What functional group can be converted into a carboxylic acid?

The functional group that can be converted into a carboxylic acid is indeed an aldehyde. Aldehydes contain a carbonyl group (C=O) at the end of the carbon chain, and they can undergo oxidation to form carboxylic acids. During this oxidation process, the hydrogen atom attached to the carbon of the aldehyde group is oxidized to form a hydroxyl group (-OH), resulting in the formation of a carboxylic acid functional group (-COOH).

This transformation is significant in organic chemistry and biochemistry because it allows for the formation of more complex molecules and is an essential step in various metabolic pathways. In contrast, while alcohols can be oxidized to give aldehydes or ketones, they do not convert directly into carboxylic acids without an additional oxidation step. Amines and sulfhydryls do not share the same transformation into carboxylic acids, as their structures and functional roles differ from that of aldehydes.