Cooper_Panda
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Scaling Up
I can't seem to formulate my question exactly, but I am struggling with understanding how a paper is scaling up a process they are referencing in
another paper performing a reaction on a much smaller scale. I suspect I will have to do multiple batches at some point, but not really sure how to
rationalize the batch sizes. Paper A is working on a larger scale than I think I should, but it's not out of the question that I might do that. Paper
B is working on a smaller scale than I'd like, but I'm not sure how to bridge the gap. Maybe I should just start at the scale of paper B?
Paper A describes the general method of transforming 1 into 3 via the two step process as in Paper B, with a few modifications. In paper A they
started with 175mmol of 1 and ended with 133mmol of 3, an overall 75% yield, no further details are given.
Paper B describes transforming 2.57 mmol of 1 to 2.10 mmol of 2 (83%). Then, in the next step, transforms 14.08 mmol of 2 to 12.2 mmol of 3 (87%) for
an overall yield of 72%.
So it seems that the researchers in paper B repeated the first step 5-6 times and the second step once. In order to follow this procedure on the same
scale, the researchers of Paper A would have to perform step 2 about 10 times and step 1 about 50 times.
I doubt they did that. I suspect my issue is just not intuitively knowing how to scale reactions like this up. Which quantities I need to scale up
proportionally (stoichiometric reactants) seem fairly obivous, but reagents that are used in excess, and solvents, seem to take on absurd values when
you scale them up too much.
I have attached a PDF with the sources and relevant sections of the papers. The first part is paper A the second part is paper B
[Edited on 29-7-2021 by Cooper_Panda]
[Edited on 29-7-2021 by Cooper_Panda]
Attachment: Cyanostar Synthesis Procedure clean.pdf (418kB)
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Texium
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Generally solvents used for extraction are not scaled up proportionately. The same amount, or potentially just a slightly larger amount, would
probably be just fine. Reagents used in stoichiometric amounts must of course be scaled up accordingly, as you stated. Usually it’s also best to
keep the concentration of the reaction mixture the same when scaling up, because sometimes running a reaction at a different concentration will allow
for competing side reactions to become more favorable. Knowing when this is relevant comes from a combination of intuition and trial-and-error.
I wouldn’t assume that the authors of these papers repeated reactions absurd amounts of times. It may be that they had a higher yield on the first,
smaller scale reaction, and decided to report those results instead of the second, larger scale run that they did, even if they used the product from
that second run in the next reaction that they’re reporting. Typically you only report the most successful run of any particular reaction for
publication.
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Cooper_Panda
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Thanks so much for your response, that's very helpful!
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