Exchange Reactions with Deuterium II. The Photochemical Exchange Between Deuterium and Hydrogen Chloride

The exchange reaction between hydrogen chloride and deuterium, initiated photochemically, is found to be a chain reaction with quantum yields ranging from 2 to 19 under the experimental conditions employed. The rate determining step is the reaction Cl+D2→DCl+D. The proportions at the photostationary state are shifted from those at thermal equilibrium in a direction which indicates a somewhat stronger absorption by HCl than by DCl in the region 2000–2150A.