Influence Of Acetic Acid Research Articles

Influence of acetic acid and ammonia catalyst on microstructure and properties of fluorinated polyimide–organosilicate hybrids

This work investigates the preparation, microstructure and thermal/electrical properties of fluorinated polyimide–organosilicate hybrids utilizing acetic acid and ammonia as the catalysts for sol–gel process to grow organosilicate filler particles. Nano-scale organosilicate was observed in the base-catalyzed hybrids, which was ascribed to the relative inertness of base catalysts in promoting the hydrolysis reaction. This postponed the formation of particles and hence smaller particle size. Electrical measurements found that the base-catalyzed hybrids possess lower dielectric constants ( κ = 2.40 at nominal Si content = 0.4 mol) due to the absence of polar groups and formation of silica xerogels with high porosity in the samples. In both hybrids, leakage current densities increase with the increase of Si content. However, leakage current density of base-catalyzed hybrid was higher than that of acid-catalyzed hybrid at the same Si content due to the smaller particle size and highly porous feature of organosilicate embedded in the base-catalyzed hybrids.

Morphological and phase evolution of TiO 2 nanocrystals prepared from peroxotitanate complex aqueous solution: Influence of acetic acid

Nanosized anatase and rutile TiO 2 having different shape, phase and size have been prepared from aqueous solutions of peroxo titanium complex starting from titanium(IV) isopropoxide (TTIP), acetic acid and hydrogen peroxide (H 2O 2) in water/isopropanol media by a facile sol–gel process. The TiO 2 nanocrystals are characterized by powder X-ray diffraction (XRD), Raman spectroscopy, FT-IR spectroscopy, TEM, high resolution transmission electron microscopy (HRTEM) and selected area electron diffraction (SAED) techniques. The influence of pH and the sequence of addition of reaction contents on the phase and morphology of TiO 2 are studied. The reasons for the observation of only anatase and/or mixture of anatase and rutile are given.

Focused-Ion Beam and Electron Microscopy Analysis of Corrosion of Lead-Tin Alloys: Applications to Conservation of Organ Pipes

AbstractAcross Europe, lead-tin alloy organ pipes are suffering from atmospheric corrosion. This deterioration can eventually lead to cracks and holes, preventing the pipes from producing sound. Organ pipes are found in compositions ranging from >99% Pb to >99% Sn. For very lead-rich (>99% Pb) pipes, organic acids emitted from the wood of organ cases have previously been identified as significant corrosive agents. In order to study the role of alloy composition in the susceptibility of pipes to organic acid attack, lead-tin alloys containing 1.2-15 at.% Sn were exposed to acetic acid vapors in laboratory exposure studies. Corrosion rates were monitored gravimetrically, and corrosion product phases were identified using grazing incidence angle X-ray diffraction. In a new method, focused-ion beam (FIB) cross-sections were cut through corrosion sites, and SEM and WDX were used to obtain detailed information about the morphology and chemical composition of the corrosion layers. The combination of FIB and SEM has made it possible to obtain depth information about these micron-scale layers, providing insight into the influence of acetic acid on alloys in the 1.2-15 at.% Sn range.

Synthesis of silica xerogels with high surface area using acetic acid as catalyst

The influence of acetic acid on the pore structure and surface area of silica prepared by the sol-gel method was investigated. Experimental conditions of synthesis, such as gelation temperature and solvents, were also studied. N2 adsorption isotherms of the samples were type 1, typical of microporous materials, explaining the high surface area values (BET) observed. The simultaneous addition of acetic and hydrochloric acids as catalysts and of acetone as solvent, together with the use of a gelation temperature of 20 ºC, made it possible to prepare amorphous silica materials with surface area values up to 850 m² g-1. The high surface area value of these samples could be explained by the microporosity and the nanometric size of the particles.

