Restricted rotation about Nsp(2)-Csp(3) bond through pi-electronic interactions: A H-1 NMR study

The electronic repulsion of a carboxyl group from a phenyl ring has been found to restrict relation about Nsp(2)-Csp(3) bond. A stable sp(3)-geometry of a carbon in N-CHR-COOH derivatives of alpha,beta(9,10-dihydroanthracene-9,10-diyl)succinimde has been demonstrated on the basis of shielding parameters of N'-alkyls. The carboxyl group does not exhibit hydrogen bonding with the carbonyls of the succinimide and remains in anti orientation. Though the anisotropic effect of an olefinic bond is fairly small, the interaction of carboxyl group with the olefinic bond is evident in CPD-MA adduct derivative.