On the structural and electronic properties of methylenemalonaldehyde

Abstract

Electronic and structural properties, especially rotational isomerism and geometries, of methylenemalonaldehyde (MMA) were studied using ab initio molecular orbital theory at the 3-21G, 4-31G and 6-31G levels. Supplementary calculations were done with the semiempirical AM1 and MMP2 molecular mechanics methods. The calculations indicate that the cis.trans conformation is the most stable and that the 90° rotation of the formyl group demands energy of about 20–25 kJ mol −1. Consideration of the formyl-fonnyl coulombic interactions suggests that the conformational equilibrium can be quite effectively influenced by solvent. Some topological properties of the potential energy surface of MMA are discussed briefly. The extremely high reactivity and instability of MMA is rationalized with the frontier electron theory. The supporting role of NMR coupling constants in molecular modeling studies of larger MMA based systems is described.