Question

The major product of the following reaction is

• A. a hemiacetal
• B. an acetal
• C. an ether
• D. an ester

Hint:

Hemiacetal: Same carbon with alcohol group and −OR group.
Acetal: Same carbon with two −OR groups.
In the reaction, the double bond is replaced with −OCH2R group.

Answer 1

The Correct Option is B

The given reaction involves a carbonyl compound reacting with an alcohol in the presence of an acid catalyst (H^+). The general mechanism of this reaction results in the formation of an acetal.

Let's understand the steps:

1. The carbonyl group (C=O) in the cyclic structure is activated by the H^+ ion, turning it into a more reactive intermediate.
2. The alcohol (RCH_2OH) attacks this activated carbonyl group, forming a hemiacetal as an intermediate.
3. Further reaction with another molecule of alcohol leads to acetal formation, as the hydroxyl group is replaced by an alkoxyl group (from the alcohol). This step is facilitated by the acidic environment.

The formation of an acetal involves the replacement of the carbonyl oxygen with two alkoxy groups. In this context, the major product is indeed an acetal.

Other options can be ruled out based on their definitions:

• Hemiacetal: An intermediate formed in the first step, not the final product under acidic conditions.
• Ether: Consists of two alkyl groups bonded to the same oxygen, not formed here.
• Ester: Formed from an acid and an alcohol, not applicable here.

The correct answer is an acetal.