Acetals can serve as protecting groups for 1,2-diols, as well as for aldehydes and ketones. When the acetal is formed from acetone plus the diol, the acetal is called an acetonide. Show the acetonides formed from these diols with acetone under acid catalysis.

Verified step by step guidance

1. Step 1: Recognize the functional groups involved in the reaction. The provided diol structure contains two hydroxyl (-OH) groups on adjacent carbons, which can react with acetone under acid catalysis to form an acetal (specifically an acetonide).
2. Step 2: Understand the mechanism of acetal formation. Under acidic conditions, acetone reacts with the diol through a series of steps: protonation of the carbonyl oxygen in acetone, nucleophilic attack by one of the hydroxyl groups, and subsequent elimination of water to form a cyclic acetal.
3. Step 3: Analyze the structure of the diol. The two hydroxyl groups are on adjacent carbons, which allows for the formation of a five-membered cyclic acetal (acetonide) when reacting with acetone.
4. Step 4: Draw the intermediate steps. First, protonate the carbonyl oxygen of acetone. Then, one hydroxyl group attacks the carbonyl carbon, forming a hemiacetal intermediate. Next, the second hydroxyl group attacks, leading to the formation of the cyclic acetal.
5. Step 5: Represent the final acetonide structure. The cyclic acetal (acetonide) will consist of a five-membered ring where the two oxygen atoms from the diol are part of the ring, and the remaining methyl groups from acetone are attached to the ring.

Key Concepts

Acetals and Their Formation

Acetals are formed from the reaction of an aldehyde or ketone with an alcohol under acidic conditions. This reaction involves the nucleophilic attack of the alcohol on the carbonyl carbon, leading to the formation of a hemiacetal, which can further react with another alcohol molecule to yield the acetal. Acetals are important in organic synthesis as they can protect carbonyl groups from unwanted reactions.

1,2-Diols

1,2-Diols, also known as glycols, contain two hydroxyl (-OH) groups on adjacent carbon atoms. They are versatile compounds in organic chemistry, often used as intermediates in synthesis. When reacted with acetone, 1,2-diols can form acetonides, which serve as protecting groups, preventing the diol from undergoing further reactions that could alter its structure.

Acid Catalysis

Acid catalysis involves the use of an acid to increase the rate of a chemical reaction. In the context of acetal formation, the acid protonates the carbonyl oxygen, making the carbonyl carbon more electrophilic and susceptible to nucleophilic attack by the alcohol. This step is crucial for the successful formation of acetals and acetonides, as it facilitates the reaction between the carbonyl compound and the alcohol.