Showing papers on "Benzoic acid published in 1997"

Catalytic Oxidation of Alkylbenzenes with Molecular Oxygen under Normal Pressure and Temperature by N-Hydroxyphthalimide Combined with Co(OAc)2

Abstract: A practical catalytic method to convert alkylbenzenes into the corresponding carboxylic acids under atmospheric dioxygen at ambient temperature using a combined catalytic system consisting of N-hydroxyphthalimide (NHPI) and Co(OAc)2 was developed. For instance, the oxidation of toluene was completed by NHPI combined with Co(OAc)2 under an oxygen atmosphere at room temperature to give benzoic acid in 81% yield. Under these conditions, o- and p-xylenes were selectively converted into the corresponding monocarboxylic acids without the formation of the dicarboxylic acids. ESR measurements showed that Co(II) species assists in the formation of phthalimide-N-oxyl (PINO), which is a key species in this oxidation, from NHPI.

Hydrogen Atom Abstraction by Permanganate: Oxidations of Arylalkanes in Organic Solvents.

Abstract: Oxidations of arylalkanes by nBu4NMnO4 have been studied in toluene solvent: toluene, ethylbenzene, diphenylmethane, triphenylmethane, 9,10-dihydroanthracene, xanthene, and fluorene. Toluene is oxidized to benzoic acid and a small amount of benzaldehyde; other substrates give oxygenated and/or dehydrogenated products. The manganese product of all of the reactions is colloidal MnO2. The kinetics of the reactions, monitored by UV/vis spectrometry, show that the initial reactions are first order in the concentrations of both nBu4NMnO4 and substrate. No induction periods are observed. The same rate constants for toluene oxidation are observed in neat toluene and in o-dichlorobenzene solvent, within experimental errors. The presence of O2 increases the rate of nBu4NMnO4 disappearance. The reactions of toluene and dihydroanthracene exhibit primary isotope effects: kC7H8/kC7D8 = 6 (±1) at 45 °C and kC14H12/kC14D12 = 3.0 (±0.6) at 25 °C. The rates of oxidation of substituted toluenes show only small substituent...

Mechanism of Polyphosphoric Acid and Phosphorus Pentoxide−Methanesulfonic Acid as Synthetic Reagents for Benzoxazole Formation

Abstract: The mechanism of 2-phenylbenzoxazole formation from benzoic acid and o-aminophenol in polyphosphoric acid (PPA) is studied by NMR spectroscopy and chemical analysis. Benzoic acid reacts with PPA to form benzoic−phosphoric anhydride and benzoic−polyphosphoric anhydride. The ratio of mixed anhydride to free carboxylic acid increases dramatically as the P2O5 content of PPA increases, but this ratio is independent of reaction temperature and time. When o-aminophenol dissolves in PPA, part of the hydroxyl group is converted to phosphate ester, and only protonated amine is detected. Benzoic acid, mixed anhydride, and PPA are in dynamic equilibrium, and so are PPA, o-aminophenol, and its phosphate ester. The mixed anhydride and o-aminophenol react to form 2-aminophenyl benzoate as the first reaction intermediate which undergoes rapid acyl migration to generate 2-hydroxybenzanilide. Ring closure of 2-hydroxybenzanilide to form 2-phenylbenzoxazole is acid catalyzed. The reactive components in phosphorus pentoxide−...

Conversion reactions of various phenoxyalkanoic acid herbicides in soil. 1. Enantiomerization and enantioselective degradation of the chiral 2-phenoxypropionic acid herbicides

Abstract: The degradation of selected phenoxyalkanoic acid herbicides in soil under laboratory conditions was studied by using enantioselective high-resolution gas chroma tography/mass spectrometry (HRGC/MS). The compounds investigated were the chiral 2-(4-chloro-2-methylphenoxy)propionic acid (MCPP) and 2-(2,4-dichlorophenoxy)propionic acid (DCPP) and the achiral (4-chloro-2-methylphenoxy)acetic acid (MCPA), 2,4-(dichlorophenoxy)acetic acid (2,4-D), and dicamba, a benzoic acid derivative. Racemic and enantiopure MCPP and DCPP were incubated in separate experiments. In case of MCPP and DCPP, the herbicidally active R enantiomers were significantly slower degraded than the inactive S enantiomers. Incubation of enantiopure MCPP and DCPP revealed significant enantiomerization with formation of the R enantiomers from the S enantiomers, and vice-versa. Enantiomerization was found to be biologi cally mediated and was not observed in sterilized soil. Degradation followed initially approximate first-order kinetics with ove...

