Thermal evolution of acetic acid nanodeposits over 123-180 K on noncrystalline ice and polycrystalline ice studied by FTIR reflection-absorption spectroscopy: hydrogen-bonding interactions in acetic acid and between acetic acid and ice

Acetic acid vapor-deposited on ultrathin noncrystalline ice (NCI) and polycrystalline ice (PCI) films (less than 6 nm thick) under ultrahigh vacuum conditions has been investigated by using Fourier Transform Infrared Reflection-Absorption Spectroscopy. Pristine acetic acid deposited at 123 K (on a copper support) appears as an amorphous solid, which undergoes an irreversible phase transformation to a more structurally ordered (polycrystalline) form upon annealing to 153 K. Acetic acid is found to adsorb on NCI and PCI films initially through hydrogen bonding between C=O and dangling OH (of ice), followed by the formation of multilayers at 123 K. Thermal evolution studies of a low exposure of acetic acid on the ultrathin NCI and PCI films show that acetic acid undergoes coevaporation with water likely as an acetic acid hydrate at 155 K, which continues until the entire ice film has been exhausted at 165 K. Above 165 K, the remaining acetic acid solid appears to evaporate without undergoing the phase transformation, in contrast to the case of a high acetic acid exposure. Coevaporation of acetic acid with water is also found to proceed at a faster rate than the subsequent evaporation of acetic acid, which is consistent with the weaker interactions observed in the H-bonded acetic acid hydrate than that in acetic acid solid.     

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

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.     

Esterification of alcohols with acetic acid over ferric oxide

Ferric oxide has been found to promote both the ketonization of acetic acid and its esterification with methyl alcohol, isopropyl alcohol, and benzyl alcohol. The competitive kinetic technique, where the esterification reaction is made to compete with the ketonization of acetic acid, has been used to elucidate the mechanistic model for the ketonization of acetic acid on iron oxide. The ketonization of acetic acid at 375°C is found to be a second-order reaction which proceeds through a Langmuir-Hinshelwood mechanism.     

Synthesis of mixed acid anhydrides from methane and carbon dioxide in acid solvents

[reaction: see text] The reaction of CH(4) with CO(2) has been performed in anhydrous acids using VO(acac)(2) and K(2)S(2)O(8) as promoters. NMR analysis establishes that the primary product is a mixed anhydride of acetic acid and the acid solvent. In sulfuric acid, the overall reaction is CH(4) + CO(2) + SO(3) --> CH(3)C(O)-O-SO(3)H. Hydrolysis of the mixed anhydride produces acetic acid and the solvent acid. When trifluoroacetic acid is the solvent, acetic acid is primarily formed via the reaction CH(4) + CF(3)COOH --> CH(3)COOH + CHF(3).     

Reaction of sterically hindered gem-dialkylcyclohexadienones with acid agents

Conclusions A study was made of the reactions of six sterically hindered gem-dialkylcyclohexadienones with hydrogen chloride, aluminum bromide, acetic acid, and solutions of sulfuric acid in acetic acid and in acetic anhydride.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 1, pp. 178–180, January, 1972.     

Anion exchange of some elements in acetic acid-hydrochloric acid medium

A comparative study of the adsorbability of Cd(II), Ni(II), Mn(II), Ga(III), La(III), Mo(VI) and bromide from aqueous acetic acid solutions on' Dowex 1-X8, 100–200 mesh, in the acetate and chloride forms, proved that chloride ions are indispensable for high adsorption from concentrated acetic acid solutions. A study of the adsorption isotherms of Ni(II), Mn(II) and Cd(II) on the acetate-form resin from acetic acid-hydrochloric acid solutions, showed that these elements form anionic complexes. The K_d values on RCl-exchanger, for a given acetic acid concentration, were highly dependent on the total exchange capacity of the resin. A simplified anion-exchange separation procedure in aqueous acetic acid was developed, with an adsorption step from a mixture of acetic and hydrochloric acids.     

