Phthalic anhydride is the organic compound with the formula C6H4(CO)2O. It is the anhydride of phthalic acid. Phthalic anhydride is a principal commercial form of phthalic acid. It was the first anhydride of a dicarboxylic acid to be used commercially. This colourless solid is an important industrial chemical, especially for the large-scale production of plasticizers for plastics. In 2000, the worldwide production volume was estimated to be about 3 million tonnes per year.
o-Phthalic acid anhydride
Appearance & Physical State
white crystalline solid with choking odour
6 g/L (20 ºC)
Stable. Combustible. Incompatible with strong oxidizing agents, strong bases, moisture, strong acids. Dust may form an explosive mixture with air.