Bobross - 13-8-2009 at 12:00
Hello everyone, my first post here but I recognise plenty of names from a past life 
I was wondering if anyone had any knowledge of where to find detailed solubility data for 2,5-dimethoxybenzaldehyde. For the purposes of
recrystallisation. I've checked in all the usual places but nobody seems to have done any research in this area. If nobody knows of any data then
maybe I'll have to work some out myself. All that I know is it's apparently practically insoluble in water.
Thanks all.
kclo4 - 13-8-2009 at 12:19
What is your purpose of recrystallizing it? Is this in order to get it more pure? If so, wouldn't you also need to know the solubility of the possible
impurities? Considering 2,5-DMB doesn't apear to have much information on its solubility in other solvents, finding the solubility of the impurities
could be a daunting task.
You could go about means of finding other ways to purify it however.
Bobross - 13-8-2009 at 12:21
It is to purify the compound. I know it's currently around 97% pure, so the solubility of any impurities isn't terribly important, assuming (as I am)
that they are within an order of magnitude or so of the solubility of the DMB.
kclo4 - 13-8-2009 at 12:22
You wouldn't happen to know the compounds that make up the ~2% would you?
Bobross - 13-8-2009 at 12:25
Absolutely no idea, other than something brownish! The DMB is well within the purity I need for further reactions I want to do with it, it'd just be
nice to purify it as an exercise in pure practical chemistry
kclo4 - 13-8-2009 at 12:46
I'd attempt to just recrystallize it using hot ethanol. I would think that would at least allow large DMB crystals to grow and be more pure then
before. You'd lose some however, and I bet its not worth it.
Perhaps there could be a way of purifying it using a bisulfite adduct if the impurity isn't also an aldehyde or a ketone.
JohnWW - 13-8-2009 at 16:10
There may be data on its solubility in various solvents in either the Handbook of Chemistry & Physics, the International Critical tables, Lange's
Handbook Of Chemistry, or Perrys Chemical Engineers Handbook, or Albright's Chemical Engineering Handbook. Links for these are in References.
P.S. 594 results were found for this search string on Google:
"2,5-dimethoxybenzaldehyde" solubility
but there is very little numerical data about it of any sort in these results, and not much beyond the MSDS (safety data) sheets.
Here is some general info about the stuff, being usable as an intermediate for several good drugs, including 2,5-dimethoxyphenethylamine:
http://en.wikipedia.org/wiki/2,5-Dimethoxybenzaldehyde
http://www.sciencelab.com/page/S/PVAR/10411/SLD4453
http://www.drugs-forum.com/forum/showthread.php?t=58862
http://www.chemindustry.com/chemnames/2/2,5-Dimethoxybenzald...
It has figured before in previous threads here:
http://www.sciencemadness.org/talk/viewthread.php?tid=5178
http://www.sciencemadness.org/whisper/viewthread.php?tid=124...
http://sciencemadness.org/talk/viewthread.php?tid=5215
[Edited on 14-8-09 by JohnWW]
Bobross - 14-8-2009 at 08:26
Well I'll have a look round the references available here, but if I don't find anything then I guess my project for the start of next week is to push
back the frontiers of science and do the research myself
Cheers guys
Sandmeyer - 14-8-2009 at 14:17
Wouldn't it be easier (and more rewarding) to simply try some solvents on small amount of the aldehyde? It's not even an reaction, you can recover it.
Bobross - 14-8-2009 at 16:26
That's exactly what I intend to do next week.
flyingbanana - 14-8-2009 at 19:30
Ether.
Tetrahedron 62 (2006) 3550–3556.
Also for those interested, the above reference contains a procedure for 1,4-dimethoxybenzene --> 2,5-dimethoxybenzaldehyde via TiCl4 and
dichloromethylether, though that route is far from OTC.
Bobross - 15-8-2009 at 17:01
Excellent, thanks. I'll have to see if I can get access somewhere. If not at least I know to try ether!
