NONEMPIRICAL QUANTUM-CHEMICAL CALCULATION FOR NITRAMIDE, ITS CHLOROSUBSTITUTED AND METHYL-SUBSTITUTED DERIVATIVES .2. STRUCTURES AND ENERGIES OF TRANSITION-STATES FOR INTERNAL-ROTATION AND INVERSION OF THE AMINO GROUP

For five N-nitramines (H2NNO2, MeNHNO2, ClNHNO2, MeNClNO2, Me2NNO2) us ing the program GAUSSIAN-90 we have carried out quantum chemical calcu lations by the restricted Hartree-Fock method, taking into account ele ctron correlation by second-order Moller-Plesset perturbation theory i n a standard 6-31G basis. In this paper, we consider the transition s tates for inversion of the amine nitrogen atom and rotation about the NN bond. We have obtained data on the changes in the geometric paramet ers during inversion and rotation. The changes in the NN bond length a re especially significant: they increase by 0.06-0.08 angstrom in the transition states for internal rotation compared with the equilibrium forms. We have calculated the barriers to inversion and internal rotat ion, the height of which strongly depends on the electronegativity of the substituents on the amine nitrogen atom. Estimates of the barriers to inversion lie within the range 0.4-60 kcal/mole while estimates of the barriers to rotation lie within the range 6-13 kcal/mole, which a re 1.5-2 times lower than in amides and N-nitrosoamines.