Organic Chemistry MCAT Practice Exam

What is the primary feature of carboxylic acids that enhances their reactivity?

1. Low polarity

2. Formation of hydrogen bonds

3. High steric hindrance

4. Weak acidity

The correct answer is: Formation of hydrogen bonds

The primary feature of carboxylic acids that enhances their reactivity is the ability to form hydrogen bonds. Carboxylic acids contain both a carbonyl group (C=O) and a hydroxyl group (–OH), which are polar functional groups. This polarity allows for strong intermolecular interactions, specifically hydrogen bonding, both within carboxylic acids themselves and with other molecules. This hydrogen bonding capability significantly increases their boiling points compared to hydrocarbons and enhances their solubility in polar solvents. Moreover, the hydrogen bonding can facilitate various chemical reactions, including catalyzing nucleophilic attacks on the carbonyl carbon. The resulting stability of the carboxylate ion formed through the deprotonation of carboxylic acids also plays a critical role in their acidity and in the reactivity of carboxylic acids in condensation and esterification reactions. In contrast, options associated with low polarity, high steric hindrance, or weak acidity do not adequately describe a primary feature that enhances the reactivity of carboxylic acids. The intrinsic polarity enhances reactivity through hydrogen bonding, making it a key characteristic of these compounds.