4-Aminophenol

4-Aminophenol

Names
Preferred IUPAC name 4-Aminophenol[1]
Other names p-Aminophenol para-Aminophenol
Identifiers
CAS Number	123-30-8^Y
3D model (JSmol)	Interactive image Interactive image
Beilstein Reference	385836
ChEBI	CHEBI:17602^Y
ChEMBL	ChEMBL1142^Y
ChemSpider	392^Y
ECHA InfoCard	100.004.198
EC Number	204-616-2
Gmelin Reference	2926
KEGG	C02372^Y
MeSH	Aminophenols
PubChem CID	403
UNII	R7P8FRP05V^Y
UN number	2512
CompTox Dashboard (EPA)	DTXSID3024499
InChI InChI=1S/C6H7NO/c7-5-1-3-6(8)4-2-5/h1-4,8H,7H2^Y Key: PLIKAWJENQZMHA-UHFFFAOYSA-N^Y InChI=1/C6H7NO/c7-5-1-3-6(8)4-2-5/h1-4,8H,7H2 Key: PLIKAWJENQZMHA-UHFFFAOYAD
SMILES Oc1ccc(N)cc1 c1cc(ccc1N)O
Properties
Chemical formula	C6H7NO
Molar mass	109.128 g·mol^−1
Appearance	Colorless to reddish-yellow crystals
Density	1.13 g/cm^3
Melting point	187.5 °C (369.5 °F; 460.6 K)
Boiling point	284 °C (543 °F; 557 K)
Solubility in water	1.5 g/100 mL
Solubility	Very soluble in dimethylsulfoxide Soluble in acetonitrile, ethyl acetate, and acetone Slightly soluble in toluene, diethyl ether, and ethanol Negligible solubility in benzene and chloroform
log P	0.04
Acidity (pKa)	5.48 (amino; H2O) 10.30 (phenol; H2O)[2]
Structure
Crystal structure	orthorhombic
Thermochemistry
Std enthalpy of formation (ΔfH^⦵298)	-190.6 kJ/mol
Hazards
GHS labelling:
Pictograms
Signal word	Warning
Hazard statements	H302, H332, H341, H410
Precautionary statements	P201, P202, P261, P264, P270, P271, P273, P281, P301+P312, P304+P312, P304+P340, P308+P313, P312, P330, P391, P405, P501
NFPA 704 (fire diamond)	2 1 0
Flash point	195 °C (383 °F; 468 K) (cc)
Lethal dose or concentration (LD, LC):
LD50 (median dose)	671 mg/kg
Related compounds
Related aminophenols	2-Aminophenol 3-Aminophenol
Related compounds	Aniline Phenol
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Y verify (what is ^YN ?) Infobox references

4-Aminophenol (or para-aminophenol or p-aminophenol) is an organic compound with the formula H₂NC₆H₄OH. Typically available as a white powder,[3] 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).[4]

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.[5]

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. [6][7]

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:[8][9][10]

It is a precursor to amodiaquine, mesalazine, AM404, parapropamol, B-86810 & B-87836 (c.f. WO 2001042204 ).

4-Aminophenol converts readily to the diazonium salt.[11]

References

1. Nomenclature of Organic Chemistry : IUPAC Recommendations and Preferred Names 2013 (Blue Book). Cambridge: The Royal Society of Chemistry. 2014. p. 690. doi:10.1039/9781849733069-FP001. ISBN 978-0-85404-182-4.
2. Haynes, William M., ed. (2016). CRC Handbook of Chemistry and Physics (97th ed.). CRC Press. pp. 5–89. ISBN 978-1498754286.
3. CRC Handbook of Chemistry and Physics 65th Ed.
4. Mitchell, S.C. & Waring, R.H. "Aminophenols." In Ullmann’s Encyclopedia of Industrial Chemistry; 2002 Wiley-VCH, doi:10.1002/14356007.a02_099
5. Polat, K.; Aksu, M.L.; Pekel, A.T. (2002), "Electroreduction of nitrobenzene to p-aminophenol using voltammetric and semipilot scale preparative electrolysis techniques", Journal of Applied Electrochemistry, 32 (2), Kluwer Academic Publishers: 217–223, doi:10.1023/A:1014725116051, S2CID 54499902
6. US2998450A, Godfrey, Wilbert & De, Angelis John, "Process of preparing nu-acetyl-p-amino phenol", issued 1961-08-29 
7. Bellamy, F. D.; Ou, K. (1984-01-01). "Selective reduction of aromatic nitro compounds with stannous chloride in non acidic and non aqueous medium". Tetrahedron Letters. 25 (8): 839–842. doi:10.1016/S0040-4039(01)80041-1. ISSN 0040-4039.
8. Ellis, Frank (2002). Paracetamol: a curriculum resource. Cambridge: Royal Society of Chemistry. ISBN 0-85404-375-6.
9. Anthony S. Travis (2007). "Manufacture and uses of the anilines: A vast array of processes and products". In Zvi Rappoport (ed.). The chemistry of Anilines Part 1. Wiley. p. 764. ISBN 978-0-470-87171-3.
10. Elmar Friderichs; Thomas Christoph; Helmut Buschmann. "Analgesics and Antipyretics". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a02_269.pub2. ISBN 978-3-527-30673-2.
11. F. B. Dains, Floyd Eberly (1935). "p-Iodophenol". Organic Syntheses. 15: 39. doi:10.15227/orgsyn.015.0039.