HEATS OF FORMATION OF IMINE AND ENAMINE RADICAL CATIONS AND THE CORRESPONDING NEUTRAL MOLECULES

The heats of formation of imines and enamines with up to four carbon a toms were determined with the CBS-Q and G2 (MP2) composite high-level ab initio procedures. The imines are lower in energy than the correspo nding enamines; the energy difference is typically some 15 kJ mol(-1), which is considerably less than that observed for isomeric keto-enol pairs. N-alkyl enamines are more stable as the syn form, by approximat ely 7 kJ mol(-1). The heats of formation of enamine radical cations ar e between 80 and 170 kJ mol(-1) lower than the heats of formation of t heir imine counterparts, depending on the presence of substituents on the double bond and the nitrogen atom. (C) 1998 Elsevier Science B.V.