Vibrational spectra and conformations of bis(N-ethyl)nitramine molecule

The Raman (50-3200 cm(-1)) and infrared (50-3200 cm(-1)) spectra of bis(N-e thyl)nitramine, (CH3CH2)(2)NNO2, in the liquid and crystal states have been recorded, Optimized geometries and conformational stabilities have been ob tained from ab initio calculations utilizing the RHF/6-31G** level, This co mpound was shown to have two stable conformations with a planar nitramine f ragment and the CH3 groups orthogonal to it and located either on the same or on the different sides of it. The computed energy difference between two conformers is 0.57 kcal/mol. (CH3CH2)(2)NNO2 exists as a mixture of the tw o conformations in the liquid state, while only the most stable one, with t he CH3 groups located on the different sides of the nitramine fragment, rem ains in crystal state. The vibrational frequencies have been calculated usi ng ab initio scaled force fields, and the vibrational spectra have been int erpreted in detail. (C) 1999 Elsevier Science B.V. All rights reserved.