A fermentation strategy for anti-MUC1 C595 diabody expression in recombinantEscherichia coli

The development of fermentation conditions for the production of C595 diabody fragment (dbFv) inE. coli HB2151 clone has been explored. Investigations were carried out to study the effect of carbon supplements over the expression period, the comparison of C595 dbfv production in synthetic and complex media, the influence of acetic acid upon antibody production, and comparison of one-stage and two-stage processes operated at batch or fed-batch modes in bioreactor. Yeast extract supplied during expression yielded more antibody fragment than any other carbon supply. The synthetic medium presented higher specific productivity (0.066 mg dbFv g−1 dry cell weight) when compared to the complex medium (0.044 mg dbFv g−1 DCW). The comparison of fermentation strategies demonstrated that (1) one-stage fed-batch fermentation performed higher C595 dbFv production than that operated in batch mode which was significantly affected by acetate concentration; (2) a two-stage batch operation could enhance C595 dbFv production. It was found that a concentration of 12.3 mg L−1 broth of C595 dbFv and a cell concentration of 10.8 g L−1 broth were achieved at the end of two-stage operation in 5-L fermentation.

The influence of phase inversion process modified by chemical reaction on membrane properties and morphology

In this study, the chemical reaction between acetic acid (CH 3COOH) used as non-solvent additive of casting solution and sodium carbonate (Na 2CO 3) dissolved in water as coagulant was employed to modify the classical phase inversion process. By means of this method, the polyethersulphone (PES) ultrafiltration (UF) membranes were prepared. The influence of acetic acid on the properties of the polymer solution was examined by viscometry and related to the morphology of the membrane prepared from the casting solution. The membranes were characterized in terms of the pure water flux, solute transport and field emission scanning electron microscope (FESEM) observation. It was found that chemical reaction between the additive and coagulant increases membrane permeability and mean pore size while maintaining the relatively narrow pore size distribution. FESEM images also confirmed that the chemical reaction contributes to suppress the formation of macrovoid and enhance the interconnectivity of pore. Furthermore, the potential mechanism of membrane formation influenced by chemical reaction was explored tentatively.

Molecularly imprinted polymer with salicylaldehyde-Cu(OAc)2 as template.

In the report molecularly imprinted polymer (MIP) with salicylaldehyde-Cu(OAc)(2) as the template was synthesized and characterized by SEM, porosity and elemental analysis. Copper acetate was introduced since salicylaldehyde alone cannot display imprinting effect for its intramolecular hydrogen bond. The strong coordination interaction between salicylaldehyde and copper acetate made the complex have high retention on the HPLC column based on the SAD-Cu(OAc)(2) imprinted polymer. Several structural analogues such as salicylaldoxime, sulfosalicylic acid, p-hydroxybenzaldehyde and their complexes with copper acetate were chosen to study the selectivity of the MIPs. The influence of acetic acid and H(2)O in methanol mobile phase was studied. The experimental results showed that small amount of either acetic acid or H(2)O in mobile phase would weaken the interaction between the complex and the polymer, therefore, the retention of the complex was lowered to a large extent, but that of salicylaldehyde remained almost unchanged. The polymer imprinted with the complex showed high selectivity to both the acetate and copper (II). In addition, the MIP showed an enhanced selectivity to its template compared with the polymer prepared without copper acetate.

Effects of the use of acetic acid as the conservant in lucerne ensiling

The influence of acetic acid as the chemical conservant in three doses (4, 6 8 g/kg green mass) on the intensity of fermentation and proteolysis in lucerne silage was investigated. On the basis of chemical analysis, it was found that with the increase of conservant dose the pH value decreased aminogenesis and nitrogen solubility was limited. In silages treated the absolute and relative domination of acetic acid was found in total acid content. The increase of free and bonded acetic acid was discovered with the increase of conservant dose. Free butyric acid was not detected, while bonded butyric acid was present in negligible concentration, without effect on silage quality. Compared to control silage (III quality class according to DLG and Zelter method), a significant increase of acetic acid in silages resulted in the decline of their quality, and they were ranked as not useful (V quality class according to DLG method), or on the margin of usefulness (IV quality class according to Zelter method). In spite of some foreign references, domestic experiences show that acetic acid is not an effective conservant and it is not recommended for that use for lucerne that is not simple to ensile.

