I have just reduced 2-Chloro-4-Nitrobenzoic acid to he corresponding amine using alkaline Sodium dithionite.
After 3 hours reflux i lt the solution cool and filtered off the remainding salt (mixture of sodium sulphates). I am now left with a yellow liquid
which contains my product (hopefully).
Does somebody know a method i can use to seperate it? I preferably want to do an organic solvent extraction but the problem is when it is alkaline it
is a benzoic acid salt and when it is acidic it is the amine salt. Anybody have any ideas?UnintentionalChaos - 10-12-2010 at 00:41
Welcome to why ampholytes suck. See if you can find a lit value for it's isoelectric point and adjust pH accordingly, then extract.
Alternately, if you have some Ac2O or AcCl to piss away, make the acetanilide, which will kill the basicity. Acidify with say, acetic acid, and
extract.
[Edited on 12-10-10 by UnintentionalChaos]ScienceSquirrel - 10-12-2010 at 14:06
I would use a weak acid like acetic added dropwise to bring the pH down to around 6-7 eg slightly acidic.
I would then extract with a suitable solvent like diethyl ether and see what I would get.
It is a pretty weak base and acid and I doubt that the neutral form is very soluble in water so I reckon if you get it somewhere close to neutral it
will fall out and extract quite nicely.
Try it with a small sample to start and then do the bulk if it is looking good.garage chemist - 10-12-2010 at 14:38
I have made 2- and 4-aminobenzoic acid myself.
The acids precipitate from aqueous solution at the correct pH.
For me, it was sufficient to buffer the solution with acetate/acetic acid to obtain a good yield of the solid acid.
The aqueous solution should be boiled down to a suitably low volume before precipitation to reduce losses by the solubility of the acid even at the
correct pH.
Extraction is unnecessary, just filter the precipitate.
If I may ask, how did you prepare the 4-nitro-2-chlorobenzoic acid?
[Edited on 10-12-2010 by garage chemist]TheOrbit - 10-12-2010 at 21:18
dithonite form "Na amine bisulfite salt" with the reduced amine, u will need to adjust PH of the solution.
[Edited on 11-12-2010 by TheOrbit]Picric-A - 11-12-2010 at 02:19
If I may ask, how did you prepare the 4-nitro-2-chlorobenzoic acid?
[Edited on 10-12-2010 by garage chemist]
I started with 4-nitrotoluene, bought in from Acros. This was chlorinated with Cl2 and I2 as a catalyst. This gave a yield of 95% 2-chloro isomer, the
remainding 5% was removed by crystalisation.
The 2-Choro-4-Nitrotoluene was then oxidised by refluxing with KMnO4 in 50:50 water:t-butyl alcohol.
