Detection of intermediates in grignard reaction on the magnesium surface

Benzyl radicals and ion‐radical pairs have been detected on a magnesium surface by electron spin resonance (ESR) spectroscopy during benzyl halide reactions with magnesium at low temperatures. The ratio of these intermediates depends on the carbon‐halogen bond energy in the starting benzyl halide, the nature of the magnesium surface and the degree of magnesium aggregation. Polymagnesiumbenzyl chlorides were formed in small amounts and only monomagnesium organic compounds were formed from benzyl bromide and benzyl iodide.