[ASQ]

Hello forum members,

I need your help.I tried reducing 4-nitrophenol to 4-aminophenol using hydrazine hydrate, Pd on Charcoal and ethanol as solvent. TLC showed completion of reaction.So I rotavaped the solvent. Added small amount of remaining reaction mixture to water to see if precipitation occurs. Unfortunately, no precipitates of product formed. This could be due to the fact that 4-aminophenol is soluble in water.

Can anyone suggest me a possible way to precipitate 4-aminophenol from that solution.
Looking forward
Thank you

[C-hemCards]

The first thing you should do is filter the reaction mixture through celite or other appropriate filter aid to remove the Pd/C. Do not filter only using filter paper, as the Pd will have some H2 on it and will set fire to the paper.

You could try precipitating the product directly from the ethanol by adding a suitable antisolvent, perhaps acetone, MTBE, or maybe hexanes/heptanes if you really wanted to push it.

Otherwise, I think removal of the ethanol, dissolution in something like dicholoromethane, filtration through a plug of silica gel and then concentration will give you relatively clean material. You could also do a proper column to get highly pure material.

[ASQ]

@C-hemCards

Thankyou for your advice.  I filtered Pd/C. and tried to precipitate product with Chloroform because the product is insoluble in chloroform.This didnt work either. I'll try out your suggestions.

Thank you.

[Dan]

I think at this stage it would be a good idea to get some data to determine whether or not the crude contains what you think it does (NMR, MS). You should also run a TLC of your crude against an authentic sample of 4-aminophenol.

The compound may not be soluble in chloroform, but it might be soluble in a chloroform/ethanol mixture. 

[C-hemCards]

Dan makes a great point. Plus, 4-amino phenol can oxidize rather quickly. It will make a nice deep red color when it does. If I remember correctly from my experience with this compound, it is very soluble in alcohols (I think I was using MeOH at the time).

BTW, I'm not sure why you chose to go with hydrazine, but if you have the option, hydrogen gas is infinitely more easy to deal with.

[dcunhana]

I have succesfully reduced a molecule that had nitro phenol as its moiety using the same reagents Pd/C and Hydrazine. For my work up there are two routes that I go.

1. Filter, Reduce filtrate to half volume and let cool down. If it crystalize good. If not I add little amount water(or insoluble solvent)  if it crystalize then good.

2. Filter. Add water and extract using Methylene chloride. Dry in MgSO4. Filter and the rotovap

I got most of my product using the first way. I hope that helps. GOod Luck

[clarkstill]

@C-hemCards

Thankyou for your advice.  I filtered Pd/C. and tried to precipitate product with Chloroform because the product is insoluble in chloroform.This didnt work either. I'll try out your suggestions.

Thank you.

Are you sure the product is insoluble in chloroform? I don't know for sure, but I'd imagine all that aromatic grease would help it dissolve in organic solvents...

If it's a phenol you could try an acid/base workup? I.e. dissolve the crude in aqueous base (e.g. hydroxide), wash with something organic to remove any organic soluble by-products, then acidify (carefully, not to protonate the aniline) and extract again to remove the neutral product?