乙酸和一氯乙酸电离常数的高效毛细管区带电泳法测定

首次建立了测定一氯乙酸和乙酸的电离常数的高效毛细管区带电泳新方法.该方法利用中性标记物和电流突跃两种方法来标记电渗流,通过测定乙酸和一氯乙酸在一定pH的缓冲溶液中的电泳淌度,结合数据回归分析拟合,求得乙酸和一氯乙酸的电离常数;所得数据和文献报道值较为接近.总体而言,毛细管区带电泳法可简单、快速、可靠地用于测定待测化合物的电离常数.     

Feasibility of monitoring acetic acid process using near-infrared spectroscopy

Near-infrared (NIR) spectroscopy has been utilized to demonstrate its feasibility for the measurement of major components in the acetic acid process. In order to simulate the acetic acid process, synthetic mixtures were prepared from five different components: acetic acid, methyl acetate, methyl iodide, water, and potassium iodide. Partial least squares (PLS) regression was utilized to differentiate the spectral characteristics as well as to quantify each component for the mixtures. The spectral features of acetic acid, methyl acetate, methyl iodide, and water are noticeably different with each other over the entire NIR region. The quantity of iodide ion, which does not absorb NIR radiation, was determined using the wavelength shift and intensity change of water absorption band caused by the change of iodide ion concentration. The PLS calibration results of the five components show good correlation with reference data. They also demonstrate the technical feasibility of NIR spectroscopy for monitoring important components in the acetic acid process.     

Improved two-step hydrothermal process for acetic acid production from carbohydrate biomass

An improved two-step process for converting carbohydrate biomass to acetic acid under hydrothermal conditions is proposed. The first step consists of the production of lactic acid from carbohydrate biomass, and the second step consists of conversion of the lactic acid obtained in the first step to acetic acid using CuO as an oxidant. The results indicated that CuO as an oxidant in the second step can significantly improve the production of high-purity acetic acid from lactic acid, and the maximum yield of acetic acid was 61%, with a purity of 90%. The yield of acetic acid obtained using the improved two-step hydrothermal process from carbohydrate biomass, such as glucose, cellulose and starch, was greater than that obtained using traditional two-step process with H2O2 orO2. In addition, a proposed pathway for the production of acetic acid from lactic acid in the second step with CuO was also discussed. The present study provides a useful two-step process for the production of acetic acid from carbohydrate biomass.     

高效毛细管电泳分离测定水中的乙酸和氯代乙酸

用邻苯二甲酸氢钾(pH=5.4)缓冲液作为电泳的背景电解质,以十六烷基三甲基溴化铵作为电渗流抑制剂,用甲基叔丁基醚作为萃取剂处理水样,建立了一种测定水中的乙酸和氯代乙酸的简单灵敏的毛细管区带电泳(紫外检测)法.测定结果表明,分析物的迁移时间和峰面积的日内相对标准偏差分别低于0.33%和4.45%,日间相对标准偏差分别低...     

The combined effects of acetic acid, formic acid, and hydroquinone on Debaryomyces hansenii physiology

The combined effects of inhibitors present in lignocellulosic hydrolysates was studied using a multivariate statistical approach. Acetic acid (0–6 g/L), formic acid (0–4.6 g/L) and hydroquinone (0–3 g/L) were tested as model inhibitors in synthetic media containing a mixture of glucose, xylose, and arabinose simulating concentrated hemicellulosic hydrolysates. Inhibitors were consumed sequentially (acetic acid, formic acid, and hydroquinone), alongside to the monosaccharides (glucose, xylose, and arabinose). Xylitol was always the main metabolic product. Additionally, glycerol, ethanol, and arabitol were also obtained. The inhibitory action of acetic acid on growth, on glucose consumption and on all product formation rates was found to be significant (p≤0.05), as well as formic acid inhibition on xylose consumption and biomass production. Hydroquinone negatively affected biomass productivity and yield, but it significantly increased xylose consumption and xylitol productivity. Hydroquinone interactions, either with acetic or formic acid or with both, are also statistically signficant. Hydroquinone seems to partially lessen the acetic acid and amplify formic acid effects. The results clearly indicate that the interaction effects play an important role on the xylitol bioprocess.     

