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Mixture Extrapolation Approaches
Published in Keith R. Solomon, Theo C.M. Brock, Dick de Zwart, Scott D. Dyer, Leo Posthuma, Sean M. Richards, Hans Sanderson, Paul K. Sibley, Paul J. van den Brink, Extrapolation Practice for Ecotoxicological Effect Characterization of Chemicals, 2008
Theo C. M. Brock, Keith R. Solomon, René van Wijngaarden, Lorraine Maltby
Some responses, such as mortality, are irreversible. However, many sublethal responses may be reversible, such as the impact of the photosynthesis-inhibiting herbicide linuron on macrophytes (Snel et al. 1998). Linuron inhibits photosynthesis by disturbing electron transport in photosystem II. Table 6.2 presents the kinetics of photosynthesis inhibition when shoots of macrophytes are placed in water with 50 μg/L linuron, and subsequent recovery when placed in uncontaminated water. The EC50 values are remarkably similar between macrophytes, and half-life estimates for inhibition and recovery are less than 2 hours (Table 6.2). Except for Potamogetoncrispus, inhibition is more rapid than recovery; however, differences between species are relatively small. Not surprisingly, Chara chlobularis, with its small distance between chloroplasts and external medium, shows the most rapid kinetics. These data are in accordance with observations on other photosynthesis-inhibiting herbicides. For instance, recovery of algae from exposure to 50 μg/L of atrazine was nearly instantaneous, once the herbicide was removed from the overlying water (Klaine et al. 1997), and reversibility of the effect of metribuzin on the photosynthesis of periphyton communities could be demonstrated by placing periphyton in clean water (Gustavson et al. 2003).
Benign synthesis of unsymmetrical arylurea derivatives using 3-substituted dioxazolones as isocyanate surrogates
Published in Green Chemistry Letters and Reviews, 2020
Supakarn Chamni, Jinquan Zhang, Hongbin Zou
The optimized protocol was employed for the preparation of herbicides including linuron and daimuron. The one-gram scale syntheses were performed separately using functionalized 3-(3,4-dichlorophenyl)-1,4,2-dioxazol-5-one (1ab) and 3-(p-tolyl)-1,4,2-dioxazol-5-one (1j) as the isocyanate precursors in the presence of the corresponding amines, which were N,O-dimethylhydroxylamine (2ay) and 2-phenylpropan-2-amine (2az). After chromatographic purification, linuron (4) and daimuron (5) were obtained in excellent yields of 82% and 98%, respectively (Scheme 6).