Dicarboxylic acid

Malonic acid is a dicarboxylic acid. The black balls are carbon atoms. The red balls are oxygen atoms. The white balls are hydrogen atoms. The left and right sides of the drawing are COOH groups. Each of them is connected to the carbon atom in the middle.

A dicarboxylic acid is an organic chemical compound that has two −COOH functional groups. They are also known as diacids.

The simplest dicarboxylic acid is oxalic acid (COOH)₂, where the acid groups are directly connected. Malonic acid, HOOC−CH₂−COOH, is shown in the picture. In general, diacids have the structure HOOC−R−COOH, where R can be any organic structure.

Dicarboxylic acids are important ingredients in making some plastics, like nylon (made from adipic acid) and polyethylene terephthalate (made from terephthalic acid). Derivatives of dicarboxylic acids, especially their acyl chlorides and acid anhydrides, are also used in plastics.