Enantioselective Hydrogenation over Cinchona-Modified Pt: The Special Role of Carboxylic Acids

The influence of acetic acid (AcOH) and trifluoroacetic acid (TFA) on the hydrogenation of ethyl-4,4,4-trifluoroacetoacetate has been investigated by using Pt/Al(2)O(3) modified by cinchonidine and O-methylcinchonidine. We have shown that the sometimes dramatic changes in enantioselectivity and rate cannot simply be interpreted by protonation of the alkaloid modifier. We propose a new three-step reaction pathway, involving interaction of the carboxylic acid with the reactant and the chiral modifier. The mechanism is supported by IR spectroscopic identification of cyclic TFA-modifier ion pairs. This new approach can rationalise the poorly understood role of acids in the enantioselective hydrogenation of activated ketones over cinchona-modified platinum metals.

Phase equilibria for liquid mixtures of (butanenitrile + a carboxylic acid + water) at 298.15 K

Liquid–liquid equilibrium data are presented for mixtures of (butanenitrile (1)+acetic acid or propanoic acid or butanoic acid or 2-methylpropanoic acid or pentanoic acid or 3-methylbutanoic acid (2)+water (3)) at 298.15 K. The relative mutual solubility of all the carboxylic acids is higher in the butanenitrile layer than in the aqueous layer. The influence of acetic acid and propanoic acid on the solubility of water in butanenitrile is greater than that of the other acids. Three parameter equations have been fitted to the binodal curve data. These equations are compared and discussed in terms of statistical consistency. Selectivity values for solvent separation efficiency were derived from the tie-line data. The NRTL and UNIQUAC models were used to correlate the experimental results and to calculate the phase compositions of the ternary systems. The NRTL equation fitted the experimental data far better than the UNIQUAC equation.

Kinetic studies on the interactions of manganese–porphyrins with peracetic acid. Part 2. The influence of acetic acid and porphyrin substituents

The one-electron oxidation of 1,1-diphenyl-2-picrylhydrazine (DPPH) and Zn–tetra-tert-butylphthalocyanine (PcZn) to the corresponding stable radical (DPP·) and π-radical cation (PcZn+·) with peracetic acid in acetonitrile–acetic acid has been studied, in the presence of MnIII complexes of meso-tetra(2,6-dichloro-4-R-phenyl)porphyrins (RTDCPPMnCl; R = CH3O, H, Br, Cl or NO2) as catalysts. The formation of a two-centre donor–acceptor complex of "catalyst–oxidant" type (adduct ‘A’) with rate constant k1 is the first stage of the reaction. The balance of the electron donating properties of the porphyrin ring and electron accepting properties of MnIII determines the formation of ‘A’, as shown by the independence of k1 of catalyst structure. The influence of added acetic acid on the UV–Vis spectra of RTDCPPMnX in CH3CN and on the oxidation rate of DPPH and PcZn evidenced that a molecule of AcOH is included in the internal co-ordination sphere of RTDCPPMnX and of the reaction intermediates. The rate constant k2 for the irreversible transformation of ‘A’ into an equilibrium mixture of MnV and MnIV oxo-species (established in Part 1) must thus refer to the acetic acid adducts of Mn–porphyrins {[RTDCPPMn(AcOH)](X)}. A non-linear dependence of log k2rel on σpara of the porphyrin substituents R has also been found. However, electron-withdrawing substituents are particularly effective for enhancement of the rate of formation of the high-valent oxomanganese species.

Fluorescence spectroscopy of the cervix: influence of acetic acid, cervical mucus, and vaginal medications.

Fluorescence spectroscopy has been shown to provide information useful in the detection of cervical dysplasia. The goal of this study was to determine if substances found on the cervix such as acetic acid, mucus, and vaginal medications can influence the fluorescence in the spectral region useful for discriminating normal cervical tissue from abnormal tissue. Fluorescence spectra were collected at 337 nm excitation from the cervix in vivo both before and after application of acetic acid; the data were analyzed to identify the effects of the acetic acid on the spectra. Cervical mucus was acquired from patients referred for colposcopy and frozen until measurements were taken. Fluorescence excitation-emission matrices (EEMs) were measured for the mucus samples. Additionally, the transmission spectra of mucus were measured to determine if its absorption could influence the fluorescence signal measured from the tissue. EEMs were measured for samples of commonly prescribed vaginal medications. All EEMs were compared to those of cervical biopsies. Acetic acid introduces changes in both the lineshape and intensity of the spectra. On average, the changes are more significant in spectra of abnormal tissue. Cervical mucus was found to have no significant absorption bands, but the measured fluorescence was approximately the same order of magnitude as that measured from the cervix in vitro. Most medications exhibited significant fluorescence in the spectral region of diagnostic interest for the cervix. Acetic acid appears to increase the differences in fluorescence emission spectra of normal and pre-cancerous cervical tissues; thus, its use is beneficial. The presence of cervical mucus can possibly interfere with the collection of fluorescence spectra for tissue classification. Patients should not use vaginal preparations during the 48 hours prior to tissue fluorescence measurements.

