Allyl isothiocyanate

Allyl isothiocyanate (AITC) is the organosulfur compound with the formula CH2CHCH2NCS. This colorless oil is responsible for the pungent taste of mustard, horseradish, and wasabi. This pungency and the lachrymatory effect of AITC is mediated through the TRPA1 and TRPV1 ion channels. It is slightly soluble in water, but well soluble in most organic solvents.

Biosynthesis and biological functions
Allyl isothiocyanate comes from the seeds of black mustard (Brassica nigra) or brown Indian mustard (Brassica juncea). When these mustard seeds are broken, the enzyme myrosinase is released and acts on a glucosinolate known as sinigrin to give allyl isothiocyanate.

Allyl isothiocyanate serves the plant as a defense against herbivores; since it is harmful to the plant itself, it is stored in the harmless form of the glucosinolate, separate from the myrosinase enzyme. When an animal chews the plant, the allyl isothiocyanate is released, repelling the animal.

Commercial and other applications
Allyl isothiocyanate is produced commercially by the reaction of allyl chloride and potassium thiocyanate:
 * CH2=CHCH2Cl +  KSCN  →  CH2=CHCH2NCS  +  KCl.

The product obtained in this fashion is sometimes known as synthetic mustard oil. Allyl isothiocyanate can also be liberated by dry distillation of the seeds. The product obtained in this fashion is known as volatile oil of mustard and is usually around 92% pure. It is used principally as a flavoring agent in foods. Synthetic allyl isothiocyanate is used as an insecticide, bacteriocide, and nematocide, and is used in certain cases for crop protection.

Hydrolysis of allyl isothiocyanate gives allyl amine.

Safety
Allyl isothiocyanate is fairly toxic with LD50 of 151 mg/kg and is a dangerous lachrymator.