Abstract
Isouron (1) and its isomer, 1-(3-tert-butylisoxazol-5-yl)-3, 3-dimethylurea (2), were determined by a colorimetric method with p-dimethylaminocinnamaldehyde (DACA) as the reagent. Compounds 1 and 2 were hydrolyzed to give 3-amino-5-tert-butylisoxazole (3) and 5-amino-3-tert-butylisoxazole (4), respectively, which were transformed into colored substances by reaction with DACA. The former colored product was a Schiff base but the latter product had a different absorption maximum from the corresponding Schiff base. The latter color reaction resulted in a bathochromic shift as compared with Schiff base formation at the 5-position. Traces of 2 (more than 0.05%) in 1 could be estimated precisely together with the quantitation of 1 by making use of this bathochromic effect.