Also, far from OTC that method may be, but I think OTC is a bit much to hope for for some things. A bit of social engineering usually helps 
[Edited on 16-8-2009 by Jhonbus]
solo - 15-8-2009 at 22:27
Reference Information
Synthesis of 5,8-dimethoxynaphtho[2,3-c]furan-4(9H)-one
Matthew J. Piggott* and Dieter Wege
Tetrahedron Volume 62, Issue 15, 10 April 2006, Pages 3550-3556
Abstract
Abstract
The synthesis of the title compound, which shares its skeleton with a number of biologically active natural products, is described. The key steps are
construction of a 3,4-disubstituted furan by a tandem Diels–Alder-retro-Diels–Alder reaction of an alkyne with 4-phenyloxazole, and an
intramolecular Friedel–Crafts acylation.
Attachment: Synthesis of 5,8-dimethoxynaphtho[2,3-c]furan-4(9H)-one .pdf (150kB)
This file has been downloaded 1227 times
sergide - 16-8-2009 at 18:39
It probably doesn't help but here (the first sentence), 100 g 2,5-dimethoxybenzaldehyde is dissolved in 220g nitromethane...
And here, 10g is dissolved in 50ml acetic acid.
[Edited on 17-8-2009 by sergide]
Bobross - 17-8-2009 at 02:59
Thanks for the ref, Solo.
I'll recrystallise a small portion from ether today (Since I know that works) and then measure some solubility in other solvents at 5 degrees, room
temp, and boiling. Some other solvent might work better than ether (and I don't especially enjoy the smell from having boiling ether around...) this
could be useful for other people later on.
[Edited on 17-8-2009 by Jhonbus]
Bobross - 18-8-2009 at 02:59
Looks like ether should be pretty much perfect for this, I could barely get 100mg/ml to dissolve at 20 degrees, but at boiling it took 45 grams in
less than 15ml. Just waiting for it to recrystallise now but it looks like I'll need some activated charcoal to remove this horrible brown impurity,
whatever it is.
I don't have the patience to try any other solvents at the moment, perhaps later. I hate the smell of ether but the smell of the 2,5-DMB is starting
to grow on me
[Edited on 18-8-2009 by Jhonbus]
Bobross - 18-8-2009 at 03:14
OK, the stuff is so soluble at boiling that all the ether is absorbed into the solids at room temp. It works TOO well!
Methyl.Magic - 18-8-2009 at 03:19
I personally recrystallised it from H2O/EtOH 50:50. It worked well, but be careful because the mp of DMB is low and when your solvent boils the DMB is
in the liquid form.
Bobross - 18-8-2009 at 03:25
I might give that a try, I don't think I can face more ether today! What sort of solubility did you find with your mix?
Bobross - 18-8-2009 at 06:06
EtOH/H2O is working much better, thanks.
Bobross - 18-8-2009 at 06:55
So, I've stumbled upon a really effective way to purify this compound, at least to remove the unknown impurity in the sample I had.
I started off dissolving about 50g of the impure (~97%) benzaldehyde in approx 200ml of boiling 70/30 EtOH/H2O.
What you want to aim for is to have not quite enough solvent so you get a layer of liquid benzaldehyde at the bottom of the vessel. You can adjust the
solubility quite easily by adding more water or ethanol.
When all of the benzaldehyde is dissolved you'll see a dark orange/brown solution of both the desired compound and the impurity. But as soon as you
get a small layer of liquid benzaldehyde at the bottom, the solution will clear up and you'll get a light yellow solution with some suspended solids.
It appears that the impurity is far more soluble in liquid benzaldehyde than it is in the ethanol solution.
Then simply separate the two layers with a sep funnel, the bottom one will be the super impure benzaldehyde, and the top one is your saturated
solution in alcohol.
If you pour the bottom layer into a dish it will immediately crystallise, and then you can recrystallise the benzaldehyde in the normal way from the
top layer. For me this yielded some lovely pure colourless crystals. As soon as they're dry I'll report the yield.
Klute - 19-8-2009 at 02:04
Try DCM/Pet ether, it works wonders for similar compounds, giving colorless needles with 2-methoxybenzaldehyde for example.