Fumaric acid

Fumaric acid is a dibasic carboxylic acid, the structure of which is made clear by the synonym trans-butenedioic acid. The compound consists of a butene structure with a central double bond and two terminal carboxylic acid groups, the arrangement of which is mirror-symmetrical with respect to the double bond. Because of these two functional groups, fumaric acid has a high reactivity and can undergo polymerizations together with suitable reaction partners. For example, the substance can form long chain polyesters with dihydric alcohols. The double bond in the center of the molecule represents another reactive site and is suitable for, among other things, converting the acid in the course of addition reactions.

The compound is an isomer of maleic acid, which is also known as cis-butenedioic acid and differs from fumaric acid only in the spatial arrangement of its components, since their carboxylic acid groups are on the same side of the double bond.

Fumaric acid is a colorless to white solid that is in the form of a crystalline powder. The compound is odorless, its taste is described as tart and sour to fruity. The acid is hardly hygroscopic and absorbs almost no moisture. When heated, it does not go into a melt, but sublimes directly into the gaseous state at a temperature of 200 °C. Fumaric acid is poorly soluble in water. However, it is readily soluble in some organic solvents such as ethanol and concentrated sulfuric acid. The compound is acidic and has a pH of 2.1 in aqueous solution.

Fumaric acid is chemically stable at room temperature. However, dry and airtight storage is necessary, as dangerous reactions can occur if the substance comes into contact with bases, reducing agents, strong oxidizing agents and amines.

The compound is combustible, but in its pure form it is difficult to ignite. However, if dusts of the fine powder are swirled, an easily ignitable and explosive mixture with the surrounding air can form. Fumaric acid should therefore be kept away from sparks, open flames, electrostatic discharge, hot surfaces and other sources of ignition. Greater caution is required when handling open containers of the substance.

Fumaric acid is considered to be hardly toxic and already occurs in the human body as a normal metabolic product. However, long-term intake of high doses of the acid is suspected to have a damaging effect on kidneys. Contact with compound dust may be irritating to eyes, mucous membranes and skin. Affected parts of the body should be rinsed with plenty of water to dilute and remove acid residues. After oral ingestion, temporary gastrointestinal symptoms may occur. If the substance is accidentally swallowed, rinse the mouth out with water and then drink water. Medical treatment should also be arranged.

The compound is categorized as slightly hazardous to water. The release of fumaric acid into the soil, drains or open water must therefore be prevented. In addition, any leakage of the substance into the environment must be reported to the responsible authorities. The connection is not subject to any special transport regulations.