The synthesis of 3-octyne is achieved by adding a bromoalkane into a mixture of sodium amide and an alkyne. The bromoalkane and alkyne respectively are
- (A) and
- (B) and
- (C) and
- (D) and ✓ Correct
Answer: (D)
Solution
3-Octyne is CH₃–CH₂–C≡C–CH₂–CH₂–CH₂–CH₃. The synthesis uses sodium amide to deprotonate a terminal alkyne, forming an acetylide anion that acts as a nucleophile in an SN2 reaction with a primary bromoalkane. To form 3-octyne, we need 1-butyne (CH₃CH₂C≡CH, 4 carbons) which after deprotonation reacts with 1-bromobutane (BrCH₂CH₂CH₂CH₃, 4 carbons) to give the 8-carbon product with the triple bond at position 3.
JEE Advanced · 2010 · 11 Apr 2010 · Paper 1 · Single correct option