Reactions of lead tetra-acetate. Part XIII. Homolytic and heterolytic mechanisms in the oxidation of alcohols

The products formed during the oxidation of PhCH2·CPhAr·OH, Me3C·CPhAr·OH (Ar = Ph or p-anisyl), AnCH2·CPh2·OH, PhCH2·CHAn·OH, and Me3C·CHAn·OH (An =p-anisyl) by lead tetra-acetate in various solvents have been determined. For the tertiary alcohols, it is argued that the t-butyl-alcohols react essentially completely by a heterolytic mechanism in which the t-butylcarbonium ion departs from an alkoxy-lead(IV) derivative, whereas the benzyl alcohols react predominantly by a homolytic mechanism in which the benzyl (or 4-methoxybenzyl) radical is formed. For the secondary alcohols, the heterolytic and homolytic fragmentations are competitive with simple oxidation to the corresponding ketone.