Accession Number : ADA294300

Title :   Vibrational Mode Selectivity in the Unimolecular Decomposition of CH2NNO2.

Descriptive Note : Final rept. Sep 94-Jan 95,

Corporate Author : ARMY RESEARCH LAB ABERDEEN PROVING GROUND MD

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

PDF Url : ADA294300

Report Date : MAY 1995

Pagination or Media Count : 52

Abstract : Vibrational mode selectivity has been investigated for the unimolecular decomposition of methylene nitramine (MN), CH2NNO2, by using classical trajectories computed on a (previously reported) potential-energy surface (PES) that is based on ab initio results. The PES allows for the two known primary decomposition pathways: (I)N-N bond scission to form H2CN and NO2 and (11) concerted molecular elimination giving HONO and HCN. Rates were computed for 57.7 kcalAnol above the zero-point energy for initial conditions corresponding to overtone excitations of each of the 15 normal modes. One calculation was done at this energy with initial conditions corresponding to a microcanonical (statistical) distribution in which the energy was randomly distributed among all of the vibrational modes. Comparisons of the mode selective results with this statistical rate show that there is substantial enhancement of the decomposition rates for the two reactions for excitation of three of the normal modes. Excitation of the other 12 modes yielded rates in accord with the statistical rates for the two reactions. The results show that projection of a vibrational mode onto the reaction coordinate is necessary for mode selective reaction, but is not sufficient since energy transfer into the reaction coordinate must compete with energy flow to other modes that do not project onto (that is, are uncoupled from) the reaction coordinates.

Descriptors :   *MOLECULAR VIBRATION, *ENERGY TRANSFER, *METHYLENES, *DECOMPOSITION, *NITRAMINES, COMPUTATIONS, REACTION KINETICS.

Subject Categories : Organic Chemistry

Distribution Statement : APPROVED FOR PUBLIC RELEASE