US EPA

1143879 

Technical Report 

Photolysis of thiabendazole 

Watkins, DAM 

1976 

PESTAB/76/1875 

2 

2 

77-78; 1976 

PESTAB. A solution of thiabendazole in methanol was irradiated with a medium pressure Hanovia lamp (100 w) in a borosilicate glass apparatus. After 9 days, the peak at 302 nm had almost disappeared, and the pale yellow solution was concentrated in a rotary evaporator at 40DEG C to give a residual oil with a pH of 2.9 in aqueous solution. An aqueous solution of the residual oil was rotary evaporated at 40DEG C and treated with ammonia. Vacuum evaporation of this solution left a white solid identified as ammonium formate. The oil remained after removal of the precipitate. The filtrate was absorbed on alumina, added to an alumina column packed in light petroleum, and eluted with ether containing methanol to yield a fraction containing thiabendazole. Increasing the methanol content gave an initial fraction which yielded thiazole-4-carboxamide. The next fraction contained benzimidazole-2-carboxamide, elution of which with 25% methanol in ether yielded benzimidazole. Elution using pure methanol yielded thiazol-4-ylamidine and methyl thiazole-4-carboxylate. Further elution with increasing proportions of water in the methanol and 1% aqueous acetic acid yielded several unidentified fractions.