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Author: Subject: Reaction kinetics - very long stirrings?
Fyndium
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[*] posted on 28-11-2020 at 12:18
Reaction kinetics - very long stirrings?


There were a synthesis which called for very long stirring - 48 hours - while another source stated that only 4 hours was enough. On the other hand, the long stir produced almost twice the yield. What could explain this kind of difference, except for time saving? Also, how could I determine a speed of reaction, what I need to know or learn?
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chemship1978
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[*] posted on 28-11-2020 at 12:24


I think this will prove useful to you https://en.wikipedia.org/wiki/Reaction_rate ;) The maths isn't that hard when considering simple processes.
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[*] posted on 28-11-2020 at 13:13


What synthesis was it?
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greenlight
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[*] posted on 28-11-2020 at 13:53


Basically put, stirring increases the chance of collisions between the reagents to produce the desired product. The molecules not only have to collide but also hit each other the right way (positive and negative charges) to interact and form the product. The longer you stir, the more collisions which results in higher yield.

Did the reaction require you to heat it (reflux)?

Temperature is another major factor. The higher the temperature, the more energy the molecules gain from the heat energy. This means they move at a faster speed proportional to the amount of heat applied.
Faster moving molecules means more collisions too.




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Fyndium
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[*] posted on 28-11-2020 at 13:56


It was just a common example of biphasic ester base hydrolysis with stirring at NTP. I don't believe a research paper has a misprint, but supposedly the rate of diminishing returns applies here. Just caught my eye because the time difference is 10-fold.
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