Fluorescence spectroscopy of the cervix: Influence of acetic acid, cervical mucus, and vaginal medications

Fluorescence spectroscopy of the cervix: Influence of acetic acid, cervical mucus, and vaginal medications

Oxidation of N-benzylidene-2-hydroxyaniline by dioxygen catalysed by a dicobalt complex †

The oxidation of N-benzylidene-2-hydroxyaniline and its related derivatives by O2 catalysed by [Co2L(µ-OH)] {H3L = 2,6-bis[(2-hydroxyphenyl)iminomethyl]-4-methylphenol} in DMF at 363 K was investigated. The oxidation products were the corresponding 2-substituted benzoxazoles. However, a side reaction leading to 2-aminophenoxazine-3-one via hydrolysis of the starting compound with water produced in the oxidation, followed by the oxidation of aminophenol, was established. If a dehydrating agent such as anhydrous Na2SO4 or 4 A molecular sieves was present in the reaction mixture the isolated product yields were above 87%. The fact that the reaction rate of the oxidation process in the presence of a radical scavenger was similar to that without suggests that it was a non-radical process. The initial oxidation rates depended linearly on the concentration of catalyst. The rates also depended linearly on the concentration of the organic substrate N-benzylidene-2-hydroxyaniline and O2 pressure when these variables were small ([substrate] < 0.2 M, O2 pressure < 70 kPa). At high concentration of substrate and O2 pressure the rate showed saturation behavior. These kinetic data could be satisfactorily accounted for by a mechanism with initial co-ordination of substrate to [Co2L(µ-OH)], followed by the co-ordination of O2 to the catalyst, then the rate limiting step of oxidation of substrate. The formation of the adduct between N-benzylidene-2-hydroxyaniline and catalyst at 298 K was characterized by UV-Vis spectroscopy. The variation of the initial rates among the organic substrates could be explained by stereoelectronic effects. Moreover, the influence of acetic acid which slowed the initial rate of oxidation and weak base (2,6-di-tert-butylpyridine) which had little effect on the rate could also be satisfactorily accounted for based on the acid–base properties of the proposed reaction intermediates.

Delayed gastric emptying rate may explain improved glycaemia in healthy subjects to a starchy meal with added vinegar.

The aim of the study was to evaluate the possible influence of acetic acid (administered as vinegar) on the postprandial glucose and insulin responses, and the potential involvement of a modified gastric emptying rate was studied by use of paracetamol as a marker. The white bread reference meal as well as the corresponding meal supplemented with vinegar had the same content of starch, protein and fat. The meals were served in the morning after an over-night fast and in random order. Capillary blood samples for analysis of glucose, insulin and paracetamol were collected postprandially. The study was performed at the Department of Applied Nutrition and Food Chemistry, Lund University, Sweden. Ten healthy volunteers, seven women and three men, aged 22-51 y, with normal body mass indices were recruited. The presence of acetic acid, given as vinegar, significantly reduced the postprandial glucose (GI=64) and insulin responses (II=65) to a starchy meal. As judged from lowered paracetamol levels after the test meal with vinegar, the mechanism is probably a delayed gastric emptying rate. Fermented foods or food products with added organic acids should preferably be included in the diet in order to reduce glycaemia and insulin demand.

