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T, J, HARDWTCK
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ferent charge types. At least, the failure of the rate effects to appear in the entropy term cannot
be cited as evidence against the electrostatic origin of those rat8eeffects.
THE REACTIVITY OF HYDROGES ATOMS IN THE LIQUID PHASE. IV. THE REACTION WITH SOME HALOGENATED CONPOUNDS BY T. J. HARDWICK Gulf Research !d Development Compuny, Pittsburgh $0,Pennsylvania Recetued Jzlnt 11, 156W
Studies have been made on the reactivity of hydrogen atoms with a variety of halogenated allraries (RX) in liquid n-hexane at 23". With such compounds, hydrogen atoms abstract halogen atoms to form HX, and in many cases, hydrogen to form HL For halocarbons of analogous structure, the rate for halogen abstraction is invariably greatest for iodides, least for chlorides. Successive substitution of halogen atoms in an alkane molecule increases the rate of halogen removal. The rates of iodine abstraction from iodoalkanes are among the highest which have been observed in non-ionic solution chemistry (0.6-2 X 1018 GO, mole-' sec.-l).
Introduction The reaction of hydrogen atoms with halogenated hydrocarbons heretofore has been studied only in the gas phase. With only one or two exceptions this has been limited t o the halogenated methanes. The most thorough work is that of Cremer, Curry, and Polaiiyil in which hydrogen atoms, produced by electrical discharge, reacted with methyl chloride, methylene chloride, chloroform, and carbon tetrachloride, In all cases chlorine was abstracted to form hydrogen chloride. I n addition, evidence was obtained for hydrogen abstraction fmm the first three compounds. With the advent of a method of measuring the reactivity of hydrogrn atoms in solution, it became possible to study the reactions of hydrogen atoms with a variety of halogenated hydrocarbons. It is the purpose of this paper to report such experiments.
GI RH---+ Hz-t- Products (1) The method of measuring hydrogen atom reactivity in solution has been described in detail previously.* Briefly, hydrogel1 atoms are produced in sztu during the radiolysis of a saturated hydrocarbon (rz-hexane in our experiments). G2
R€l --m+ H
+R
(2) The hydrogen atoms diffuse a t thermal energies, reacting competitively with solvent by hydrogen abstraction or added solute (
