Substituent Effects and Isokinetic Relations in the Homolysis of Hyponitrite Esters. The Question of Free-Radical Homoconjugation

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Activation parameters for first-order homolysis of 14 trans-hyponitrites (alkyl, benzylic, and benzhydryl) in tert-butylbenzene are reported. Activation energies varied from 25–30 kcal/mol and log A/s from 13.2-15.9. These and published activation parameters on hyponitrites could be represented by isokinetic relationships, with all the compounds appearing on a single line (r = 0.99) in a double-log plot of calculated rate constants at 70 and 43.7 °C. The effects of a-phenyl substitution and of aromatic ring substituents on the rate constants are discussed in light of possible homoconjugation in the developing alkoxy radicals. © 1985, American Chemical Society. All rights reserved.

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Journal of Organic Chemistry