Advances in Photochemistry, Volume

Some Problems of Structure and Reactivity in Free Radical and Molecule Reactions in the Gas Phase  

SIDNEY W. BENSON, University of Southern California, Los Angeles, 

The past decade has been an extremely fruitful one in the field of quantitative free radical kinetics. Two papers can be identified as the starting point of much of this work. The first of these is the acetone photolysis study by Noyes and Dorfman1 which gave confidence to the use of acetone as a reproducible source of methyl free radicals in a fairly simple kinetic environment. The second is the study of Gomer and Kistiakow-sky2 of the absolute rate of recombination of CH3 radicals. The latter study made it possible to give absolute values for the Arrhenius parameters for the reactions of alkyl free radicals with stable molecules. It also opened the way for putting the reactions of methyl radicals with other alkyl radicals on an absolute basis. 

To the present time about 100 reactions of CHa radicals with stable molecules have been reported. These are almost all of the atom abstraction type and in particular, they involve the abstraction of an H atom from a molecule we can label RH. Table I lists the Arrhenius parameters for a representative number of these reactions and it appears to 

The bulk of them also have activation energies in the range of 8 3 kcal./mole. In fact the atom abstraction reactions of most free radicals from molecules, when exothermic, have activation energies in this same range. Table II lists a representative series of such reactions. 

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Advances in Photochemistry, Volume 27 Edited by Douglas C. Neckers, Gunther von Biinau and William S. Jenks Copyright 2002 John Wiley Sons, Inc. 

Advances in Photochemistry, Volume 6 Edited by M. Albert Noyes, Jr., George S. Hammond, J. N. Pitts, Jr. 

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