Inactivation of escherichia coli o157:h7 by the combination of organic acids and pulsed electric field

Abstract: Inactivation of Escherichia coli O157:H7 by pulsed electric field, benzoic or sorbic acid, alone or in combination was investigated. When the cells of E. coli O157:H7 were suspended in 10% glycerol and treated with a single high-voltage (12. 5 kv/cm) electric pulse at 25C, the count decreased by 1.1-1.6 log 10 CFU/mL. Presence of benzoic and sorbic acid (1000 ppm) in the suspending medium, at pH 3.4 without electric treatment, decreased the count by 1.9-2.5 and 0.6-1.1 log, respectively. A synergistic killing effect between the high electric pulse and organic acid was observed at pH 3.4, but not at pH 6.4. When the cell suspension of E. coli O157:H7 was treated with five electric pulses in the presence of benzoic or sorbic acid at pH 3.4, the count decreased by 5.6 and 4.2 logs, respectively. Inactivation of the pathogen by combinations of electric pulse and organic acid was enhanced by an increase in temperature, field strength, and number of electric pulses. Inactivation was greater when the cells were suspended in ionic suspending media (0.1 % NaCl or 5mM phosphate buffer) than in nonionic media (10% glycerol or 1% sucrose).

Proteins induced in Escherichia coli by benzoic acid.

Abstract: Proteins induced by benzoic acid in Escherichia coli were observed on two-dimensional electrophoretic gels (2-D gels). Cultures were grown in glucose-rich medium in the presence or absence of 20 mM benzoate at an external pH of 6.5, where the pH gradient (deltapH) is large and benzoate accumulates, and at an external pH of 8.0, where deltapH is inverted and little benzoate is taken up. Radiolabeled proteins were separated on 2-D gels and were identified on the basis of the index of VanBogelen and Neidhardt. In the absence of benzoic acid, little difference was seen between pH 6.5 and pH 8.0; this confirms that the mechanisms of protein homeostasis in this range are constitutive, including the transition between positive and inverted deltapH. Addition of benzoate at pH 6.5 increased the expression of 33 proteins. Twelve of the benzoate-induced proteins were induced at pH 8.0 as well, and nine of these matched proteins induced by the uncoupler dinitrophenol. Eighteen proteins were induced by benzoate only at pH 6.5, not at pH 8.0, and were not induced by dinitrophenol. One may be the iron and pH regulator Fur, which regulates acid tolerance in Salmonella spp. The other 13 proteins had not been identified previously. The proteins induced by benzoate only at a low pH may reflect responses to internal acidification or to accumulation of benzoate.

Influence of pH, Benzoic Acid, EDTA, and Glutathione on the Pressure and/or Temperature Inactivation Kinetics of Mushroom Polyphenoloxidase

Abstract: The pressure and/or temperature inactivation of mushroom polyphenoloxidase (PPO; EC 1.14.18.1) in the absence and presence of EDTA, benzoic acid, and glutathione was studied on a kinetic basis. In addition, the effect of pH was evaluated. The temperature stability of PPO at atmospheric pressure increased with increasing pH up to pH 6.5. The pressure stability of PPO at room temperature (25 °C) also increased with increasing pH. EDTA slightly increased the thermal stability of the enzyme but did not alter the pressure stability of PPO. Benzoic acid protected the enzyme toward temperature but caused sensitization toward pressure when used at a concentration of 50 mM. Glutathione produced sensitization to both temperature and pressure. It is suggested that the sensitizing effect of glutathione is due to an interaction with a disulfide bond of the enzyme.

Controlling the Work Function of GaAs by Chemisorption of Benzoic Acid Derivatives

Abstract: Control of the work function of GaAs single crystals, under ambient conditions, was achieved by chemisorption of a series of benzoic acid derivatives with varying dipole moments. Quantitative Fourier transform infrared spectroscopy shows that the benzoic acid derivatives bind as carboxylates, via coordination to oxidized Ga or As atoms, with a surface coverage of about one layer and a binding constant of 2.1 104 M-1 for benzoic acid. Contact potential difference measurements reveal that molecules affect the work function by changing the electron affinity while band bending is not affected significantly. The direction of the electron affinity changes depends on the direction of the dipole moments, and the extent of the change increases linearly with the dipole's magnitude. Investigation of the surface composition by X-ray photoelectron spectroscopy shows that the etched surface, onto which the molecules adsorb, is covered by an oxide layer. This may prevent the molecules from affecting band bending.

