Year 2005, Month 5 (Section Full Articles, Page 1100)
Comparative quantum chemical investigation of
structures and properties of diazocyclopropane and other diazoalkanes*
E. G. Baskir,* I. P. Klimenko, Yu. V. Tomilov, and O. M. Nefedov
The electronic structures and dissociation energies of diazocyclopropane (1), diazomethane (2), 2-diazopropane (3), and diazocyclobutane (4) were calculated at the density
functional B3LYP and the ab initio MP2 levels using the 6-31G(d) basis set and at the
G2(MP2,SVP)//B3LYP/6-31G(d) level. Distinctive features of diazocyclopropane 1 are the
low energy of dissociation with loss of the nitrogen molecule; ∆E = 18.7 kcal mol–1, B3LYP;
9.2 kcal mol–1, G2 at 0 K) and a nonplanar structure, in which the C=N bond forms an angle
of 115.7° with the plane of the cyclopropane ring. The behavior of molecules 1 and 2 in the
1,3-dipolar cycloaddition to ethylene (5), acrylonitrile (6), and methyl acrylate (7) was studied. The reactions of 1 with 6 and 7 have very low activation barriers (∆Ea = 4.7 and
4.4 kcal mol–1, respectively; at the B3LYP level). For these reactions, the G2 method gives
even smaller activation parameters (1.8 and 0.3 kcal mol–1, respectively). The results of our
calculations provide a good explanation for high reactivity of diazocyclopropane 1.
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