Theoretical studies on the competitive S(N)2 reactions of O-imidomethyl derivatives of phenols with OH-

Nucleophilic substitution reactions of O-imidomethyl derivatives of phenols with OH- were studied theoretically using the semiempirical AM1 and Solvat ion Model 2.1 (SM2.1) methods in the gas phase and aqueous solution, respec tively. In the gas phase, the two reaction paths, in which the imide (1a) o r phenol (1b) is functioning as a leaving group, can occur competitively. I n contrast, in aqueous solution, path (1b) becomes more favorable than (1a) because the transition states (TS) of path (1b) are more stabilized by sol vent. Differences in solvation energies are caused by the structural differ ences of TS, i.e., the TS via path (1b) is more dissociative than that via path (1a). Therefore we conclude that the solvent effects play an important role in the hydrolysis of O-imidomethyl derivatives of phenols. However, r eactivity is dependent on the acidities of both the imide and the phenol fr agments since the rho (Z) values vary progressively from 4.2 (Z'= I) to 2.5 (Z'=IV) as the acidities of imide increase. These are in good agreement wi th the experimental results.