Thiocarbamate

{{Short description|Organosulfur compounds of the forms ROC(S)NR2 or RSC(O)NR2}}

File:Thiocarbamates-general-2D.png structural formulae of O-organyl (1) and S-organyl (2) thiocarbamates]]

In organic chemistry, thiocarbamates (thiourethanes) are a family of organosulfur compounds. As the prefix thio- suggests, they are sulfur analogues of carbamates. There are two isomeric forms of thiocarbamates: O-thiocarbamates, {{chem2|ROC(\dS)NR2}} (esters), and S-thiocarbamates, {{chem2|RSC(\dO)NR2}} (thioesters).

Synthesis

Thiocarbamates can be synthesised by the reaction of water or alcohols upon thiocyanates (Riemschneider thiocarbamate synthesis):{{March6th|page=1269}}{{cite journal |last1=Walter |first1=W. |last2=Bode |first2=K.-D. |title=Syntheses of Thiocarbamates |journal=Angewandte Chemie International Edition in English |date=April 1967 |volume=6 |issue=4 |pages=281–293 |doi=10.1002/anie.196702811}}

:RSCN + H₂O → RSC(=O)NH₂

:RSCN + R'OH → RSC(=O)NR'H

Similar reactions are seen between alcohols and thiocarbamoyl chlorides such as dimethylthiocarbamoyl chloride; as well as between thiols and cyanates. The herbicide Cycloate is produced in this way:

:{{chem2|C6H11(C2H5)NCOCl + C2H5SH -> C6H11(C2H5)NCOSC2H5 + HCl}}

Other related thiocarbamate herbicides include vernolate {{chem2|(C3H7)2NCOSC3H7}} and triallate ({{chem2|(i\sC3H7)2NCOSCH2CCl\dCCl2}}.{{cite journal |last1=Appleby |first1=Arnold P. |last2=Müller |first2=Franz |last3=Carpy |first3=Serge |date=2001 |title=Weed Control |journal=Ullmann's Encyclopedia of Industrial Chemistry |doi=10.1002/14356007.a28_165 |isbn=3-527-30673-0}}

Salts of thiocarbamate arise by the reaction of amines with carbonyl sulfide:

:{{chem2|2 R2NH + COS → [R2NH2+][R2N\sCOS−]}}

Reactions

In the Newman-Kwart rearrangement O-thiocarbamates can isomerise to S-thiocarbamates.{{cite journal |title=Thiophenols from Phenols: 2-Naphthalenethiol |last1=Newman |first1=Melvin S. |last2=Hetzel |first2=Frederick W. |journal=Org. Synth. |year=1971 |volume=51 |page=139 |doi=10.15227/orgsyn.051.0139}} This reaction, which generally requires high temperatures, is an important method for the synthesis of thiophenols.

File:Newman-Kwart-rearrangement-general.png

Occurrence

File:Goitrin.png]]

Goitrin is a cyclic thiocarbamate found in some vegetables.{{cite journal |vauthors=McMillan M, Spinks EA, Fenwick GR |title=Preliminary Observations on the Effect of Dietary Brussels Sprouts on Thyroid Function |journal=Hum Toxicol |volume=5 |issue=1 |pages=15–19 |date=January 1986 |pmid=2419242 |doi=10.1177/096032718600500104}}

Uses

Thiocarbamate based herbicides (e.g. prosulfocarb) were introduced in 1957 and in 2017 was a $200,000,000 market.{{cite journal |title=Agrochemical industry development, trends in R&D and the impact of regulation |journal=Pest Management Science |date=19 Dec 2019 |url=https://scijournals.onlinelibrary.wiley.com/doi/full/10.1002/ps.5728 |access-date=6 August 2024}}

References

Category:Functional groups