Textbook Question
Predict the product of the following benzylic bromination reactions.
(a)
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19. Reactions of Aromatics: EAS and Beyond
Side-Chain Halogenation
Multiple Choice
Which of the following reagents will prepare the given target from the given starting material?
A
HBr
B
Br2, FeBr3
C
HBr, H2O2
D
NBS, heat
Verified step by step guidance1
Identify the type of reaction needed: The transformation involves the bromination of an allylic position, which is a common reaction type in organic chemistry.
Recognize the starting material and target structure: The starting material is an alkene with an allylic position, and the target structure has a bromine atom at the allylic position.
Consider the reagents: N-bromosuccinimide (NBS) in the presence of heat is a reagent commonly used for allylic bromination. It selectively brominates the allylic position without affecting the double bond.
Understand the mechanism: NBS generates a small amount of bromine radical in situ, which abstracts a hydrogen from the allylic position, forming an allylic radical. This radical then reacts with bromine to form the allylic bromide.
Apply the conditions: Use NBS and heat to achieve the desired bromination at the allylic position, resulting in the target compound with bromine at the specified location.
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