`R-C-=N underset(-40^(@)C)overset(DIBAL+H,H_(@)O)rarr` Product
The product formed is :

Options

A. `R-CO-NH_(2)`
B. `R-CH_(2)-NH_(2)`
C. `R-CHO`
D. `R-CH_(2)-NO_(2)`

Answer

To solve the question regarding the reaction of the compound \( R-C \equiv N \) (a nitrile) with DIBAL-H and water at -40°C, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Reactant:**
The reactant is a nitrile, represented as \( R-C \equiv N \). This structure indicates that there is a carbon atom (C) triple-bonded to a nitrogen atom (N), with an alkyl group (R) attached to the carbon.

2. **Understand the Reagent:**
The reagent used in the reaction is DIBAL-H, which stands for diisobutylaluminium hydride. DIBAL-H is a selective reducing agent that is commonly used to reduce nitriles to aldehydes.

3. **Reaction Conditions:**
The reaction is performed at a low temperature of -40°C. This low temperature is crucial as it helps in controlling the reaction, ensuring that the nitrile is converted to an aldehyde without further reduction to an alcohol.

4. **Reduction Mechanism:**
When the nitrile \( R-C \equiv N \) is treated with DIBAL-H, the triple bond between carbon and nitrogen is reduced. The nitrogen atom is converted to a less oxidized state, while the carbon atom that was part of the nitrile becomes part of an aldehyde functional group.

5. **Hydrolysis:**
After the reduction step, the reaction mixture is hydrolyzed with water (H2O). This step is necessary to convert the intermediate formed during the reduction into the final aldehyde product.

6. **Final Product:**
The final product of this reaction is an aldehyde, represented as \( RCHO \). The structure indicates that the carbon atom from the nitrile has now formed a double bond with an oxygen atom (C=O), characteristic of aldehydes, while the number of carbon atoms remains the same.

### Conclusion:
The product formed from the reaction of \( R-C \equiv N \) with DIBAL-H and water at -40°C is \( RCHO \) (an aldehyde).