carboxyl vs carboxylic

carboxyl is a noun but carboxylic is not a noun.

Word	Noun	Adjective	Verb	Adverb
carboxyl	Yes	Yes	No	No
carboxylic	No	Yes	No	No

As adjectives, carboxyl and carboxylic are synonyms defined as:

carboxyl and carboxylic: relating to or containing the carboxyl group or carboxyl radical

carboxyl (noun)	carboxylic (noun)
the univalent radical -COOH; present in and characteristic of organic acids

carboxyl (adjective)	carboxylic (adjective)
relating to or containing the carboxyl group or carboxyl radical	relating to or containing the carboxyl group or carboxyl radical