The most appropriate reagent for conversion of C₂H₅CN into CH₃CH₂CH₂NH₂ is

Solution

Chemistry ma’am · 2 steps

A nitrile is a tough triple bond to reduce, so reach for the strongest hydride donor, LiAlH₄.

1. What has to happen. C₂H₅CN is propanenitrile. Turning -C≡N into -CH₂NH₂ needs four hydrogens: two hydride ions add to the carbon, and two protons add to the nitrogen during workup.

   CH₃CH₂C≡N →((i) LiAlH₄, (ii) H₂O) CH₃CH₂CH₂NH₂

   Reagent	What it does	Reduces -C≡N to amine?
   NaBH₄	Mild hydride donor; reduces aldehydes and ketones	No
   CaH₂	Ionic hydride, acts as a base and drying agent	No
   NaBH₃CN	Even milder than NaBH₄; reduces iminium ions in reductive amination	No
   LiAlH₄	Strong hydride donor; the Al–H bond is more polar than B–H	Yes

2. So. Only LiAlH₄ is strong enough to reduce the nitrile all the way to propan-1-amine, so the answer is (d).

The idea to keep. Nitriles, amides and nitro compounds need a strong reducer like LiAlH₄ (or H₂/Ni) to reach amines. NaBH₄ stops at aldehydes and ketones.

Answer from the NTA final answer key. Solution by PrepWiser.