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Abstract  

The vapour pressures of six para-substituted benzoic acids were measured using the Knudsen effusion method within the pressure range (0.1–1 Pa) in the following temperature intervals: 4-hydroxybenzoic acid (365.09–387.28) K; 4-cyanobenzoic acid (355.14–373.28) K; 4-(methylamino)benzoic acid (359.12–381.29) K; 4-(dimethylamino)benzoic acid (369.29–391.01) K; 4-(acetylamino)benzoic acid (423.10–443.12) K; 4-acetoxybenzoic acid (351.28–373.27) K. From the temperature dependence of the vapour pressure, the standard molar enthalpy, entropy and Gibbs energy of sublimation, at the temperature 298.15 K, were derived for each of the studied compounds using estimated values of the heat capacity differences between the gaseous and the crystalline phases. Equations for estimating the vapour pressure of para substituted benzoic acids at the temperature of 298.15 K are proposed.

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Abstract  

A one-step method has been elaborated for the deuteriation of hydroxybenzoic acids in the presence of homogeneous divalent platinum salt in a medium containing solution of deuteriated acetic acid in heavy water. The quasiunimolecular H/D exchange rate constants have been determined at 130 °C for the particular position of proton on the aromatic ring by 1H NMR integration signals. Different kinetic patterns of H/D exchange are shown for 2-hydroxy-, 3-hydroxy-, and 4-hydroxybenzoic acid.

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Summary  

The complex formation of uranium(VI) with 4-hydroxy-3-methoxybenzoic acid as well as with benzoic acid and 4-hydroxybenzoic acid was studied. In aqueous solution weak carboxylic 1 : 1 complexes, are formed in which the carboxyl group is bidentately coordinated to the metal atom. The logarithmic stability constants of these complexes regarding the reaction of the uranyl ion with the single charged anion of the respective ligands are 2.78±0.02, 2.68±0.04, and 2.71±0.04 at an ionic strength of 0.1 mol/l (NaClO4) and at 25 °C. Bis(4-hydroxy-3-methoxybenzoato)dioxouranium(VI) was obtained as a crystalline compound if the concentrations of the starting components for the synthesis are increased. The monoclinic compound has a reflections-rich X-ray powder diffraction pattern. The lattice constants are a = 13.662(9) Å, b = 21.293(7) Å, c = 11.213(3) Å, b = 107.49(4), and V = 3111(2) Å.3

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The aim of this study was to determine the profile of fungal metabolites and antioxidant substances from plants on a representative population of wheat cultivars grown in Poland. Tests were conducted on grain of 23 wheat cultivars in three experimental variants: natural infection (control), chemical crop protection, and artificial inoculation with the fungi F. graminearum and F. culmorum. Grains were analysed in terms of infection rate, mycotoxin, ergosterol, free and bound phenolic acid content, as well as antioxidant capacity. Calculated Fusarium head blight index (FHB index) ranged from 0% to 24% in the control, from 0% to 95% after inoculation and from 0 to 3% following chemical crop protection treatments. The highest concentration of ergosterol was detected in seeds from inoculated plots, with a mean value of 26.69 mg/kg. The highest mean concentration calculated for total toxin content was recorded after inoculation (7.833 mg/kg). The mean value for ferulic acid for inoculated samples resulted 2574 mg/kg, while for chemically protected samples 1158 mg/kg was obtained.

Based on of discriminant analysis genotypes can be separated for inoculation 100%, for chemical crop protection 95%, and for natural infection 90%. Amongst 12 analysed phenolic acids the highest discrimination power was found for gallic acid, 4-hydroxybenzoic acid and vanillic acid.

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.T. Accumulation of salicylic acid and 4-hydroxybenzoic acid in phloem fluids of cucumber during systemic acquired resistance is preceded by a transient increase in phenylalanine ammonia-lyase activity in petioles and stems Plant

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Acta Biologica Hungarica
Authors: Ahmad Hegazy, Shahira Ezzat, Iman Qasem, Mohamed Ali-Shtayeh, Mohammed Basalah, Hayssam Ali, and Ashraf Hatamleh

469 470 Chong, K. P., Rossall, S., Atong, M. (2009) In vitro antimicrobial activity and fungitoxicity of syringic acid, caffeic acid and 4-hydroxybenzoic acid against Ganoderma

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Horváth, E., Pál, M., Szalai, G., Páldi, E., Janda, T. (2007): Exogenous 4-hydroxybenzoic acid and salicylic acid modulate the effect of short-term drought and freezing stress on wheat plants. Biol. Plant. ., 51 , 480

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Acta Agronomica Hungarica
Authors: G. Kocsy, Magda Pál, A. Soltész, G. Szalai, Á. Boldizsár, V. Kovács, and T. Janda

Horváth, E., Pál, M., Szalai, G., Páldi, E., Janda, T. (2007): Exogenous 4-hydroxybenzoic acid and salicylic acid modulate the effect of short-term drought and freezing stress on wheat plants. Biol. Plant. , 51 , 480

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Acta Chromatographica
Authors: Milica Atanacković Krstonošić, Jelena Cvejić Hogervorst, Mira Mikulić, and Ljiljana Gojković-Bukarica

Compounds Resolution Chlorogenic/4-hydroxybenzoic acid 1.64 Caffeic/Syringic acid

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