Maleic acid is an important raw material used in the manufacture of lubricant additives, unsaturated polyester resins, surface coatings, plasticizers, copolymers and agricultural chemicals [1–5].       Malic acid is a chemical found in certain fruits and wines. It is sometimes used as medicine. Malic acid is used most commonly for dry mouth. It is also used for fibromyalgia, fatigue, and skin conditions, but there is no good scientific evidence to support these other uses.

Maleic acid was commercially available in 1928 and fumaric acid production began in 1932 using an acid-catalyzed isomerization of maleic acid process. Maleic anhydride can be commercially produced by the vapor-phase oxidation of benzene or butene/butane using O2 as an oxidant 

Maleic acid has a heat of combustion of -1,355 kJ/mol.,[4] 22.7 kJ/mol higher than that of fumaric acid. Maleic acid is more soluble in water than fumaric acid. The melting point of maleic acid (135 °C) is also much lower than that of fumaric acid (287 °C). 

MALEIC ACID FOR SYNTHESIS