Organic thiocyanates

Phenyl thiocyanate and phenyl isothiocyanate are isomers.

Organic thiocyanates are organic compounds containing the functional group RSCN. the organic group is attached to sulfur: R−S−C≡N has a S–C single bond and a C≡N triple bond.[1]

Organic thiocyanates are valued building blocks. They allow to access efficiently various sulfur containing functional groups and scaffolds.[2]

## Contents

* 1 Synthesis
* 2 Structure
* 3 Reactions
* 4 See also
* 5 References

## Synthesis

Several synthesis routes exist,[3] the most common being the reaction between alkyl halides and alkali thiocyanate in aqueous media.[4] Illustrative is the preparation of isopropyl thiocyanate by treatment of isopropyl bromide with sodium thiocyanate in boiling ethanol.[5] The main complication with this route is the competing formation of alkyisothiocyanates. "SN1-type" substrates (e.g., benzyl halides) tend to give the isothiocyanate derivatives.

Some organic thiocyanates are generated by cyanation of some organosulfur compounds. Sulfenyl thiosulfates (RSSO3−) react with alkali metal cyanides to give thiocyanates with displacement of sulfite. This approach has been applied to allyl thiocyanate:[6]

2=CHCH
2Cl + Na

3 → CH
2=CHCH

3Na + NaCl

2=CHCH

3Na + NaCN → CH
2=CHCH
2SCN + Na
2SO

Sulfenyl chlorides (RSCl) also convert to thiocyanates.

Aryl thiocyanates are traditionally produced by the Sandmeyer reaction, which involves combining copper(I) thiocyanate and diazonium salts:[3]

[ArN
2]BF
4 \+ CuSCN → ArSCN + CuBF
4 \+ N

Some arylthiocyanates can also often be obtained by thiocyanogenation, i.e. the reaction of thiocyanogen. This reaction is favored for electron-rich aromatic substrates.[1]

## Structure

In methyl thiocyanate, N≡C and C–S distances are 116 and 176 pm. By contrast, N=C and C=S distances are 117 and 158 pm in isothiocyanates.[7]

Typical bond angles for C–S–C are 100°.[3] By contrast C–N=C in aryl isothiocyanates is 165°. Again, the thiocyanate isomers are quite different with C–S–C angle near 100°.

In both organic thiocyanate and isothiocyanate isomers the SCN angle approaches 180°.

## Reactions

Organic thiocyanates are hydrolyzed to thiocarbamates in the Riemschneider thiocarbamate synthesis.

Electrochemical reduction typically converts thiocyanates to thioates and cyanide, although sometimes it can replace the thiocyanate group as a whole with hydride.[8]

Some thiocyanates isomerize to the isothiocyanates. This reaction is especially rapid for the allyl isothiocyanate:[6]

2=CHCH
2SCN → CH
2=CHCH
2NCS

Likewise, acyl thiocyanates are difficult to synthesize because any excess thiocyanate ion catalyzes isomerization to the acyl isothiocyanate.[9]

## See also

* Isothiocyanate, isomers of organic thiocyanates with the formula R−N=C=S
* Methyl thiocyanate, the simplest organic thiocyanate

## References

1. ↑ 1.0 1.1 R. G. Guy (1977). "Syntheses and Preparative Applications of Thiocyanates". in Saul Patai. Cyanates and Their Thio Derivatives: Part 2, Volume 2. PATAI'S Chemistry of Functional Groups. pp. 619–818. doi:10.1002/9780470771532.ch2. ISBN 9780470771532.
2. ↑ Castanheiro, Thomas; Suffert, Jean; Donnard, Morgan; Gulea, Mihaela (2016-02-01). "Recent Advances in the Chemistry of Organic Thiocyanates". Chem. Soc. Rev. 45 (3): 494–505. doi:10.1039/c5cs00532a. ISSN 1460-4744. PMID 26658383.
3. ↑ 3.0 3.1 3.2 Erian, Ayman W.; Sherif, Sherif M. (1999). "The chemistry of thiocyanic esters". Tetrahedron 55 (26): 7957–8024. doi:10.1016/S0040-4020(99)00386-5.
4. ↑ "Synthesis of thiocyanates". https://www.organic-chemistry.org/synthesis/C1S/thiocyanates.shtm.
5. ↑ R. L. Shriner (1931). "Isopropyl Thiocyanate". Organic Syntheses 11: 92. doi:10.15227/orgsyn.011.0092.
6. ↑ 6.0 6.1 Emergon, David W. (1971). "The Preparation and Isomerization of Allyl Thiocyanate. An Organic Chemistry Experiment". Journal of Chemical Education 48 (1): 81. doi:10.1021/ed048p81. Bibcode: 1971JChEd..48...81E.
7. ↑ Majewska, Paulina; Rospenk, Maria; Czarnik-Matusewicz, Bogusława; Kochel, Andrzej; Sobczyk, Lucjan; Dąbrowski, Roman (2008). "Structure and polarized IR spectra of 4-isothiocyanatophenyl 4-heptylbenzoate (7TPB)". Chemical Physics 354 (1–3): 186–195. doi:10.1016/j.chemphys.2008.10.024. Bibcode: 2008CP....354..186M.
8. ↑ Patai, Saul, ed (1977). The Chemistry of Cyanates and Their Thio Derivatives. The Chemistry of Functional Groups. 1. Chichester: Wiley. pp. 331–335. ISBN 0-471-99477-4.
9. ↑ Patai 1977, pp. 451–453.

