Final answer:
The reaction of 2-pentanone with a Grignard reagent yields a tertiary alcohol, where the new alcohol group is connected to a carbon atom bonded with three other carbon atoms.
Step-by-step explanation:
When 2-pentanone reacts with one equivalent of a Grignard reagent, the product formed is a tertiary alcohol.
The Grignard reagent adds to the carbonyl carbon of 2-pentanone, and the resulting addition compound then undergoes protonation to form the alcohol. Since the carbonyl carbon of 2-pentanone is attached to two other carbon atoms, the addition of the Grignard reagent leads to a carbon atom that is connected to three other carbon atoms, resulting in a tertiary alcohol.