Fyndium
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Synthetic procedures in research papers?
In general, how elaborate are the synthetic procedures stated in research papers? Are they just general layouts of mols reacted and treated and yields
and purities GC'd, or could they be used as a viable source for actual replicable synthesis run?
I've faced a few instances that a synthesis was much more vague in research paper and the same procedure in a forum was much more detailed and
contained significant details. The issue with forum presentations are missing or mixed details, writing errors and unnecessary thinkering which should
have been added in the notes preferably and sometimes they need to be transliterated with pre-known chemistry knowledge to understand what the actual
reaction mechanism is and how it could possibly be tweaked.
For example, one research paper does not mention anything about cooling the reaction in an ice bath, and it constantly achieves almost quantitative
yields. Another example is a reaction that is instructed to stir for 1 hour, and gives less than 50% of the yield while research paper asks for 24
hour stir run with exact reaction kinetics.
[Edited on 22-11-2020 by Fyndium]
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RedDwarf
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I find most syntheses in research papers are frustratingly vague, often skipping steps and omitting reaction or separation conditions.
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Bezaleel
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I think that there are huge differences between one article and another. Some authors are just more explicit than others.
When amateur chemists want to synthesise something they are usually interested in the end product and its yield, but less interested in studying the
kinetics or testing bond models etc. So naturally they will elaborate more on the reaction conditions.
One article where I had almost no yield was due to concentrations not being mentioned. This was about an iodoplumbate complex. I could have known
though, because the equilibrium PbI2 + I- <--> [PbI3]- lies quite far to the left, so only if you work with high I- concentration, there will be
any iodoplumbate in solution. Logically, if you add a concentrated [PbI3]- solution to a dilute solution of something else, most of the [PbI3]- will
precipitate PbI2 and no complexation with [PbI3]- will take place. So knowledge of the equilibrium constant is the key here to a successful synthesis.
I guess it's not mentioned, because the reader is supposed to be familiar with the related chemistry.
But I must say that in the literature post, say, 1990 often too little information is given to get a good idea of how to do the synthesis.
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DraconicAcid
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Most synthetic procedures are written by grad students who have done the reaction a dozen times, and think everything is obvious.
That being said, it does vary from author to author. There was one guy (R Eisenberg) who had a research area very close to the one I did my thesis
work with, so we were constantly referencing his papers and attempting to duplicate his vague syntheses. We often complained about the "Eisenberg
Uncertainty Principle".
I wasted months trying to make a compound that he said was made "by reacting compound A with excess methylmagnesium bromide in THF". This was a
communication, so the lack of detail wasn't surprising, but when he published the full paper, he simply said "the title compound was prepared
according to reference 1", where reference 1 was the vague-as-all-crap communication.
[Edited on 23-11-2020 by DraconicAcid]
Please remember: "Filtrate" is not a verb.
Write up your lab reports the way your instructor wants them, not the way your ex-instructor wants them.
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AvBaeyer
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I agree that much of the experimental detail that is published these days is often vague or incomplete especially when compared to full papers
published prior to say 1990. I believe that there are two reasons for this. First is that much experimental detail is now shifted from papers to
supplemental material which is often difficult to get. The second, and I think more important reason, is that reviewers spend little time reading and
thinking about the experimental details in papers. That is too bad because much is lost. When I was reviewing for various journals I spent a good deal
of time on the experimental parts looking for missing details and inconsistencies. I have heard from colleagues still active that they are so
inundated with submissions that they spend little time on the experimentals - too bad as we all lose.
AvB
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