2931.90.10.00 - 4,4'-Diphenylbisphosphonous acid, di(2',2",4',4"-di-tert-butyl)phenyl ester

This HTS code, 2931.90.10.00, specifically covers the organo-inorganic compound 4,4'-Diphenylbisphosphonous acid, di(2',2",4',4"-di-tert-butyl)phenyl ester. This substance falls under the broader category of "Other organo-inorganic compounds" within Chapter 29 of the Harmonized Tariff Schedule, which deals with organic chemicals. The classification highlights the specific chemical structure and composition, involving both organic phenyl groups and inorganic phosphorus atoms linked together.

To distinguish this entry from its siblings, consider the specific nature of the compounds listed. 2931.90.05.00 covers specific organosilicon compounds like diphenyldichlorosilane and phenyltrichlorosilane, which are characterized by silicon-carbon bonds. In contrast, 2931.90.15.00 refers to Sodium tetraphenylboron, an organoboron compound. The current classification for 2931.90.10.00 focuses exclusively on a particular phosphonous acid ester with a complex aromatic structure, clearly differentiating it based on the central inorganic element and its organic substituents.

As this HTS code represents a leaf node, there are no further subcategories branching from this specific classification. Therefore, the focus for classification purposes remains on accurately identifying the described chemical compound, 4,4'-Diphenylbisphosphonous acid, di(2',2",4',4"-di-tert-butyl)phenyl ester, ensuring its unique chemical characteristics and structure align precisely with the entry. This means that any import or export of this specific ester would fall under this definitive tariff line.