HPLC. Use of the ion-exclusion mechanism completely resolves isobutyric acid and butyric acid on a cation-exchange column. The mean (+/- SD) percentage distribution values of VFAs (measured by GLC) from five healthy subjects were 56.0 +/- 3.5 (acetic acid), 17.0 +/- 5.3 (propionic acid), 2.9 +/- 1.5 (isobutyric acid), 18.8 +/- 5.8 (butyric acid), 2.3 +/- 1.2 (isovaleric acid), and 2.9 +/- 0.8 (valeric acid).
TL;DR: In this article, the effects of selected organic acids and salts on microbial numbers, pH, exudate, and color were studied for vacuum-packaged, fresh pork chops, which were stored at 2 degrees-4 degrees C for 6 weeks.
Abstract: The effects of selected organic acids and salts on microbial numbers, pH, exudate, and color were studied for vacuum-packaged, fresh pork chops. Pork chops were dipped for 2 min in (v/v) 1% acetic acid, 1% acetic/1% lactic acid, 1.5% acetic/1.5% sodium acetate, 3% acetic/3% sodium ascorbate, 3% acetic/2% NaCl or sterile, distilled water before being vacuum-packaged and stored at 2 degrees-4 degrees C for 6 weeks. Treatments containing 3% acid resulted in lower aerobic microbial numbers (P less than 0.05) and effectively inhibited Enterobacteriaceae. Treatments containing 1% acetic acid, with or without 1% lactic acid, were ineffective. All acid treatments increased exudate and were detrimental to meat color (P less than 0.05) although sodium ascorbate reduced color damage. Chops treated with 3% acetic acid/3% sodium ascorbate had the highest Hunter a and L color scores.
TL;DR: Two bacterial strains were dominant in anaerobic enrichment cultures with betaine as a substrate and intertidal mud as an inoculum and the isolated strain PM1 was identified as Desulfuromonas acetoxidans, a rod-shaped, gram-negative, motile bacterium which fermented betaine.
Abstract: Two bacterial strains were dominant in anaerobic enrichment cultures with betaine (N,N,N-trimethylglycine) as a substrate and intertidal mud as an inoculum. One was a coccoid bacterium which was a trimethylamine (TMA)-fermenting methanogen similar to Methanococcoides methylutens. The other strain, a rod-shaped, gram-negative, motile bacterium, fermented betaine. On the basis of its ability to oxidize acetate and ethanol to CO2 with sulfur as an electron acceptor, its inability to reduce sulfate and sulfite, its morphology, the presence of c-type cytochromes, and other characteristics, the isolated strain PM1 was identified as Desulfuromonas acetoxidans. Although only malate and fumarate were known as substrates for fermentative growth of this species, the type strain (DSM 684) also fermented betaine. Strain PM1 grew with a doubling time of 9.5 h at 30°C on betaine and produced approximately 1 mol of TMA per mol of betaine, 0.75 mol of acetate, and presumably CO2 as fermentation products but only in the presence of selenite (100 nM). In this fermentation, betaine is probably reductively cleaved to TMA and acetate, and part of the acetate is then oxidized to CO2 to provide the reducing equivalents for the initial cleavage reaction. In the presence of sulfur, betaine was converted to TMA and presumably CO2 with the formation of sulfide; then, only traces of acetate were produced.
TL;DR: Clostridium formicoaceticum homofermentatively converts lactate to acetate at 37°C and pH 6.6–9.6, but this fermentation is strongly inhibited by acetic acid at acidic pH, and a mathematical model for this homoacetic fermentation was developed.
Abstract: Clostridium formicoaceticum homofermentatively converts lactate to acetate at 37 degrees C and pH 6.6-9.6. However, this fermentation is strongly inhibited by acetic acid at acidic pH. The specific growth rate of this organism decreased from a maximum at pH 7.6 to zero at pH 6.6. This inhibition effect was found to be attributed to both H(+) and undissociated acetic acid. At pH values below 7.6, the H(+) inhibited the fermentation following non-competitive inhibition kinetics. The acetic acid inhibition was found to be stronger at a lower medium pH. At pH 6.45-6.8, cell growth was found to be primarily limited by a maximum undissociated acetic acid concentration of 0.358 g/L (6mM). This indicates that the undissociated acid, not the dissociated acid, is the major acid inhibitor. At pH 7.6 or higher, this organism could tolerate acetate concentrations of higher than 0.8M, but salt (Na(+)) became a strong inhibitor at concentrations of higher than 0.4M. Acetic acid inhibition also can be represented by noncompetitive inhibition kinetics. A mathematical model for this homoacetic fermentation was also developed. This model can be used to simulate batch fermentation at any pH between 6.9 and 7.6.
