Dithiocarbamate
In organic chemistry, a dithiocarbamate is a functional group with the general formula R2N−C(=S)−S−R and structure >N−C(=S)−S−. 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 thiocarbamate).
Dithiocarbamate also refers to the dithiocarbamate ion R2N−CS−2 and its salts. A common example is sodium diethyldithiocarbamate. Dithiocarbamates and their derivatives are widely used in the vulcanization of rubber.[1]
Formation
Many secondary amines react with carbon disulfide and sodium hydroxide to form dithiocarbamate salts:[2]
- R2NH + CS2 + NaOH → R2NCS−2Na+ + H2O
Ammonia reacts with CS2 similarly:
- 2 NH3 + CS2 → H2NCS2−NH4+
Dithiocarbamate salts are pale colored solids that are soluble in water and polar organic solvents.
Dithiocarbamic acid
A primary amine and carbon disulfide react to give a dithiocarbamic acid:
- RNH2 + CS2 → R(H)NCS2H
In the presence of diimides or pyridine, these acids convert to isothiocyanates:[3]
- R(H)NCS2H + C(=NR')2 → RN=C=S + S=C(NHR')2
Reactions
Dithiocarbamates are readily S-alkylated. Thus, methyl dimethyldithiocarbamate can be prepared by methylation of the dithiocarbamate:[4]
- (CH3)2NCS2Na + (CH3O)2SO2 → (CH3)2NC(S)SCH3 + Na[CH3OSO3]
Oxidation of dithiocarbamates gives the thiuram disulfide:
- 2 R2NCS2− → [R2NC(S)S]2 + 2e−
Thiuram disulfides react with Grignard reagents to give esters of dithiocarbamic acid:[5]
- [R2NC(S)S]2 + R'MgX → R2NC(S)SR' + R2NCS2MgX
Dithiocarbamates react with transition metal salts to give a wide variety of transition metal dithiocarbamate complexes.
Structure and bonding
Dithiocarbamates are described by invoking resonance structures that emphasize the pi-donor properties of the amine group. This bonding arrangement is indicated by a short C–N distance and the coplanarity of the NCS2 core as well as the atoms attached to N.[6]
![](http://upload.wikimedia.org/wikipedia/commons/thumb/f/fa/DTCresSt%27s.png/290px-DTCresSt%27s.png)
Because of the pi-donation from nitrogen, dithiocarbamates are more basic than structurally related anions such as
Applications
Several
![](http://upload.wikimedia.org/wikipedia/commons/thumb/3/36/Zn%28Me2dtc%292Improved.png/244px-Zn%28Me2dtc%292Improved.png)
Some dithiocarbamates, specifically ethylene bisdithiocarbamates (EBDCs), in the form of complexes with
![](http://upload.wikimedia.org/wikipedia/commons/thumb/8/86/CH2_dtc_2.svg/220px-CH2_dtc_2.svg.png)
See also
References
- ISBN 978-3527306732.
- ISBN 3-527-30673-0.
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- .
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- ISBN 978-0-470-16627-7.
- ISBN 978-0-08-037941-8.
- ^ "A Short History of Fungicides". The American Phytopathological Society. Archived from the original on 16 April 2016. Retrieved 10 May 2016.
- ^ S2CID 172137916.
- ISBN 978-3-527-30673-2.