Crotonic acid

Crotonic acid is an unsaturated, aliphatic monocarboxylic acid with the structural formula CH3-C = C-COOH . There are 2 isomers, the trans-crotonic acid and the iso- or allocrotonic acid.

Crotonic acid forms colorless, butyric acid-like smelling substance. It is soluble in hot water, alcohol, acetone and ether. The salts of crotonic acid are called "crotonates".

When heated, crotonic acid isomerises to form the more unstable Z-form, isocrotonic acid, which is converted back into crotonic acid at about 180 °C.

Crotonic acid is used for the production of copolymers. Its esters are used as plasticizers. Crotonic acid is also used for the production of vitamin A (retinol) and DL-threonine.

Crotonic acid can be copolymerized with vinyl acetate for the production of plastics (see below VA/crotamitate) and is used as VA/copolymer for lacquers and plasticizers in various applications. It is also used in hair cosmetics.

Crotonic acid chloride reacts with N-ethyl-2-methylaniline (N-ethyl-o-toluidine) to form N-ethyl-o-crotonotoluidine(crotamiton), which is used as an antiscabiosum.

In cosmetic products croton acid (INCI) stabilizes the resistance and shelf life of ingredients or formulations.