In organic chemistry, isothiocyanate is a functional group as found in compounds with the formula . Isothiocyanates are the more common isomers of thiocyanates, which have the formula .
Occurrence
Many isothiocyanates from plants are produced by
enzymatic conversion of metabolites called
. A prominent natural isothiocyanate is allyl isothiocyanate, also known as
.
Cruciferous vegetables, such as bok choy, broccoli, cabbage, cauliflower, kale, and others, are rich sources of glucosinolate precursors of isothiocyanates.
Structure
The and distances are 117 and 158
picometer.
By contrast, in methyl thiocyanate, and distances are 116 and 176 pm.
Typical for in aryl isothiocyanates are near 165°. Again, the thiocyanate isomers are quite different with angle near 100°.
Synthesis
Allyl thiocyanate isomerizes to the isothiocyanate:
Isothiocyanates can be prepared by treating organic dithiocarbamate salts with lead nitrate or tosyl chloride.
Isothiocyanates may also be accessed by the fragmentation reactions of 1,4,2-oxathiazoles.
Reactions
Isothiocyanates are weak electrophiles, susceptible to hydrolysis. In general, nucleophiles attack at carbon:
Electrochemical reduction gives thioformamides.
Flavor research
Isothiocyanates occur widely in nature and are of interest in food science and
medical research.
[ Vegetable foods with characteristic flavors due to isothiocyanates include bok choy, broccoli, cabbage, cauliflower, kale, wasabi, horseradish, mustard, radish, , watercress, papaya seeds, tropaeolum, and .][ These species generate isothiocyanates in different proportions, and so have different, but recognizably related, flavors. They are all members of the order Brassicales, which is characterized by the production of , and of the enzyme myrosinase, which acts on glucosinolates to release isothiocyanates.][
]
Uses
Phenyl isothiocyanate, is used for amino acid sequencing in the Edman degradation.
Coordination chemistry
Isothiocyanate and its linkage isomer thiocyanate are ligands in coordination chemistry. Thiocyanate is a more common ligand.
See also
