2918.30 - Carboxylic acids with aldehyde or ketone function but without other oxygen function, their anhydrides, halides, peroxides, peroxyacids and their derivatives:

This HTS category, 2918.30, encompasses carboxylic acids that possess an aldehyde or ketone functional group. Crucially, these compounds must *not* have any other oxygen-containing functional groups, such as hydroxyl (alcohol) or phenolic groups, in addition to the carboxylic acid and the aldehyde/ketone. This classification also includes anhydrides, halides, peroxides, peroxyacids, and other derivatives of these specific carboxylic acids. Examples within this grouping might include keto-acids or formyl-acids where the defining characteristic is the presence of both a carboxyl group and either an aldehyde or a ketone, and no further oxygen-based functionalities.

It is essential to distinguish this category from its siblings. Unlike carboxylic acids with an additional alcohol function (2918.1), those with a phenol function (2918.2), or simple carboxylic acids without further oxygen functions, this category is specifically defined by the presence of an aldehyde or ketone in conjunction with the carboxyl group. The "Other" sibling category (2918.9) serves as a residual for carboxylic acids with other oxygen functions not otherwise specified in the preceding subheadings. Similarly, VIII. ESTERS OF INORGANIC ACIDS is entirely distinct, relating to inorganic compounds rather than organic carboxylic acids.

The subcategories under 2918.30, namely "Aromatic" and "Other," allow for further refinement based on the structure of the carbon skeleton to which the functional groups are attached. The "Aromatic" subdivision will classify compounds where the carboxylic acid, aldehyde, or ketone group is directly bonded to an aromatic ring system. The "Other" subdivision will capture all remaining compounds within the scope of 2918.30 that do not meet the criteria for aromatic classification, typically encompassing aliphatic structures.