Herbicides, thiocarbamates

EPTC was introduced by Stauffer in 1959 (Fig. 3). It is a thiocarbamate and an important member of a large family of herbicides. Thiocarbamates are usually soil incorporated. EPTC is used in crops... 

Miyashita, Y, Ohsako, H., Takayama, C. and Sasaki, S. (1992). Multivariate Structure-Activity Relationships Analysis of Fungicidal and Herbicidal Thiocarbamates Using Partial Least Squares Method. Quant.Struct.-Act.Relat, 11,17-22. 

The growth inhibitory mechanism of the thiocarbamate herbicides, eg, EPTC, butylate, cycloate, diaHate, and triaHate, is not well defined. Cell elongation, rather than cell division, appears to be inhibited (183), although mitotic entry may be inhibited by diaHate (184). Thiocarbamates have a greater effect on shoot than toot tissue (163,184). The weU-documented inhibition of Hpid synthesis by thiocarbamates certainly contributes to the observed inhibitions of cell division and elongation. These compounds may also inhibit gibbereUic acid synthesis (185). 

Phenylcarbamates. Phenylcarbamate herbicides represent one of two subgroups of carbamate herbicides, the phenylcarbamates and the thiocarbamates (299). Both groups are prone to volatilization losses the thiocarbamates are particularly susceptible and should be sod-incorporated immediately after apphcation (2). The carbamate herbicides are used, in general, for the selective pre-emergence control of grass and broadleaved weeds (299). Exceptions would include barban, desmedipham, and phenmedipham which are appHed post-emergence. 

The encapsulation of herbicides has received much attention. Encapsulated alachlor is a high volume herbicide product generally sold as a Hquid formulation, although a dry granule version is also available. The capsules, produced by interfacial polymeri2ation (11), are reported to be spherical with a diameter of 2—15 p.m (75). Two thiocarbamate herbicides, EPTC and vemolate [1929-77-7], were encapsulated by interfacial polymeri2ation because they are volatile compounds. When appHed in unencapsulated form, they must be incorporated in the soil within two hours in order to provide effective weed control. When appHed as a microencapsulated formulation, the rate of volatili2ation is lower and soil incorporation can be delayed 24 hours (76). 

The anhydride of 1,8-naphthalenedicarboxyHc acid has fungicidal properties (97). This anhydride has been commercially introduced, under the trade name Protect, as a seed treatment (eg, for com) to prevent injury to the seed by thiocarbamate herbicides. The effectiveness of the antidote 1,8-naphthaHc anhydride has also been successfully studied with several plants and herbicides (98,99). 

Uses. There may be some captive use of carbonyl sulfide for production of certain thiocarbamate herbicides (qv). One patent (38) describes the reaction of diethylamine with carbonyl sulfide to form a thiocarbamate salt which is then alkylated with 4-chloroben2yl haUde to produce 3 -(4-chloroben2yl) A[,A/-diethylthiocarbamate [28249-77-6] ie, benthiocarb [28249-77-6]. Carbonyl sulfide is also reported to be useful for the preparation of abphatic polyureas. In these preparations, potassium thiocyanate and sulfuric acid are used to first generate carbonyl sulfide, COS, which then reacts with a diamine ... 

Au iuducible euzyme iu the hacttimvaRhodococcus erythropolis NI86/21 that is iuvolved iu the degradatiou of thiocarbamate herbicides is a uouheme haloperoxidase, which does uot occur iu other straius of rhodococci that cau degrade thiocarbamates (de Schrijver etal. 1997). 

In addition to these mechanisms, the degradation of thiocarbamates may be carried out in Rhodococcus erythropolis NI86/21 by a herbicide-inducible nonheme haloperoxidase (de Schrijver et al. 1997). 

Analysis of pesticides in water was performed by fully automated online solid-phase extraction-liquid chromatography-tandem mass spectrometry (SPE-LC-MS/ MS) [25, 31]. These pesticides (a total of 22 belonging to the classes of triazines, OP, chloroacetanilides, phenylureas, thiocarbamates, acid herbicides, and anilides) were selected on the basis of previously published studies [20, 25], information gathered from the water authorities, and known use in rice crops. 

Metabolism of the Thiocarbamate Herbicide Molinate (Ordram) in Japanese Carp... 

Other examples of nonionic compounds (Fig. 10, Table 3) are the phenyl-amide herbicides (e. g., Diphenamid, moderately water soluble and nonvolatile), thiocarbamate, and carbothioate herbicides (e. g., Thiobencarb, low water solubility, high vapor pressure, relative mobility in soil systems) and benzonitrile herbicides (e.g., Dichlobenil, low water solubility, low vapor pressure, relative immobility in most soils) [151]. 

Casida, J.E., Gray, R.A., and Tides, H. Thiocarbamate sulfoxides potent, selective, and biodegradable herbicides. Science (Washington, DC), 184(4136) 573-574, 1974. 

Ruzo, L.O. and Casida, J.E. Photochemistry of thiocarbamate herbicides oxidative and free radical processes of thiobencarb and diallate, J. Agric. Food Chem., 33(2) 272-276, 1985. 

Molinate Thiocarbamate 2212-67-1 2.49 1964, USA Herbicide A herbicide used to control germinating broad-leaved and grassy weeds... 

Many organosulfur compounds undergo biological oxidation at the sulfur atom to yield products which have pronounced physiological activity or serve as intermediates in generating bioactive compounds. Three examples are the lachrymating agent in onions ( ) (1), the oxo intermediate ( ) in metabolic desulfuration of phosphorothionate insecticides to form potent cholinesterase inhibitors (2), and the sulfoxides QJ produced on metabolism of thiocarbamate herbicides (3). 

The herbicidal activity of -alkyl thiocarbamates (3-5) and the mutagenic activity of an -(2,3-dichloroallyl) thiocarbamate (6) are probably due to the reactivity or decomposition products of their metabolically-formed sulfoxides. 

Proherbicides. Thio- and dithiocarbamates probably require metabolic activation prior to exerting their herbicidal effects. Sulfoxide metabolites of the -alkyl thiocarbamates are generally more potent herbicides than the parent compounds ( -5). The herbicidal action of these sulfoxides probably results from their carbamylating action for thiols, although the specific target site or receptor is not defined (23, 24). It is conceivable that the -chloroallyl thiocarbamate herbicides may act in the same way, since their sulfoxides are also potent carbamylating agents... 

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