Organic acids are, in general, weak acids. That is, they do not ionize nearly completely in weak aqueous solution. Some inorganic acids (also known as mineral acids) are strong acids. That is, they ionize nearly completely in weak aqueous solution. Some common strong mineral acids are hydrochloric acid, sulfuric acid, and nitric acid. The acid properties listed above are 'stronger' or more noticeable for the strong mineral acids than for the weak organic acids. Strong acids (in aqueous solution) will have a pH much lower than 7, will produce many hydrogen ions, and will be very corrosive to the skin. Weak organic acids, on the other hand, will have a pH closer to 7 than a strong acid; will produce some hydrogen ions when dissolved in water, but not as many as a strong acid; and will not be as corrosive to the skin as a strong acid.
Most common organic acids contain a carboxyl group, usually written as - COOH. The structure of the carboxyl group is shown in the diagram at the left. The hydrogen-oxygen bond in the OH is the weakest bond in the carboxyl group, so Hydrogen ions are released from carboxyl containing organic acids when they are dissolved in water.
One of the simpler organic acid is acetic acid (vinegar) with the formula: CH 3 COOH (or C 2 H 4 O 2 ). An expanded version of the formula, showing the carboxyl group is shown in the diagram at the right. Some other common organic acids are:
propionic acid - CH3CH2COOH (or C3H6O2)
lactic acid - CH3CH(OH)COOH (or C3H6O3)
formic acid - HCOOH (or CH2O2)
oxalic acid - COOHCOOH (or H2C2O4)
citric acid - COOHCH2C(OH)COOHCH2COOH (or C6H8O7)
The formulas for each of these organic acids are shown first in a format that emphasizes the functional groups (including COOH at least once in each of them) and then in the more compact, less descriptive format that you will often see.