Reactions of cyclic alkyl radicals. Part 1.—Methyl-radical-sensitized decomposition of cyclopropane carboxyldehyde

Abstract

The methyl-radical-induced decomposition of cyclopropane-carboxaldehyde has been studied in the temperature range 100–200°C in order to investigate the use of the aldehyde as a source of cyclopropyl radicals. Decarbonylation of the cyclopropylcarbonyl radical although not complete is extensive and cyclopropyl radicals are produced. Cyclopropyl radicals react by hydrogen atom abstraction from the aldehyde and by combination with methyl radicals. About 10 % of the cyclopropyl radicals formed react by ring fission to form allyl radicals. These radicals undergo combination reactions with methyl radicals and, to a small extent, abstract hydrogen atoms from the aldehyde. An activation energy of ca. 20 kcal mole^–1 has been estimated for the ring fission of the cyclopropyl radical. Arrhenius parameters are reported (based on a value of 10^13.34 mole^–1 cm³ sec^–1 for the rate of combination of methyl radicals) for the following reactions: [graphic omitted]