Pre-emergent herbicides

DichlorobenzotrifIuoride. This dichloro compound is produced from 2,4-dichloroben2otrichloride and hydrogen fluoride. One commercial appHcation is the manufacture of the pre-emergent herbicide, dinitramine [29091 -05-2]. 

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). 

In addition to the use of 2,4-dichlorophenol in the synthesis of 2,4-D herbicides (acid 2,4-D, acid 2,4-DP, acid 2,4-DB), it is also found in the selective post-emergence herbicide, diclofop-methyl [51338-27-3] (61) and as a selective pre-emergence herbicide, oxadia2on [19666-30-9] (62). A postemergence herbicide is appHed between the emergence of a seedling and the maturity of a crop plant. 

Use pattern Orbencarb is a systemic pre-emergence herbicide to control most annual grasses and broad-leaved weeds... 

Sulfentrazone is a broad-spectrum, pre-emergent herbicide that provides good control over broadleaf weeds, grasses and sedges in crops and turf. The metabolism of sulfentrazone in animals and plants is similar. The major plant metabolite of sulfentrazone is 3-hydroxymethyl sulfentrazone (HMS). The soybean tolerance of 0.05 mg kg includes residues of sulfentrazone plus its major metabolite, HMS. The rotational crop tolerance includes residues of sulfentrazone and its major metabolites, HMS and... 

Dacthal is a widely used pre-emergent herbicide that is applied to many crops for the control of annual weeds. Dacthal is typically applied to agricultural soils at 6-14kg ha [214], In the soil environment, Dacthal transforms to mono- and diacid-metabolites that are more water soluble than the parent herbicide [215-217]. In eastern Oregon, where Dacthal is applied to onions, the diacid metabolite is the principal form of Dacthal detected in groundwater obtained from domestic wells [218, 219],... 

One of the major problems in rice production is grass control. Various grasses compete with rice and drastically reduce yields. Results of preliminary experiments in Venezuela (9) indicate that rice yields may be increased by the application of dinitrophenol as a pre-emergence herbicide, even though rice stands are reduced by this chemical. Additional research is needed in this field, as the possibility exists... 

Uses Pre-emergence herbicide used in soil to control germinating broadleaf grasses and weeds in crops such as apples, cotton, grapes, pears, pineapples, and alfalfa sugar cane flowering depressant. 

Pre-emergence herbicides are applied pre-weed emergence and this will usually mean pre-crop emergence as well. Such compounds are taken up underground by the roots or hypocotyls of the weed. It is important for such compounds to possess some water solubility, in order that they become available to the germinating weed, but not so much that they are leached away from the weed germination zone. They must also be relatively persistent in the soil so that weeds that germinate over a period of time are all controlled. 

Isosorbide or isomannide derivatives 168 O-alkylated with certain phenyl-and heteroaryl-methyl groups at the endo position are used as pre-emergence herbicides for grass culture.201... 

Fretz, T.A. (1974). Pre-emergent herbicide combinations for container-grown nursery stock. Ohio Agricculture Research and... 

The S-chloroallylthiocarbamates exist in cis and trans configurations, by virtue of their allyl moiety. Commercial mixtures of the isomers have been used extensively as pre-emergence herbicides in growing vegetable and grain (wheat, barley) crops. 

Uses as pre-emergence herbicide for the control of annual grasses and broadleaf weeds in chicory, cucumbers, endive, groundnuts, lettuce, lucerne, and other foliage crops. 

Chemical Name l-butyl-3-(3,4-dichlorophenyl)-l-methylurea N-butyl-N (3,4-dichloro-phenyl)-iV-methylurea Uses pre-emergence herbicide to control grasses and broadleaf weeds in peas, beans, lucerne, garlic, beets, cereals, strawberries, ornamentals and forestry. 

Uses selective pre-emergence herbicide to control annual grasses and broadleaf weeds in tomatoes, sugar beet, and tobacco. 

Synonym Albrass, Bexton, CIPA, CP 31393, Niticid, Propachlore, Prolex, Ramrod, Satecid Chemical Name 2-chloro-AL(l-methylethyl)-Af-phenylacetamide 2-chloro-V-isopropyl-acetanilide Uses selective pre-emergence herbicide to control most annual grasses and some broadleaf weeds in brassicas, corn, cotton, flax, leeks, maize, milo, onions, peas, roses, ornamental trees and shrubs, soybeans, and sugar cane. 

Uses pre-emergence herbicide to control many grass and broadleaf weeds. 

Uses insecticide/fungicide/herbicide control of termites as wood preservatives to protect against fungal rots and wood boring insects as a pre-harvest defoliant in cotton and also as a general pre-emergence herbicide. 

Dinitroaniline herbicides. Trifluralin (Treflan ), a 4-trifluoromethyl substituted 2,6-dinitroaniline derivative, was the first main fluorine-containing herbicide to be marketed, with 18,000 tons sold in 1982 in the United States alone [16]. Trifluralin, which was introduced in 1960 by Eli Lilly, is a pre-emergence herbicide used in soybean for the control of a variety of grass and broadleaf weeds [17]. It is prepared from the nitration of 4-chlorobenzotrifluoride, followed by nucleophilic displacement of chlorine with di-n-propyl amine (Fig. 3). Following the success of trifluralin, a number of related A/,A/-dialkyl 4-trifluoromethyl 2,6-dinitroaniline herbicides were later introduced [18]. 

X (Disinfection by-product) intermediate or reagent in the synthesis of a variety of chemicals pre-emergence herbicides 111,3511,3512, 3529, 354... 

Structure-Activity Correlations for Meta-and Para-Substituted Trifluoromethane-sulfonanilide Pre-Emergence Herbicides... 

Table I. Pre-Emergence Herbicidal Activity of Substituted Trifluoromethane Sulfonanilides (5)a...

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