Chloroanilic acid

It is used mainly for seed treatment against smut and diseases of vegetable seeds (Schoene et al., 1949). Its use as a foliage fungicide is limited because it decomposes partly by hydrolysis and partly photochemically (Burchfield and McNew, 1950), and sublimates in hot weather. Neither can it be used efficiently as a soil fungicide, because it also rapidly decomposes in the soil (Domsch, 1958). One of its degradation products is chloroanilic acid (21), 2,5-dichloro-3,6-dihydroxy-l,4-benzoquinone, which is also biologically inactive. The acute oral lDj chloranil for rats is 4000 mg/kg. 

Quinones such as alizarin redS (l,2-dihydroxyanthraquinone-3-sulfonate) and chloroanilic acid have long been used as analytical reagents for spectrophotometric determination of zirconium. These reagents form 1 1 complexes with Zr in strongly acidic solu-tions. The binding site in alizarin red S has been a matter of some controversy, " but it now appears, on the basis of voltametric and spectrophotometric evidence, that Zr coordinates to alizarin red S through the two adjacent phenolic oxygen atoms. ... 

Other types of organic reagent include those used to form colored ion-association systems, precipitants forming insoluble normal salts, and the insoluble salts of chloroanilic acid. 

The insoluble salts of chloroanilic acid may be exemplified by barium chloroanilate, which is still used for the automated monitoring of sulfur dioxide emissions, after conversion to sulfate with hydrogen peroxide. Solid barium chloroanilate reacts with solutions containing sulfate to form insoluble barium sulfate, thus releasing an equivalent concentration of chloroanilic acid, which is measured by ultraviolet spectrophotometry. 

Scheme 2.32 Formation of optically active a-hydroxyesters by reaction of acid chlorides with benzoylquinidine acting a catalytic chiral nucleophile, followed by [4+2]-cycloaddition with o-chloroanil.

Sulfate is usually determined by reaction with barimn chloroanilate at pH 4 to form barium sulfate and the acid chloranilate ion. At this pH value, the acid chloranilate ion is purple (530 nm). Another method is based on the formation of the FeSO/ cation (355 nm). An indirect method has been proposed based on the reduction of sulfate to sulfite with metallic sodimn. The product is then reacted with iron(ni) phenantroline to reduce iron(III) to iron(II), forming a red colored complex (515 nm). 

Hydroxy-5-sulfobenzoic acid, H-00538 Tetraphenylstibonium(l -1-), T-00122 Thorium chloroanilate, in D-00262... 

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