Draw structures of the following derivatives.
(e) acetaldehyde dimethyl acetal

Verified step by step guidance

1. Understand the structure of acetaldehyde: Acetaldehyde is an aldehyde with the formula CH₃CHO. It contains a carbonyl group (C=O) attached to a methyl group (CH₃) and a hydrogen atom.
2. Recall the concept of an acetal: An acetal is formed when an aldehyde reacts with two equivalents of an alcohol in the presence of an acid catalyst. The carbonyl group (C=O) is replaced by two alkoxy groups (-OR).
3. Identify the alcohol used: In this case, the alcohol is methanol (CH₃OH), as the product is a dimethyl acetal. This means two methoxy groups (-OCH₃) will replace the carbonyl oxygen.
4. Draw the intermediate hemiacetal: The first step in the reaction involves the addition of one methanol molecule to the carbonyl group, forming a hemiacetal. The structure will have one -OCH₃ group and one -OH group attached to the central carbon.
5. Draw the final structure of acetaldehyde dimethyl acetal: Replace the -OH group in the hemiacetal with another -OCH₃ group, resulting in a central carbon atom bonded to two -OCH₃ groups, one CH₃ group, and one hydrogen atom. The final structure is CH₃-CH(OCH₃)₂.

Key Concepts

Acetaldehyde

Acetaldehyde is a simple aldehyde with the chemical formula CH3CHO. It consists of a carbonyl group (C=O) attached to a methyl group (CH3) and a hydrogen atom. Understanding its structure is crucial for recognizing how it can react to form derivatives, such as acetals.

Acetal Formation

Acetals are formed when an aldehyde or ketone reacts with alcohol in the presence of an acid catalyst. 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 a full acetal. This process is essential for understanding how acetaldehyde dimethyl acetal is synthesized.

Dimethyl Acetal

Dimethyl acetal refers to a specific type of acetal where two methyl groups are attached to the oxygen atoms of the acetal functional group. In the case of acetaldehyde dimethyl acetal, the structure features two methoxy (–OCH3) groups replacing the hydrogen atom of the aldehyde. Recognizing this structure is key to drawing the correct molecular representation.