Applications
Maleic acid is used as a precursor to fumaric acid, dimethyl maleate and glyoxalic acid. It is an electrophile and acts as dienophine in Diels-Alder reactions. It reacts with drugs to form more stable addition salts like indacaterol maleate, carfenazine, chlorpheniramine, pyrilamine, methylergonovine and thiethylperazine. Its maleate ion is useful in biochemistry as an inhibitor of transaminase reactions.

Solubility
Soluble in water, acetone, glacial acetic acid, alcohol and concentrated sulfuric acid. Slightly soluble in diethyl ether. Insoluble in benzene and chloroform.

Notes
Incompatible with oxidizing agents, bases, reducing agents, metals and alkalis.