(Stranger)
02-12-02 13:13
No 268713
(Rated as: excellent)
5-Iodovanillin
12.6g I2 was added in 4 portions during 30min to a rapidly stirred suspension of 7.5g vanillin in 200mL H2O containing 5g NaHCO3 and 10g KI. Stirring was continued for 3h and the mixture left overnight. The filtered product was wasched with dilute Na2S2O3 and H2O and dried at 45°C (11.8g, mp 175°C). Crystalised from EtOH(aq), it had mp 180°C.
Journal of the Chemical Society, 1958, Part III, 3740-3741, P.Smith
5-Hydroxyvanillin
2.8g 5-Iodovanillin, 1.6g hydrated CuSO4 and 76mL 4N NaOH were refluxed (105°) for 4.5h with continuous stirring under N2. After cooling to 60-70°, the mixture was filtered under suction and the residue washed with 3x10mL hot water. The alkaline solution was cooled to 10° and acidified to pH 3-4, by the dropwise addition of concentrated HCl. During this addition the mixture was stirred continuously and the tmperature maintained below 25°.
The resulting mixture, which contained a small amount of percipitate, was extracted continuously with ether for 16h. After being dried over anhydrous MgSO4, the ether was removed(60-65°) to leave 1.5g dark gray product. All but 0.10g was dissolved in hot benzene, from which, after concentration to 75mL, 1.15g 5-hydroxyvanillin crystallized, yield 68%, mp 128-129°. Recrystallization from benzene, with charcoaling, gave a chromatographically pure product, mp 133-134°; reported 132-134° by W.Bradley, R.Robinson and G.Schwarzenbach, J.Chem.Soc 793 (1930).
With the exception of traces of 5-hydroxyvanillin the mother liquors contained only vanillin as indicated by gas-liquid chromatography.
Paper Chromatography
5-Hydroxyvanillin, vanillin and 5-iodovanillin were separated by descending chromatography using Whatman No.1 paper and the solvent system of n-butanol saturated with 2% ammonia. A saturated solution 2,4-dinitrophenylhydrazine in 1N HCl was the spay reagent. For these compounds the Rf values were 0.38, 0.50 and 0.48 respectively.
Canadian Journal of Chemistry, Volume 40 (1962), 2175-2177, S.K.Banerjee, M.Manolopoulo and J.M.Pepper
"Whatever there is to learn has to be learned the hard way."
Don Juan Matus
(Hive Bee)
02-13-02 04:44
No 269066
vanillin > 5-Bromovanillin > 5-hydroxyvanillin
would be cheaper...is there any advantage in yield or ease?
(Hive Bee)
02-13-02 05:37
No 269081
yield nope
ease some, you don't need NaOMe but look at Post 257912 (Antoncho: "Alkali metal alkoxides: finally, OTC!", Novel Discourse)
(Hive Photographer)
02-14-02 03:37
No 269600
nice find 3base,
it's a bit different than the US patent. And it gives a method -however an inconveniant one- to seperate the product from the also produced vanillin.
Carpe Diem
(Stranger)
02-14-02 10:11
No 269702
> And it gives a method -however an inconveniant one-
> to seperate the product
hi uemura !
i've read in Post 263157 (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
(Chief Bee)
02-14-02 12:22
No 269740
3base: Very nice! What was your yields in the iodination and hydroxylation step, compared to the papers?
(Hive Photographer)
02-15-02 00:06
No 269922
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
(Hive Bee)
02-15-02 03:33
No 269953
I'm sure you don't need the continuous extraction . It's an industrial thing (patents :) Just extract 3 times with DCM.
The bromovaniline patent also sayes continuous extraction with toluene for 12 houers, but 3 times extracition works greath.
And for the cleanup, rextalice!! collum chrom is a dead end with more than a couple of grams. Try with the solvents used in the vaniline->bromo..(at Rhodiums site) I'm sure they works.
(Stranger)
02-16-02 05:18
No 270421
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
../rhodium /345-tmb
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