When treated with alkalies, they lose their carboxyl groups and become ætioporphyrin.
The carboxyl group constitutes another convenient starting-point for the orientation of many types of organic compounds.
Entrance of the carboxyl or sulpho groups weakens toxic action.
carboxyl car·box·yl (kär-bŏk'səl)
The univalent radical, COOH, characteristic of all organic acids.