Question

The major product formed in the following reaction is 

• A. A
• B. B
• C. C
• D. D

Hint:

CF$_3$COOH/H$_2$O acts as a mild acid for hydrolyzing acetals and thioacetals to the corresponding carbonyl compounds.

Answer 1

The Correct Option is A

Step 1: Reaction type identification.
The reaction is an **acetal (or thioacetal) hydrolysis** under acidic conditions. CF$_3$COOH/H$_2$O is a mild acidic system that can cleave acetals or thioacetals to the corresponding carbonyl compounds.
Step 2: Mechanism.
The methoxy (–OCH$_3$) and thioether (–S–) substituents form a cyclic dithioacetal protecting group around the carbonyl precursor. Upon treatment with CF$_3$COOH/H$_2$O, this cyclic acetal hydrolyzes, regenerating the **aldehyde**.
Step 3: Product formed.
Therefore, the product is a **carbonyl compound (aldehyde)** having the same carbon skeleton.
Hence, structure (B) is correct, representing the aldehyde after deprotection.
Step 4: Conclusion.
The major product is an aldehyde (Option B) obtained via acid-catalyzed hydrolysis of a cyclic thioacetal.