isothiocyanate

Isothiocyanates are organic compounds characterized by the functional group N=C=S attached to an R group (R–N=C=S). They are a class of sulfur-containing electrophiles used as building blocks in organic synthesis and occur naturally in plants.

In nature, isothiocyanates arise from the hydrolysis of glucosinolates in cruciferous vegetables such as broccoli, kale, cabbage, mustard, horseradish, and wasabi. The enzyme myrosinase cleaves glucosinolates upon tissue damage, releasing volatile isothiocyanates such as allyl, phenethyl, and benzyl isothiocyanate. These compounds contribute the characteristic pungent odors and flavors of these foods.

Preparation methods in the laboratory and industry typically convert primary amines to isothiocyanates using reagents such as thiophosgene or related thionyl chloride equivalents (phosgene substitutes like triphosgene can also be used) under basic conditions. These routes provide a straightforward means to access a wide range of R–N=C=S compounds for further chemistry.

Reactivity and applications: The carbon atom of the N=C=S group is highly electrophilic, enabling reactions with nucleophiles such as amines and thiols to form thioureas or thio-carbamates. Isothiocyanates thus serve as versatile intermediates in the synthesis of pharmaceuticals, agrochemicals, and fine chemicals. In addition to their synthetic utility, certain isothiocyanates—such as allyl, phenethyl, and benzyl derivatives—are studied for biological activity and are notable for their roles in plant defense and human nutrition.

Safety: Isothiocyanates can be irritants and lachrymators; handling is typically performed in well-ventilated areas or fume hoods, with attention to potential sensitization and toxicity.