Question

A dibromide \( X (C_4H_8Br_2) \) on dehydrohalogenation gave \( Y \), which on reduction with \( Z \) gave a non-polar isomer of \( C_4H_8 \). What are \( X \) and \( Z \) respectively?

• A.

  

• B.

  

• C.

  

• D.

  

Hint:

Na/NH\(_3\) (liq) selectively reduces alkynes to trans-alkenes, while Pd/C leads to cis-alkenes.

Answer 1

The Correct Option is A

Step 1: Identifying \( X \) and \( Y \). 
- \( X \) is a vicinal dibromide (contains two Br atoms on adjacent carbons).
- Dehydrohalogenation (\(-HBr\)) leads to the formation of an alkyne (Y). 

Step 2: Identifying \( Z \).
- Reduction of \( Y \) using Na/NH\(_3\) (liq) results in a non-polar alkene (trans-isomer).
- Pd/C reduction would give a cis-alkene, which is polar. 
Since the question specifies a non-polar product, the reduction must have been performed using Na/NH\(_3\) (liq), leading to a trans-alkene. 
Thus, the correct answer is (1).