The oxidation of 4-bromacetophenone by ozone in acetic acid

The kinetics and mechanism of oxidation of 4-bromoacetophenone by ozone in acetic acid solution have been studied. It was shown that 77% of the starting material is oxidized by the benzene ring; 8% of 4-bromobenzoic acid and small amounts of carbon (IV) oxide were identified among the side chain ozonation products. The main reaction products are aliphatic peroxide compounds, which have in their structure one hydroperoxide group. Manganese (II) acetate was shown to be the most effective catalyst for the side chain reaction of 4-bromoacetophenone in acetic acid. High selectivity for the side chain is achieved only at sufficiently high concentrations of catalyst ([Mn(OAc)2]0:[ArH]0=1:4). The main product of the catalytic oxidation of 4-bromoacetophenone is 4-bromobenzoic acid with a yield of 82.5%. The found dependences of the rate of oxidation of 4-bromoacetophenone by ozone on the concentration of reactants are described by the kinetic equation of the third order, the reaction rate has the first order with respect to each reagent. It was found that the decisive role in the selective oxidation of 4-bromoacetophenone is played by two-stage oxidation, in which ozone predominantly reacts with the reduced form of manganese, and the introduction of the substrate into side chain oxidation is carried out by the reaction with the oxidized form of metal. According to the research results, the mechanism of catalytic ozonation of 4-bromoacetophenone in acetic acid has been proposed, which involves ion-radical non-chain oxidation of the substrate.

THE VALUES OF ΔfHo298.15 AND So298.15 OF THE RADICALS, FORMED BY THE ABSTRACTION OF H ATOM FROM THE p-BENZYLPHENOL AND DIMETHYL PHTHALATE

In the present work, the standard thermochemical properties of the most thermochemically stable radicals (p-Benzylenephenol and 1-Methyl-2-methylene phthalate), formed by abstraction of the hydrogen atom from the p-Benzylphenol and Dimethyl phthalate are determined using the results of B3LYP/6-311++G(d,p), M06-2X/6-311++G(d,p) and RO/CBS-4M calculations. The consistent values of the standard enthalpies of formation of these structures are determined using the corrected thermochemistry of the homodesmotic and atomization reactions. The values of the standard entropies of these compounds and the temperature dependencies of their thermochemical properties are also calculated in the present work. It is found that the H-transfer reaction of HO2 with p-Benzylenephenol is thermochemically favorable and can lead to the chain oxidation of p-Benzylenephenol at relatively low temperatures.