Sciencemadness Discussion Board

Sulfonation of Phenol

JawadWalker - 25-7-2016 at 05:21

Hello people of the internet, I am trying to sulfonate phenol into ORTHO-phonolsufonic acid.

The reaction is C6H6O + H2SO4 = C6H6O4S + H2O.

The ortho isomer is produced if the temperature is kept under 25 degrees celsius.

How long does the reaction take to complete (the sulfonation of phenol takes about 4 hours), how would I remove the unreacted sulfuric acid (I was thinking of reacting it with something and vacuum filtering the resulting precipitate out), and is it possible to separate the para isomer (if any forms) (maybe using a solvent that only one of the isomers is soluble in). Thank you :)

Dr.Bob - 25-7-2016 at 07:15

Most organic reactions are ended by simply diluting the reaction in water, adjusting the pH, doing an extraction of the product into an organic solvent, and then combining the organics and washing with various pH aqueous to remove any residual byproducts. If you dump the reaction mixture into water, it will be very acidic, which should allow the organic acid to be extracted into organic, while the sulfuric acid would stay mostly in the water. After several extractions, you combine the organics and wash it with water once or twice to remove any traces of sulfuric acid left.

As for purifying the product, you can try to recrystallize the product to purity, that is the most likely method for any real scale of the reaction. Separating the isomers is best done by reading the literature to see what others have already figured out. Most people would rather use other people's hard work in research and writing it up than to rediscover how to do a known reaction, so bets to find an experimental writup and see how they purified it that to ask us to speculate on it.

JawadWalker - 25-7-2016 at 07:50

Thank you so much. I didn't think it would be as simple as just using water instead of another reaction. Do you know how long it will take? I googled it and the're really isn't much information specific to phenolsulfonic acid out there. I found one patent where the preparation of the para isomer was done by refluxing it for 6-8 hours, and another one where it was refluxed at 100 degrees celsius for 3 hours, then left at room temprature for a week, but nothing on the ortho isomer.

[Edited on 25-7-2016 by JawadWalker]

Waffles SS - 25-7-2016 at 09:09

Separation of isomer is not easy and i really could not find trustable method.

I usually separate sulfonic acid from acid by adding calcium carbonate.separate calcium sulfate by filtration and add Stoichiometry amount of sulfuric acid for converting sulfonic salt to acid and calcium sulfate
Quote:

Phenol 4-sulfonic acid:
Phenol (25 kg) and 96% sulfuric acid (28 kg) are heated to 50 deg C; then 1.25 kg additional sulfuric acid is added and the reaction mixture is heated at 110 deg C for 5-6 hours. Reaction water, together with about 5% of the phenol, is distilled off during this period. Yield 95%.
Gerhartz, W. (exec ed.).

Ullmann's Encyclopedia of Industrial Chemistry. 5th ed.Vol A1: Deerfield Beach, FL: VCH Publishers, 1985 to Present., p. VA3 528


I have experience on making para isomer


[Edited on 25-7-2016 by Waffles SS]

wg48 - 25-7-2016 at 09:27

I happened to read this

http://www.umich.edu/~chemh215/CHEM216/HonorsCup/HC%20250-IV...

The first part of the synthesis is for o-phonolsufonic acid.

JawadWalker - 25-7-2016 at 09:51

I read that. The first part is p-phenolsulfonic acid.

wg48 - 25-7-2016 at 10:00

Quote: Originally posted by JawadWalker  
I read that. The first part is p-phenolsulfonic acid.


Sorry I must have got my p's and o's mixed up

JawadWalker - 25-7-2016 at 10:10

It's okay :)

Lonelypegasus - 9-6-2017 at 03:18

Hello everyone!
this is a very useful page i've found on preparation of phonolsufonic acid! thank you for all the info everyone. I was wondering if anyone know any other method for purification/obtaining the final product other than the one in the link provided by wg48 ? the product is obtained in DCM in the file right?
any help would be appreciated.