Showing papers on "Benzoic acid published in 1999"

Benzoic and Cinnamic Acid Derivatives as Antioxidants: Structure−Activity Relation

Abstract: The antioxidant activity of four derivatives of benzoic acid was systematically compared with the activity of the four homologous derivatives of cinnamic acid. The couples of compounds differed for the kind of aromatic substitution (p-hydroxy, p-hydroxymethoxy, p-hydroxydimethoxy, dihydroxy). The antioxidant activity was measured using (i) a competition kinetic test, to measure the relative capacity to quench peroxyl radical and (ii) the in vitro oxidative modification of human low-density lipoprotein (LDL), initiated by 2,2'-azobis(amidinopropane) dihydrochloride or catalyzed by Cu(II). In both models, cinnamic acids were more efficient than their benzoic counterparts. As for the influence of the aromatic substitution, in the kinetic test the antioxidant activity increased in the sequence p-hydroxy < p-hydroxymethoxy < dihydroxy < p-hydroxydimethoxy. In contrast, in the LDL system, the dihydroxy acids had an antioxidant capacity equal to or higher than that of the p-hydroxydimethoxy acids.

Photocatalytic oxidation of gaseous toluene on anatase TiO2 catalyst: mechanistic aspects and FT-IR investigation

Abstract: Photo-oxidation of toluene has been carried out in gas–solid regime by using polycrystalline anatase TiO2 as the catalyst. The reacting gaseous mixture was toluene, air and water in various molar ratios. A pyrex fixed-bed continuous photoreactor irradiated by a medium pressure Hg lamp was used for performing the photoreactivity experiments. The main oxidation product was benzaldehyde but benzene, benzyl alcohol and traces of benzoic acid, phenol and unidentified compounds were also detected. The molar conversion to benzaldehyde with respect to the initial amount of toluene was ca. 20% in the best experimental conditions. Benzene was produced only as a transient product during the first 3–4 h of irradiation. The dependence of feed composition and flow rate on the toluene fractional conversion was investigated. Selected experiments were performed by using N2 or CO2 instead of air. The presence of oxygen was essential for the occurrence of the photoreaction while water played an important role in order to maintain the catalyst activity. Moreover, a Fourier-transform infrared spectroscopy (FT-IR) investigation was carried out simulating the experimental conditions used during the photoreactivity experiments. The results indicated that toluene is weakly stabilised on the hydrated TiO2 particles by hydrogen-bonding with surface hydroxyl groups, and that it is photo-oxidised to benzaldehyde only in the presence of surface OH groups.

Assaying for hydroxyl radicals: hydroxylated terephthalate is a superior fluorescence marker than hydroxylated benzoate.

Abstract: Generation of hydroxyl radicals in terephthalate (benzene-1,4-dicarboxylic acid) solution yields fluorescent 2-hydroxy-terephthalate. The reaction product is stable for hours and can readily be assessed using standard fluorimeters. The efficiency, i.e. the relative increase of fluorescence per *OH radical, is about three times higher than that of the formation of salicylate (2-hydroxy-benzoate) from benzoic acid and approximately hundred-fold higher than that of the hydroxylation of phenylalanine. As the terephthalate molecule is symmetric with respect to ring-hydroxylation, only one isomer is formed; hence, mechanistic interpretation of the hydroxylation reaction is facilitated. The scavenging rate constant of terephthalate for *OH yielding the hydroxycyclohexadienyl adduct as first intermediate is close to the diffusion controlled limit (k = 3.3 x 10(9) M(-1) s(-1)). Therefore, competition of the detector molecule with biomolecules being present under physiological conditions is expected to be efficient. The assay can be used to detect 'free' *OH radicals produced by the radiolysis of water as well as 'hydroxyl analogous species' that have been suggested to arise from the interaction of complex-bound reduced metal with either oxygen or hydrogen peroxide, e.g. from Fenton reactions. Based on calibration with radiolytically generated hydroxyl radicals the detection limit of the method is estimated to be around 50 nmol/dm3. Terephthalate is classified non-toxic and hence may also prove useful for microdialysis and continuous flow experiments as observation of fluorescence is 'non-destructive' and the reporter substance does not necessarily have to be subjected to HPLC.

4-3,5-bis(2-hydroxyphenyl)-1,2,4-triazol-1-yl-benzoic acid : a novel efficient and selective iron(iii) complexing agent

Abstract: An exceptionally stable 1:2 complex [FeL2]3− is formed from the ligand H3L and FeIII. In contrast, the affinity of this ligand for other biometals is relatively small. These properties make H3L a highly promising candidate for medical applications (e.g. for the treatment of iron overload).

