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8-Hydroxyquinoline

Names
Preferred IUPAC name Quinolin-8-ol
Other names 1-Azanaphthalene-8-ol, Fennosan H 30, Hydroxybenzopyridine, Oxybenzopyridine, Oxychinolin, Oxyquinoline, Phenopyridine, Quinophenol, Oxine, 8-Quinolinol
Identifiers
CAS Number	148-24-3
3D model (JSmol)	Interactive image
ChEBI	CHEBI:48981
ChEMBL	ChEMBL310555
ChemSpider	1847
ECHA InfoCard	100.005.193
KEGG	D05321
PubChem CID	1923
UNII	5UTX5635HP
CompTox Dashboard (EPA)	DTXSID5020730
InChI InChI=1S/C9H7NO/c11-8-5-1-3-7-4-2-6-10-9(7)8/h1-6,11HKey: MCJGNVYPOGVAJF-UHFFFAOYSA-N InChI=1/C9H7NO/c11-8-5-1-3-7-4-2-6-10-9(7)8/h1-6,11HKey: MCJGNVYPOGVAJF-UHFFFAOYAG
SMILES C1=CC2=C(C(=C1)O)N=CC=C2
Properties
Chemical formula	C9H7NO
Molar mass	145.16 g/mol
Appearance	White crystalline powder
Density	1.034 g/cm
Melting point	76 °C (169 °F; 349 K)
Boiling point	276 °C (529 °F; 549 K)
Pharmacology
ATC code	G01AC30 (WHO) A01AB07 (WHO) D08AH03 (WHO) R02AA14 (WHO)
Hazards
GHS labelling:
Pictograms
Signal word	Danger
Hazard statements	H301, H317, H318, H360D, H410
Precautionary statements	P202, P273, P280, P301+P310, P302+P352, P305+P351+P338
Safety data sheet (SDS)	External MSDS
Except where otherwise noted, data are given for materials in their standard state (at 25 °C , 100 kPa). Infobox references

8-Hydroxyquinoline (also known as oxine) is an organic compound derived from the heterocycle quinoline. A colorless solid, its conjugate base is a chelating agent, which is used for the quantitative determination of metal ions.

In aqueous solution 8-hydroxyquinoline has a pK_a value of ca. 9.9 It reacts with metal ions, losing the proton and forming 8-hydroxyquinolinato-chelate complexes.

The aluminium complex, is a common component of organic light-emitting diodes (OLEDs). Substituents on the quinoline ring affect the luminescence properties.

In its photo-induced excited-state, 8-hydroxyquinoline converts to zwitterionic isomers, in which the hydrogen atom is transferred from oxygen to nitrogen.

History

8-hydroxyquinoline was first obtained by Hugo Weidel and his student Albert Cobenzl in 1880. They decarboxylated so-called oxycinchoninic acid (from cinchonine) and characterized the resulting compound as melting at about 70°C. They identified that the hydroxy group is on the benzene ring (but not its particular place) and called the compound oxyquinoline and α-quinophenol.

In the following year more chemists found other ways to make the compound. Zdenko Hans Skraup discovered a way to synthesize substituted quinolines from substituted phenols and described three isomers of oxyquinoline, identifying the structure of 8-hydroxyquinoline. Otto Fischer [de] and his student Karl Bedall made the compound from a sulphonic acid independently at about the same time, but misidentified its structure.

By 1888 azo dyes were made from the compound.

In the 1920s insoluble chelates of 8-hydroxyquinoline were discovered.

This section needs expansion. You can help by adding to it. (December 2024)

Bioactivity

The complexes as well as the heterocycle itself exhibit antiseptic, disinfectant, and pesticide properties, functioning as a transcription inhibitor. Its solution in alcohol is used in liquid bandages. It once was of interest as an anti-cancer drug.

A thiol analogue, 8-mercaptoquinoline is also known.

The roots of the invasive plant Centaurea diffusa release 8-hydroxyquinoline, which has a negative effect on plants that have not co-evolved with it.

