THEORETICAL-STUDY OF SUBSTITUTED CHNO ISOMERS

A detailed ab initio molecular orbital study using minimal and split-valence basis sets has been carried out for singlet isomers of R(CNO), R = Li, BH2, CH3, NH2, OH, F, Cl, CN, C6H5, p-NH2C6H4, and p-NO2C6H4. Calculated structures are in reasonable agreement with available experimental data. The predicted equilibrium structures generally resemble those of the parent compounds (R = H). Only the lithium substituent leads to large structural distortions: LiNCO, LiOCN, and LiONC are all predicted to be linear molecules. Methyl fulminate (CH3ONC) is predicted to be quite stable toward intramolecular rearrangement and of comparable thermodynamic stability to acetonitrile oxide (CH3CNO). There is no theoretical evidence that any of the substituted oxazirines RCNO are kinetically stable compounds. The calculations suggest that hydroxycarbonyl- and fluorocarbonylnitrene are low-energy isomers but with relatively small barriers toward intramolecular rearrangement. Other substituted singlet carbonyl nitrenes (R = Li, CH3, Cl) rearrange without activation to the corresponding isocyanate. © 1978, American Chemical Society. All rights reserved.