Maleic acid is a colorless crystalline solid. It is the cis isomer of of butenedioic acid, whereas fumaric acid is the trans isomer. Maleic acid is easily converted into succinic acid by hydrogenation.
Maleic acid is produced by the hydration of maleic anhydride which is prepared commercially by the oxidation of benzene or by the reaction of butane with oxygen in the presence of vanadium catalyst.
in the manufacture of polyester resins, alkyd resins and plasticizers;
to produce tartaric acid and malic acid;
for preparation of fumaric acid;