Alachlor

IUPAC name 2-chloro-2, 6 -diethyl-N-(methoxymethyl) acetanilide Molecular formula C14H20CINO2 Toxicity class USEPA III WHO III 

Uses Alachlor is a colorless to yellow crystal compound.111 13 Alachlor is an aniline herbicide used to control annual grasses and broadleaf weeds in field corn, soybeans, and peanuts. It is a selective systemic herbicide, absorbed by germinating shoots and roots. It works by interfering with a plant s ability to produce protein and by interfering with root elongation. This compound is one of the most extensively used herbicides. The USEPA categorizes alachlor under restricted use pesticides (RUP), and it should be purchased and used only by certified applicators. 

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Much of the chloroacetyl chloride produced is used captively as a reactive intermediate. It is useful in many acylation reactions and in the production of adrenalin [51-43-4] diazepam [439-15-5] chloroacetophenone [532-27-4] chloroacetate esters, and chloroacetic anhydride [541-88-8]. A major use is in the production of chloroacetamide herbicides (3) such as alachlor [15972-60-8]. 

Acid amide herbicides are nonionic and moderately retained by soils. The sorption of several acid amide herbicides has been investigated (369). Acetochlor [34256-82-1] is sorbed more than either alachlor or metolachlor, which are similarly sorbed by a variety of soils. Sorption of all the herbicides is well correlated to soil organic matter content. In a field lysimeter study, metolachlor has been found to be more mobile and persistent than alachlor (370) diphenamid [957-51-7] and napropamide [15299-99-2] have been found to be more readily leached (356). 

Chlorine adds to ketene to form chloroacetyl chloride [79-04-9] (78). Chloroacetyl chloride (CAC) is used in large volume in the manufacture of the pre-emergence herbicides alachlor [15972-60-8] and butachlor [23184-66-9]. It is estimated that the CAC requirement for this appHcation was in excess of 45,000 metric tons in 1992. Significant volumes of CAC are also used in pharmaceutical manufacture, such as anesthetics of the Hdocaine type, and in the production of the tear gas chloroacetophenone [532-27-4]. Other commercial methods for the manufacture of CAC have been described (79). 

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). 

Alkyl-Hyd.roxyla.tion. This is commonly observed as the initial transformation of alkyl-substituted aromatic pesticides such as alachlor [15972-60-8] and metolachlor [51218-45-2] (eq. 2) (2) (16). These reactions are typically catalyzed by relatively nonspecific oxidases found in fungi and actinomycetes. 

Hydrodechlorination is a common reaction of chlorinated pesticides such as atrazine (eq. 15), alachlor, and metolachlor (2) (eq. 16). These reactions are catalyzed primarily by transition metals or by soil surfaces (clays or humic substances). 

The documented occurrence of pesticides in surface water is indicative that mnoff is an important pathway for transport of pesticide away from the site of appHcation. An estimated 160 t of atra2ine, 71 t of sima2ine, 56 t of metolachlor, and 18 t of alachlor enter the Gulf of Mexico from the Mississippi River annually as the result of mnoff (47). Field appHcation of pesticides inevitably leads to pesticide contamination of surface mnoff water unless mnoff does not occur while pesticide residues remain on the surface of the soil. The amount of pesticides transported in a field in mnoff varies from site to site. It is controUed by the timing of mnoff events, pesticide formulation, physical—chemical properties of the pesticide, and properties of the soil surface (48). Under worst-case conditions, 10% or more of the appHed pesticide can leave the edge of the field where it was appHed. 

Observing the amount and variety of pesticides analyzed by GC chromatography we decided to observe 14 of the most represented pesticides Prometryn, Deltamethrin, Fenitrothion, Tebuconazole, Buprofezin, Malathion, Myclobutanyl, Atrazine, Acetochlor, Bifenthrin, Alachlor, Pendimethalin, Dichlonuid and Trifluralin. 

Alachlor zero 0.002 Eye, liver, kidney or spleen problems anemia increased risk of cancer Runoff from herbicide used on row crops... 

Alabama Depailment of Agriculture and Industries, 289 Alabama Depailment of Environmental Management, 289 Alabama Depailment of Public Health, 289 Alabama Poison Control Center, 311 Alachlor, 9... 

Figure 15.13 Comprehensive two-dimensional GC chromatogram of a supercritical fluid exti act of spiked human semm. Peak identification is as follows 1, dicamha 2, tiifluralin 3, dicliloran 4, phorate 5, pentachlorophenol 6, atrazine 7, fonofos 8, diazinon 9, cWorothalonil 10, terhufos 11, alachlor 12, matalaxyl 13, malathion 14, metalochlor 15, DCPA 16, captan 17, folpet 18, heptadecanoic acid. Adapted imm Analytical Chemistry, 66, Z. Liu et al., Comprehensive two-dimensional gas chromatography for the fast separation and determination of pesticides exuacted from human senim , pp. 3086-3092, copyright 1994, with pemiission from the American Chemical Society.

Figure 5.2 Electrospray-MS-MS signal response of seven of the pesticides versus eluent flow rate, based on (a) peak area, and (b) peak height , atrazine , simazine , diuron x, isoproturon , chlorfenvinphos , chlorpyrifos O, alachlor. Reprinted from 7. Chromatogr., A, 937, Asperger, A., Efer, J., Koal, T. and Engewald, W., On the signal response of various pesticides in electrospray and atmospheric pressure chemical ionization depending on the flow rate of eluent applied in liquid chromatography-mass spectrometry , 65-72, Copyright (2001), with permission from Elsevier Science.

Pothuluri JV, JP Freeman, FE Evans, TB Moorman, CE Cerniglia (1993) Metabolism of alachlor by the fungus Cunninghamella elegans. J Agric Food Chem 41 483-488. 

Resistance of house flies (Musca domestica) to DDT was attributed to its transformation to the nontoxic DDE, and the enzyme that carries the dehydrochlorination has been characterized in DDT-resistant flies (Lipke and Kearns 1959a,b). The herbicide alachlor is transformed by chironomid larvae by O-demethylation followed by loss of the chloroacetyl group to produce 2,6-diethylaniline... 

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