Laser Photolysis Study of the Reactions of Alkoxyl Radicals Generated in the Photosensitized Decomposition of Organic Hyponitrites

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The triplet photosensitized decomposition of organic hyponitrites produces alkoxy radicals in good yields. For example, the quenching of p-methoxyacetophenone triplets by di-tert-butyl hyponitrite in benzene at 27 °C occurs with kq= 1.41 × 108M−1s−1, and ∼50% of the quenching events lead to a pair of tert-butoxy radicals. Steric effects play an important role in the kinetics of the quenching process; e.g., phenanthrene triplets are quenched 23 times faster by di-2-phenylethyl hyponitrite than by di-tert-butyl hyponitrite. The 2-phenylethoxy radicals undergo efficient β-cleavage to yield PhĊH2radicals with log (kβ/s−1) = 10.89 − 4830/θ, with θ = 2.3RT in cal/mol. The rate is markedly enhanced by polar solvents. The reaction of alkoxy radicals with diphenylmethanol is also sensitive to steric effects and occurs with rate constants (benzene, 27 °C) of 5.8 × 106and 2.6 × 107M−1s−1for tert-butoxy and 2-phenylethoxy radicals, respectively. © 1982, American Chemical Society. All rights reserved.

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Journal of the American Chemical Society