Adsorption of acetic acid on ice: experiments and molecular dynamics simulations

Adsorption study of acetic acid on ice surfaces was performed by combining experimental and theoretical approaches. The experiments were conducted between 193 and 223 K using a coated wall flow tube coupled to a mass spectrometric detection. Under our experimental conditions, acetic acid was mainly dimerized in the gas phase. The surface coverage increases with decreasing temperature and with increasing concentrations of acetic acid dimers. The obtained experimental surface coverages were fitted according to the BET theory in order to determine the enthalpy of adsorption deltaH(ads) and the mololayer capacity N(M(dimers)) of the acetic acid dimers on ice: deltaH(ads) = (-33.5 +/- 4.2) kJ mol(-1), N(M(dimers)) = (l1.27 +/- 0.25) x 10(14) dimers cm(-2). The adsorption characteristics of acetic acid on an ideal ice I(n)(0001) surface were also studied by means of classical molecular dynamics simulations in the same temperature range. The monolayer capacity, the configurations of the molecules in their adsorption sites, and the corresponding adsorption energies have been determined for both acetic acid monomers and dimers, and compared to the corresponding data obtained from the experiments. In addition, the theoretical results show that the interaction with the ice surface could be strong enough to break the acetic acid dimers that exist in the gas phase and leads to the stabilization of acetic acid monomers on ice.     

Atmospheric oxidation pathways of acetic acid

One of the most abundant carboxylic acids measured in the atmosphere is acetic acid (CH(3)C(O)OH), present in rural, urban, and remote marine environments in the low-ppb range. Acetic acid concentrations are not well reproduced in global 3-D atmospheric models because of the poor inventory of sources and sinks to model its global distribution. To understand the complete oxidation of acetic acid in the atmosphere initiated by OH radicals, ab initio calculations are performed to describe in detail the energetics of the reaction potential energy surface (PES). The proposed reaction mechanism suggests that the CH(3)C(O)OH + OH reaction takes place via three pathways: the addition of OH to the central carbon, the abstraction of a methyl hydrogen, and the abstraction of an acidic hydrogen. The PES is characterized by prereactive H-complexes, transition states, and more interestingly unique radical-mediated isomerization reactions. From the analysis of the energetics, acetic acid atmospheric oxidation will proceed mainly via the abstraction of the acidic hydrogen, consistent with previous experimental and theoretical studies. The major byproducts from each pathway are identified. Glyoxylic acid is suggested to be a major byproduct of the atmospheric oxidation of acetic acid. The atmospheric fate of glyoxylic acid is discussed.     

New process for producing cellulose acetate from wood in concentrated acetic acid

To explore further potential applications of acetic acid pulp, an investigation was conducted to develop a direct method for producing cellulose acetate from wood in combination with atmospheric acetic acid pulping. The process consists of delignification, totally chlorine-free bleaching, and esterification, with the concentrated acetic acid aqueous solution being used as only solvent throughout the process. The acetic acid pulp with kappa number of 30 and ISO brightness of 16 was bleached with 5% ozone on pulp to kappa number of 1.4 and brightness of 61. The resulting bleached pulp was further bleached with peracetic acid to kappa number of less than 1.0 and brightness of 68. The final bleached acetic acid pulp was acetylated with acetic anhydride in the concentrated acetic acid for 45 min to produce cellulose acetate with an apparent degree of substitution (DS) of 2.54. Although the product was lower grade compared with commercially available cellulose diacetate because it was prepared from the chemical pulp but not dissolving pulp, the product was almost soluble in acetone. Eventually, the DS of the acetone-soluble fraction was 2.62. The acetone solubility might be attributed to the original acetic acid pulp that had been partially acetylated during the pulping.     

Excess molar volumes of formic acid + water acetic acid + water and propionic acid + water systems at 288.15, 298.15 and 308.15 K

Densities and excess molar volumes were determined in the formic acid + water, acetic acid + water and propionic acid + water systems at 288.15, 298.15 and 308.15 K. The results are satisfactorily described using the ideal association model of the type A + B + A₂ for the system with formic acid. The Mecke—Kempter model is adequate for the acetic acid + water and propionic acid + water systems. In both models the formation of open dimers and open higher associates is postulated for the self-association of carboxylic acids in water.     