Influence of acetic acid on the growth of Escherichia coli K12 during high-cell-density cultivation in a dialysis reactor

High-cell-density cultivations of Escherichia coli K12 in a dialysis reactor with controlled levels of dissolved oxygen were carried out with different carbon sources: glucose and glycerol. Extremely high cell concentrations of 190 g/l and 180 g/l dry cell weight were obtained in glucose medium and in glycerol medium respectively. Different behaviour was observed in the formation of acetic acid in these cultivations. In glucose medium, acetic acid was formed during the earlier phase of cultivation. However, in glycerol medium, acetic acid formation started later and was particularly rapid at the end of the cultivation. In order to estimate the influence of acetic acid during these high-cell-density cultivations, the inhibitory effect of acetic acid on cell growth was investigated under different culture conditions. It was found that the inhibition of cell growth by acetic acid in the fermentor was much less than that in a shaker culture. On the basis of the results obtained in these investigations of the inhibitory effect of acetic acid, and the mathematical predictions of cell growth in a dialysis reactor, the influence of acetic acid on high-cell-density cultivation is discussed.

MICROBIOLOGICAL AND SENSORY ANALYSES OF REFRIGERATED CATFISH FILLETS TREATED WITH ACETIC AND LACTIC ACIDS

ABSTRACTThe influence of acetic acid (AA) and/or lactic acid (LA) dips on microbial numbers, pH, and sensory scores of catfish fillets was assessed during storage at 4C. Fillets were treated by dipping in 4C AA and/or LA solutions for 0–60s. Fillets treated with either 3–4% AA or 2% AA and 2% LA for 30–60s suppressed growth of aerobic microorganisms for 4 days and extended shelf‐life to 16 days. Treatment with either 3–4% LA or 1% AA and 1% LA for 5–60s prolonged microbiological shelf life to 12 days. AA had greater antimicrobial activity than LA. Fillets treated with AA alone or combinations of AA and LA were liked less by sensory panels than controls due to acidic odor and flesh discoloration. Thus, concentrations of AA or LA greater than 2% or exposure times greater than 30s are not recommended for catfish fillets.

The Influence of Acetic Acid and Glycerol on the Preparation of Strontium Titanate

The Influence of Acetic Acid and Glycerol on the Preparation of Strontium Titanate

Distribution of acetic acid between water and organic solutions of tri- n-octylamine

Organic solutions of a tertiary amine are being used increasingly to separate organic acids from aqueous solutions by reactive extraction. The present paper deals with experimental investigations and the modeling of the liquid-liquid equilibria encountered when toluene, chloroform or methyl isobutyl ketone are used as solvents for the tertiary amine tri- n-octylamine. Acetic acid was used as an example of a carboxylic acid. All measurements were carried out at 298.15 K. Experimental results for the compositions of the coexisting phases are reported. Infrared spectroscopic investigations were carried out to determine the equilibrium constants of some of the chemical reactions observed in the organic solvents toluene and chloroform. The results of the liquid-liquid equilibrium measurements were correlated by a model which takes into account chemical reactions as well as physical interactions. Some of the model parameters were deduced from the spectroscopic investigations and others were determined from literature data on binary subsystems. The remaining parameters (chemical equilibrium constants and physical interaction parameters) were fitted to the liquid-liquid equilibrium data. The final correlation gives a good description of the distribution of acetic acid between the coexisting phases over a wide concentration range. The model also describes reliably the solubility of water in the acetic-acid-containing organic phases and the influence of acetic acid on the solubility of the organic solvents in the aqueous phase.

Synthesis of 1-substituted 1,2,3,9a-tetrahydro-9H-imidazo[1,2-a]indol-2-ones

1-R-9,9,9a-Trimethyl-1,2,3,9a-tetrahydro-9H-imidazo[1,2-a]indol-2-ones and the corresponding 2-methylene-2,3-dihydroindoles were obtained by the reaction of 2,3,3-trimethyl-3H-indole with a number of N-substituted chloroacetic acid amides and subsequent reaction of the resulting quaternary salts with bases. The kinetics of intramolecular cyclization of 1-(N-alkylcarbamoylethyl)-2-methylene-2,3-dihydroindoles under the influence of acetic acid were studied. Under the influence of strong protic acids 1-R-imidazo[1,2-a]indol-2-ones undergo decyclization and are converted to 3H-indolium salts.