Structures of herbicides

Molecular structure of herbicides in the Fenton s reaction system. 

The chemical structures of herbicides are shown in Figure 9.7. Herbicides containing secondary amino moieties such as Basagran and diuron are more... 

Briggs, G.G. (1969) Molecular structure of herbicides and their sorption by soils. Nature 223, 1288. 

Figure 3. Structures of herbicides that bind to the Qb site in PSII.

This paper illustrates how the principle of vinylogy may serve to direct attention to possible structural similarities in a large number of diverse structures of herbicides with similar activity and mode of action which might otherwise appear unlikely. Structural information such as this on various classes of PS II herbicides in conjunction with intuitive-empirical or computer oriented approaches should facilitate the design of new inhibitors. 

Fig.1 A General structure of herbicidal l-aryl-4-substituted-A -tetrazoline-5-ones 159, structure of fentrazamide (160) and l-aryl-4-(3-fluoropropyl)-A -tetrazoline-5-one 161 B A -tetrazoline-5-ones with insecticidal activity 162 (R = CH2COOEt) and 164 show high insecticidal activity against T. cinnabarinus, 163 (R = Et) shows insecticidal activity against A. medicagini [113-125]...

Fluorescence microscopy, autoradiography, and energy-dispersive X-ray analysis have been used to examine the retention and redistribution of pesticides of widely differing physicochemical properties applied as solutions of commercial formulations to leaves of differing surface characteristics. The fine structure of herbicide deposits has been studied using SEM with a secondary electron detector, and the information has been used to interpret uptake data. For example, the relatively low rate of absorption of maleic hydrazide (MH) by maize, recorded over a 72-h period, was related to the annular distribution of the a.i. in groups of fine crystals. ... 

On the other hand, the thiazole is also found in the structures of numerous pesticides, fungicides, herbicides, and nematocides. Association of thiazoles with other heterocycUc compounds has been widely used in this field. 

The herbicide tnflurahn is prepared by the following sequence of reactions Identify com pound A and deduce the structure of trifluralin... 

The commercial exploitation of our increased understanding of protein stmcture will not, of course, be restricted to the pharmaceutical industry. The industrial use of enzymes in the chemical industry, the development of new and more specific pesticides and herbicides, the modification of enzymes in order to change the composition of plant oils and plant carbohydrates are all examples of other commercial developments that depend, in part, on understanding the structure of particular proteins at high resolution. 

C21-0017. Shown below is a ball-and-stick model of the active ingredient in Roundup, a commercial herbicide. Draw the Lewis structure of Roundup and describe its functional groups. 

Sulfonylureas are the basis of a large group of herbicides. Cytochrome P450 enzymes in Streptomyces griseolus transform the sulfonylureas by hydroxylation (Omer et al. 1990) leaving the -SO2NHCONH- part of the structure unaltered (Harder et al. 1991). 

Then there are a number of pesticides, e.g. the phenolic herbicide dinoseb and the fungicide pentachlorophenol, whose speciation varies strongly in the environmental pH-range. For this reason, one has to consider the pwhen estimating their environmental fate. Structures of the compounds discussed in this section are depicted in Table 1, together with a listing of their pand octanol-water partition coefficients, Kow, of the neutral species (unless otherwise indicated). Typical basic pollutants include the industrial chemicals aniline and jV.jV-dimethylaniline. 

Paraquat (1,1 dimethyl, 4,4 bipyridyl) is a nonselective contact herbicide. It is used almost exclusively as a dichloride salt and usually is formulated to contain surfactants. Both its herbicidal and toxicological properties are dependent on the ability of the parent cation to undergo a single electron addition, to form a free radical that reacts with molecular oxygen to reform the cation and concomitantly produce a superoxide anion. This oxygen radical may directly or indirectly cause cell death. Diquat, l,T-ethylene-2,2 -dipyridylium, is a charged quaternary ammonium compound often found as the dibromide salt. The structure of diquat dibromide and that of the closely related herbicide paraquat can be seen in Fig. 4.5. 

Based on these and other compounds prepared in this series, several conclusions on the effect of structure on herbicidal activity can be drawn ... 

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