ESR spin-trap study of the radicals present during the thermolysis of some novel dialkyl peroxides.

Mekarbane, P. G. and Tabner, B. J. (2001) ESR spin-trap study of the radicals present during the thermolysis of some novel dialkyl peroxides. Magnetic Resonance in Chemistry, 39 (1). pp. 9-14. ISSN 0749-1581

Abstract

The thermolysis of two bifunctional dialkyl peroxides [2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane (1) and 2,5-dimethyl-2,5-bis(tert-butylperoxy)-3-hexyne (2)] and two novel monofunctional dialkyl peroxides [2-methyl-(2-tert-amylperoxy)pentan-4-ol (3) and 2-methyl-(2-tert-butylperoxy)pentan-4-ol (4)] was undertaken, in various solvents, between 353 and 383 K and the radicals generated trapped employing DMPO, PBN-d14 and 2,4,6-tri-tert-butylnitrosobenzene (TTBNB). We established that both 1 and 2 release the tert-butoxyl radical (and the methyl radical via -scission) following cleavage of one of the O - O bonds. During the thermolysis of 1 a ·CH2R radical was trapped which we assign to the 3-methyl-3-(tert-butylperoxy)butyl radical (6). We found no evidence for the presence of an alkynyl radical during the thermolysis of 2. The tert-amyloxyl (and the ethyl radical via -scission) and the tert-butoxyl radical (and the methyl radical via -scission) were trapped during the thermolysis of 3 and 4, respectively. The 2-hydroxypropyl radical (10) was trapped employing TTBNB during the thermolysis of both 3 and 4 with its adduct exhibiting two magnetically non-equivalent -protons as a consequence of the adjacent chiral carbon atom. Reaction schemes for the thermolysis all four peroxides are proposed based on the nature of the trapped radicals.