Department of Chemistry, University College, Thiruvananthapuram-695034, Kerala (INDIA)
e-mail : drmksdharuc@hotmail.com

The ene reaction proceeds through a concerted mechanism in which H of the alkene is transferred to the enophile while another bond is formed and the π bond migrates within the ene fragment. Concerted electron shift results in the cyclic transition state, which are stabilized by favourable orbital interactions. The molecular instances of ene reaction in selected systems were studied with a focus on the relationship among their properties, geometries and associated electronic delocalization. Relation between the HOMO-LUMO energy gap and electronegativity of hetero atom with activation energy were computed. Ab initio studies on ene reactions between propene and (i) ethene (ii) iminomethane and (iii) methanal were performed using GAMMES suite of programmes by geometry optimization method. Transition state geometries were located and confirmed by frequency calculations at B3LYP/aug-cc-pVDZ level of theory. The bond lengths, bond angles, dihedral angles and energetics of the optimized structures are reported. It is found that the hydrogen bond shrinks with the increase in electronegativity of the reaction centre of the enophile.