Reaction profile, chiral phase

Figure 10. Chiral phase- transfer reaction profile.

The rate constants calculated by EF profiles (Equation (4.6)) are necessarily crude as several assumptions must hold the initial enantiomer composition is known, only a single stereoselective reaction is active, and the amount of time over which transformation takes place is known. These assumptions may not necessarily hold. For example, for reductive dechlorination of PCBs in sediments, it is possible for degradation to take place upstream followed by resuspension and redeposition elsewhere [156, 194]. The calculated k is an aggregate of all reactions, enantioselective or otherwise, involving the chemical in question. This includes degradation and formation reactions, so more than one reaction will confound results. Biotransformation may not follow first-order kinetics (e.g. no lag phase is modeled). The time period may be difficult to estimate for example, in the Lake Superior chiral PCB study, the organism s lifespan was used [198]. Likewise, in the Lake Hartwell sediment core PCB dechlorination study, it is likely that microbial activity stopped before the time periods selected [156]. However, it should be noted that currently all methods to estimate biotransformation rate constants in field studies are equally crude [156]. 

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