Colorimetric Determination of Carboxylic Acid Derivatives as Hydroxamic Acids

来自 ACS

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Aqueous alkaline hydroxylamine is widely used to form hydroxamic acids which may be estimated by their color reaction with ferric ion, in the analytical determination of carboxylic acid derivatives. This study determined the influence of substituents on the ease of hydroxamic acid formation by monocarboxylic acid derivatives. The esters tested required 2 to 120 minutes for maximum hydroxamic acid formation. The data show a correlation beween structure and rate of hydroxamic acid formation. Bulky and electron-donating groups inhibit hydroxamic acid formation by substituted benzoic acid esters. Replacement of the hydrogen atoms of formamide by a methyl or phenyl group results in decreased rate of hydroxamic acid formation. In setting up the conditions for the determination of α-hydroxy, α-amino, and α-chloro aliphatic esters as hydroxamic acids, the hypochromic effect of these substituents must be considered.

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When tomatoes were planted in steamed soil inoculated with spores of Didymella lycopersici Kleb., a large proportion became infected but very few became infected in unsteamed soil similarly inoculated. In soil treated with formalin and subsequently inoculated the number of diseased plants was about half that in steamed soil. Reinfecting steamed soil with soil micro-organisms before inoculation with D. lycopersici reduced the amount of disease. Covering steamed soil with a layer of maiden loam filtered out a large proportion of D. lycopersici spores applied in water suspension and reduced the amount of disease. Addition of stable manure either before or after steaming did not affect the number of diseased plants Steamed soil remained susceptible to infection by D. lycopersici for 4 months