guy - 2-8-2007 at 11:19
My aim goes something like:
salicylic acid ---> salicylamide --hofmann reaction--> 2-aminophenol
So step 1, conversion to the amide. What is the best way, decomposition of ammonium salt or addition of ammonia to the ester?
And step 2, can hypochlorite be used effectively as hypobromite for the Hofmann rearrangement?
garage chemist - 2-8-2007 at 11:54
The best way to the amide is conversion to the acyl chloride and reaction with aqueous ammonia.
As you probably dont have access to SOCl2, the next best method would be melting salicylic acid with urea and H3PO4 catalyst as I have described in
the Benzamide thread.
The Hoffmann degradation needs a hypochlorite of exactly known molar amount, and also a lot of NaOH in addition to the hypochlorite since the pH needs
to stay at 14 all the time.
And 2-aminophenol is likely susceptible to oxidation by air in the alkaline solution.
I would go a different route, via mononitration of phenol, separation of the isomers by steam distillation (see Organikum) and reduction with Fe/HCl.
So convert your salicylic acid to phenol (remember that the thermal decarboxylation makes phenyl salicylate, which has to be hydrolysed and separated
by the difference in acid strength of phenol and SA) and nitrate it with 40% aqueous HNO3 (no H2SO4, and no nitrate/H2SO4!).
guy - 7-8-2007 at 21:24
OK after some time I have decided to try the nitration. But can I ask why I cant use KNO3 and H2SO4?
armo - 9-8-2007 at 15:36
The best way to get 2-aminophenol is hydrogenation from 2-nitrophenol using acetic anhydride as solvent. You will end up with the corresponding
acetamide that ca be hydrolized and use as needed. 2-aminophenol realy oxidizes very fast.
good luke
armo
guy - 11-8-2007 at 13:59
A few questions:
I am going to prepare the phenol by NaOH + sodium salicylate. Should I bother separating the carbonate and phenol? Doesn't phenol get hard to
crystallize when it is mixed with water?
Also I only have 29% HCl. Is this ok for reduction of nitrophenol?
[Edited on 8/11/2007 by guy]