Computed effects of electric fields upon the CNO2 and NNO2 bonds of nitromethane and dimethylnitramine

Abstract

AbstractWe report the results of a computational (B3PW91/6‐31G**) investigation of the effects of electric fields of different strengths and directions upon some properties related to the CNO2 and NNO2 bonds in nitromethane, H3CNO2, and dimethylnitramine, (H3C)2NNO2. We look at the interaction energies of the fields with the molecules, the dipole moments of the latter, the lengths of the CNO2 and NNO2 bonds, and we particularly focus upon their stretching vibration frequencies. The field‐induced frequency shifts are determined by means of a formula linking them to the dipole moment derivatives and the field strengths. This formula was derived originally for hydrogen‐bonded systems, but we show that it is applicable as well to these CNO2 and NNO2 bonds; their predicted relative frequency shifts correlate extremely well with directly computed Δω(ϵ) (R2 = 0.9992). It was found that the fields that reinforce the intrinsic H3CNO2 and (H3C)2NNO2 polarities also interact favorably energetically with the molecules and, particularly important, increase the CNO2 and NNO2 stretching frequencies. This presumably indicates the strengthening of these bonds. Fields in the opposite direction do the reverse. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2009