The product of the above reaction is: $CH_{3}-CH=CH-CH_{2}-CH_{2}CN \xrightarrow[(2)H_{2}O]{(1)AlH(iBu)_{2}}$

Question

Accepted Answer

The reaction in question involves the conversion of a nitrile group to an aldehyde using diisobutylaluminum hydride (DIBAL-H) followed by hydrolysis. Let's analyze why Option 3 is the correct answer and why the other options are incorrect.

### Explanation for Option 3:

1. **Reagent and Reaction Conditions:**
   - The reagent used here is diisobutylaluminum hydride (DIBAL-H), which is a selective reducing agent. It is known for its ability to reduce nitriles to aldehydes when used in controlled conditions, typically at low temperatures.
   - The reaction involves two steps: the first step is the reduction with DIBAL-H, and the second step is hydrolysis with water.

2. **Mechanism:**
   - In the first step, DIBAL-H partially reduces the nitrile group ($-CN$) to an imine intermediate.
   - In the second step, hydrolysis of the imine intermediate occurs, leading to the formation of an aldehyde.

3. **Product Formation:**
   - The starting compound is $CH_{3}-CH=CH-CH_{2}-CH_{2}-CN$. The nitrile group ($-CN$) is reduced to an aldehyde group ($-CHO$) while the rest of the molecule remains unchanged.
   - Therefore, the product is $CH_{3}-CH=CH-CH_{2}-CH_{2}-CHO$, which corresponds to Option 3.

### Explanation for Why Other Options are Incorrect:

1. **Option 1: $CH_{3}-CH_{2}-CH_{2}-CH_{2}-CH_{2}-CN$**
   - This option suggests that the nitrile group remains unchanged, which is incorrect because DIBAL-H is a reducing agent and will not leave the nitrile group intact.

2. **Option 2: $CH_{3}-CH_{2}-CH_{2}-CH_{2}-CH_{2}-CH_{2}-NH_{2}$**
   - This option implies the complete reduction of the nitrile to a primary amine. However, DIBAL-H does not reduce nitriles to amines; it selectively reduces them to aldehydes under controlled conditions.

3. **Option 4: $CH_{3}-CH=CH-CH_{2}-CH_{2}-COOH$**
   - This option suggests the formation of a carboxylic acid. DIBAL-H does not oxidize nitriles to carboxylic acids; instead, it reduces them to aldehydes. Therefore, this option is incorrect.

In conclusion, the correct product of the reaction is $CH_{3}-CH=CH-CH_{2}-CH_{2}-CHO$, which is Option 3. This is consistent with the known reactivity of DIBAL-H as a selective reducing agent for converting nitriles to aldehydes.