4-Aminophenol
{{Chembox
|Watchedfields = changed
|verifiedrevid = 477220971
|ImageFileL1 = p-Aminophenol.svg
|ImageSizeL1 = 70
|ImageAltL1 = Skeletal formula of 4-aminophenol
|ImageFileR1 = 4-Aminophenol3d.png
|ImageSizeR1 = 120
|ImageAltR1 = Space-filling model of the 4-aminophenol molecule
|PIN = 4-Aminophenol{{cite book | title = Nomenclature of Organic Chemistry : IUPAC Recommendations and Preferred Names 2013 (Blue Book) | publisher = The Royal Society of Chemistry | date = 2014 | location = Cambridge | page = 690 | doi = 10.1039/9781849733069-FP001 | isbn = 978-0-85404-182-4}}
| OtherNames = {{Unbulleted list
| p-Aminophenol
| para-Aminophenol
}}
|Section1={{Chembox Identifiers
|Abbreviations =
|ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
|ChemSpiderID = 392
|PubChem = 403
|UNII_Ref = {{fdacite|correct|FDA}}
|UNII = R7P8FRP05V
|InChIKey = PLIKAWJENQZMHA-UHFFFAOYAD
|SMILES1 = c1cc(ccc1N)O
|ChEMBL_Ref = {{ebicite|correct|EBI}}
|ChEMBL = 1142
|Gmelin = 2926
|Beilstein = 385836
|UNNumber = 2512
|StdInChI_Ref = {{stdinchicite|correct|chemspider}}
|StdInChI = 1S/C6H7NO/c7-5-1-3-6(8)4-2-5/h1-4,8H,7H2
|StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}
|StdInChIKey = PLIKAWJENQZMHA-UHFFFAOYSA-N
|CASNo_Ref = {{cascite|correct|CAS}}
|CASNo = 123-30-8
|EINECS = 204-616-2
|SMILES = Oc1ccc(N)cc1
|InChI = 1/C6H7NO/c7-5-1-3-6(8)4-2-5/h1-4,8H,7H2
|MeSHName = Aminophenols
|ChEBI_Ref = {{ebicite|correct|EBI}}
|ChEBI = 17602
|KEGG_Ref = {{keggcite|correct|kegg}}
|KEGG = C02372
}}
|Section2={{Chembox Properties
|C=6
|H=7
|N=1
|O=1
|Appearance = Colorless to reddish-yellow crystals
|Density = 1.13 g/cm3
|MeltingPtC = 187.5
|MeltingPt_notes =
|BoilingPtC = 284
|BoilingPt_notes =
|Solubility = 1.5 g/100 mL
|SolubleOther = {{bulletedlist|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}}
|pKa = {{Unbulleted list
| 5.48 (amino; H2O)
| 10.30 (phenol; H2O){{cite book | editor= Haynes, William M. | year = 2016 | title = CRC Handbook of Chemistry and Physics | edition = 97th | publisher = CRC Press | isbn = 978-1498754286 | pages=5–89 | title-link = CRC Handbook of Chemistry and Physics }}
}}
| LogP = 0.04
}}
|Section3={{Chembox Structure
| CrystalStruct = orthorhombic
}}
|Section4={{Chembox Thermochemistry
| DeltaHf = −190.6 kJ/mol
}}
|Section7={{Chembox Hazards
|ExternalSDS =
|NFPA-H = 2
|NFPA-F = 1
|NFPA-R = 0
|NFPA-S = -
|GHSPictograms = {{GHS07}}{{GHS08}}{{GHS09}}
|GHSSignalWord = Warning
|HPhrases = {{H-phrases|302|332|341|410}}
|PPhrases = {{P-phrases|201|202|261|264|270|271|273|281|301+312|304+312|304+340|308+313|312|330|391|405|501}}
|FlashPtC = 195
|FlashPt_notes = (cc)
|LD50 = 671 mg/kg
}}
|Section8={{Chembox Related
|OtherFunction = 2-Aminophenol
3-Aminophenol
|OtherFunction_label = aminophenols
|OtherCompounds = Aniline
Phenol
}}
}}
4-Aminophenol (or para-aminophenol or p-aminophenol) is an organic compound with the formula H2NC6H4OH. Typically available as a white powder,CRC Handbook of Chemistry and Physics 65th Ed. 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.
__TOC__
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).Mitchell, S.C. & Waring, R.H. "Aminophenols." In Ullmann's Encyclopedia of Industrial Chemistry; 2002 Wiley-VCH, {{doi|10.1002/14356007.a02_099}}
: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.{{citation|journal=Journal of Applied Electrochemistry|volume=32|pages=217–223|year=2002|publisher=Kluwer Academic Publishers|title=Electroreduction of nitrobenzene to p-aminophenol using voltammetric and semipilot scale preparative electrolysis techniques |first1=K. |last1=Polat |first2=M.L. |last2=Aksu |first3=A.T. |last3=Pekel |issue=2 |doi=10.1023/A:1014725116051|s2cid=54499902 }}
= 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. {{Cite patent|number=US2998450A|title=Process of preparing nu-acetyl-p-amino phenol|gdate=1961-08-29|invent1=Godfrey|invent2=De|inventor1-first=Wilbert|inventor2-first=Angelis John|url=https://patents.google.com/patent/US2998450A/en}}{{Cite journal |last=Bellamy |first=F. D. |last2=Ou |first2=K. |date=1984-01-01 |title=Selective reduction of aromatic nitro compounds with stannous chloride in non acidic and non aqueous medium |url=https://www.sciencedirect.com/science/article/pii/S0040403901800411 |journal=Tetrahedron Letters |language=en |volume=25 |issue=8 |pages=839–842 |doi=10.1016/S0040-4039(01)80041-1 |issn=0040-4039|url-access=subscription }}
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:{{cite book |author =Ellis, Frank |title=Paracetamol: a curriculum resource |publisher=Royal Society of Chemistry |location=Cambridge |year=2002 |isbn=0-85404-375-6 }}{{cite book|author = Anthony S. Travis|year = 2007|chapter = Manufacture and uses of the anilines: A vast array of processes and products|editor = Zvi Rappoport|title = The chemistry of Anilines Part 1|url = https://archive.org/details/chemistryaniline01rapp_644|url-access = limited|publisher = Wiley|isbn = 978-0-470-87171-3|page = [https://archive.org/details/chemistryaniline01rapp_644/page/n784 764]}}{{Ullmann | title = Analgesics and Antipyretics | author = Elmar Friderichs |author2=Thomas Christoph |author3=Helmut Buschmann | doi = 10.1002/14356007.a02_269.pub2}}
:File:Synthesis of paracetamol from phenol.png
It is a precursor to amodiaquine, mesalazine, AM404, parapropamol, B-86810 & B-87836 (cf. {{Cite patent|country=WO|number=2001042204}}).
4-Aminophenol converts readily to the diazonium salt.{{cite journal |author=F. B. Dains, Floyd Eberly|doi=10.15227/orgsyn.015.0039|title=p-Iodophenol |journal=Organic Syntheses |year=1935 |volume=15 |page=39 }}