COMPUTATIONAL STUDY OF THE CONCERTED GAS-PHASE TRIPLE DISSOCIATIONS OF 1,3,5-TRIAZACYCLOHEXANE AND ITS 1,3,5-TRINITRO DERIVATIVE (RDX)

Concerted triple dissociation reactions of 1,3,5-triazacyclohexane (I) and 1,3,5-trinitro-1,3,5-triazacyclohexane (II, RDX) were investigated by using semiempirical, ab initio, and local density functional (LDF) methods. Gaseous phase structures and energies for the ground and the transition states of I and II are presented and analyzed. The activation barriers for both processes are predicted to be in the range 72-75 kcal/mol. The LDF results are comparable to those obtained by the highest level ab initio procedure [MP4(SDTQ)/6-31G*//3-21G]. The dipole moments and the electrostatic potentials associated with the amine nitrogen lone pairs have been computed and are used to interpret the structural and electronic factors involved in the formation of the transition states.