Radical–nucleophilic substitution (SRN1) reactions: electron spin resonance studies of electron capture processes

Abstract
We have probed two of the steps postulated for the radical–nucleophilic substitution (SRN1) mechanism for α-substituted aliphatic nitro-compounds [Me2C(X)NO2] by detecting the intermediates involved by e.s.r. spectroscopy. These two steps are the electron capture by Me2C(X)NO2 to form radical-anions, and their break-down to yield radicals and anions [equations (1) and (A2) or (B2) in Scheme 1]. A range of radical-anions, [Me2C(X)NO2]–˙ with X = Br, Cl, SCN, NO2, CN, PO3Et2, CO2Et, COMe, SO2Me, SO2Ar, and Me have been unambiguously identified by e.s.r. spectroscopy and shown to be infinitely long lived at low temperature. Our results indicate that one or more of at least three pathways are followed on the reaction of Me2C(X)NO2 with electrons: (a) electron-capture to yield a stable radical-anion, [Me2C(X)NO2]–˙, (b) dissociative electron capture to yield Me2ĊNO2 and X–(for X = Br, Cl, and SCN); (c) dissociative electron-capture to yield Me2ĊX and NO2 –(for X = CN, NO2, PO3Et2, and CO2Et). The effect of solvent on these processes, and the structure of the radical-anions and the radicals Me2ĊNO2, Me2ĊPO3Et2, and Me2ĊCN are discussed.

This publication has 0 references indexed in Scilit: