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In organic chemistry, a dithiocarbamate is a functional group with the general
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.
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 
In organic chemistry, a dithiocarbamate is a functional group with the general formula
In science, a formula is a concise way of expressing information symbolically, as in a mathematical formula or a ''chemical formula''. The informal use of the term ''formula'' in science refers to the general construct of a relationship betwee ...
and structure
A structure is an arrangement and organization of interrelated elements in a material object or system, or the object or system so organized. Material structures include man-made objects such as buildings and machines and natural objects such as ...
. It is the analog of a carbamate
In organic chemistry, a carbamate is a category of organic compounds with the general formula and structure , which are formally derived from carbamic acid (). The term includes organic compounds (e.g., the ester ethyl carbamate), formally o ...
in which both oxygen atoms are replaced by sulfur
Sulfur (or sulphur in British English) is a chemical element with the symbol S and atomic number 16. It is abundant, multivalent and nonmetallic. Under normal conditions, sulfur atoms form cyclic octatomic molecules with a chemical formula ...
atoms (when only 1 oxygen is replaced the result is thiocarbamate).
A common example is sodium diethyldithiocarbamate
Sodium diethyldithiocarbamate is the organosulfur compound with the formula NaS2CN(C2H5)2. It is a pale yellow, water soluble salt.
Preparation
This salt is obtained by treating carbon disulfide with diethylamine in the presence of sodium hydrox ...
. Dithiocarbamates and their derivatives are widely used in the vulcanization of rubber.
Formation
Many primary and secondary amines react with carbon disulfide andsodium hydroxide
Sodium hydroxide, also known as lye and caustic soda, is an inorganic compound with the formula NaOH. It is a white solid ionic compound consisting of sodium cations and hydroxide anions .
Sodium hydroxide is a highly caustic base and alkali ...
to form dithiocarbamate salts:
:R2NH + CS2 + NaOH → R2NCS2−Na+ + 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.
Reactions
Dithiocarbamates are readily S-alkylated. Thus, methyl dimethyldithiocarbamate can be prepared by methylation of the dithiocarbamate: :(CH3)2NCS2Na + (CH3O)2SO2 → (CH3)2NC(S)SCH3 + Na H3OSO3 Oxidation of dithiocarbamates gives the thiuram disulfide: :2 R2NCS2− → 2NC(S)Ssub>2 + 2e− Thiuram disulfides react with Grignard reagents to give esters of dithiocarbamic acid: : 2NC(S)Ssub>2 + R'MgX → R2NC(S)SR' + R2NCS2MgX Dithiocarbamates react with transition metal salts to give a wide variety oftransition metal dithiocarbamate complexes 133px, Tris(dithiocarbamate) complexes have idealized D3 symmetry.
Transition metal dithiocarbamate complexes are coordination complexes containing one or more dithiocarbamate ligand, which are typically abbreviated R2dtc−. Many complexes are k ...
.
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.
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
Severaltransition metal dithiocarbamate complexes 133px, Tris(dithiocarbamate) complexes have idealized D3 symmetry.
Transition metal dithiocarbamate complexes are coordination complexes containing one or more dithiocarbamate ligand, which are typically abbreviated R2dtc−. Many complexes are k ...
are useful industry. Zinc dithiocarbamates are used to modify the crosslinking of certain polyolefin
A polyolefin is a type of polymer with the general formula (CH2CHR)n where R is an alkyl group. They are usually derived from a small set of simple olefins (alkenes). Dominant in a commercial sense are polyethylene and polypropylene. More speciali ...
s 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 Sooty blotch and flyspeck (SBFS) or apple summer disease is a plant disease caused by a complex of saprophytic fungi which colonize the epicuticular wax layer of apple (''Malus'' x ''domestica'' Borkh.). It is found worldwide in regions with moist g ...
. 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
A biophysical environment is a biotic and abiotic surrounding of an organism or population, and consequently includes the factors that have an influence in their survival, development, and evolution. A biophysical environment can vary in scale f ...
banned EBDCs within 77 days to harvest. This effectively made summer use impossible, reduced EBDC use overall, and radically increased SBFS.
See also
* XanthateReferences