Theoretical study of the structure and vibrational spectra of formyl and methyl azides

The structure and conformational stability of formyl azide CHO-NNN and methyl azide CH3-NNN were investigated using DFT-B3LYP and ab initio MP2 calculations. The calculations were carried out using 6-311++G** basis set. From the calculation formyl azide was predicted to exist predominantly in the planar cis conformation. The potential functions for internal rotation in each of the molecules were determined at the two levels. The three-fold barrier of the methyl group in methyl azide was calculated at MP/6-311 ++G(--) level to be of about 0.7 kcal/mol in good agreement with experimental value obtained from microwave study. The vibrational wavenumbers were computed at B3LYP/6-311++G** level for the two molecules. Normal coordinate calculations were carried out and potential energy distributions (PED) among symmetry coordinates of the normal modes were calculated for the molecules. (C) 2002 Elsevier Science B.V. All rights reserved.