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xuqinyao8239铁杆木虫 (著名写手)
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40金币求翻译一段话
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In monitoring a reaction it is important to know the reaction “kinetics.”When developing a process, “kinetics” refers to the rate of formation of the product and the amount of time needed to reach the desired process endpoint. The goals of knowing reaction kinetics are to complete processing efficiently and to limit degradation from overreaction. Periodic in-process monitoring generates the relevant kinetic data. Changing a parameter can have more than one effect on a process. For instance, pH is a critical factor in Schotten-Baumann reactions .Acid chlorides are readily hydrolyzed under strongly acidic or strongly basic conditions, so neutral conditions would minimize hydrolysis. Most primary and secondary amines exhibit pKas of 10–11.5, so that maximal reactivity would be found at high pH and poor reactivity would be expected under neutral conditions, where the amines would be predominantly protonated. Schotten-Baumann reactions are conducted under weakly basic conditions, pH 8–10, by balancing the hydrolysis of the acid chloride with the decreased reactivity of the amine. In many cases it is wise to examine changes to a process instead of rejecting such conditions on a theoretical bias. While optimizing a process the chemist usually learns its tolerance limits, the ranges of process parameters at which a process will operate successfully. Knowing these ranges is very helpful for guiding scale-up operations under suboptimal conditions, such as overcharging or undercharging components and exposing the reaction to temperatures above the optimal ranges. [ Last edited by xuqinyao8239 on 2010-1-11 at 15:01 ] |
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