Density functional theory study of piperidine and diazocine compounds.

Density functional theory calculations at the B3LYP/6-311G** level were performed to predict the heats of formation (HOFs) for three eight-membered ring compounds and four six-membered ring compounds via designed isodesmic reactions. In the isodesmic reactions designed for the computation of HOFs (CH(3)CH(2))(2)NNO(2) and piperidine were chosen as reference compounds. The HOFs for -NO(2) substituted derivations are larger than those of -NF(2) substituent groups. Thermal stability were evaluated via bond dissociation energies (BDE) at the UB3LYP/6-311G** level. As a whole, the homolysis of CNF(2) or CNO(2) bonds is the main step for bond dissociation of the title compounds. Detonation properties of seven title compounds were evaluated by using the Kamlet-Jacobs equation based on the calculated densities and HOFs. It is found that 3,3,7,7-tetrakis(difluoroamino)octahydro-1,5-dinitro-1,5-diazocine (HNFX) and 3,3,5,5-tetrakis (difluoroamino)-1-nitro piperidine (N-nitro TDFAPP), with predicted density of ca. 2.0 g/cm(3), detonation velocity (D) about 9.9 km/s, and detonation pressure (P) of 47GPa that are lager than those of HMX, are expected to be the novel candidates of high energy density materials (HEDMs). The detonation data of 1,3,3,5,7,7-hexanitro-1,5-diazacyclooctane (HNDZ) and TNBDFAPP show that they meet the requirements for HEDMs.