chemx01 - 11-5-2013 at 23:54
I'm working on a synthesis of bitrex and I need to prepare lidocaine first, for this I need 2,6-dimethylaniline.
But the easiest route by reduction of m-nitroxylene isn't an option for me since i don't have pure m-xylene but only a mixture of isomers which are
quite hard to separate.
I was looking arount some articles and I found this:
http://www.tandfonline.com/doi/pdf/10.1080/00304946909458373...
But unfortunately i don't have acces to this article so if anyone would be so kind and provided it to me i'd be very grateful.
From what i read in the preview it seems quite complicated for such a small molcule, but it could be a fun synthesis.
If you have actually made 2,6-dimethylaniline or you have some idea how to make it i would be very happy.
paw_20 - 14-5-2013 at 10:52
I have a procedure (from Purification of Laboratory Chemicals, 6th Edition) for separating m-xylene if you're interested. I've never done it myself
mind you, and it's fairly involved.
Separation of nitration products
roXefeller - 17-9-2013 at 02:12
When I first saw that compound I also thought of a reduction of the nitro group. But you are right, the isomers would cause a problem. Like the
products of the nitration of toluene, it looks like the isomers of the nitration of xylene might be easier to separate
2-nitro-m-xylene bp 225oC
3-nitro-o-xylene bp 245oC
2-nitro-p-xylene bp 121oC (is this right?)
Then do a reduction of the purified 2-nitro-m-xylene. Do you think this might do the trick, or would there be other compounds present to muddle the
distillation?
sonogashira - 17-9-2013 at 12:31
There is an interesting paper for the reduction of 2,6-dimethylnitrobenzene in 95% yield using zinc in water/ammonium chloride.
Attachment: b008219h.pdf (99kB)
This file has been downloaded 1084 times
And nitration of xylenes in DCM, just for reference:
[Edited on 17-9-2013 by sonogashira]
Attachment: 0040403995021744.pdf (117kB)
This file has been downloaded 2754 times
Methyl.Magic - 17-9-2013 at 13:13
Your synthese will be a big problem because during the nitration the aimed product is not predominant but you should have something like 15 -20% I
guess. Regarding the statistic, you will have 33% of 2-6 isomer and 66% of 2-4 isomer. Because of the steric effect the isomer 2-4 is preferred but
not that much because the methyl is a small group. Thus you will get about 15%.
You can find a method of cristallisation by cooling based on the TLC method. If you have TLC aluminium plates you can develop a method of separation
first then i will help you finding a method of separation but I could be tricky if you dont have sillica.
sonogashira - 18-9-2013 at 08:11
In section 1.2.1 of this monograph (http://monographs.iarc.fr/ENG/Monographs/vol57/mono57-22.pdf) it states that:
"
2,6-Dimethylaniline is prepared by nitration of xylene and reduction, followed by
removal of the 2,4-isomer by formation of the acetate salt, removal of the 2,5-isomer by
formation of the hydrochloride salt, and recovery of the 2,6-isomer by sublimation.
"
The isomers are sometimes referred to as xylidines in patents, if it helps:
https://docs.google.com/viewer?url=patentimages.storage.goog...
References given by the Merck Index (nitro-xylene route):
JACS v.71, p.1362
JOC v.26, p.919
[Edited on 18-9-2013 by sonogashira]