Maleic Acid

Synonyms:  Acidum maleicum; cis-butenedioic acid; cis-2-butenedioic acid; (Z)- 2-butenedioic acid; cis-ethene-1,2-dicarboxylic acid; cis-1,2-ethylenedicarboxylic acid; cis-maleic acid; maleinic acid; toxilic acid

Description: Maleic acid occurs as a white crystalline (monoclinic) powder and possesses a faint acidulous odor and an astringent taste. Fumaric acid and maleic acid are the simplest unsaturated carboxylic diacids. These acids experience two-step dissociation in aqueous solutions. They have the same structural formula but different spatial configurations. Fumaric acid is the trans and maleic acid the cis isomer. The physical properties of maleic acid and fumaric acid are very different. The cis isomer is less stable. Maleic acid is used in the preparation of fumaric acid by catalytic isomerization.

Chemical Name: Z-But-2-enedioic acid

Acidulant; buffering agent.

• Maleic acid is used in the pharmaceutical industry as a pH modifier and a buffering agent

• It is also used to prevent rancidity of oils and fats; a ratio of 1 : 10 000 is usually sufficient to retard rancidity.

• Maleic acid is commonly used as a pharmaceutical intermediate to form the maleate salts of several categories of therapeutic agents, such as salts of antihistamines and other drug substances.

Maleic acid can react with oxidizing materials. Aqueous solutions are corrosive to carbon steels.

Maleic acid is generally regarded as a nontoxic and nonirritant material when used at low levels as an excipient. Maleic acid is used in oral, topical, and parenteral pharmaceutical formulations in addition to food products.

Observe normal precautions appropriate to the circumstances and quantity of the material handled. Maleic acid is considered very hazardous in the case of eye contact, which can result in corneal damage. It is also hazardous with respect to skin contact and inhalation. Skin contact can produce inflammation and blistering, with the amount of tissue damage dependent on the length of contact. Gloves, eye protection, and approved or certified respirators should be employed.

Fumaric acid.