Vibrational analysis of high-energy compounds: 1,3,3-trinitroazetidine and 1-acetyl-3, 3-dinitroazetidine

Abstract Infrared spectra were obtained and normal coordinate calculations were made for 1,3,3-trinitroazetidine (TNAZ) and N-acetyl-3,3-dinitroazetidine (ADNAZ) in an effort to learn more about the conformational behavior of these compounds and to make assignments of the infrared bands to the appropriate normal modes of vibration. Semi-empirical molecular orbital calculations were also made in order to obtain additional information about the molecular structures. Normal coordinate calculations were made first for ADNAZ. Appropriate force constants obtained for ADNAZ were then used as starting values for TNAZ. It was shown that the observed frequency shift of the C=O stretch band of ADNAZ and the NO2 antisymmetric stretch and NO2 out-of-plane wag bands of the N-NO2 group of TNAZ can be explained by a change from the conformation that is initially present to another conformation during recrystallization after mixtures are melted. However, these shifts may also be explained by intermolecular interactions that cause changes in the force constants of the bonds and angles that affect the frequencies of the three bands just mentioned.