Our first group of carbonyls are aldehydes and ketones. Thecarbonyl carbon of an aldehyde is attached to a carbon and a hydrogen. The carbonyl carbon of a ketone is attached to two carbons.
In contrast to our study of alkenes, the pi bond of a carbonyl will not act as a nucleophile. Rather, recall from our discussion of carbonyls, the carbonyl carbon has a partial positive charge and is therefore electrophilic. Good nucleophiles like amines, hydride from NaBH4, and Grignard reagents can attack the carbonyl carbon. With weaker nucleophiles, like water or alcohols, an acid catalyst is needed to protonate the oxygen of the carbonyl, thereby making the carbonyl carbon more electrophilic.
Watch the videos below to learn more about the specific steps of the mechanism for each nucleophile. Then practice these reactions by playing the recommended puzzles.