Hydroxycinnamic acids in the digestive tract of livestock and humans

Abstract: Hydroxycinnamic acids are consumed as water-soluble conjugates and in larger amounts bound to plant cell walls Bound acids are primarily released by microbial action in the modified forestomach of ruminants and the hindgut of non-ruminant species, including humans In the rumen, rapid hydrogenation of p-coumaric, ferulic and caffeic acids, followed by dehydroxylation at C4 and more slowly at C3 yields 3-phenylpropionic acid Phenylpropionate is absorbed and undergoes β-oxidation in the liver to benzoic acid which is then excreted predominately (75-95%) as its glycine conjugate (hippuric acid), but also as the free acid or glucuronide In non-ruminants, hydroxycinnamates may be absorbed unchanged in the upper digestive tract via a Na + -dependent saturable transport system or escape to the hindgut where they are subject to microbial transformations with further absorption of metabolites Metabolites of p-coumaric acid found in rat urine are the unchanged compound and its glycine conjugate, the reduced derivative and the β-oxidation product, 4-hydroxybenzoic acid Caffeic acid and its methyl ethers (ferulic and iso-ferulic acids) are interconvertable and share metabolites As in the rumen, reduction of the C 3 side-chain, demethylation of ferulate and dehydroxylation at C4 are products of microbial action Dehydroxylation at C3 is more rarely encountered The resulting 3-hydroxyphenylpropionic acid is commonly found in the urine of all species and is the major metabolite in rats where relatively little chain-shortening occurs A larger range of metabolites including C 6 -C 1 compounds have been detected in human urine Metabolism of hydroxycinnamate dimers found as cross-links between polysaccharide chains has been little studied although evident differences in the ability to metabolise such compounds exist between the human and rumen microflora

Synthesis and Properties of Hyperbranched Aromatic Polyamide

Abstract: Previous experiments from our group [Macromolecules 1998, 31, 5964] have established that thermal polymerization of 3,5-bis(4-aminophenoxy)benzoic acid (monomer 1) gave a hyperbranched aromatic pol...

Synthesis of Functional Polystyrenes by Atom Transfer Radical Polymerization Using Protected and Unprotected Carboxylic Acid Initiators

Abstract: Well-defined polystyrene (PSt) with terminal carboxylic acid groups can be prepared via atom transfer radical polymerization (ATRP). One method involves the use of protected α-halocarboxylic acid initiators. Unprotected α-halocarboxylic acid initiators, such as 2-bromobutyric acid (BBA), had low initiator efficiency of 0.1−0.2 and were not effective for the ATRP of styrene. Protection of the carboxylic acid group of BBA by a trimethylsilyl, tert-butyldimethylsilyl, or tert-butyl group led to improved initiator efficiencies of ca. 0.6, 0.8, and 1, respectively, for the ATRP of styrene. Subsequent hydrolysis of the protecting groups can afford well-defined PSt with terminal carboxylic acid groups. Another method involves the use of carboxylic acid initiators with remote halogens, such as 4-(1-bromoethyl)benzoic acid and 4-(2-(2-bromopropionyloxy)ethoxy)benzoic acid. Well-defined PSt with terminal carboxylic acid groups and low polydispersities were prepared with initiator efficiencies close to 0.7.

Antimicrobial Food Packaging Materials from Poly(ethylene-co-methacrylic acid)

Abstract: A technique of combining poly(ethylene-co-methacrylic acid), PEMA, with benzoic acid and sorbic acid to form antimicrobial food packaging material was developed. Heat-pressed film was first modified with NaOH (1 mol/L) or HCl (1 mol/L) and then incorporated with benzoic acid and sorbic acid, respectively, by using acetone as a swelling agent. The incorporation of preservatives into fabricated antimicrobial films was confirmed by characterization of the specific vibrational stretching shown on the IR spectra of the resulting films. Sodium hydroxide and preservative-treated films exhibited dominantly antimicrobial properties in fungal growth inhibition tests, presumably due to the higher amount of preservatives released from the films (75 mg benzoic acid or 55 mg sorbic acid per g of film) than other types of films. Based on the results, we demonstrated that the combination technique with acetone as swelling agent was feasible to manufacture antimicrobial food packaging films.

