Structural relaxations and energy effects of intramolecular motions in N,N-dimethylnitramine: a theoretical studyстатья
Информация о цитировании статьи получена из
Web of Science,
Scopus
Статья опубликована в журнале из списка Web of Science и/или Scopus
Дата последнего поиска статьи во внешних источниках: 18 июля 2013 г.
Аннотация:The equilibrium geometry of the N,N-dimethylnitramine molecule and changes in the energy and structural parameters due to the internal rotation of the nitro group and the inversion of the N atom in the amino fragment were calculated by the restricted Hartree-Fock (RHF) method and at the second-order Moller-Plesset (MP2) level of perturbation theory with inclusion of electron correlation using the 6-31G* and 6-31G+* basis sets. The one-dimensional potential functions of these motions calculated at the RHF/6-31G* level were approximated by a truncated Fourier and power series, respectively. The frequencies of torsional and inversion transitions were determined by solving direct vibrational problems for a non-rigid model, i.e., taking into account the molecular geometry relaxation. The equilibrium conformation of the molecular skeleton of N,N-dimethylnitramine is nonplanar. Transition states of the internal rotation of the nitro group and inversion of the amine N atom are characterized by pronounced concerted changes in its bond angles and the length of the N-N bond. In the MP2/6-31G* approximation, the height of the barrier to internal rotation calculated taking into account the difference in the zero-point vibrational energies is equal to 9.7 kcal mol(-1). Inversion in the amino fragment is accompanied by a relatively small energy change at the barrier height of similar to 1.0 kcal mol(-1) calculated in the same approximation.