Dithiocarbamate

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Chemical structure of dithiocarbamates

A dithiocarbamate is a functional group in organic chemistry. It is the analog of a carbamate in which both oxygen atoms are replaced by sulfur atoms. Sodium diethyldithiocarbamate is a common example. Dithiocarbamates and their derivatives are widely used in the vulcanization of rubber.[1]

Formation and reactions[edit]

Many primary and secondary amines react with carbon disulfide and sodium hydroxide to form dithiocarbamate salts:[1]

R2NH + CS2 + NaOH → R
2
NCS
2
Na+
+ H2O

Ammonia reacts with CS2 similarly:

2 NH3 + CS2H
2
NCS
2
NH+
4

Dithiocarbamate salts are pale colored solid that are soluble in water and polar organic solvents.

Structure and bonding[edit]

Dithiocarbamates is 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.[2]

Main resonance structures of a dithiocarbamate anion.

Because of the pi-donation from nitrogen, dithiocarbamates are more basic than structurally related anions such as dithiocarboxylates and xanthates. Consequently, they tend to bind as bidentate ligands. Another consequence of the C–N multiple bonding is that rotation about that bond is subject to a high barrier.

Applications[edit]

Zinc dithiocarbamates are used to modify the crosslinking of certain polyolefins with sulfur, a process called vulcanization. They are used as ligands for chelating metals.[3]

Dithiocarbamates specifically ethylene bisdithiocarbamates (EBDCs), in the form of complexes with manganese (maneb), zinc (zineb) or a combination of manganese and zinc (mancozeb), have been used extensively as fungicides in agriculture from the 1940s.[4]

See also[edit]

References[edit]

  1. ^ a b Engels, Hans-Wilhelm; et al. (2005), "Rubber, 4. Chemicals and Additives", Ullmann's Encyclopedia of Industrial Chemistry, Weinheim: Wiley-VCH, doi:10.1002/14356007.a23_365.pub2 
  2. ^ Coucouvanis, Dimitri (1979). "The chemistry of the dithioacid and 1,1-dithiolate complexes, 1968–1977". Prog. Inorg. Chem. 26: 301–469. doi:10.1002/9780470166277.ch5. 
  3. ^ Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 0-08-037941-9. 
  4. ^ "A Short History of Fungicides". The American Phytopathological Society. Retrieved 10 May 2016.