Why are aldehydes and ketones classified as electrophiles?

Aldehydes and ketones are classified as electrophiles primarily because of the presence of the carbonyl group (C=O), where the carbon atom exhibits a partial positive charge. This partial positive charge arises due to the electronegativity difference between carbon and oxygen; oxygen is more electronegative and attracts the bonding electrons, which leaves the carbon atom slightly electron-deficient.

This electron deficiency makes the carbon atom of the carbonyl group susceptible to attack by nucleophiles, which are electron-rich species seeking positive charges. Therefore, the electrophilic nature of aldehydes and ketones is fundamentally driven by the geometry and properties of the carbonyl functional group, where the carbon is less electron-rich and can readily interact with nucleophiles.

The other aspects mentioned in the choices do not accurately describe why aldehydes and ketones act as electrophiles. High reactivity is a consequence of their electrophilic nature rather than a defining characteristic. Electron-donating groups would typically decrease electrophilicity, making compounds less susceptible to nucleophilic attack, and aromatic character pertains to a different set of compounds with distinct bonding and resonance structures.