Fumaric acid is a colorless crystalline solid with a fruitlike taste. It is the trans isomer of of butenedioic acid, whereas maleic acid is the cis isomer. Fumaric acid can be easily reduced to succinic acid.
Fumaric acid is produced by catalytic isomerization of maleic acid in the presence of HCl, bromates or thiourea;
in the manufacture of polyester resins, alkyd resins, plasticizers and polyhydric alcohols;
as a mordant for dyes;
as an oil and fat preservative and food acidulant as a substitute for tartaric acid or citric acid;
in medicine fumaric acid esters are sometimes used to treat psoriasis;