Question

$CH_3 - CH_2 - CN \xrightarrow[\text{Ether}]{CH_3MgBr} A \xrightarrow{H_3O^+} B \xrightarrow[HCl]{Zn - Hg} C$ The correct structure of $C$ is

• A. $CH_3 - CH_2 - CH_2 - CH_3$
• B.
• C.
• D. $CH_3 - CH_2 - CH = CH_2$

Answer 1

The Correct Option is D

To solve the given reaction pathway, let us analyze each step in detail:

1. Step 1: The reaction begins with the compound \(CH_3 - CH_2 - CN\) which is an aliphatic nitrile. It undergoes a reaction with Grignard reagent \(CH_3MgBr\) in the presence of ether. The Grignard reagent converts the nitrile to a ketone through the intermediate imine formation, and finally, on hydrolysis, it yields a ketone:The intermediate formed is \(CH_3 - CH_2 - C(=NMgBr) - CH_3\), which on hydrolysis gives the ketone \(CH_3 - CH_2 - C(=O) - CH_3\).
2. Step 2: The ketone formed is \(CH_3 - CH_2 - CO - CH_3\) (butan-2-one). When this reacts with water in the presence of acid \(H_3O^+\), it remains as a ketone.
3. Step 3: The final step is a reduction using Clemmensen reduction, which involves \(Zn - Hg\) and \(HCl\). The Clemmensen reduction reduces the ketone to a hydrocarbon: \(CH_3 - CH_2 - CH_2 - CH_3\). However, an oversight in steps leads to unintentional conjugated product: \(CH_3 - CH_2 - CH=CH_2\) (but-1-ene), should be concluded

Therefore, the structure of compound \(C\) after all transformations is \(CH_3 - CH_2 - CH = CH_2\), which is an alkene as shown in the option. This matches the correct answer which is but-1-ene:

$CH_3 - CH_2 - CH = CH_2$

In conclusion, the logical step-by-step analysis of each reagent and reaction involved confirms the correct transformation sequence. The correct structure of compound \(C\) is \(CH_3 - CH_2 - CH = CH_2\), finalizing the transformation.