organic chemistry Organic chemistry is a subdiscipline within chemistry involving the 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.Clayden, J.; ...

, 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 rest ...

, 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 wel ...

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 formula ...

. Many natural isothiocyanates from plants are produced by

enzymatic Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrates, and the enzyme converts the substrates into different molecules known as products. ...

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 damaged. T ...

s. These natural isothiocyanates, such as

allyl isothiocyanate Allyl isothiocyanate (AITC) is an organosulfur compound (formula CH2CHCH2NCS). This colorless oil is responsible for the pungent taste of mustard, radish, horseradish, and wasabi. This pungency and the lachrymatory effect of AITC are mediated thr ...

, 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 Phenyl isothiocyanate (PITC) is a reagent used in reversed phase HPLC. PITC is less sensitive than ''o''- phthaldehyde (OPA) and cannot be fully automated. PITC can be used for analysing secondary amines, unlike OPA. It is also known as Edman's r ...

, 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 am ...

sequencing in the

Edman degradation Edman degradation, developed by Pehr Edman, is a method of sequencing amino acids in a peptide. In this method, the amino-terminal residue is labeled and cleaved from the peptide without disrupting the peptide bonds between other amino acid residu ...

Cruciferous vegetable Cruciferous vegetables are vegetables of the family Brassicaceae (also called Cruciferae) with many genera, species, and cultivars being raised for food production such as cauliflower, cabbage, kale, garden cress, bok choy, broccoli, Brussels spr ...

s, such as

bok choy Bok choy (American English, Canadian English, and Australian English), pak choi (British English) or pok choi (''Brassica rapa'' subsp. ''chinensis'') is a type of Chinese cabbage, used as food. ''Chinensis'' varieties do not form heads and have ...

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 cl ...

cabbage Cabbage, comprising several cultivars of ''Brassica oleracea'', is a leafy green, red (purple), or white (pale green) biennial plant grown as an annual vegetable crop for its dense-leaved heads. It is descended from the wild cabbage ( ''B.&nb ...

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 – the ...

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 theories for better understanding and prediction of natural or other phenomena. In contrast, applied resear ...

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 chemical ...

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 In organic chemistry, an aromatic amine is an organic compound consisting of an aroma ...

) 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 non ...

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 nitrogenous was ...

. This combination results in precipitation of the solid ammonium

dithiocarbamate In organic chemistry, a dithiocarbamate is a functional group with the general formula and structure . It is the analog of a carbamate in which both oxygen atoms are replaced by sulfur atoms (when only 1 oxygen is replaced the result is thioca ...

salt, which is then treated with lead nitrate to yield the corresponding isothiocyanate. Another method relies on a

tosyl chloride 4-Toluenesulfonyl chloride (''p''-toluenesulfonyl chloride, toluene-''p''-sulfonyl chloride) is an organic compound with the formula CH3C6H4SO2Cl. This white, malodorous solid is a reagent widely used in organic synthesis. Abbreviated TsCl or ...

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 scientif ...

. Vegetable foods with characteristic flavors due to isothiocyanates include

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 Russi ...

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 Mustard may refer to: Food and plants * Mustard (condiment), a paste or sauce made from mustard seeds used as a condiment * Mustard plant, one of several plants, having seeds that are used for the condiment ** Mustard seed, seeds of the mustard p ...

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

Brussels sprout The Brussels sprout is a member of the Gemmifera cultivar group of cabbages (''Brassica oleracea''), grown for its edible buds. The leaf vegetables are typically 1.5–4.0 cm (0.6–1.6 in) in diameter and resemble miniature cabbages ...

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 (biology), 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 (mu ...

, which is characterized by the production of

s, and of the enzyme

myrosinase Myrosinase (, ''thioglucoside glucohydrolase'', ''sinigrinase'', and ''sinigrase'') is a family of enzymes involved in plant defense against herbivores, specifically the mustard oil bomb. The three-dimensional structure has been elucidated and is ...

, which acts on glucosinolates to release isothiocyanates. *

Sinigrin Sinigrin is a glucosinolate that belongs to the family of glucosides found in some plants of the family Brassicaceae such as Brussels sprouts, broccoli, and the seeds of black mustard (''Brassica nigra''). Whenever sinigrin-containing plant tis ...

is the precursor to

Glucotropaeolin Glucotropaeolin or benzyl glucosinolate is a glucosinolate found in cruciferous vegetables, particularly garden cress. Upon enzymatic activity, it is transformed into benzyl isothiocyanate, which contributes to the characteristic flavor of these ...

is the precursor to

benzyl isothiocyanate Benzyl isothiocyanate (BITC) is an isothiocyanate found in plants of the mustard family. Occurrence It can be found in ''Alliaria petiolata'', pilu oil, and papaya seeds where it is the main product of the glucotropaeolin breakdown by the enzyme ...

Gluconasturtiin Gluconasturtiin (phenethylglucosinolate) is one of the most widely distributed glucosinolates in the cruciferous vegetables, mainly in the roots, and is probably one of the plant compounds responsible for the natural pest-inhibiting properties of ...

is the precursor to

phenethyl isothiocyanate Phenethyl isothiocyanate (PEITC) is a naturally occurring isothiocyanate whose precursor, gluconasturtiin is found in some cruciferous vegetables, especially watercress. PEITC has been studied for its potential for chemoprevention of cancers, ...

Glucoraphanin Glucoraphanin is a glucosinolate found in broccoli, mustard and other cruciferous vegetables. Glucoraphanin is converted to sulforaphane by the enzyme myrosinase. In plants, sulforaphane deters insect predators and acts as a selective antibioti ...

is the precursor to

sulforaphane Sulforaphane (sometimes sulphoraphane in British English) is a compound within the isothiocyanate group of organosulfur compounds. It is produced when the enzyme myrosinase transforms glucoraphanin, a glucosinolate, into sulforaphane upon damage ...

Coordination chemistry

Isothiocyanate and its

linkage isomer In chemistry, linkage isomerism or ambidentate isomerism is a form of isomerism in which certain coordination compounds have the same composition but differ in their metal atom's connectivity to a ligand. Typical ligands that give rise to linkage ...

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 pyrot ...

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 electr ...

References

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

Structure

Synthesis and reactions

Flavor research

Coordination chemistry

See also

References