Purification, characterization, and properties of an aryl aldehyde oxidoreductase from Nocardia sp. strain NRRL 5646.

Abstract: An aryl aldehyde oxidoreductase from Nocardia sp strain NRRL 5646 was purified 196-fold by a combination of Mono-Q, Reactive Green 19 agarose affinity, and hydroxyapatite chromatographies The purified enzyme runs as a single band of 140 kDa on sodium dodecyl sulfate-polyacrylamide gel electrophoresis The molecular mass was estimated to be 163 +/- 38 kDa by gel filtration, indicating that this enzyme is a monomeric protein The binding of the enzyme to Reactive Green 19 agarose was Mg2+ dependent The binding capacity was estimated to be about 02 mg of Reactive Green agarose per ml in the presence of 10 mM MgCl2 This enzyme can catalyze the reduction of a wide range of aryl carboxylic acids, including substituted benzoic acids, phenyl-substituted aliphatic acids, heterocyclic carboxylic acids, and polyaromatic ring carboxylic acids, to produce the corresponding aldehydes The Km values for benzoate, ATP, and NADPH were determined to be 645 +/- 75, 293 +/- 31, and 573 +/- 125 microM, respectively The Vmax was determined to be 0902 +/- 004 micromol/min/mg of protein Km values for (S)-(+)-alpha-methyl-4-(2-methylpropyl)-benzeneacetic acid (ibuprofen) and its (R)-(-) isomer were determined to be 155 +/- 18 and 345 +/- 25 microM, respectively The Vmax for the (S)-(+) and (R)-(-) isomers were 133 and 015 micromol/min/mg of protein, respectively Anthranilic acid is a competitive inhibitor with benzoic acid as a substrate, with a Ki of 261 +/- 30 microM The N-terminal and internal amino acid sequences of a 76-kDa peptide from limited alpha-chymotrypsin digestion were determined

Extrusion of benzoic acid in Saccharomyces cerevisiae by an energy-dependent mechanism

Abstract: When grown in the presence of benzoic acid, Saccharomyces cerevisiae was able to extrude [14C]benzoic acid when a pulse of glucose was given to preloaded cells. While octanoic, sorbic, hexanoic, salicylic, butyric and propionic acids were also inducers, ethanol and acetic acid were not. The mechanism of extrusion required energy and prior growth in the presence of the inducers. Diethylstilbestrol, an inhibitor of ATPases, prevented benzoic acid extrusion. Propionic acid was not actively extruded in cells adapted to either benzoic or propionic acid, behaving as an appropriate probe to measure intracellular pH. Even though the extrusion mechanism was active, benzoic acid entered the cells by a simple diffusion mechanism.

Hydrogen bonding of some organic acid in supercritical CO2 with polar cosolvents

Abstract: FTIR spectroscopy was used to study the hydrogen bonding of benzoic acid and salicylic acid with ethanol and methanol in supercritical CO 2 . The extent of hydrogen bonding was estimated from the hydrogen-bonded and nonhydrogen-bonded infrared absorption bands. It was found that the solutes and the cosolvents can form hydrogen bondings even their concentrations are very low. At constant solute concentrations, the extent of hydrogen bonding increases with cosolvent concentrations.

Theoretical studies of inclusion complexes of α- and β-cyclodextrin with benzoic acid and phenol

Abstract: A series of semiempirical molecular orbital calculations using the AM1 method were performed on the inclusion complexes of α- and β-cyclodextrin with benzoic acid and phenol in the “head-first” and “tail-first” positions. The AM1 results show that α-cyclodextrin complexes with both guest compounds in the “head first” position are more stable than in the “tail-first” position, while the β-cyclodextrin complex with phenol in the “tail-first” position is more stable, but with benzoic acid, the “head-first” position is more stable. The driving forces for complex formation were investigated based on different intramolecular and intermolecular interactions. In addition, 1SCF AM1 calculations were performed on the β-cyclodextrin complexes with benzoic acid in the “tail-first” and “head-first” positions with the benzoic acid moved stepwise along the Z-axis of the β-cyclodextrin principal axis coordinate system. © 1997 John Wiley & Sons, Inc. Int J Quant Chem 65: 1135–1152, 1997

Theoretical studies of inclusion complexes of β‐cyclodextrin with methylated benzoic acids

