Retentive solvolysis. Part 12. Mechanism of the reaction of optically active 1-(p-methoxyphenyl)ethyl trifluoroacetate with phenol and methanol in benzene and cyclohexane

Abstract

The rate, product distribution, and stereochemical course for the reactions of 0.05–0.1 M-1-(p-methoxyphenyl)ethyl trifluoroacetate (1) with methanol and phenol have been investigated in benzene or cyclohexane as solvent at 25.0 °C. Below 10^–3M-methanol or -phenol the total kinetic order is two overall [first order in both the trifluoroacetate(1) and the reactant methanol or phenol]. The rates are virtually independent of the pyridine used to bind the trifluoroacetic acid produced. The major product from the phenol reaction, 1-(p-methoxyphenyl)ethyl phenyl ether, shows net retention (6–9%) of configuration along with predominant racemization. In addition, the methyl ether product from the methanol reaction also undergoes net retention (24% with 0.2M-methanol). The formation of the ethers with net retention of configuration can be accounted for by an intermolecular S_Ni mechanism.