Ureide solubility

Ureides (e.g., diuron, linuron) and triazines (e.g., atrazine, simazine, ametryne) all act as inhibitors of photosynthesis and are applied to soil (see Figure 14.1 for structures). They are toxic to seedling weeds, which they can absorb from the soil. Some of them (e.g., simazine) have very low water solubility and, consequently, are persistent and relatively immobile in soil (see Chapter 4, Section 4.3, which also mentions the question of depth selection when these soil-acting herbicides are used for selective weed control). 

When human urine was treated with ethyl ether, the majority of carbonyls were able to be detected in the aqueous fraction, with only a small amount in soluble in the organic (ethyl ether) phase. Further, when human urine was distilled by steam, a large amount of carbonyls fractionated into the non-volatile fraction. However a small but detectable amount remained in the volatile fraction. Importantly, it is generally recognized that most simple carbonyls are soluble in ethyl ether and volatiles. By contrast, ureides are insoluble in ethyl ether and not volatile. Base on these facts, we hypothesized that many carbonyls in urine might be derivatized in vivo with urea. Furthermore, these considerations imply that DNPH analysis of total urinary carbonyls may partly reflect hydrolysis of ureides as well as free dicabonyls. 

---