RATES AND MECHANISM OF SOLVOLYSIS OF N-PHENYLCYCLOSILAZOXANES

Article abstract of DOI:10.1016/0022-328X(84)85132-3

The rates of solvolysis of some N-phenyl-1-aza-3,5-dioxa-2,4,6-tris(dimethylsilyl)cyclohexanes, substituted in the benzene ring, have been measured spectrophotometrically in methanol containing a small quantity of water.The reaction is subject to general acid catalysis and is inhibited by weak bases.Electron-donating substituents accelerate the solvolysis.The ρ-constant, derived from the linear relation between the logarithms of the rate constants and Hammett ? constants is -1.2 (ρ = -1.0 in a neutral medium).A reverse deuterium isotope effect has been found(k_H/k_D = 0.82).The proposed mechanism for the Si-N bond cleavage, and the associated ring-opening, involves simultaneous nucleophilic attack of a solvent molecule on silicon and electrophilic assistance by proton transfer from the catalysing acid to the nitrogen.