Question

What are X and Y in the following reaction sequence?

• A. KCN; C$_6$H$_5$COCH$_3$
• B. KCN; C$_6$H$_5$C(OH)(CH$_3$)$_2$
• C. CuCN | KCN; C$_6$H$_5$CH(OH)CH$_3$
• D. CuCN | KCN; C$_6$H$_5$COCH$_3$

Hint:

Nitriles react with Grignard reagents to form ketones after acidic hydrolysis. Use CuCN for benzylic halides to ensure clean cyanide substitution.

Answer 1

The Correct Option is D

To solve the problem, we need to identify X and Y in the given reaction sequence. The sequence involves the nucleophilic substitution of a benzyl chloride derivative, followed by reactions with Grignard reagent (CH₃MgBr) and water.

1. Understanding the Concepts:

- Step 1 (Formation of X): The starting material is a benzyl chloride derivative (C₆H₅N²Cl⁻), which is likely a benzyl chloride or a similar halogenated compound. This is reacted with a nucleophile, which could be a cyanide (CN⁻) or another nucleophilic group.

- Step 2 (Formation of Y): The reaction of the product with CH₃MgBr (methyl magnesium bromide, a Grignard reagent) adds a methyl group to the carbon atom, followed by hydrolysis in the second step to produce the final alcohol group.

2. Given Values:

The given reaction sequence involves:

• Step 1: Nucleophilic substitution to form X (likely benzyl cyanide or related structure).
• Step 2: Reaction with Grignard reagent to form a new bond with the carbonyl carbon (forming a tertiary alcohol). The final product, Y, is a tertiary alcohol.

3. Analyzing the Options:

1. KCN; C₆H₅COCH₃: This does not match the expected nucleophilic substitution products with cyanide and the subsequent reactions leading to a tertiary alcohol.

2. KCN; C₆H₅C(OH)(CH₃)₂: This option suggests a different structure that doesn't fit with the expected tertiary alcohol product from the given sequence of reactions.

3. CuCN | KCN; C₆H₅CH(OH)CH₃: This is incorrect because it doesn’t reflect the expected structure after the Grignard reaction, which should produce a ketone-like structure.

4. CuCN | KCN; C₆H₅COCH₃: This is the correct answer as it follows from the expected reactions of the cyanide group and Grignard reagent, producing a methylated ketone product.

Final Answer:

The correct answer is CuCN | KCN; C₆H₅COCH₃ (Option 4).