TL;DR: It was found that the solutions of the derivatives of the chitosan derivatives with more than 50% acetyl content were stable even in alkaline conditions and the gelation and precipitation of the solutions did not occur.
TL;DR: Alkyl-substituted p-benzoquinones were easily synthesized in good yields by the oxidation of the corresponding phenols with a hydrogen peroxide/heteropolyacid couple in acetic acid as discussed by the authors.
TL;DR: In this paper, the kinetics of oxirane ring cleavage in epoxidized soybean oil have been studied using glacial acetic acid at 60, 70, 80 and 90°C.
Abstract: The kinetics of oxirane ring cleavage in epoxidized soybean oil have been studied using glacial acetic acid at 60, 70, 80 and 90°C. It was shown that the reaction can be successfully modelled as first order with respect to the epoxide concentration and second order with respect to acetic acid. The reaction velocity constant at 70°C was found to be 2 × 10−3 1−3 hr−1 mol−2, the frequency factor, A, = 2.321 × 107 hr−1 and the energy of activation, Ea = 15.84 k cal mol−1. The effects of the concentration of acetic acid and the temperature on the net yield of epoxides by in situ epoxidation were also studied on the basis of the predicted kinetic parameters of the reaction system.
TL;DR: Fermentation rate by immobilized propionibacteria was best in Ca(OH)2-neutralized whey, and at lactate concentrations between 1 and 2%.
Abstract: Growth of Propionibacterium shermanii B-123 was faster on media containing lactate than on that containing lactose. Cheese whey was therefore fermented with Lactobacillus helveticus and neutralized with NaOH or Ca(OH)2, before inoculation with B-123. Fermentation rate by immobilized propionibacteria was best in Ca(OH)2-neutralized whey, and at lactate concentrations between 1 and 2%. Calcium propionate concentrations of 1 and 3% reduced fermentation rates by 40% and 55% respectively. Optimum temperature for propionate fermentation by immobilized cells was 37°C. Ratios of propionic acid to acetic acid increased as incubation temperature was increased. Agitation increased propionic acid fermentation rates but lowered the ratio of propionic acid to acetic acid. Beads containing immobilized propionibacteria were re-utilized for ten consecutive fermentations. Fermentation rates increased upon re-utilization. Escherichia coli and Staphylococcus aureus were inhibited by the propionic fermentation but did not die; they kept growing at a reduced rate.
TL;DR: Acetic acid at concentrations as may occur during vinification and other alcoholic yeast fermentations induced death of glucose-grown cell populations of Saccharomyces cerevisiae IGC 4072 at temperatures at which thermal death was not detectable.
Abstract: Acetic acid at concentrations as may occur during vinification and other alcoholic yeast fermentations induced death of glucose-grown cell populations of Saccharomyces cerevisiae IGC 4072 at temperatures at which thermal death was not detectable. The Arrhenius plots of specific death rates with various concentrations of acetic acid (0-2%, w/v) pH 3.3 were linear and could be decomposed into two distinct families of parallel straight lines, indicating that acetic acid induced two types of death: (1) High enthalpy death (HED) predominated at lower acetic acid concentrations (> 0.5%, w/v) and higher temperatures; its enthalpy of activation (DeltaH( not equal)) approached that of thermal death (12.4 x 10(4) cal/mol); (2) Low enthalpy death (LED) predominated at higher acetic acid concentrations and lower temperatures with DeltaH( not equal) of 3.9 x 10(4) cal/mol. While the DeltaH( not equal) values for HED induced by acetic acid were similar with those reported earlier for HED induced by other fermentation endproducts, the values for the entropy coefficients were different: 127-168 entropy units mol(-1)L for acetic acid as compared with 3.6-5.1 entropy units mol(-1)L for ethanol, which agreed with experimental results indicating that acetic acid is over 30-times more toxic than ethanol with respect to yeast cell viability at high process temperatures.
TL;DR: In this paper, a combination of acetic acid and a silicon hydride in the presence of a Pd(0) catalyst is used to reduce acetylenes and some dienes to olefins.
