Hydrolysis of N-sulflnylamines and isocyanates:: A computational comparison

A comparative study of the concerted hydrolysis of H-, CF3-, CH3-, and Ph-substituted N-sulfinylamines (R-NSO) and isocyanates (R-NCO) was performed using B3LYP/6-31+G(2d,2p). The two-water-molecule model was found to be sufficient for a proper description of the hydrolysis reaction for both classes of compounds. Despite their overall similar reactivity, N-sulfinylamines react across both the N=S and the S=O bonds, whereas isocyanates hydrolyze predominantly through the N=C bond, in agreement with the proton affinities of the nitrogen and oxygen atoms. The charges on sulfur (N=S=O) and carbon (N=C=O) were found to correlate well with the activation enthalpy for hydrolysis. While the reactivity of an N-sulfinylamine toward water increases with increasing electron-withdrawing ability of the substituent, the substituent effect on isocyanates becomes notable only in the presence of the strongly electron-withdrawing CF3 group.