Organic Chemistry MCAT Practice Exam

Which functional group is represented by ethanoic acid?

1. Aldehyde

2. Amine

3. Carboxylic acid

4. Alcohol

The correct answer is: Carboxylic acid

Ethanoic acid, also known as acetic acid, is characterized by the presence of a carboxylic acid functional group. The defining feature of a carboxylic acid is the presence of a carbonyl group (C=O) directly bonded to a hydroxyl group (–OH). In the case of ethanoic acid, the molecular structure can be simplified as CH₃COOH, where the –COOH group is indicative of a carboxylic acid. Carboxylic acids are known for their acidic properties due to the ability of the hydrogen atom in the –COOH group to dissociate in solution, leading to the release of protons (H⁺). This results in the characteristic sour taste of carboxylic acids and their reactivity in various chemical reactions. In contrast, aldehydes contain a carbonyl group bonded to at least one hydrogen atom, amines are characterized by the presence of nitrogen atoms bonded to carbon chains, and alcohols feature hydroxyl groups directly attached to carbon atoms. Each of these functional groups has distinct structural features and chemical properties that differentiate them from carboxylic acids. Hence, the correct identification of ethanoic acid as a carboxylic acid