A quantum chemical study of HCN, HNC and CN −: Application to aspects of organic chemistry and prebiotic organic synthesis

Abstract

Extended Hückel Self Consistent Change (EH-SCC) molecular orbital calculations have been made for some molecules of possible importance in prebiotic organic synthesis: hydrogen cyanide, hydrogen isocyanide and cyanide ion. In this paper, attention is focused on the bonding picture for these species which emerges from the calculations. Notably, isocyanide carbon appears to have very electron deficient pi orbitals as well as non-bonding electrons, and cyanide ion has essentially equal negative charge on carbon and nitrogen and no non-bonding electrons. Aspects of prebiotic organic synthesis and the organic chemistry of cyanides, isocyanides and cyanide ion are discussed in terms of these and other conclusions derived from the calculations. In addition, insight is gained into the energetics of hydrogen cyanide and hydrogen isocyanide formation from a study of the potential energy variation in the reverse process, linear stretching of the H—CN and H—NC bonds to the point of heterolytic dissociation, thus providing a basis for a discussion of the possible formation and existence of hydrogen isocyanide.