Carboxyl n. (Chem.) The complex radical, CO.OH, regarded as the essential and characteristic constituent which all oxygen acids of carbon (as formic, acetic, benzoic acids, etc.) have in common; called also oxatyl.
... >C:O (sometimes termed the carbonyl or keto group) characterizes the ketones (q.v.). A third hydroxyl group may be introduced into the -CH:O residue with the formation of the radical -C(OH):O; this is known as the carboxyl group, and characterizes ... — Encyclopaedia Britannica, 11th Edition, Volume 6, Slice 1 - "Chtelet" to "Chicago" • Various
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