Abstract: AM1 semiempirical molecular orbital calculations have been performed on the inclusion complexes of β-cyclodextrin (β-CD) with methylated benzoic acids in two orientations, the “head-first” and “tail-first” positions. In the former, the CO2H group points toward the primary hydroxyls of the CD. In the latter, it points away from them. Out of 30 possible inclusion complexes, AM1 results predict only three clearly stable inclusion complexes. These are β-CD with 4-methyl benzoic acid in the head-first position, β-CD with 2,4-dimethyl benzoic acid in the head-first position, and β-CD with 3,5-dimethyl benzoic acid in the tail-first position. The orientations of the stable inclusion complexes correlate with the total number of intramolecular hydrogen bonds and intermolecular hydrogen bonds. The stability of a complex also correlates with the closeness of the host and guest geometries in the complex to their isolated molecule geometries. © 1997 John Wiley & Sons, Inc. Int J Quant Chem 64: 711–719, 1997

Anaerobic Degradation of m-Cresol by a Sulfate-Reducing Bacterium.

Abstract: m-Cresol metabolism under sulfate-reducing conditions was studied with a pure culture of Desulfotomaculum sp. strain Groll. Previous studies with a sulfate-reducing consortium indicated that m-cresol was degraded via an initial para-carboxylation reaction. However, 4-hydroxy-2-methylbenzoic acid was not degraded by strain Groll, and no evidence for ring carboxylation of m-cresol was found. Strain Groll readily metabolized the putative metabolites of a methyl group oxidation pathway, including 3-hydroxybenzyl alcohol, 3-hydroxybenzaldehyde, 3-hydroxybenzoic acid, and benzoic acid. Degradation of these compounds preceded and inhibited m-cresol decay. 3-Hydroxybenzoic acid was detected in cultures that received either m-cresol or 3-hydroxybenzyl alcohol, and trace amounts of benzoic acid were detected in m-cresol-degrading cultures. Therefore, we propose that strain Groll metabolizes m-cresol by a methyl group oxidation pathway which is an alternate route for the catabolism of this compound under sulfate-reducing conditions.

Origin of the Oxygen Atom in C-H Bond Oxidations Catalyzed by a Water-Soluble Metalloporphyrin.

Abstract: The monopersulfate oxidation of 4-isopropylbenzoic acid performed in H218O and catalyzed by a water-soluble metalloporphyrin indicated that half of the oxygen atoms incorporated in 4-(1-hydroxy-1-methylethyl)benzoic acid, the primary hydroxylation product, came from water. A redox tautomerism of the active high-valent hydroxo−metal−oxo porphyrin intermediate coupled with an oxygen rebound mechanism explained this result. Under similar conditions, ketoprofen was directly oxidized to 3-benzoylacetophenone, via at least two different reaction pathways. Trapping of radical intermediates by molecular oxygen competed with the oxygen rebound mechanism.

Synthesis of a Monofunctional Phthalocyanine on Silica

Abstract: Silica of different surface area and grain size modified by aminopropyl groups reacted with 4-(3,4-dicyanophenoxy)benzoic acid chloride. The reaction of these benzamidophenoxydicarbonitrile modified silica gels with 4-(4-tert-butyl-phenoxy)-1,2-benzenedicarbonitrile in the presence of a zinc(II) salt results in covalently bonded phthalocyanine zinc(II) complexes with a loading between 1.8 × 10−5 and 1.7 × 10−6mol g−1 silica. UV/vis reflectance spectra show that the phthalocyanines on the surface exist in a monomeric state. Cleavage at the amide bond between the silica and the phthalocyanine led to the corresponding monocarboxylic acid phthalocyanine derivative.

Benzoyl chloride modified ionomer films as antimicrobial food packaging materials

Abstract: Modified ionomer films were prepared and their antimicrobial abilities were investigated. The anhydride linkage of the modified films was manufactured via the reaction of acid/base-treated films with benzoyl chloride as evidenced by the specific anhydride absorption (–CO–O–CO–, 1807 cm−1 and 1741 cm−1; –C–O–C–, 1009 cm−1) in Fourier-transform infrared (FT-IR) spectra. Release of benzoic acid from the modified ionomer films either immersed in buffer solutions or buried between two layers of potato dextrose agar (PDA) media was detected by high performance liquid chromatography (HPLC) that implied the feasibility of the modified ionomer films as an antimicrobial food packaging material. It showed that the base-treated modified films expressed better choice as an antimicrobial food packaging materials than the acid-treated ones because of the higher amount of benzoic acid released from the former than from the later. The antimicrobial ability of modified ionomer films was further demonstrated by its inhibition against the growth of Penicillium sp. and Aspergillusniger. The modified ionomer films successfully exhibited high efficiency in the inhibition of microbial growth.

