Identify compound B in the following reaction sequence:

Step-by-step solution

When 1,2-dibromocyclopentane reacts with 1 equivalent of magnesium (Mg) in the presence of dry ether, magnesium inserts into one of the carbon-bromine bonds. This results in the formation of a mono-Grignard reagent. Thus, compound A is 2-bromocyclopentylmagnesium bromide. Grignard reagents formed from 1,2-dihalides are generally unstable at higher temperatures. Upon heating ( ), compound A undergoes an intramolecular -elimination reaction. The -MgBr group and the adjacent -Br atom are eliminated as MgBr₂ , leading