Accession Number : ADA290886

Title :   Classical Dynamics Simulations of Unimolecular Decomposition of CH2NNO2: HONO Elimination vs. N-N Bond Scission

Descriptive Note : Final rept. Sep 1993-Jun 1994

Corporate Author : ARMY RESEARCH LAB ABERDEEN PROVING GROUND MD

Personal Author(s) : Rice, Betsy M ; Thompson, Donald L

PDF Url : ADA290886

Report Date : Feb 1995

Pagination or Media Count : 36

Abstract : Classical dynamics simulations of the unimolecular decomposition of CH2NNO2 have been performed. The potential energy function was based on MCSCF and MRCI calculations of Mowrey et al. (1990). CH2NNO2 primary decomposition rates and mechanisms are presented. The two primary decomposition pathways are (1) N-N bond scission to form H2CN and NO2 and (2) concerted dissociation via a five-center transition state to eliminate HONO + HCN. The classical barrier heights differ by 2 kcal/mol. Reactions (1) and (2) are first-order decay processes and are well-behaved with increasing energy. At low energies, (1) is the major decomposition pathway, but at high energies, (2) becomes equally probable. Product energy distributions for (1) are unremarkable, with the relative translational and rotational distributions peaked near zero; however, distributions for (2) show interesting behavior. The trajectories resulting in (2) that do not experience secondary HONO decomposition have a translational energy distribution shifting significantly away from zero, as expected with large back reaction barriers. The trajectories resulting in (2) that undergo secondary HONO decomposition, however, have a distribution that is similar to the distributions in (1), indicating little translational energy excitation upon formation. Rotational energy distributions for (2) are peaked near zero, regardless of whether HONO decomposes. Most of the available product energy for (2) goes into vibration. Our results, calculated under microcanonical conditions in which energy is partitioned in a statistical manner among the internal modes, are not consistent with the RDX molecular beam measurements in which CH2NNO2 is a primary decomposition product which decomposes only through concerted molecular eliminations.

Descriptors :   *DECOMPOSITION, *DYNAMICS, *METHYLENES, *MOLECULAR PROPERTIES, *NITRAMINES, *SIMULATION, BARRIERS, CHEMICAL BONDS, DECAY, DISSOCIATION, ELIMINATION REACTIONS, ENERGY TRANSFER, HIGH ENERGY, INTERNAL, LOW ENERGY, MEASUREMENT, MOLECULAR BEAMS, MOLECULES, NITROGEN, POTENTIAL ENERGY, RDX, RESPONSE, ROTATION, SHIFTING, TRAJECTORIES, VIBRATION

Subject Categories : Inorganic Chemistry
      Organic Chemistry
      Physical Chemistry
      Atomic and Molecular Physics and Spectroscopy

Distribution Statement : APPROVED FOR PUBLIC RELEASE