Identify the correct set of reagents or reaction conditions 'X' and 'Y' in the following set of transformation. CH3-CH2-CH2-Br 'X' Product 'Y' CH3- Br |CH-CH3
- X = dil.aq. NaOH, 20°C, Y = HBr/ acetic acid
- X = conc.alc. NaOH, 80°C, Y = Br2/CHCl3
- X = dil.aq. NaOH, 20°C, Y = Br2/CHCl3
- X = conc.alc. NaOH, 80°C, Y = HBr/ acetic acid
Answer
(4) X = conc.alc. NaOH, 80°C, Y = HBr/ acetic acid
Solution
Required: 1-bromopropane → 2-bromopropane (Br shifts to C-2) ⇒ via propene
CH3CH2CH2Br [80 C]conc. alc. NaOH CH3CH=CH2 (E2, dehydrohalogenation)
CH3CH=CH2 HBr/CH3COOH CH3CHBrCH3 (Markovnikov addition)
(A), (C): dil. aq. NaOH, 20°C ⇒ substitution ⇒ CH3CH2CH2OH, not an alkene ⇒ wrong
(B): Br2/CHCl3 adds two Br ⇒ CH3CHBrCH2Br ⇒ wrong
(D): elimination, then HBr addition ⇒ correct
Answer: (4)