2.4- Dichlorophenoxyacetic acid structure

Bell, G.R. Photochemical degradation of 2,4-dichlorophenoxyacetic acid and structurally related compounds, Botan. Gaz., 118 133-136, 1956. 

Crystal structures of the related complexes tetraaquabi (2,4-dichlorophenoxyacetato)zmc(II) and diaquabi (2,4-dichlorophenoxyacetato)zinc(II) have been reported, in which two distinct metal environments occur. In the [Zn(H20)4L2] (HL = 2,4-dichlorophenoxyacetic acid) molecule (109) the metal is in an octahedral 06 environment, with a trans diaxial arrangement of... 

Despite the chemical diversity of the several hundred structures representing herbicidal activity, most reactions of herbicides fall within only a limited number of mechanistic types oxidation, reduction, nucleophilic displacements (such as hydrolysis), eliminations, and additions. "Herbicides", after all, are more-or-less ordinary chemicals, and their principal transformations in the environment are fundamentally no different from those in laboratory glassware. Figure 2 illustrates three typical examples which have received their share of classical laboratory study—the alkaline hydrolysis of a carboxylic ester (in this case, an ester of 2,4-dichlorophenoxyacetic acid, IX), the cycloaddition of an alcohol to an olefin (as in the acetylene, VI), and the 3-elimination of a dithiocarbamate which provides the usual synthetic route to an isothiocyanate (conversion of an N.N-dimethylcarbamic acid salt, XI, to methyl isothiocyanate). Allow the starting materials herbicidal action (which they have), give them names such as "2,4-D ester" or "pronamide" or "Vapam", and let soil form the walls of an outdoor reaction kettle the reactions and products remain the same. 

Synonyms 2,4,5-Trichlorophenol Chemical/Pharmaceutical/Other Class Chlorinated phenoxyacetic acids. A closely related compound is 2,4-D (2,4-dichlorophenoxyacetic acid) Chemical Structure ... 

Fig. la. Structures of plant hormones (a) Auxins Indole-3-acetic acid (lAA) Indoleacetonitrile (IAN) Phenylacetic acid (PAA) 2,4-dichlorophenoxyacetic acid (2,4-D) a-naphthalene acetic acid (NAA). 

Both the above agents may be classified as dichlorophenoxyacetic acid derivatives, similarly to indacrinone. However, comparison of the structures (Fig. 10) indicates that the center of chirality occurs at opposite ends in the molecules, which presumably results in the considerable degree of selectivity in the case of the enantiomers of the two benzofuran derivatives. 

Chemical structures of 2,4-dichlorophenoxyacetic acid (left), 2,4,5-trichlorophenoxyacetic acid (middle), and 2,3,7,8-tetrachlorodibenzodioxin (right) ... 

Many chemicals are applied to soil and crops to control insects, fungi, and weeds. The potential toxi-cities of these substances to humans, wildlife, and beneficial plants is of course a concern. A comprehensive coverage of the toxicological chemistry of agricultural pesticides is beyond the scope of this chapter. However, three important herbicides, 2,4-dichlorophenoxyacetic acid (2,4-D), atrazine, and glyphosate, are mentioned here their structural formulas are shown in Figure 10.4. Herbicides are mentioned because they are so widely used in agriculture and are spread over wide areas. 

Rates of hydrolysis may be influenced by the presence of dissolved organic carbon or sediment and the effect is determined by the structure of the compound and by the kinetics of its association with these components. For example, whereas the neutral hydrolysis of chlorpyrifos was unaffected by sorption to sediments, the rate of alkaline hydrolysis was considerably slower (Macalady and Wolf 1985) humic acid also reduced the rate of alkaline hydrolysis of 1-octyl 2,4-dichlorophenoxyacetate (Perdue and Wolfe 1982). Conversely, sediment sorption had no effect on the neutral hydrolysis of 4-chlorostilbene oxide although the rate below pH 5 where add hydrolysis dominates was reduced (Metwally and Wolfe 1990). 

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