The reactions of a series
of α-substituted p-nitrobenzyl chlorides, p- NO2C6H4CH(Cl)R (R = Me, Et, Prt,
But), with the lithium salt of 2- nitropropane
in dimethyl sulphoxide and dimethylformamide have been studied. When R = Me or
Et, competing SRN1 and SN2 processes take place, giving
C- and O-alkylated products respectively. In the more sterically hindered cases
where R = Pri or But, the only
reaction taking place has been shown to be an SRN1 reaction with
exclusive O-alkylation. These observations indicate that the SRN1
reaction is prone to steric hindrance, and that radical alkylation of the
ambident nitronate ion occurs on the more accessible oxygen atom in sterically
hindered situations.