TL;DR: During aerobic growth of Escherichia coli on protein hydrolysate and a carbon source (glucose), acetic acid is produced via glucose metabolism until the late log phase, when the culture pH starts to increase and the growth rate decreases.
Abstract: During aerobic growth of Escherichia coli (recombinant K-12 and strain B) on protein hydrolysate (L-broth) and a carbon source (glucose), acetic acid is produced via glucose metabolism until the late log phase. At this point, the culture pH starts to increase and the growth rate decreases. In cultures without further glucose supplementation, these changes are associated with the accumulation of ammonia, the utilization of acetic acid, the depletion of amino acids, and the complete depletion of glucose. We hypothesize that, after depletion of the glucose, the bacteria catabolize amino acids for energy and carbon and give off the nitrogen as ammonia. Also contributing to the overall increase in pH is the depletion of the acetic acid produced earlier as it is metabolized upon exhaustion of glucose. However, there is a lag time of about 1 hour after the initial pH increase before the sustained accumulation of ammonia begins. This lag indicates that an unidentified factor, in addition to the increase in ammonia, contributes to the increase in pH. Advantage was taken of the turnaround from acid production to base production as reflected in the culture pH to implement the addition of glucose. In growth experiments during which the pH was controlled in the basic direction by glucose addition, the observed decrease in growth rate was significantly postponed and the pH change in the basic direction was reversed as a result of acid production by the cells from the newly added glucose. Furthermore, coll densities of twice that obtained without glucose feeding were demonstrated. Based on the media cost per unit cell density, the data indicate a 31% cost savings.
TL;DR: A series of 3-alkyl-4-aminobutanoic acids were prepared via the Michael addition of nitromethane to 2-alkenoic esters, followed by catalytic hydrogenation of the resultant 3-(nitromethyl)alkanoic Esters using 10% palladium on carbon in acetic acid, and acid hydrolysis of the reduction products as mentioned in this paper.
Abstract: A series of 3-alkyl-4-aminobutanoic acids were prepared via the Michael addition of nitromethane to 2-alkenoic esters, followed by catalytic hydrogenation of the resultant 3-(nitromethyl)alkanoic esters using 10% palladium on carbon in acetic acid, and acid hydrolysis of the reduction products
TL;DR: Small cucumbers brined to equalize at 2.3% NaCl in an anaerobic tank underwent a normal primary lactic acid fermentation that resulted in 1.09% titratable acidity (as lactic) and pH 3.7, but was observed to have spoiled, as evidenced by an unpleasant ordor.
Abstract: Small cucumbers brined to equalize at 2.3% NaCl in an anaerobic tank underwent a normal primary lactic acid fermentation that resulted in 1.09% titratable acidity (as lactic) and pH 3.7. Nine months later the product was observed to have spoiled, as evidenced by an unpleasant ordor. Products formed during spoilage in order of concentration were acetic acid greater than butyric acid greater than n-propanol greater than propionic acid. No lactic acid remained. No botulinal toxin was detected. Clostridium tertium was identified as contributing to the spoilage, but did not produce propionic acid or n-propanol under test conditions. Evidence indicated that unidentified bacteria, possibly propionibacteria sp., degraded lactic acid causing a rise in pH which allowed C. tertium to grow.
TL;DR: Tests for survivors showed the most effective sanitizing treatment to be 3% acetic acid applied at 70°C, and S. typhimurium counts were affected least by temperature, and E. coli was least affected.
TL;DR: In this paper, the rate constants for the reactions of hydroxyl radicals with the monomer and dimer of acetic acid, deuterated acetic acids, and propionic acid have been determined by a laser photolysis-resonance absorption technique.
Abstract: Rate constants for the reactions of hydroxyl radicals with the monomer and dimer of acetic acid, deuterated acetic acids, and propionic acid have been determined by a laser photolysis-resonance absorption technique. Hydroxyl radicals were generated by photolysis of the acids at 222 nm with a KrCl laser and their decay was followed by time-resolved resonance absorption. The monomers of acetic and deuterated acetic acids reacted with OH much faster than the dimers, whereas the monomer and dimer of propionic acid reacted with about equal rate constants. A primary isotope effect was observed when carboxylic but not alkyl hydrogen was substituted by deuterium in acetic acid. The results are entirely consistent with the two-channel mechanism that we proposed for the reaction of OH with formic acid. The results are interpreted in terms of the variations in C-H bond strengths and in equilibrium constants for adduct formation of the acids studied.