Benzimidazole oxidative degradation

Oxidation is, of course, the dominant reaction. For example, vaporized trifluralin ( a, a, < -trifluoro-2,6-dinitro-ll,ll-dipropyl-p-toluidine) was demethylated (Figure 7) (26), and its atmospheric half-life was found to be 8 minutes (27). However, the reaction occurred to a small extent even at night, and oxidation by ozone was implicated. In fact, there is evidence (28) that parathion photooxidation actually required the presence of ozone or other highly reactive oxidants. Degradation not requiring external reagents also may proceed rapidly trifluralin was cyclized to a substituted benzimidazole (11, 26), and dieldrin again formed photodieldrin (29). 

In proving the structure of the anhydro compound, Huebner, Lohmar, Dimler, Moore, and Link22 established first the presence of the benzimidazole moiety through its ultraviolet absorption spectrum and through its oxidative degradation by permanganate to 2-benzimidazole-... 

C for about 1 h. Poly benzimidazole adhesives have a higher temperature ceiling than polyimide formulations but are markedly susceptible to oxidative degradation above 260 °C. The relationships between low-temperature performance and the structure and formulation of the adhesive have also been considered [78,79], and the polyurethane adhesives are particularly good at very low test temperatures. 

Vigorous oxidation (e.g., with KMn04) usually degrades fused benzene rings in preference to many azole rings, especially under acidic conditions. Thus, benzimidazoles are oxidized by chromic acid or 30% hydrogen peroxide to imidazole-4,5-dicarboxylic acid, and 2,1,3-benzothiadiazole is oxidized by ozone or potassium permanganate to the dicarboxylic acid 553. 

Diethofencarb can be used against benzimidazole-resistant strains of Botrytis spp. It also inhibits mitosis. It is quickly degraded in soil and in animals through oxidation of the 4-ethoxy group. 

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