Dithiocarbamate

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

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

R2NH + CS2 + NaOH → R2NCS2−Na+ + H2O

Ammonia reacts with CS2 similarly:

2 NH3 + CS2 → H2NCS2−NH4+

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

Structure and bonding

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

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][5]

See also

References

  1. 1 2 Hans-Wilhelm Engels et al., "Rubber, 4. Chemicals and Additives" in Ullmann's Encyclopedia of Industrial Chemistry, 2007, Wiley-VCH, Weinheim. doi:10.1002/14356007.a23_365.pub2
  2. ↑ Coucouvanis, Dimitri "The chemistry of the dithioacid and 1,1-dithiolate complexes, 1968-1977" Progress in Inorganic Chemistry 1979, volume 26, pp. 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. ↑ http://www.apsnet.org/publications/apsnetfeatures/Pages/Fungicides.aspx
  5. ↑ Gullino, Maria Lodovica, et al. "Mancozeb: past, present, and future." Plant Disease 94.9 (2010): 1076-1087.


This article is issued from Wikipedia - version of the Saturday, April 16, 2016. The text is available under the Creative Commons Attribution/Share Alike but additional terms may apply for the media files.