Ambident neighbouring groups. Part V. Effects of solvent on several O-5 ring closures

Abstract

Kinetic studies in various binary mixtures of ethanol and water have shown that cyclisations involving either neighbouring benzamido- or neighbouring phenylcarbamoyloxy-groups (the cyclisation reaction in each case being an O-5 process) are insensitive to such solvent variation. Plots of log k against the Winstein–Grunwald parameter Y are rectilinear in both cases, with the m values being ca. 0·13 and 0·18 for the benzamido- and phenylcarbamoyloxy-systems, respectively. These data are consistent with the O-5 closure being an internal S_N2 process. Plots of ΔH^‡ against ΔS^‡ values obtained from the solvolysis rates are also linear.