Kinetics and mechanism of reaction of aryl oxiranes with dinitrogen pentoxide in dichloromethane

Abstract

4-X-Phenyloxiranes (X = H, Cl, CF₃, NO₂) in dichloromethane react with N₂O₅ to give 1-(4-X-pheny1)ethane-1,2-diol dinitrates and with HNO₃ to give 2-(4-X-phenyl)-2-nitroethanols. Both reactions give quantitative yields. Kinetics of both reactions, mostly at reduced temperatures, have been investigated. The former reaction is second order in N₂O₅ and the latter reaction is between second and third order in HNO₃. Both reactions are retarded strongly by electron-withdrawing substituents and show large and negative entropies of activation. Mechanisms are discussed.