When alkyl substituted acetylene undergoes addition with hydrogen in presence of Lindlar's catalyst, the alkene formed is

Options

A. A mixture of cis and trans isomers
B. Trans isomer
C. Cis isomer
D. No addition does not take place

Answer

To solve the question regarding the product formed when alkyl substituted acetylene undergoes addition with hydrogen in the presence of Lindlar's catalyst, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Reactant**:
We start with an alkyl substituted acetylene. For example, let's consider dimethylacetylene, which has the structure CH3-C≡C-CH3.

2. **Understand the Reaction Conditions**:
The reaction is performed in the presence of Lindlar's catalyst. Lindlar's catalyst is a poisoned palladium catalyst that facilitates the partial hydrogenation of alkynes to alkenes, specifically favoring the formation of cis alkenes.

3. **Perform the Hydrogenation Reaction**:
When dimethylacetylene (CH3-C≡C-CH3) undergoes hydrogenation, the triple bond (C≡C) is converted to a double bond (C=C) with the addition of hydrogen (H2).

4. **Determine the Product Structure**:
The addition of hydrogen occurs in a syn fashion due to the nature of the Lindlar's catalyst. This means that both hydrogen atoms add to the same side of the double bond. Therefore, the product formed is cis-2-butene (CH3-CH=CH-CH3), where the two methyl groups (CH3) are on the same side of the double bond.

5. **Conclusion**:
The alkene formed from the hydrogenation of the alkyl substituted acetylene in the presence of Lindlar's catalyst is cis-2-butene.

### Final Answer:
The alkene formed is **cis-2-butene**.

---