organic chemistry Organic chemistry is a subdiscipline within chemistry involving the science, scientific study of the structure, properties, and reactions of organic compounds and organic materials, i.e., matter in its various forms that contain carbon atoms.Clay ...

, isothiocyanate is the

functional group In organic chemistry, a functional group is a substituent or moiety in a molecule that causes the molecule's characteristic chemical reactions. The same functional group will undergo the same or similar chemical reactions regardless of the res ...

, formed by substituting the

oxygen Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as we ...

in the

isocyanate In organic chemistry, isocyanate is the functional group with the formula . Organic compounds that contain an isocyanate group are referred to as isocyanates. An organic compound with two isocyanate groups is known as a diisocyanate. Diisocyan ...

group with a

sulfur Sulfur (or sulphur in British English) is a chemical element with the symbol S and atomic number 16. It is abundant, multivalent and nonmetallic. Under normal conditions, sulfur atoms form cyclic octatomic molecules with a chemical formul ...

. Many natural isothiocyanates from plants are produced by enzymatic conversion of metabolites called

glucosinolate Glucosinolates are natural components of many pungent plants such as mustard, cabbage, and horseradish. The pungency of those plants is due to mustard oils produced from glucosinolates when the plant material is chewed, cut, or otherwise damage ...

s. These natural isothiocyanates, such as allyl isothiocyanate, are also known as

mustard oil Mustard oil can mean either the pressed oil used for cooking, or a pungent essential oil also known as volatile oil of mustard. The essential oil results from grinding mustard seed, mixing the grounds with water, and extracting the resulting vol ...

s. An artificial isothiocyanate, phenyl isothiocyanate, is used for

amino acid Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although hundreds of amino acids exist in nature, by far the most important are the alpha-amino acids, which comprise proteins. Only 22 alpha ...

sequencing in the Edman degradation. Cruciferous vegetables, such as bok choy,

broccoli Broccoli (''Brassica oleracea'' var. ''italica'') is an edible green plant in the cabbage family (family Brassicaceae, genus ''Brassica'') whose large flowering head, stalk and small associated leaves are eaten as a vegetable. Broccoli is clas ...

, cabbage,

cauliflower Cauliflower is one of several vegetables in the species '' Brassica oleracea'' in the genus ''Brassica'', which is in the Brassicaceae (or mustard) family. It is an annual plant that reproduces by seed. Typically, only the head is eaten – t ...

kale Kale (), or leaf cabbage, belongs to a group of cabbage (''Brassica oleracea'') cultivars grown for their edible leaves, although some are used as ornamentals. Kale plants have green or purple leaves, and the central leaves do not form a head ...

, and others, are rich sources of

precursors of isothiocyanates. Although there has been some

basic research Basic research, also called pure research or fundamental research, is a type of scientific research with the aim of improving scientific theory, theories for better understanding and prediction of natural or other phenomena. In contrast, applied ...

on how isothiocyanates might exert biological effects ''

in vivo Studies that are ''in vivo'' (Latin for "within the living"; often not italicized in English) are those in which the effects of various biological entities are tested on whole, living organisms or cells, usually animals, including humans, and ...

'', there is no high-quality evidence to date for its efficacy against human diseases.

Structure

Typical

bond angle Bond or bonds may refer to: Common meanings * Bond (finance), a type of debt security * Bail bond, a commercial third-party guarantor of surety bonds in the United States * Chemical bond, the attraction of atoms, ions or molecules to form chemi ...

s for and linkages in aryl isothiocyanates are 165° and 177°, respectively. The and distances are 117 and 158 pms.

Synthesis and reactions

Isothiocyanates are generally prepared by the reaction of a primary amine (e.g.

aniline Aniline is an organic compound with the formula C6 H5 NH2. Consisting of a phenyl group attached to an amino group, aniline is the simplest aromatic amine. It is an industrially significant commodity chemical, as well as a versatile start ...

) and

carbon disulfide Carbon disulfide (also spelled as carbon disulphide) is a neurotoxic, colorless, volatile liquid with the formula and structure . The compound is used frequently as a building block in organic chemistry as well as an industrial and chemical ...

in aqueous

ammonia Ammonia is an inorganic compound of nitrogen and hydrogen with the formula . A stable binary hydride, and the simplest pnictogen hydride, ammonia is a colourless gas with a distinct pungent smell. Biologically, it is a common nitrogeno ...

