The IUPAC name of CH3COCH(CH3)2 is
- isopropylmethyl ketone
- 4-methylisopropyl ketone
The longest carbon chain has 4 carbon atoms. So, the root word is but.
Parent compound has ketonic functional group at second position. A methyl group is present at the third methyl group.
IUPAC name is 3-methyl-2-butanone
The correct option is D.