spanner
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After RXN how to extract aldehyde
i have just finished a Rxn of converting piperic acid to piperanol via CUSO4 redox can anyone help me in understanding how to now remove the aldeyde
from the reaction flask and purifying it
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solo
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You might try using the search engine , had you done so you might have found the thread that talks about that particular problem with the
reaction.......solo
http://www.sciencemadness.org/talk/viewthread.php?tid=4465
It's better to die on your feet, than live on your knees....Emiliano Zapata.
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spanner
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i did use the serch engine but if you read my question properly i was asking if anyone could help me to understand the process not just find the
process because last i looked it just tells you which process to use
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not_important
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| Quote: | Originally posted by spanner
i have just finished a Rxn of converting piperic acid to piperanol via CUSO4 redox can anyone help me in understanding how to now remove the aldeyde
from the reaction flask and purifying it |
That doesn't sound too much more than asking for cookbook information.
You should have been ready to run product isolation right away, aldehydes tend not to stick around when there's air and/or acids or bases around.
The write-up in the reference give says to filter, wash copper oxide with water, add wash water to filtrate - thus removing the reacted copper from
the mixture, then acidify and extract with ether to remove the organics from the reaction mix. Finally form the bisulfite addition product to isolate
the aldehyde from unreacted raw material and any carboxylic acid formed through over- or air oxydation. Bisulfite addition compounds are likely talked
about in other threads, as well as in many preparative org chem books - check those in the Library section.
The thread also had an entry saying | Quote: | | The CuO procedure does not work as published on substrates having no phenolic group in my experience. Maybe it is because you need the Phenolate anion
in solution which is oxidised by the CuO. |
so your yield may be poor to none.
So what is lacking in the write-up in that thread, that you wish was there? It's typical technical journal reporting, targetted at readers with
experience in the field. Lab textbooks are better for a 'how and why' explanation, teaching general technique although perhaps not using the exact
reaction you are interested in.
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chochu3
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sodium iodide I think can make a salt from an aldehyde. This may be found in Vogel's Pratical Chemistry.
\"Abiding in the midst of ignorance, thinking themselves wise and learned, fools go aimlessly hither and thither, like blind led by the blind.\" -
Katha Upanishad
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spanner
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thanks guys that was a lot more helpfull, i start uni next year so im sure this will only get easier for me as i gain more knowledge and i hope that i
can pass it on some day
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mick
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The sodium bisulphate addition compound was good for separating aldehydes.
mick
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not_important
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| Quote: | Originally posted by mick
The sodium bisulphate addition compound was good for separating aldehydes.
mick |
bisulfite, not bisulfate. I've mistyped that one myself.
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spanner
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Would it possible set up a distillation in stead of a reflux and distill the aldeyde off as its being formed then do a bisulfite purification after
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S.C. Wack
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The solubility of piperonal in water decreases dramatically with decreasing temperature. One may find that it crystallizes out if left undisturbed for
a while in the fridge if they actually have more than a smell. It sublimes easily, this is likely the best purification method for it.
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spanner
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I do seem to get that sweet marshmallow smell after the Rxn . I also am left with after the filtration step a clear yellow liquid, if i leave it for
a little while a white precipitate forms but has a high m.p so i assume that cant be the piperanol i think i may try the distillation and see if
distilling while the Rxn progresses ill let you know how it goes
any more help appreciated
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