4-Aminophenol

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4-Aminophenol

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Template:Longitem	Template:Unbulleted list
Template:Longitem	385836
ChEBI	Template:Unbulleted list
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DrugBank	Template:Unbulleted list
EC Number	Template:Unbulleted list
Template:Longitem	2926
KEGG	Template:Unbulleted list
MeSH	Aminophenols
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RTECS number	Template:Unbulleted list
UN number	2512
Template:Longitem	Template:Chembox Elements/molecular formula
Molar mass	Template:Chem molar mass
Appearance	Colorless to reddish-yellow crystals
Density	1.13 g/cm3
Melting point	Template:Chembox CalcTemperatures
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log P	0.04
Acidity (pKa)	Template:Unbulleted list
Template:Longitem	orthorhombic
Template:Longitem	−190.6 kJ/mol
Template:Longitem	2-Aminophenol 3-Aminophenol
Template:Longitem	Aniline Phenol

4-Aminophenol (or para-aminophenol or p-aminophenol) is an organic compound with the formula H₂NC₆H₄OH. Typically available as a white powder, it is commonly used as a developer for black-and-white film, marketed under the name Rodinal.

Reflecting its slightly hydrophilic character, the white powder is moderately soluble in alcohols and can be recrystallized from hot water. In the presence of a base, it oxidizes readily. The methylated derivatives N-methylaminophenol and N,N-dimethylaminophenol are of commercial value.

The compound is one of three isomeric aminophenols, the other two being 2-aminophenol and 3-aminophenol.

Preparation

From phenol

It is produced from phenol by nitration followed by reduction with iron. Alternatively, the partial hydrogenation of nitrobenzene affords phenylhydroxylamine, which rearranges primarily to 4-aminophenol (Bamberger rearrangement).

C₆H₅NO₂ + 2 H₂ → C₆H₅NHOH + H₂O

C₆H₅NHOH → HOC₆H₄NH₂

From nitrobenzene

It can be produced from nitrobenzene by electrolytic conversion to phenylhydroxylamine, which spontaneously rearranges to 4-aminophenol.

From 4-nitrophenol

4-nitrophenol can be reduced through a variety of methods, to yield 4-aminophenol. One method involves hydrogenation over a Raney Nickel catalyst. A second method involves selective reduction of the nitro group by Tin(II) Chloride in anhydrous ethanol or ethyl ethanoate.

Uses

4-Aminophenol is a building block used in organic chemistry. Prominently, it is the final intermediate in the industrial synthesis of paracetamol. Treating 4-aminophenol with acetic anhydride gives paracetamol:

File:Synthesis of paracetamol from phenol.png

It is a precursor to amodiaquine, mesalazine, AM404, parapropamol, B-86810 & B-87836 (cf. Template:Citation/make link ).

4-Aminophenol converts readily to the diazonium salt.