Question

Identify the 'product' in the following reaction.
Pent - 3 - enenitrile \(\rightarrow _{\text{H}_3\text{O}^+\,}^{\text{Al H (i-Bu)}_2\,}\) Product

• A. Pent - 3 - en - 1 - amine
• B. Pentanal
• C. Pent - 3 - enal
• D. Pent - 3 - en -1 - ol

Hint:

DIBAL-H reduces a nitrile to an imine, which hydrolyses to an aldehyde without touching the C=C.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Diisobutylaluminium hydride (DIBAL-H) is a mild, bulky reducing agent. With a nitrile, it adds a single hydride and stops at an imine-aluminium complex. Water then hydrolyses the imine to an aldehyde.

Step 2: Key Formula or Approach:
\[ \text{R-CN} \xrightarrow{\text{DIBAL-H}} \text{R-CH=NH} \xrightarrow{\text{H}_3\text{O}^+} \text{R-CHO} \]
It does not reduce an isolated C=C bond.

Step 3: Detailed Explanation:
Pent-3-enenitrile is \(\text{CH}_3\text{CH=CH-CH}_2\text{-CN}\). The nitrile carbon becomes the aldehyde carbon, and the chain keeps its double bond between C3 and C4.
Product: \(\text{CH}_3\text{CH=CH-CH}_2\text{-CHO}\), which is pent-3-enal.
Option (A) the amine and option (D) the alcohol need a strong reagent like \(\text{LiAlH}_4\). Option (B) pentanal would require the double bond to be reduced, which DIBAL-H does not do.

Final Answer:
The product is pent-3-enal, option (C). \[ \boxed{\text{Pent-3-enal (C)}} \]