See also

• Nitroxoline (5-nitro-8-hydroxyquinoline), an antiprotozoal drug
• PBT2
• QUPIC
• Ionophore
• Trace metal detection test

References

1. Albert, A.; Phillips, J. N. (1956). "264. Ionization Constants of Heterocyclic Substances. Part II. Hydroxy-Derivatives of Nitrogenous Six-Membered Ring-Compounds". Journal of the Chemical Society (Resumed). 1956: 1294–1304. doi:10.1039/JR9560001294.
2. Cölle, M.; Dinnebier, R. E.; Brütting, W. (2002). "The structure of the blue luminescent δ-phase of tris(8-hydroxyquinoline)aluminium(III) (Alq₃)". Chemical Communications. 2002 (23): 2908–9. doi:10.1039/b209164j. PMID 12478807. S2CID 96135270.
3. Katakura, R.; Koide, Y. (2006). "Configuration-Specific Synthesis of the Facial and Meridional Isomers of Tris(8-hydroxyquinolinate)aluminum (Alq₃)". Inorganic Chemistry. 45 (15): 5730–5732. doi:10.1021/ic060594s. PMID 16841973.
4. Montes, V. A.; Pohl, R.; Shinar, J.; Anzenbacher, P. Jr. (2006). "Effective Manipulation of the Electronic Effects and Its Influence on the Emission of 5-Substituted Tris(8-quinolinolate) Aluminum(III) Complexes". Chemistry: A European Journal. 12 (17): 4523–4535. doi:10.1002/chem.200501403. PMID 16619313.
5. Bardez, E.; Devol, I.; Larrey, B.; Valeur, B. (1997). "Excited-State Processes in 8-Hydroxyquinoline: Photoinduced Tautomerization and Solvation Effects". The Journal of Physical Chemistry B. 101 (39): 7786–7793. doi:10.1021/jp971293u.
6. Weidel, H.; Cobenzl, A. (1880). "Über Derivate der Cinchoninsäure und des Chinolins". Monatshefte für Chemie und verwandte Teile anderer Wissenschaften (in German). 1 (1): 844–868. doi:10.1007/BF01517113. ISSN 1434-4475.
7. DE 14976, Skraup, Zdenko Hanus, "Verfahren zur Darstellung der Oxychinoline durch Behandlung von Mononitro- und Monamido-Phenolen mit Glycerin und Schwefelsäure", published 1881-09-10, issued 1881-02-16 
8. Bedall, Karl; Fischer, Otto (1881). "Ueber Oxychinolin aus Chinolinsulfosäure". Berichte der deutschen chemischen Gesellschaft (in German). 14 (1): 442–443. doi:10.1002/cber.188101401101. ISSN 1099-0682.
9. Fischer, Otto (1882). "Zur Geschichte der Oxychinoline". Berichte der deutschen chemischen Gesellschaft (in German). 15 (2): 1979–1981. doi:10.1002/cber.188201502123. ISSN 1099-0682.
10. Journal of the Society of Dyers and Colourists. Society of Dyers and Colourists. 1888.
11. Berg, R. (1927). "Neue Wege zur Bestimmung und Trennung der Metalle mit Hilfe von o-Oxychinolin". Zeitschrift für analytische Chemie (in German). 71 (5): 171–185. doi:10.1007/BF01390921. ISSN 1618-2650.
12. Phillips, J. P. (1956). "The Reactions of 8-Quinolinol". Chemical Reviews. 56 (2): 271–297. doi:10.1021/cr50008a003.
13. "8-Hydroxyquinoline". Medical Dictionary Online. Archived from the original on 2016-10-09. Retrieved 2016-03-09.
14. "8-Hydroxyquinoline". Sigma-Aldrich. Retrieved 2022-02-15.
15. Shen, A. Y.; Wu, S. N.; Chiu, C. T. (1999). "Synthesis and Cytotoxicity Evaluation of some 8-Hydroxyquinoline Derivatives". Journal of Pharmacy and Pharmacology. 51 (5): 543–548. doi:10.1211/0022357991772826. PMID 10411213. S2CID 33085238.
16. Fleischer, H. (2005). "Structural Chemistry of Complexes of (n-1)dns Metal Ions with β-N-Donor Substituted Thiolate Ligands (m=0, 2)". Coordination Chemistry Reviews. 249 (7–8): 799–827. doi:10.1016/j.ccr.2004.08.024.
17. Vivanco, J.M.; Bais, H.P.; Stermitz, F.R.; Thelen, G.C.; Callaway, R.M. (2004). "Biogeographical variation in community response to root allelochemistry: novel weapons and exotic invasion". Ecology Letters. 7 (4): 285–292. Bibcode:2004EcolL...7..285V. doi:10.1111/j.1461-0248.2004.00576.x.

• Antiseptics
• Quinolinols