A NEW LOOK AT THE SIMILARITIES OF THE CONJUGATIVE ABILITY AND REACTIVITY OF -P=C AND C=C DOUBLE BONDING

Comparison of pi-ionization energies of 28 compounds containing -X=C ( (X=CH, N, P) double bonds reveals a larger similarity between the carbon and phosphorus than between nitrogen and phosphorus containing species. Ring fragmentation reaction heats of the corresponding azaphospholes and azoles show a similar behavior. All of these facts suggest that, although the strength of the -P=C bond is known to be significantly smaller, than that of the C=C or C=N bond, in conjugative interactions -P=C is more comparable to C=C than to N=C pi-systems. By using perturbation arguments, earlier observations about the similarities in chemical reactions of the -P=C and C=C bonds are understandable.