Gas to liquid to solid transition in halogen hot atom chemistry. 4. The suggestion of multiple enhancement reactions in high energy iodine-128-ethane systems

Abstract

The gas to condensed phase transition technique has been used to study the iodine-128-ethane system. Total organic product yields were found to range from 1.1 (1 atm gas) to 61.2% (-23 °C liquid). Various molecular and enhancement reactions are evaluated using available data and a comparison is made among ethane and other two carbon hydrocarbons.

Effects of a Collapsing Molecular Environment on High Energy Bromine Reactions in Ethane

“…For the determination of individual organic product yields (lOPY) in the various samples, a variable temperature gas Chromatograph similar to the one previously described [17] but modified to handle the direct injection of high pressure gaseous and liquid phase samples [13] was used employing a scintillation counter with a flow through cell. The direct injection of high pressure and liquid samples was necessary to prevent loss of volative labelled organic products such as CHsBr.…”

“…Ethane has also been studied in reaction with throughout the gas to Condensed phase transition [13] and found to exhibit multiple enhancement reaction pathways. A previous study [11 ] of bromine reactions with halomethanes in the gas to Condensed phase transition suggested only the presence of cage-ion, cageradical enhancement reactions.…”

“…The gas to Condensed phase transition technique is an important tool that has been utilized by hot atom chemists to acquire insight into the effects of collapsing molecular environment on the dynamics of high energy chemical processes [8][9][10][11][12][13][14]. The presence of enhancement yields, product yield increases above those expected from extrapolation of low pressure data, can be used with other experimental data in the evaluation of probable product formation routes.…”

“…Enhancement processes are of two general types: cage-ion or cage-radical reactions, an extension of the FRANCK-RABINOWITSCH "cage-effect" [15] in which a hot atom recombines with ions or radicals of its own creation, and "caged-complex" reactions [10] in which an electronically excited complex is held in spatial configuration by the cage walls for a time sufficient to react. Previous studies have shown that in various hot atom systems, in high pressure and the Condensed phase, product yields can be enhanced to a greater extent than by excitationstabilization of excited products, primarily by cage-ion, cage-radical processes [8,11], "caged-complex" reactions [10,12]oracombinationofboth [13]. Ethane is a low mass, saturated hydrocarbon, providing Experimental Materials.…”

Computer Simulation Evaluating Kinetic Theory Parameters in Hot Atom Chemistry

“…In the high pressure and condensed phase enhancement reactions become important. There have been many studies of these multi-molecular reactions throughout the gas to condensed phase transition [26][27][28][29][30][31][32][33], Enhancement reactions appear to be of two types: cage-radical, cage-ion reactions involving semi-random recombinations [26,30] and caged-complex reactions [29,31 ] involving the stabilization of an electronically excited cage complex. Evidence exists that these reactions may occur simultaneously [32,33], Although enhancement reactions are complex and description difficult as a result of the inseparability of enhancement events from molecular reactions, several attempts have been made to develop a semi-emperical description of enhancement events [34][35][36], These have considered the variation of bulk [34] and molecular [35] parameters in photolytically-induced cage radical recombinations and the implantation of a hot atom in a lattice matrix [33], No attempt had been made to simulate the effects of collapsing molecular environment on a chemical system which exhibits enhancement reactions.…”