Alkyl cyanides `(CH_(3)CN)` when treated with hydrogen in presence
of Pt or with `LiAlH_(4)` produces same carbon number compound.
What is the formula of that compound ?

Answer

To solve the problem, we need to determine the compound produced when alkyl cyanide (specifically CH₃CN) is treated with hydrogen in the presence of platinum or with lithium aluminium hydride (LiAlH₄).

### Step-by-Step Solution:

1. **Identify the Reactant**: The given alkyl cyanide is CH₃CN. This compound consists of a methyl group (CH₃) attached to a cyanide group (CN).

2. **Understand the Reaction**: When CH₃CN is treated with hydrogen in the presence of platinum or with lithium aluminium hydride, a reduction reaction occurs. This type of reaction is known as the Mendius reduction.

3. **Determine the Product**: The reduction of alkyl cyanides generally leads to the formation of primary amines. The general reaction can be represented as:
\[ R-C \equiv N + H_2 \text{ (or LiAlH}_4\text{)} \rightarrow R-CH_2-NH_2 \]
Here, R represents the alkyl group (in this case, CH₃).

4. **Substituting the Alkyl Group**: For CH₃CN, substituting R with CH₃ gives:
\[ CH₃-C \equiv N + H_2 \rightarrow CH₃-CH_2-NH_2 \]

5. **Final Product**: The product formed is CH₃CH₂NH₂, which is ethylamine.

6. **Conclusion**: The formula of the compound produced from the reduction of CH₃CN is **C₂H₅NH₂**.

### Final Answer:
The formula of the compound is **C₂H₅NH₂** (ethylamine).