Organic Chemistry MCAT Practice Exam

The carbonyl carbon of an aldehyde is categorized as which type of site?

1. Nucleophilic

2. Electrophilic

3. Neutral

4. Basic

The correct answer is: Electrophilic

The carbonyl carbon of an aldehyde is categorized as electrophilic due to the presence of a carbon-oxygen double bond (C=O). In this structure, the oxygen atom is more electronegative than the carbon atom, creating a dipole where the carbon atom carries a partial positive charge. This partial positive charge makes the carbonyl carbon susceptible to nucleophilic attack, as it can attract nucleophiles, which are species that donate electron pairs. In the context of organic reactions, nucleophiles seek out positively charged or partially positive regions, making the electrophilic carbonyl carbon a target for reactions such as nucleophilic addition. This characteristic is essential for numerous organic reactions, including the formation of alcohols from aldehydes and other related transformations. The remaining options do not appropriately describe the nature of the carbonyl carbon. It is not neutral, as it carries a partial positive charge, nor is it basic, since basic sites typically donate electrons rather than accept them as an electrophilic site would. Therefore, the classification of the carbonyl carbon in aldehydes as electrophilic is accurate and highlights its role in reactivity within organic chemistry.