Selective benzoylation of naphthalene to 2-benzoylnaphthalene using zeolite H-beta catalysts

Abstract: The liquid phase benzoylation of naphthalene over various zeolites has been investigated in the temperature range 333–358 K using benzoyl chloride (BOC) as the benzoylating agent. H-beta catalyzes the reaction efficiently and selectively to 2-benzoylnaphthalene (2-BON) and is found to be superior to the other zeolite catalysts and AlCl3. The conversion of benzoyl chloride to the products largely depends upon the reaction conditions and acidity of the zeolite catalysts. The acidity of the zeolite was measured by temperature programmed desorption of ammonia. It was observed that the conversion of BOC increased with the increase in time on stream, catalyst to BOC ( wt. wt. ) ratio, naphthalene to BOC molar ratio and reaction temperature. Under the reaction conditions (1 atm, 358 K, H-beta to BOC (wt. wt.) = 0.37 , naphthalene to BOC (molar ratio) = 2. 17.6 wt.−% conversion of BOC and a selectivity for 2-BON of 74.8 wt.−% were obtained. Benzoic anhydride and benzoic acid were also used in the reaction. The catalyst, H-beta, was recycled four times and a slight decrease in BOC conversion was observed after each cycle which was related to the minor dealumination of zeolite catalyst by HCl (formed during reaction). The formation of benzoylnaphthalenes is explained by an electrophilic attack of the benzoyl cation (C6H5CO+) on the naphthalene ring whose formatin is facilitated by the stronger acid sites of the zeolite catalysts.

Photobleaching and photomineralization of azobenzene and substituted azobenzenes in aqueous solution by photocatalytic membranes immobilizing titanium dioxide

Abstract: The kinetics of photobleaching (by spectrophotometric analysis) and integral photomineralization (by total organic carbon (TOC) analysis) of azobenzene ( I ) and substituted azobenzenes in aqueous solution were followed in laboratory-scale runs on photocatalytic membranes immobilizing 30±3 wt.% of semiconductor TiO 2 . Experiments were carried out by the technique described in preceding papers of this series, employing stoichiometric hydrogen peroxide as the oxygen donor. The following azobenzenes were examined: (4-diethylamino)-phenylazobenzene ( II ), 4′-(((4-diethylamino)phenyl)azo) benzoic acid ( III ), 4′-(((2-amino-5-diethylamino)phenyl)azo) benzoic acid ( IV ), 4′-(((2-acetamido-4-diethylamino)phenyl)azo) benzoic acid ( V ), 4′-(((4-dimethylamino)phenyl)azo) benzenesulphonic acid, sodium salt ( VI ) and 4′-(((2-acetamido-4-diethylamino)phenyl)azo) benzenesulphonic acid, sodium salt ( VII ). From the Langmuir-Hinshelwood treatment of the initial rate data as a function of the initial concentration ((0.10−1.0) × 10 −3 M), the kinetic parameter k and the pseudo-thermodynamic parameter K for photobleaching were obtained. With regard to photobleaching, I and II were certainly the most reactive, followed by IV . The remaining molecules showed a photo-oxidation rate of one-third to one-quarter of that of I chosen as reference structure. Consequently, the presence of an amino group in the 4-position ( II ) does not stabilize the azobenzene structure against photo-oxidation leading to bleaching, whereas the same group in the 2-position ( IV ) decreases the photobleaching rate by about 40% when a carboxylic group is also present in the I′-position. Acetylation of this amino group, such as in V , decreases the photobleaching rate more markedly. With regard to photomineralization, it was observed that, when photobleaching was virtually complete, a certain amount of TOC was already mineralized. The maximum amount of TOC remaining at the end of photobleaching ranged from about 90% to about 30%, varying with the dye structure and initial concentration as well as with the power and type of irradiation source. By examining the TOC concentration profiles as a function of the substituted azobenzene structure, the following hypotheses were proposed: 1. 1. during the photobleaching period, the ring containing the diethylamino group breaks down (more markedly if further amino or acetamido groups are present in the structure), and photomineralization of the other ring occurs more slowly: 2. 2. both rings break down, within certain limits, during photobleaching; however, the aliphatic fragments containing carboxyl or sulphonic groups are mineralized more slowly. The fact that a small initial plateau in the TOC profile is followed by another more evident plateau at the end of the photobleaching period, for both VI and VII , suggests that hypothesis (1) is more probable in these cases. When the second plateau is reduced to a sigmoidal curve or an inflection point, hypothesis (2) also needs to be considered.