The ratio of the rate constants for disproportionation and combination for ethyl radicals, k d / k kd 2C2Hs + C2H4 + C2Hs has been measured over the temperature range 298-173 K in the gas phase. Ethyl radicals were produced by direct photolysis of ethylenefollowed by addition of hydrogen atoms to ethylene. At low temperatures the only important reactions of the radicals were combination and disproportionation. The ratio kd/kc was obtained from measurements of the rates of formation of ethane, butane, and butene. No change in the ratio kd/k, was observed over the temperature range studied, leading to the conclusion that Ed -E, = 0, within the experimental error. The significance of this result is discussed in relation to other measurements in both gas and liquid phase and to the nature of the transition state for this reaction.
Measurements of the yields of products and the decrease in pressure as a function of time have shown the relation between the mecl~anisn~s for the thennal reactions of ethylene proposed in two separate studies, which jointly cover the range 776-924 ' EC and 10-600 Torr. Specifically, the measureinents relate the polymerization and decomposition processes and show the dependence on temperature and pressure of the reactions proposed.
In the photolysis of ethylene at 185 nm the rate of formation of hexene-1 has been measured. The ratio of the rates of formation of hexene-1 to butane varied from 0.6 to 1.4 at 298 K and fell to about 0.25 at 153 K. It is suggested that hexene-1 is formed by successive additions to ethylene to give hexamethylene which isomerizes to hexene-1.[Formula: see text]This interpretation is consistent with the effect of pressure of ethylene and absorbed light intensity on its rate of formation.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.