Phenylacetone (subheading 291431) is a List I chemical under the Controlled Substances Act because it is a direct precursor to amphetamine and methamphetamine. Importers must obtain DEA registration and comply with import declaration and quota requirements before any shipment can clear customs.

Simple acyclic ketones without additional oxygen functions are classified under the 291411–291419 subheadings. When a ketone compound also carries a hydroxyl or aldehyde group, it moves to subheading 291440 (ketone-alcohols and ketone-aldehydes) or 291450 (ketone-phenols and ketones with other oxygen functions). The presence and type of the secondary oxygen function determines the correct slot.