Antianexiety activity of pyridine derivatives synthesized from 2-chloro-6-hydrazino-isonicotinic acid hydrazide

A series of oxadiazole pyridine derivatives were synthesized by using 2-chloro-6-hydrazinoisonicotinic acid hydrazide as starting material. Treatment of the hydrazide with carbon disulfide to afford the oxadiazole derivative, which was treated with 5-methyl-2-furancarbaldehyde, formic acid, acetic acid/acetic anhydride, or phthalic anhydride to yield the corresponding pyridinodiazoles and on imide. Condensation of the hydrazide with p-fluorobenzaldehyde in ethanol or acetic acid in the presence of sodium acetate afforded hydrazone and oxadiazole derivatives, which were acetylated and cyclized with acetic anhydride to N-acetyloxadiazole derivatives. The hydrazone was treated with acetic acid in the presence of sodium acetate, or bromine water/sodium acetate to give on oxadiazole, while it was cyclized with chloroacetyl chloride in the presence of TEA to oxoazetidinaminoisonicotinamide. Finally, condensation of the hydrazide with acid anhydrides in refluxing glacial acetic acid afforded the corresponding bisimide derivatives. The pharmacological screening showed that many of these obtained compounds have good antianexiety activity comparable to diazepam^® as positive control.     

Effect of ethyl acetate on carbohydrate components and crystalline structure of pulp produced in aqueous acetic acid pulping

The aim of this study was to investigate the changes in carbohydrate components and the crystalline structure in hemp bast fibers by adding ethyl acetate to acetic acid/water pulping processes. It was found that ethyl acetate added to acetic acid/water process had a positive effect on yield, viscosity and carbohydrate components in pulp. It was assumed that the delignification ratio increased by adding ethyl acetate to aqueous acetic acid pulping. Xylose content in hemp bast fibers was affected more negatively in the ethyl acetate/acetic acid/water process than in the acetic acid/water one. Crystallinity and crystallite size were higher in pulp sample obtained by the acetic acid/water process without ethyl acetate.     

Trifluoromethyl sulphonic acid as a titrant in glacial acetic acid systems

Trifluoromethyl sulphonic acid in glacial acetic acid has been compared with perchloric acid in glacial acetic acid as a titrant in a limited number of cases. It does not appear that the reagent is likely to compete seriously with perchloric acid in non-aqueous titrimetry. Although comparable to perchloric acid in acid strength in acetic acid as well as in instrument response, it is unlikely that the considerably higher cost can be justified on the grounds of freedom from precipitate formation alone and no other advantageous feature has been observed which could justify this.

Abstract

Trifluoromethylsulfonsäure in Eisessig wurde mit Perchlorsäure in Eisessig als Titrationsmittel verglichen. Es scheint nicht wahrscheinlich, dass das Reagens ernsthaft mit Perchlorsäure als Titrationmittel in nichtwässrigem Medium konkurrieren kann. Das Reagens ist zwar mit Perchlorsäure vergleichbar, soweit es die Stärke (in Essigsäure) und das Ansprechen des Instrumentes betrifft; es ist aber unwahrscheinlich, dass sich die beträchtlich höheren Kosten lediglich wegen Nichtauftretens von Niederschlägen rechtfertigen lassen. Dies ist der einzige auffindbare Vorteil.     

Amidoalkylation of phosphorous acid

Amidoalkylation of phosphorous acid by the reaction of mixture of phosphorous acid and amide with carbonyl compounds in acetic anhydride, followed by hydrolysis to give 1-aminoalkanephosphonic acids, is described.     

A continuous acetic acid system for polyacrylamide gel electrophoresis of gliadins and other prolamines

A polyacrylamide gel electrophoresis system buffered by acetic acid alone was developed for electrophoresis of prolamines. When applied to gliadin electrophoresis, the acetic acid system produces more bands than does a conventional aluminum lactate-lactic acid system (using 12% acrylamide gels). The acetic acid system is relatively simple, requiring a single buffer component that is universally available in high purity.