Aqua-regia - 28-7-2014 at 03:56
I am looking to methode purification of 2,6-dichloropyridine-4-carboxilic acid. The product should be white or tan. The route to get
2,6-dichloro-pyridine-4 carboxilic acid was treating citrazinic acid + POCl3 in autoclave. I got a brown powder. Mp. was near to lit. mp. I tried to
purify with meOH esterification, extracted with DCM and desdtillated in vacuo. The result: pruduct idecomposed in 5 hgmm instead boiling.
Any idea?
Cactuar - 28-7-2014 at 04:14
Maybe (if you work fast) you could wash the methyl esters with alkaline water (~pH 10). Then the mono- and di-phenolic compounds would stay in the
water phase. As I'm sure you know, this would in time cleave the ester as well so don't leave it in there for too long.
Boffis - 28-7-2014 at 06:52
Have you tried dissolving in a suitable solvent and treating with decolourizing carbon?
Aqua-regia - 28-7-2014 at 08:45
What kind of solvent suitable for it? In my opinion isonicotinic acid and their relevant does not dissolve none solvent. If you make the sodium
salt of this one, the water solution cannot filtrate cause the solution is very viscose.
UnintentionalChaos - 28-7-2014 at 09:03
When you did the methanol esterification, how much acid catalyst did you use? You need to use more than 1eq since the pyridine ties up the first eq.
Thermal decarboxylation on heating wouldn't surprise me.
Aqua-regia - 28-7-2014 at 09:17
The molar ratio:
substrate: 1m meOH 10 m H2SO4 4,45 m
Source: K. Winterfeld: Praktikum der organischen preparativen pharmazeutischen Chemie und Lehrbuch der organisch-chemischen Arzneimittelanalyse Verlag
Theodor Steinkopff Dresden und Leipzig 1965 (221. page.) This recipe was an esterification of isonicotinic acid with etOH.
unionised - 28-7-2014 at 10:23
According to this
http://books.google.co.uk/books?id=4ViVUQi7Z60C&pg=PA430...
you can recrystallize it from water
Mercedesbenzene - 28-7-2014 at 18:18
Column chromatography would most likely clean it up just fine. The ester might be easier to purify than the acid though due to the tendency for
carboxylic acids to trail on silica
Aqua-regia - 29-7-2014 at 09:00
Thank you all for your advise.
Unionised:
the thing not enough soluble in water for transkristallisation. Less 1g / lit /80 deg.
Mercedes:
I've more than 3 kg crude one. But idea is good.