Failure of intramolecular energy relaxation in unimolecular reaction systems

Abstract

[[abstract]]We describe here a novel and comprehensive demonstration of the failure of internal randomization of energy in a series of decomposing fluoroalkyl cyclopropanes. Recently, Rynbrandt and Rabinovitch reported the demonstration of failure of neutral molecules to complete intramolecular energy randomization prior to decomposition. In that work, chemically activated fluorinated bicyclopropane molecules having isotopically labeled rings were formed by reaction with methylene radicals, and also by the isotopically interchanged counterpart reaction with lCH2 which put the 2 H atoms into the nascent ring. The hot molecule can decompose by CF2 split off from either ring. Upon activation, energy deposition occurred in the D-Iabeled nascent ring of I which underwent preferential (nonrandomized) decomposition to the extent of - 3.5% of the total activated substrate to form excess of over the inverse proportion arose from the isotopic counterpart system. Thus, decomposition of the unrelaxed nascent ring competed with intramolecular relaxation at short elapsed times. From their data, the relaxation time for internal energy randomization was calculated by RR as T- 9 x 10-13 sec.[[fileno]]2010323010099[[department]]化學