The reduction of 3-hexyne with `H_(2)`/Lindlar’s catalyst gives predominantly -

Options

A. n-Hexane
B. Trans-3-hexene
C. Cis-3-hexene
D. A mixture of cis-and trans-3-hexene

Answer

To solve the question regarding the reduction of 3-hexyne with hydrogen in the presence of Lindlar's catalyst, we will follow these steps:

### Step-by-Step Solution:

1. **Identify the Structure of 3-Hexyne**:
- 3-Hexyne is an alkyne with the molecular formula C6H10. Its structure can be represented as:
\[ CH_3-CH_2-C \equiv C-CH_2-CH_3 \]
- The triple bond is located between the third and fourth carbon atoms.

2. **Understand the Role of Lindlar's Catalyst**:
- Lindlar's catalyst is a palladium-based catalyst that is used for the partial hydrogenation of alkynes to cis-alkenes. It consists of palladium on calcium carbonate and lead acetate.
- It facilitates syn addition of hydrogen across the triple bond, meaning both hydrogen atoms will add to the same side of the double bond formed.

3. **Perform the Reduction Reaction**:
- When 3-hexyne is treated with hydrogen gas (H2) in the presence of Lindlar's catalyst, the triple bond will be reduced to a double bond.
- The reaction can be represented as:
\[ CH_3-CH_2-C \equiv C-CH_2-CH_3 + H_2 \xrightarrow{Lindlar's \, catalyst} CH_3-CH_2-CH=CH-CH_2-CH_3 \]
- The product formed is a cis-alkene due to the syn addition of hydrogen.

4. **Determine the Product**:
- The product of this reaction is cis-3-hexene, which can be represented as:
\[ CH_3-CH_2-CH=CH-CH_2-CH_3 \]
- The double bond is located between the third and fourth carbon atoms, and the spatial arrangement is such that the hydrogen atoms added during the reduction are on the same side of the double bond.

5. **Final Answer**:
- The predominant product of the reduction of 3-hexyne with H2 using Lindlar's catalyst is **cis-3-hexene**.