The role of benzoate in anaerobic degradation of terephthalate

Abstract: The effects of acetate, benzoate, and periods without substrate on the anaerobic degradation of terephthalate (1,4-benzene-dicarboxylate) by a syntrophic methanogenic culture were studied. The culture had been enriched on terephthalate and was capable of benzoate degradation without a lag phase. When incubated with a mixture of benzoate and terephthalate, subsequent degradation with preference for benzoate was observed. Both benzoate and acetate inhibited the anaerobic degradation of terephthalate. The observed inhibition is partially irreversible, resulting in a decrease (or even a complete loss) of the terephthalate-degrading activity after complete degradation of benzoate or acetate. Irreversible inhibition was characteristic for terephthalate degradation only because the inhibition of benzoate degradation by acetate could well be described by reversible noncompetitive product inhibition. Terephthalate degradation was furthermore irreversibly inhibited by periods without substrate of only a few hours. The inhibition of terephthalate degradation due to periods without substrate could be overcome through incubation of the culture with a mixture of benzoate and terephthalate. In this case no influence of a period without substrate was observed. Based on these observations it is postulated that decarboxylation of terephthalate, resulting in the formation of benzoate, is strictly dependent on the concomitant fermentation of benzoate. In the presence of higher concentrations of benzoate, however, benzoate is the favored substrate over terephthalate, and the culture loses its ability to degrade terephthalate. In order to overcome the inhibition of terephthalate degradation by benzoate and acetate, a two-stage reactor system is suggested for the treatment of wastewater generated during terephthalic acid production.

Effects of solvents on the hydrogenation of mono-aromatic compounds using noble-metal catalysts

Abstract: Toluene, phenol, benzyl alcohol, and benzoic acid in alcohols were hydrogenated using Ru/Al2O3 and Pt/Al2O3 catalysts at 120 °C under a hydrogen pressure of 6 MPa. The Ru/Al2O3 catalyst exhibited a high activity for hydrogenation of mono-aromatics dissolved in alcohols. The hydrogenation activity of the Pt/Al2O3 catalyst was strongly inhibited by the presence of alcohols. To evaluate the role of solvents, nonpolar and polar solvents, some of which contained oxygen, sulfur or nitrogen, were used for the hydrogenation of benzyl alcohol over the Ru/Al2O3 catalyst. A relationship was found between the hydrogenation reactivity of benzyl alcohol in polar solvents and the δ value of the solvent, as defined by the difference between donor number and acceptor number. Nonpolar solvents had no effect on the hydrogenation reaction of benzyl alcohol. Polar solvents with negative δ values, such as methanol, ethanol, and acetic acid, also had no effect. However, polar solvents with positive δ values, such as acetone, te...

In situ scanning tunneling microscopy of highly ordered adlayers of aromatic molecules on well-defined Pt(111) electrodes in solution: Benzoic acid, terephthalic acid, and pyrazine

Abstract: In situ scanning tunneling microscopy (STM) was employed to study adlayer structures of benzoic acid, terephthalic acid, and pyrazine at a well-defined Pt(111) electrode in an aqueous HClO4 solution. Although benzoic acid formed disordered structures on Pt(111), high-resolution STM imaging was able to distinguish between the aromatic ring and two oxygen atoms of each flat lying benzoic acid molecule. Terephthalic acid formed a highly ordered adlayer with c(2√3 × 4)rect symmetry. Two carboxylic acid functional groups at the para-position were clearly discerned. Intermolecular interactions, presumably through hydrogen bonding, played an important role in the formation of the ordered adlayer. Pyrazine molecules formed an ordered adlayer at a relatively negative potential of 0.2 V vs a reversible hydrogen electrode. It was assumed that the molecules adsorbed horizontally at 3-fold hollow sites, forming a long range ordered adlattice of (√7 x √7)R19.1°. Disordered structures were found when the electrode poten...

Degradation of 3-phenylpropionic acid by Haloferax sp. D1227

Abstract: Haloferax sp. D1227, isolated from soil contaminated with highly saline oil brine, is the first halophilic archaeon to demonstrate the utilization of aromatic compounds (i.e., benzoic acid, cinnamic acid, and 3-phenylpropionic acid) as sole carbon and energy sources for growth. The degradation of 3-phenylpropionic acid in this strain was studied to examine the strategies utilized by Archaea to metabolize aromatic compounds. Based on our findings of (1) the extracellular accumulation of cinnamic acid, benzoic acid, 3-hydroxybenzoic acid, and gentisic acid in cultures of Haloferax D1227 grown on 3-phenylpropionic acid, (2) the presence of an 3-phenylpropionylCoA dehydrogenase, (3) the ATP, CoA, and NAD-dependent conversion of cinnamic acid to benzoylCoA, and (4) the presence of gentisate 1,2-dioxygenase, we propose that Haloferax D1227 metabolizes 3-phenylpropionic acid by initial 2-carbon shortening of the side chain to benzoylCoA via a mechanism similar to fatty acid β-oxidation, fol-lowed by aromatic degradation using a gentisate pathway. The upper aliphatic pathway from 3-phenylpropionic acid to benzoic acid is regulated separately from the lower gentisate pathway.

