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NEETChemistryHaloalkanes and Haloarenes

An unknown alkyl halide 'X' undergoes substitution with KCN, followed by acidic hydrolysis to form an intermediate. This intermediate on treatment with Br ₂ /Red P followed by H ₂ O yields 2-bromobutanoic acid as the major product. Identify the starting alkyl halide 'X'.

Options

  1. A1-Chlorobutane
  2. B2-Chloropropane
  3. C2-Chlorobutane
  4. D1-Chloropropane

Correct answer

D. 1-Chloropropane

Step-by-step solution

The final product is 2-bromobutanoic acid, which is formed via the Hell-Volhard-Zelinsky (HVZ) reaction. Working backwards, the intermediate carboxylic acid before the HVZ reaction must be butanoic acid ( CH ₃ CH ₂ CH ₂ COOH ). Butanoic acid is formed by the acidic hydrolysis of butanenitrile ( CH ₃ CH ₂ CH ₂ CN ). Since the reaction of an alkyl halide with KCN involves a step-up of one carbon atom, the starting alkyl halide 'X' must contain 3 carbon atoms in a straight chain. Therefore, 'X' is 1-chloropropane ( CH

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