* v
* t
* e

Functional groups

| Only carbon,
hydrogen,
and oxygen|

| Hydrocarbons|

* Allene
* Alkene (Allyl group

|

Other|

* Acetoxy
* Acetyl
* Acryloyl
* Acyl
* Aldehyde
* Alkoxy (Methoxy)
* Benzoyl
* Carbonyl
* Carboxyl
* Carboxylic anhydride
* Dioxirane
* Epoxide
* Ester
* Ether
* Ethylenedioxy
* Hydroxy
* Ketone
* Methylenedioxy
* Peroxide (Organic)
* Ynone

Only one
element
apart from
C, H, O|

| Nitrogen|

* Amine
* Azo compound
* Cyanate
* Hydrazone
* Imide
* Imine
* Isocyanate
* Isonitrile
* Nitrene
* Nitrile
* Nitro compound
* Nitroso compound
* Organic amide
* Oxime

|

Phosphorus|

* Phosphonate
* Phosphonous

Sulfur|

* Disulfide
* Sulfone
* Sulfonic acid
* Sulfoxide
* Thial
* Thioester
* Thioether
* Thioketone
* Thiol

Selenium|

* Selenol
* Selenonic acid
* Seleninic acid
* Selenenic acid
* Selone

Tellurium|

* Tellurol
* Telluroketone

Other|

* Isothiocyanate
* Phosphoramide
* Sulfenyl chloride
* Sulfonamide
* Thiocyanate

See also chemical classification, chemical nomenclature ([[Chemistry:IUPAC nomenclature of inorganic, IUPAC nomenclature of organic chemistry|organic]])

* v
* t
* e

Thyroid hormone receptor modulators

Receptor
(ligands)|

| THR|

* Agonists: Dextrothyroxine
* DIMIT
* DITPA
* Eprotirome (KB-2115)
* KB-141
* KB-2611
* KB-130015
* Levothyroxine
* Liothyronine
* Liotrix
* MB-07344
* MB-07811
* MGL-3196 (VIA-3196)
* Sobetirome (GC-1, GRX-431)
* Thyroxine
* Tiratricol (TRIAC)
* Triiodothyronine
* Thyroid extract
* VK-0214
* VK-2809
* ZYT1

* Antagonists: 1-850
* NH3
* Tetraiodothyroacetic acid (Tetrac)

|

Transporter
(blockers)|

| NIS

* Inhibitors: Cyanogenic glycosides
* Perchlorates (e.g., potassium perchlorate)
* Pertechnetates (e.g., sodium pertechnetate]])
* Thiocyanates

|

Enzyme
(inhibitors)|

| TPO|

* Inhibitors: Benzylthiouracil
* Carbimazole
* Genistein
* Methimazole
* Methylthiouracil
* Propylthiouracil
* 2-Thiouracil
* Thiourea

|

DIO|

* Inhibitors: Dexpropranolol
* Iopanoic acid
* Ipodate sodium (sodium iopodate)
* Propranolol
* Propylthiouracil

Others|

* Iodine
* Iodine-131
* Selenium
* Thyroglobulin
* Tyrosine

* See also: Receptor/signaling modulators
* Nuclear receptor modulators

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*[THR]: Thyroid hormone receptor
*[NIS]: Sodium-iodide symporter
*[TPO]: Thyroid peroxidase
*[DIO]: Iodothyronine deiodinase