Question

Which of the following reactions is not correct?

• A. \( \text{CH}_2\text{Br} - \text{CH}_2\text{Br} \xrightarrow{\text{Zn}} \text{CH}_2 = \text{CH}_2 \)
• B. \( \text{CH}_3\text{C} \equiv \text{C} \text{CH}_3 \xrightarrow{\text{Na, Liq. NH}_3} \text{CH}_3\text{CH}_2\text{C} = \text{CH} \)
• C. \( \text{CH}_3\text{C} \equiv \text{C} \text{H} \xrightarrow{H_2O, \text{Hg}^{2+}, H^+} \text{CH}_3\text{CH}_2\text{CHO} \)
• D. \( \text{Ph-CH}_2\text{Br} \xrightarrow{\text{Na}} \text{Ph-(CH}_2)_2\text{Ph} \text{ in dry ether} \)

Hint:

- The reaction conditions for alkyne reductions with sodium in liquid ammonia typically lead to trans-alkenes, not the products shown in option (2).

Answer 1

The Correct Option is B

The reactions represent common organic reactions: In option (1), the reaction of alkyl halides (CH\(_2\)Br) with zinc leads to the formation of alkene by reduction (dehalogenation), which is correct.
In option (2), the reaction of an alkyne with sodium in liquid ammonia is a reduction that leads to trans-alkene formation, which is correct. In option (3), the reaction of an alkyne with water, mercuric ions (Hg\(^{2+}\)), and acid leads to the formation of an aldehyde, which is correct.
In option (4), the reaction of an alkyl halide (Ph-CH\(_2\)Br) with sodium in dry ether leads to a coupling reaction forming biphenyl, which is correct.
Thus, option (2) is the correct answer as it involves an incorrect reaction pathway.