Intramolecular determination of substituent effects in hydroxylations catalyzed by cytochrome P-450

Hydroxylation of monosubstituted 1,3 diphenylpropanes by rat liver microsomes leads predominantly to a mixture of the isomeric benzylic alcohols at positions 1 and 3. Quantitation of the relative concentrations of these alcohols can be achieved by combined gas chromatography mass fragmentography. p Methyl, p trifluoromethyl, and p fluoro substituents yield product distributions which clearly indicate an electrophilic mechanism for the hydroxylation reaction.