This review covers hydrogen-atom transfer from carbon-hydrogen bonds in organic compounds to chlorine atom, methyl, ethyl, trichloromethyl, t-butoxy and alkylperoxy radicals in the liquid phase. Rate constant data are presented-iri 38 tables. Literature is covered throu,gh most of 1972. The review is divided into six sections; an introduction plus five sections each dealing with specific radicals. Hydrogen-atoIn trander to chlorine Iltom Ilrp pre!':f>ntp{l :I!': rpbtivp ratp eon",tant",_ For hydrogen-atom transfer to methyl, ethyl, trichloromethyl, and t-butoxy radicals, both relative and absolute rate constants are tabulated. For alkylperoxy radicals only absolute rate constants are listed. Each absolute rate constant ha.s a tabulated set of rate parameters where A has been assigned and E derived from the Arrhenius equation.

The rate constant for tert-butyl radical recombination has been measured near 700°K by the very-low-pressure pyrolysis (VLPP) technique and was found to be 108.8*0.3 M-1.sec-1 with neglibible temperature dependence. The thermochemical parameters for tert-butyl radicals were varied within reasonable limits to bring into agreement the data for the decomposition of 2,2,3,3-tetramethyl butane and the recombination of terf-butyl radicals. The revised thermochemistry also makes the gas-phase results and liquid-phase results compatible.

An absolute value of k, of ethyl radicals at 860 f 17°K of 4.5 X l o 9 M-l.sec-' was determined under VLPP conditions, where the value of k,/k," should be about M. Thus k,"(M-'.sec-')

Absolute values of the rate constant for isopropyl radical combination have been determined over the temperature range 683-808°K. The value log kr (M~1 sec-1) = 9.5 ± 0.2 fits all the data, leading to the conclusion that the temperature dependence, if any, is slight. The compatibility of this value with other values determined either directly or from the reverse process via thermochemical data depends on the particular model chosen to represent the transition state since the temperatures of the various determinations differ. It has been found that

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