In organic chemistry, a carboxylic acid is an organic acid that contains a carboxyl group (−C (=O)−OH) [1] attached to an R-group. The general formula of a carboxylic acid is often written as R−COOH or R−CO2H, sometimes as R−C (O)OH with R referring to an organyl group (e.g., alkyl, alkenyl, aryl), or hydrogen, or other groups.