THEORETICAL-STUDY OF SEVERAL DIAZAALKENES AND DIAZAALKYL RADICALS

The stabilities of different isomers of several diazaalkenes (diazapropene, diazabutene, and diazapentene) were compared at several levels of theory. For the simplest diazaalkenes, methyldiazene (1, 2-diaza-1-propene) and formaldehyde hydrazone (2, 3-diaza-1-propene), the two isomers are very close in energy. At the MP4/6-31 l+G**/MP2/6-31G* level including zero-point and heat capacity corrections, the 1, 2-isomer is 0.4 kcal/mol more stable than the 2, 3-isomer. Bond dissociation energies were calculated for the formation of the diazapropenyl radical and the diazabutenyl radical. The best calculated BDE for the C-H bond in HN═NCH3 (1, 2-diaza-1-propene) is 87.3 kcal/mol while the N-H bond in H2NN═CH2 (2, 3-diaza-1-propene) has a BDE value of 86.9 kcal/mol. The lowest energy diazabutene isomer is the hydrazone isomer, 1, 2-diaza-2-butene, which is 2.4 kcal/mol more stable than the two azo isomers. © 1990, American Chemical Society. All rights reserved.