Nuclear Magnetic Resonance Spectroscopy. The Structure of Butenylmagnesium Bromide

Crotyl bromide and α-methylallyl bromide each react with magnesium in ether to yield the same butenyl Grignard reagent, which conceivably could be crotylmagnesium bromide (I), α-methylallyl-magnesium bromide (II), a more or less mobile equilibrium mixture of I and II, or an intermediate, bridged structure such as III.