SOLVENT ATTACK IN GRIGNARD-REAGENT FORMATION FROM BROMOCYCLOPROPANE AND 1-BROMOHEXANE IN DIETHYL-ETHER

In the reaction of magnesium with bromocyclopropane in diethyl ether at reflux, intermediate cyclopropyl radicals attack the solvent, giving cyclopropane (20-30 mol/100 mol of bromocyclopropane consumed) and solvent-derived products. In contrast, the similar reaction of 1-bromohexane gives no more than 0.5 mol of hexane from solvent attack by hexyl radicals. These data are consistent with calculations based on a mechanism (D Model) with freely diffusing intermediate radicals, in which cyclopropyl and hexyl radicals have similar reactivities in their conversions to Grignard reagents, but the cyclopropyl radical is approximately 1000 times as reactive toward the solvent as the hexyl radical.