Arrhenius Parameters for Reaction of tert-Butylperoxy Radicals with some Hindered Phenols and Aromatic Amines

Abstract

The reaction of tert-butylperoxy radicals with some 2,6-di-iert-butyl-4-substituted phenols, a-naphthol, a-naphthylamine, and N-phenyl-a-naphthylaniine has been studied by following the change in radical concentration with time sing an e.p.r. spectrometer. Rates of radical decay were first-order in both reactants and were not influenced by the presence of teri-butyl hydroperoxide.Absolute values of the second-order rate constants were measured from -35 t o -100" and the preexponential factors and activation energies fell in the range lo4-lo5 M -' s -l and 0.5-1.0 kcal niol-l. Rate constants for deuterated phenols (OD) and aromatic amines (ND) were an order of magnitude lower than for the corresponding light compounds.There was no evidence for q u a n t~~m mechanical t~~n n e l i n g in these hydrogen atom transfer reactions and it would appear that the activation parameters are low because reaction initially involves the forniation of a hydrogen bonded peroxy radical -phenol (or aromatic anline) complex, followed by the transfer of a hydrogen atom within the coniplex.. . Can. J. Chem. 51, 3738 (1973)

The reactivity oftert-butylperoxy radicals with respect to aldehydes, amines, and ethers in solution. The importance of polar effect

“…Unlike the method of a direct generation of the radicals in a reaction medium [19], the pulse introduction of the reagents enables measurable concentration of the radicals without any difficulties to examine the reactions of the radicals with the compounds unstable to UV-irradiation, as well as to enlarge the class of the solvents studied by introducing the latter into a reaction system after generation of the radicals.…”

Metal complexes as antioxidants. 8. A kinetic and product study of the reaction of tertiary alkylperoxy radicals with cobalt(II) acetylacetonate

“…The concentration of this radical after the light was masked was ~h~ studies that have been made on the reaction followed by time resolved electron spin resonance spectroscopy (17). The induction period (15) and titration (16) . , -8 x lo5 M-I s-I at temDeratures of 60-74"~ (8-10).…”

“…In this paper we present the results of a direct study of the reaction of the tert-butylperoxy radical with Co(acac), using the kinetic electron spin resonance spectroscopic method that has been successful for direct studies of the reactions of t-BuO,. with hindered and non-hindered phenols and aromatic amines (15,16) Cumylperoxy radicals were produced by thermolysis of azocumene in oxygen-saturated solvent at 323 K. In the presence of Co(acac), rates of oxygen absorption were slightly faster than rates of production ofcumyl radicals and slightly more than the theoretical concentration of oxygen was absorbed. For instance, azocumene (0.0245 M) in chlorobenzene containing Co(acac), (0.049 M) absorbed oxygen at an initial rate of 2 x M s-I whereas the calculated initial rate of production of cumyl radicals was 1.6 x M s-' and 0.057 M of oxygen were absorbed.…”

Metal complexes as antioxidants. II. Reaction of nickel di-n-butyldithiocarbamate and nickel diisopropyldithiophosphate with alkylperoxy radicals

“…Elecrror~ Spill Resormrzce Sirrdies Reaction of the nickel complexes with [err-butylperoxy and 2-ethyl-2-propylperoxy radicals was studied kinetically by electron spin resonance spectroscopy (1,7,8). tert-Butylperoxy radicals were generated by photolysis of azoisobutane (0.02 M) in an oxveen saturated solvent…”