Terephthalic acid is the free dicarboxylic acid, while dimethyl terephthalate is its dimethyl ester — a distinct chemical intermediate used in polyester production. The traded form (acid vs. ester) determines the subheading; the CAS number and product specification sheet are the primary classification tools.

Yes. Certain orthophthalate plasticizers — including DEHP, DBP, and BBP — are restricted by the CPSC in children's products under the Consumer Product Safety Improvement Act. While this does not affect customs classification, importers of finished articles containing these plasticizers must ensure product compliance before entry.

Both are anhydrides of dicarboxylic acids, but maleic anhydride is an acyclic (aliphatic) compound classified in the acyclic polycarboxylic acid group, while phthalic anhydride is an aromatic compound derived from ortho-phthalic acid. The structural distinction — aliphatic vs. aromatic ring — drives the subheading split.