Dithiocarbamate
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]
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
- ^ a b 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
- ^ 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
- ^ Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8.
- ^ http://www.apsnet.org/publications/apsnetfeatures/Pages/Fungicides.aspx
- ^ Gullino, Maria Lodovica, et al. "Mancozeb: past, present, and future." Plant Disease 94.9 (2010): 1076-1087.
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