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The Relative Rates o f the Reactions of Hydrogen A toms with Hydrogen Iodide
by R. J. L e t e l i ~ rH. , ~ L. Sandoval, and R. B. Penzhorn* Chemistry Department, Faculty of Physical and Mathematical Sciences. University of Chile, Santiago, Chile (Received September 8, 1070) Publication costs borne completely by T h e Journal of Physical Chemistry
The photochemistry of hydrogen halides has been a subject of renewcd interest in recent years,2 mainly because they are a convenient source of thermal and 0-3 eV hol, hydrogen atoms.2f Nevertheless, no direct measureinents of the relative rates of the reactions of hydrogen atoms with hydrogen halides have been found in the literature. We have investigated the photolysis of H I and HBr in the presence of ethylene, monofluoroethylene, te trafluoroet hylene, and iodine. Experimentally only t,he hydrogen quantum yield (%J was measured using an appasatuo and technique described in a previous paper.3 @ H was ~ defined as the ratio of the rate of hydrogen p roclu ced from a olefin-hydrogen halideCOz mixture over that of the same hydrogen halideCOz mixture a-ithout the olefin. At low conversions and under thew m a l conditions (excess of COZ generally greater than 20 times the combined reagent pressures) only the reacticm
H H
+ N X -* H2 + X (X = I or Br) N + Xz +HX 3. x
+ C
