Rate Coefficients of Elementary Steps in the Inhibited Oxidation of Ethylbenzene, I. Interaction between Peroxy Radicals and Inhibitor Molecules

Ber Bunsenges Phys Chem

Noszek

Gál

1984

Chemical Kinetics / Elementary Reactions / Inhibition / RadicalsThe decomposition of 1-phenylethyl-hydroperoxide assisted by 1-phenyl-ethanol has been investigated in the presence of 2,6-di-tert-butyl-4-methyl-phenol (ionol). Ethylbenzene was used as solvent, the temperature range was 115 -130°C. The inhibition period was measured as a function of alcohol concentration (and inhibitor concentration as well). The activation parameters of hydroperoxide decomposition assisted by alcohol have been determined: /CHROOH+HROH = 1.13~107exp(94.9kJmol-'/R7') sC1.

Rate Coefficients of Elementary Steps in the Inhibited Oxidation of Ethylbenzene, II. Interaction between Hydroperoxide and Alcohol Molecules

Ber Bunsenges Phys Chem

Noszek

Gál

1984

On the interaction of hydroperoxide and inhibitor molecules

Int J of Chemical Kinetics

1985

Self Cite

Decomposition of 1-phenylethyl-hydroperoxide has been studied in the presence of 2,6-di-tert-butyl-4-methyl-phenol inhibitor in ethylbenzene and chlorobenzene both in oxygen and nitrogen. The oxygen consumption and the inhibitor concentrations were measured against the initial inhibitor concentrations. Two methods were applied for the determination of the rate coeficients of the reaction:Its value is about 3 x 10 4 L x mol ' x s a t 120°C. However, large experimental errors we deal with, the existence of a reaction yielding radicals, presumably an interaction between hydroperoxide and inhibitor molecules, can be established emphasizing the importance of measurements carried out with various initial concentrations of the inhibitor. 140°C: h , = 1.66 x L mol-' s-l [ 6 ] and for Zn-dialkyl dithiocarbamate at 60°C 12, = 4-5 k l L mol-' s-l [71.

Linear free energy relationships for peroxy radical‐phenol reactions. Influence of the para‐substituent, the ortho‐di‐tert‐butyl groups and the peroxy radical

Int J of Chemical Kinetics

Lopata²,

Muller³

1989

Calculations were carried out on several data sets to study the mechanism of hydrogen abstraction from phenols by peroxy radicals: Rate constants, k values, were collected for the reactions of cumyl‐, 1‐phenylethyl‐ and tert‐butyl‐peroxy radicals with ortho‐para‐substituted phenol inhibitors. The rate constants were recalculated for the same temperature. Solvent effects were neglected because the solvents used were similar in nature. The phenol ortho substituents were characterized by an indicator variable ItBu accounting for the presence or absence of di‐tert‐butyl groups. The phenol para substituents were characterized by Charton's σI, σR, and σ italicR+ substituent constants. The dependence of log k values on Itbu, σI, σR, σ italicR+ was investigated using stepwise linear regression analysis. The combined data set of 32 reactions gives: and The results suggest that hydrogen abstraction from phenols by peroxy radicals proceeds by an electrophilic mechanism, and that neither the peroxy‐radical nor the ortho‐di‐tert‐butyl groups have considerable effect on the rate of reaction (1).