5794-62-7Relevant articles and documents
Mechanisms of interference of p-diphenols with the Trinder reaction
G?sowska-Bajger, Beata,Tarasek, Damian,Wojtasek, Hubert
supporting information, (2020/03/10)
p-Diphenols, such as homogentisic acid, gentisic acid, etamsylate, and calcium dobesilate, interfere with diagnostic tests utilizing the Trinder reaction but the mechanisms of these effects are not fully understood. We observed substantial differences both in oxidation of p-diphenols by horseradish peroxidase and their influence on oxidation of 4-aminoantipyrine and various phenolic substrates. Homogentisic acid was rapidly oxidized by the enzyme and completely blocked chromophore formation. Enzymatic oxidation of the remaining p-diphenols was slow and they only moderately inhibited chromophore formation. However, in the presence of standard substrates all tested p-diphenols were rapidly converted to p-quinones. Hydrogen peroxide consumption was significantly accelerated by homogentisic acid but not much affected by the other p-diphenols. The magnitude and mechanisms of interference caused by p-diphenols therefore depend on their structure which determines their electrochemical properties – while for homogentisic acid with an electron-donating substituent and a lower reduction potential both enzymatic oxidation and reduction of the peroxidase-generated radicals occur, for p-diphenols with electron-withdrawing substituents and higher reduction potentials only the second mechanism is significant. Correlation of the effects on the Trinder reaction with reduction potentials of interfering compounds allows prediction of such properties for a wide range of other reducing compounds based on this parameter. It also explains why compounds with very different structures but strong reducing properties show such effects.
Mechanistic study of electrochemical oxidation of 2,5-dihydroxybenzoic acid and 3,4-dihydroxybenzaldehyde in the presence of 3-hydroxy-1H-phenalene-1-one
Nematollahi, Davood,Amani, Amaneh
experimental part, p. 513 - 517 (2009/04/11)
The mechanism of the electrochemical oxidation of 2,5-dihydroxybenzoic acid and 3,4-dihydroxybenzaldehyde in the presence of 3-hydroxy-1H-phenalene-1-one as a nucleophile has been studied in water/acetonitrile (80/20 v/v) solution using cyclic voltammetry and controlled-potential coulometry methods. The results indicate that the quinones derived from oxidation of 2,5-dihydroxybenzoic acid and 3,4-dihydroxybenzaldehyde participate in Michael addition reactions with 3-hydroxy-1H-phenalene-1-one and via ECE and ECEC mechanisms convert to the different products, with good yield under controlled potential conditions, at carbon electrode.
Oxidation of benzenediols by hexabromoiridate(IV): Kinetics at ambient and elevated pressures
Ciosto, Cornelia,Bajaj, Hari C.,Van Eldik, Rudi,Hubbard, Colin D.
, p. 1503 - 1507 (2007/10/03)
The kinetics of oxidation of several benzenediols by the hexabromoiridate(IV) ion have been studied spectrophotometrically by the stopped-flow method. In 0.010 mol dm-3 HClO4 and an ionic strength of 0.10 mol dm-3 (NaClO4) at 25.0°C the second-order rate constants (the reaction is first order in each reactant concentration), vary from 1.26 × 102 to 9.3 × 104 dm3 mol-1 s-1. The enthalpies of activation range from about 44 kJ mol-1 for the slowest reacting substrate to about 20 kJ mol-1 for the faster reactions. The ΔS? values do not vary over a wide range; the reaction rates are governed more by the enthalpy barrier. Application of pressure (up to 125 MPa) causes significant rate accelerations, giving rise to ΔV? values in the -17 to -26 cm3 mol-1 range, consistent with the large, negative ΔS? values. This indicates that the rate limiting step is largely characterised by an increase in species ordering and electrostriction, and in the present case slightly less than for the corresponding reactions with the less bulky hexachloroiridate(IV) ion.
