Some free radical reactions of camphor in relation to the action of cytochrome P450

Abstract

Investigations have been made of the reactions of e^–_aq, OH, O^–, H, (SCN)^–₂, Br^–₂ and CO^–₂ with camphor. Rate constants of 3.1 × 10⁹, 4.1 × 10⁹ and 1.6 × 10⁹ dm³ mol^–1 s^–1 have been obtained for the reactions of e^–_aq, OH and O^–, respectively. The other radicals did not react at measurable rates. The spectra of the radicals resulting from the reactions with camphor have been determined. The radicals formed by action of e^–_aq can exist in different protonated forms with pK_a of 12.0 but identical radicals, R·, appear to be formed from OH (in neutral solution) and O^–(in alkaline solution). The R· radicals react with each other with 2k= 8.7 × 10⁸ dm³ mol^–1 s^–1 and with oxygen with k= 1.3 × 10⁹ dm³ mol^–1 s^–1, giving RO₂· radicals. The RO₂· radicals react with each other with 2k= 3.4 × 10⁸ dm³ mol^–1 s^–1.

The possible relevance of these reactions to the enzymic hydroxylation of camphor is discussed.