Major monobrominated product which results when ethylcyclohexane is subjected to a free radical bromination is

Question

a. a quaternary bromide
b. a tertiary bromide
c. a secondary bromide
d. bromomethane
e. a primary bromide

Answer 1

b. Tertiary bromide. Br2 dissociates into Br. + Br. The first Br. abstracts a proton preferentially from CH3CH2-C-H to give the most stable free radical (most stable because most hindrered and so least likely to revert to hydrocarbon again). That free radical abstracts Br from a new Br2, giving a tertiary bromide and generating a new Br. to continue the chain reaction.