Oxidation with the “O2−H2O2—vanadium complex—pyrazine-2-carboxylic acid” reagent: 11. Oxidation of styrene, phenylacetylene, and their derivatives with the formation of benzaldehyde and benzoic acid

Abstract: The vanadium complex—pyrazine-2-carboxylic acid (PCA) system catalyzes oxidation of styrenes PhRC=CHR′ (R=H, Me; R′=H, Ph), or phenylacetylenes PhC=CR (R=H, Ph) with hydrogen peroxide in air to give aldehydes, ketones, and carboxylic acids. The reaction begins with H2O2 coordination to the vanadium ion followed by the formation of hydroxyl radicals. Catalytic action of PCA facilitates the reduction of the VV complex to the VIV complex and/or the stage of the formation of a peroxide derivative of vanadium.

Three types of acid catalysis in liquid phase of metal salts of 12-tungstophosphoric acid, Mn+xH3−nxPW12O40

Abstract: 12-Tungstophosphoric acid and its acidic salts, H3PW12O40, CsxH3−xPW12O40 (abbreviated as Csx; x=1, 2, 2.23, 2.5, 2.7, and 3), BaxH3−2xPW12O40 (abbreviated as Bax; x=0.5, 1.25, and 1.5), and CexH3−3xPW12O40 (abbreviated as Cex; x=0.33, 0.66, 0.87, and 1), were applied as acid catalysts to three organic reactions which are very different in the polarities of substrates and solvents: (1) decomposition of cyclohexyl acetate (in m-xylene), (2) esterification of benzoic acid by 1-butanol (without solvent), and (3) rearrangement of benzopinacol (in toluene). It was demonstrated that these three reactions represent three typical reaction fields in the acid-catalyzed reactions of heteropoly compounds in the liquid phase. Reaction (1) proceeded on the surface of solid catalysts (a surface-type reaction). In this case, the catalytic activities were primarily determined by the surface acidity. Reaction (2) mostly took place in the homogeneous solution and the catalytic activities were correlated with the amount of the heteropolyacids dissolved in the solvents. Catalysis in pseudoliquid phase was observed for reaction (3), where the catalytic activities depended on the amount of substrates absorbed in the solid bulk of the catalysts. Thus, heteropolyacid catalysts provide three different reaction fields, depending on the polarity of substrate and solvent. The orders of the catalytic activity very much differed reflecting the reaction field. These results demonstrate that the recognition of these reaction fields is important for the understanding and the design of heteropolyacid catalysis in the liquid phase.

Partitioning of aromatic molecules in aqueous biphasic systems

Abstract: Aqueous biphasic systems (ABS) may be suitable for the separation of aromatic molecules in industrial and environmental settings; hence it is invaluable to have predictive models of partitioning behavior in these systems for design and evaluation purposes. In a continuing study of the partition of small aromatic organic molecules, the distribution of several relatively hydrophilic substituted benzene species is reported. The partitioning behavior of five charged substituted benzene species (phthalic acid, 4-hydroxybenzoic acid, benzoic acid, salicylic acid, and p-toluic acid) and one uncharged species (1,3-dinitrobenzene) has been studied in ABS prepared from stock solutions of 40% (w/w) PEG-2000 and increasing concentrations of four water-structuring salts [K3PO4, K2CO3, (NH4)2SO4, and NaOH]. Comparison has been made with published data on the partitioning of these solutes in 1-octanol/water biphasic systems. In general, the partition of these species may be understood in terms of the free energ...

Non-aqueous electrolyte and secondary battery using the same

Abstract: PROBLEM TO BE SOLVED: To provide a battery with superior charging and discharging efficiency, load characteristic and low temperature characteristic by using an electrolytic solution composed of a non-aqueous solvent including carboxylic acid anhydride having a carbon-carbon unsaturated bond and/or aromatic ring in a molecule, and an electrolyte. SOLUTION: A non-aqueous solvent is preferably prepared by adding 0.01-15 wt.% of a maleic acid anhydride derivative, a phthalic acid anhydride derivative, an acrylic acid anhydride derivative and a benzoic acid anhydride derivative of carboxylic and anhydride having a carbon-carbon unsturated bond and/or an aromatic ring in a molecule, to the total non-aqueous solvent, and mixing the same with at least one kind of cyclic carbonic ester and/or chained carbonic ester represented by a formula I and a formula II (R1-R4 are each H or 1-6C alkyl group). A lithium ion secondary battery consists of a non-aqueous electrolytic solution composed of lithium salt and the non-aqueous solvent, a negative electrode active material such as a carbon material or the like capable of doping and dedoping a lithium ion, and a positive electrode active material such as lithium transition metal composite oxide or the like.