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 (when only 1 oxygen is replaced the result is thiocarbamate). A common example is sodium diethyldithiocarbamate. Dithiocarbamates and their derivatives are widely used in the vulcanization of rubber. Formation. Many primary and secondary amines react with carbon disulfide and sodium hydroxide to form dithiocarbamate salts: Ammonia reacts with CS similarly: Dithiocarbamate salts are pale colored solids that are soluble in water and polar organic solvents. Reactions. Dithiocarbamates are readily S-alkylated. Thus, methyl  dimethyldithiocarbamate can be prepared by methylation of the dithiocarbamate: Oxidation of dithiocarbamates gives the thiuram disulfide: Thiuram disulfides react with Grignard reagents to give esters of dithiocarbamic acid: 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 NCS core as well as the atoms attached to N. 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. Some dithiocarbamates, specifically ethylene bisdithiocarbamates (), 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 since the 1940s. In the  United States they began to be registered for use in the late 1950s and early 1960s and were quickly put to work on sooty blotch and flyspeck. Many growers switched from captan to EBDCs for the longer residual period. Both captan and EBDCs were the primary treatments for SBFS in that country until the early 1990s when the US Environmental Protection Agency banned EBDCs within 77 days to harvest. This effectively made summer use impossible, reduced EBDC use overall, and radically increased SBFS. Dithiocarbamates also serve as anchoring groups for molecular species in the functionalization of semiconductor and metal surfaces . In cadmium chalcogenide nanocrystals functionalized with dithiocarbamate ligands, the energetic alignment of the semiconductor's valence band and the HOMO level of the ligands has been shown to facilitate delocalization of holes from the nanocrystal core onto the ligand. The hole-delocalizing properties of dithiocarbamates have been used to create ligands that stabilize the nanocrystals in solution while also mediating charge transfer through the ligand shell (which typically hinders this process).