On the heats of formation of formyl cyanide and thioformyl cyanide

Abstract

Ab initio molecular orbital calculations have been applied to determine the standard enthapies of formation of formyl cyanide and thioformyl cyanide. Using electronic energies at the coupled cluster single double (triple)/ 6-311++G(3df,2p) level in conjunction with different working reactions, the following values have been obtained: ΔHf,2980(HCOCN)=56 kJ/mol and ΔHf,2980(HCSCN)=271 kJ/mol, with a probable error of ±8 kJ/mol. These values differ significantly from the experimental ones of 26±20 and 222±30 kJ/mol, respectively, recently derived from mass spectrometric measurements by Born et al. [J. Phys. Chem. 100, 17662 (1996)]. © 1999 American Institute of Physics.