yield nope
ease some, you don't need NaOMe but look at Post 257912 (https://www.thevespiary.org/talk/index.php?topic=11282.msg25791200#msg25791200)
(Antoncho: "Alkali metal alkoxides: finally, OTC!", Novel Discourse)
> And it gives a method -however an inconveniant one-
> to seperate the product
hi uemura !
i've read in Post 263157 (https://www.thevespiary.org/talk/index.php?topic=7704.msg26315700#msg26315700)
(uemura: "Confirmation needed...", Chemistry Discourse) that you are also interested in the
vanillin chemistry.
the iodine path is better than it may seems at the first look:
> The resulting mixture, which contained a small amount
> of percipitate, was extracted continuously with ether
> for 16h.
there are 2 kinds of apparatus for continuous extraction:
(a) for solvents with lower density like ether, etc. ...
(b) for solvents with higher density like CH2Cl2, etc. ...
there was (b) at hand and an experienced senior chemist
told me, that in the time of the paper 1962, CH2Cl2 wasn't
that common as today. he recommended to try it with CHCL2.
BINGO ! this was the right choice. although i've
extracted 16h, the main part of the 5-hydroxyvanillin
came over in the beginning of the extraction. in the
CHCl2 flask was a impure yellow crust of the product
on the interior glass wall at the surface of the CH2Cl2.
and the CHCl2 was also light yello and the CH2Cl2 phase
in the extraction apparatus above became more and more
uncolored.
instead of recrystallization i worked up the
5-hydroxyvanillin chromatographically.
finally i've got a very satisfying yield and the mp
was even some degrees higher than in the paper.
if there wouldn't be such a special extraction apparatus
at hand i would simply try to extract it with a plain
sepfunnel 5-10 times or more if needed.
"Whatever there is to learn has to be learned the hard way."
Castaneda's teacher Don Juan Matus
Hi 3base,
there are 2 kinds of apparatus for continuous extraction:
uemura has neither one. :( Couldn't you instead evap solvents and do a soxleth extraction with CH2Cl2 on the mix of hydroxyvanillin and vanillin?
On the Organic Synthesis site a synthesis for syringaldehyd is described where they authors mention, the syringaldehyd is not very soluable in ether but in chloroform. So it should be in CH2Cl2 as well. But uemura doesn't understand is why the hydroxyvanillin and the syringaldehyde are good soluable in CH2Cl2/CHCl3 and vanillin is not? Just a fact you have to accept or has it some deeper reasons....
instead of recrystallization i worked up the
5-hydroxyvanillin chromatographically.
Uemura thinks you did column chromatography? How do you know what solvent you have to use and how do you know which fraction are the ones which contain the product?
Carpe Diem
rhodium: as far as i can remember, in both steps the yields were similar
to those in the paper and very satisfying particularly with regard to
that it was the first time doing these 2 reactions.
> Couldn't you instead evap solvents and do a soxleth extraction with CH2Cl2
uemura: good idea, it's worth a try ! durig extraction was a bigger blot
floating within the dark upper phase. i don't know what it was, but it got
something smaller at the end.
> column chromatography?
yes
> How do you know what solvent you have to use
the solvent-mix was inspired by hest's writeup
https://www.thevespiary.org/rhodium/Rhodium/chemistry/345-tmb.html (https://www.thevespiary.org/rhodium/Rhodium/chemistry/345-tmb.html)
i used a mix of EtOAc and CH2Cl2 (instead of CH2Cl2 it could also have been
petether, i'm not sure). i made some preliminary tests on TLC plates.
> and how do you know which fraction are the ones which contain the product?
also by stippling of TLC plates during the column chromatography.
the plates were developed simply in an iodine chamber.
hest: it was a small approach and to avoid loss of product i've done chromatography.
but for a bigger run recrystallization is definitively
the way to go.
> I'm sure you don't need the continuous extraction .
> Just extract 3 times with DCM.
for the extraction you need a solvent that isn't miscible with water.
i've tried: EtOAc, Et2O, CH2Cl2 and porbably chloroform and toluene, xylene
(not sure for the last 3), but 5-hydroxyvanillin wasn't reasonably soluble
in any of them. 3 times is insufficient in this case.
i think it should be soluble in dilute NaOH(aq), but 5-iodovanillin and
vanillin are soluble in alkali as well thus this wouldn't help to separate
them.
"Whatever there is to learn has to be learned the hard way."
Castaneda's teacher Don Juan Matus