4-Aminophenol

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4-Aminophenol
P-Aminophenol.svg 4-Aminophenol3d.png
Identifiers
CAS number 123-30-8 YesY
PubChem 403
ChemSpider 392 YesY
UNII R7P8FRP05V YesY
KEGG C02372 YesY
MeSH Aminophenols
ChEBI CHEBI:17602 YesY
ChEMBL CHEMBL1142 YesY
Jmol-3D images Image 1
Image 2
Properties
Molecular formula C6H7NO
Molar mass 109.126 g/mol
Appearance colorless to reddish-yellow crystals
Density 1.13 g/cm3
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 (25 °C)
Solubility very soluble in dimethylsulfoxide
soluble in acetonitrile
ethyl acetate
acetone
slightly soluble in toluene, diethyl ether, ethanol
negligible in benzene, chloroform
log P 0.04
Acidity (pKa) 5.48
Structure
Crystal structure orthorhombic
Thermochemistry
Std enthalpy of
formation
ΔfHo298
-190.6 kJ/mol
Hazards
EU Index 616-003-00-0
EU classification Carc. Cat. 2
Muta. Cat. 2
Repr. Cat. 3
Toxic (T)
R-phrases R20/21, R22, R40
R52, R54, R68
S-phrases S28, S36, S37
S60, S61
NFPA 704
Flammability code 1: Must be pre-heated before ignition can occur. Flash point over 93 °C (200 °F). E.g., canola oil Health code 2: Intense or continued but not chronic exposure could cause temporary incapacitation or possible residual injury. E.g., chloroform Reactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g., liquid nitrogen Special hazards (white): no codeNFPA 704 four-colored diamond
Flash point 195 °C (cc)
LD50 671 mg/kg
Related compounds
Related aminophenols 2-Aminophenol
3-Aminophenol
Related compounds Aniline
Phenol
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
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Infobox references

4-Aminophenol (or para-aminophenol or p-aminophenol) is the organic compound with the formula H2NC6H4OH. Typically available as a white powder,[1] it is commonly used as a developer in black-and-white film, marketed under the name Rodinal.

Reflecting its slight hydrophilic character, the white powder is moderately soluble in alcohols and can be recrystallised from hot water. In the presence of base, it oxidizes readily. The N-methyl and N,N-dimethyl derivatives are of commercial value.

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

Preparation[edit]

From phenol[edit]

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:[2]

C6H5NO2 + 2 H2 → C6H5NHOH + H2O
C6H5NHOH → HOC6H4NH2

From nitrobenzene[edit]

It can be produced from nitrobenzene by electrolytic conversion to phenylhydroxylamine, which spontaneously rearranges to 4-aminophenol.[3]

Uses[edit]

p-Aminophenol is a building block compound. Prominently, it is the final intermediate in the industrial synthesis of paracetamol. Treating p-aminophenol with acetic anhydride gives paracetamol:[4][5][6]

Synthesis of paracetamol from phenol.png

See also[edit]

  • Metol, the N-methyl derivative of p-aminophenol. In 1891 it replaced p-aminophenol as a developing agent for black & white photography. It is worthy of note that the most common synthesis processes for these two similar molecules differ nonetheless strongly.

References[edit]

  1. ^ CRC Handbook of Chemistry and Physics 65th Ed.
  2. ^ Mitchell, S.C. & Waring, R.H. “Aminophenols.” In Ullmann’s Encyclopedia of Industrial Chemistry; 2002 Wiley-VCH, doi:10.1002/14356007.a02_099
  3. ^ 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 (Kluwer Academic Publishers) 32: 217–223, doi:10.1023/A:1014725116051 
  4. ^ Ellis, Frank (2002). Paracetamol: a curriculum resource. Cambridge: Royal Society of Chemistry. ISBN 0-85404-375-6. 
  5. ^ Anthony S. Travis (2007). "Manufacture and uses of the anilines: A vast array of processes and products". In Zvi Rappoport. The chemistry of Anilines Part 1. Wiley. p. 764. ISBN 978-0-470-87171-3. 
  6. ^ Elmar Friderichs, Thomas Christoph, Helmut Buschmann (2005), "Analgesics and Antipyretics", Ullmann's Encyclopedia of Industrial Chemistry, Weinheim: Wiley-VCH, doi:10.1002/14356007.a02_269.pub2