Dicarboxylic acid

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

The simplest dicarboxylic acid is oxalic acid , where the acid groups are directly connected. Malonic acid, , is shown in the picture. In general, diacids have the structure , 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.

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