Abstract
A new colorimetric method for the determination of 5-methyl-3-isoxazolecarboxylic acid (MIA) and 5-phenyl-3-isoxazolecarboxylic acid (PIA) was established. This method is based on the decomposition of 5-substituted 3-isoxazolecarboxylic acids to the corresponding β-ketonitriles, followed by condensation with p-dimethylaminobenzaldehyde (DABA). The 5-carboxylic isomers caused no interference in the determination of MIA and PIA. Further applications of this method to perisoxal (II), N-[(dimethylamino) carbonyl]-5-methyl-3-isoxazolecarboxamide (III), and 3-(2-oxazolin-2-yl)-5-methylisoxazole (IV), by decomposition to the corresponding 5-substituted 3-isoxazolecarboxylic acids, followed by the color reaction with DABA, are described.