. This combination results in precipitation of the solid ammonium dithiocarbamate salt, which is then treated with lead nitrate to yield the corresponding isothiocyanate. Another method relies on a tosyl chloride mediated decomposition of dithiocarbamate salts that are generated in the first step above. : Synthesis phenylisothiocyanate 1

Isothiocyanates may also be accessed via the thermally-induced fragmentation reactions of 1,4,2-oxathiazoles. This synthetic methodology has been applied to a polymer-supported synthesis of isothiocyanates. Reflecting their electrophilic character, isothiocyanates are susceptible to hydrolysis.

Flavor research

Isothiocyanates occur widely in nature and are of interest in food science and

medical research Medical research (or biomedical research), also known as experimental medicine, encompasses a wide array of research, extending from " basic research" (also called ''bench science'' or ''bench research''), – involving fundamental scienti ...

. Vegetable foods with characteristic flavors due to isothiocyanates include bok choy,

, cabbage,

wasabi Wasabi ( Japanese: , , or , ; ''Eutrema japonicum'' or ''Wasabia japonica'') or Japanese horseradish is a plant of the family Brassicaceae, which also includes horseradish and mustard in other genera. The plant is native to Japan and the Russ ...

horseradish Horseradish (''Armoracia rusticana'', syn. ''Cochlearia armoracia'') is a perennial plant of the family Brassicaceae (which also includes mustard, wasabi, broccoli, cabbage, and radish). It is a root vegetable, cultivated and used worldwide ...

, mustard,

radish The radish ('' Raphanus raphanistrum'' subsp. ''sativus'') is an edible root vegetable of the family Brassicaceae that was domesticated in Asia prior to Roman times. Radishes are grown and consumed throughout the world, being mostly eaten ra ...

, Brussels sprouts,

watercress Watercress or yellowcress (''Nasturtium officinale'') is a species of aquatic flowering plant in the cabbage family Brassicaceae. Watercress is a rapidly growing perennial plant native to Europe and Asia. It is one of the oldest known leaf ve ...

papaya The papaya (, ), papaw, () or pawpaw () is the plant species ''Carica papaya'', one of the 21 accepted species in the genus '' Carica'' of the family Caricaceae. It was first domesticated in Mesoamerica, within modern-day southern Mexico and ...

seeds, nasturtiums, and

caper ''Capparis spinosa'', the caper bush, also called Flinders rose, is a perennial plant that bears rounded, fleshy leaves and large white to pinkish-white flowers. The plant is best known for the edible flower buds (capers), used as a seasoning ...

s. These species generate isothiocyanates in different proportions, and so have different, but recognizably related, flavors. They are all members of the order

Brassicales The Brassicales (or Cruciales) are an order of flowering plants, belonging to the eurosids II group of dicotyledons under the APG II system. One character common to many members of the order is the production of glucosinolate (mustard oil) compo ...

, which is characterized by the production of

s, and of the enzyme myrosinase, which acts on glucosinolates to release isothiocyanates. * Sinigrin is the precursor to allyl isothiocyanate * Glucotropaeolin is the precursor to benzyl isothiocyanate * Gluconasturtiin is the precursor to phenethyl isothiocyanate * Glucoraphanin is the precursor to sulforaphane

Coordination chemistry

Isothiocyanate and its linkage isomer

thiocyanate Thiocyanate (also known as rhodanide) is the anion . It is the conjugate base of thiocyanic acid. Common derivatives include the colourless salts potassium thiocyanate and sodium thiocyanate. Mercury(II) thiocyanate was formerly used in pyro ...

are ligands in coordination chemistry. Thiocyanate is a more common

ligand In coordination chemistry, a ligand is an ion or molecule ( functional group) that binds to a central metal atom to form a coordination complex. The bonding with the metal generally involves formal donation of one or more of the ligand's ele ...

References

{{Transient receptor potential channel modulators Antioxidants Functional groups Isothiocyanates Oncology Phytochemicals

Structure

Synthesis and reactions

Flavor research

Coordination chemistry

See also

References