The assistance of s electron delocalization or anchimeric assistance of s electrons accounts for the large rate differences in the solvolysis of 2-exo- and 2-endo-norbornyl-p-bromobenzenesulfonates. This study was formerly analyzed by molecular orbital theory in gas phase. By revisiting this old problem from the quantum theory of atoms in molecules (QTAIM), new information on these reactions was obtained. The QTAIM results show that, in the first step of the nucleophilically unassisted solvolysis of protonated 2-exo-norbornanol and of protonated 2-endo-norbornanol, both reactions are anchimerically assisted by sigma bond participation. Similarly, in the first step of the nucleophilically unassisted solvolysis of protonated 2-endo-oxabicycloheptanol and of protonated 2-exo-oxabicycloheptanol, the QTAIM results show that both reactions are anchimerically assisted: the former from sigma bond participation from O-C bonds and valence shell electron participation from oxygen atom and the latter from sigma bond participation from C1-C2 bond.
QTAIM; 2-norbornyl cation; sigma bond participation; 2-oxabicycloheptanol; solvolysis
