Citric acid (mono-anhydride)
The compound exists under standard conditions as a white solid crystallizing in the monoclinic crystal system.
The compound readily converts to the anhydrous form of the straconic acid anhydride which is liquid at room temperature, and the modified isomer of the compound is mesonic acid.
This compound can be prepared by thermal dissociation of citric acid. It can also be prepared by heating of itaconic acid anhydride as straconic acid anhydride is firstly produced, and it is then liquefied into straconic acid.