Fantasma4500
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Selectively reacting methanol over ethanol?
so i just got onto an idea as in making ethyl salicylate, and i was wondering if i used just a small amount of salicylic acid, would it then decide to
react with methanol first and then leave the ethanol behind? im using denatured alcohol which contains maybe 5% methanol
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UC235
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No particular reason to think that methanol would have any substantial preference for reaction over ethanol, just whichever collision happens first.
5% methanol would be 5% methyl salicylate in the product.
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Fantasma4500
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aha, i guess organic chemistry really just does suck all the way through.
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Tsjerk
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Being able to design molecules and selectively make those with the right precursors indeed sucks....
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brubei
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molecular sieve 3A absorb water and methanol. (4A absorb ethanol and won't be efficient)
I'm French so excuse my language
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Tsjerk
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I'm pretty sure 3A sieves don't absorp methanol, that would make moonshiner's life very easy...
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Fantasma4500
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i guess anyone interested in truly seperating methanol from ethanol could pull an experiment on that, totally oblivious to specifications of 3A and
particle size of methanol and visocity and all that it should be possible to do like that, thanks for the idea.
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Dr.Bob
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Not sure for simple ester formation, but for some reactions, like methoxide verse ethoxide, the methoxide's smaller size provides almost 10 faster
reaction rate, so traces of ethanol in methanol cause little, but traces of methanol can react much faster than ethanol, so 5% of methanol (with an
excess of overall alcohol mix) could cause as much as 50% of the methoxide product. This is seen in biofuel, where making ethyl esters from oils is
much slower than methyl esters, so as to make using ethanol very tough for real production. And since ethanol is a relatively much larger molecule
than methanol, it takes more volume of ethanol than methanol for the same molar amount, thus limiting the maximum acheivable concentration of ethanol
compared to methanol. But even for simple esters, I am pretty confiudent than ethanol is somewhat slower reacting than methanol. But once you go
to longer chains, the differnce is much smaller, unless you add branching, like isopropanol or t-butanol, both of which would be even slower reacting
then ethanol.
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mackolol
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If you want to use mixture consisting 5% of methanol over pure methanol, It's not surprise to me that it won't work. It's the same as if you'd want to
precipitate sulfuric acid to calcium salt with tap water. It's only that you suck.
Damn man what do you think... If you want to perform a synthesis, good reagents are essential, don't be surprised when sometime a reagent doesn't work
because it is not at least 99% purity.
Organic chemistry is not some crafting in PC games, it is something way beyond, I'm now dealing with synthesis that was working every time for me and
now without any clear reason it fucks up all the time and it happened from day to day. So be prepared for this if you really want to achieve anything
in your lab...
[Edited on 27-6-2020 by mackolol]
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