Which of the following reagents is selectively used to perform side-chain bromination on ethylbenzen — Aromatic Hydrocarbons Chemistry Question
Question
Which of the following reagents is selectively used to perform side-chain bromination on ethylbenzene to predominantly yield 1-bromo-1-phenylethane without affecting the aromatic ring?
Answer: B
💡 Solution & Explanation
To achieve side-chain halogenation, a free radical mechanism is required. N-Bromosuccinimide (NBS) in the presence of light or heat generates a low, steady concentration of bromine radicals. These selectively abstract the weaker benzylic hydrogen to form a highly resonance-stabilized benzylic radical, which then reacts to form 1-bromo-1-phenylethane.
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