8-Hydroxyquinoline

8-Hydroxyquinoline[1]
Skeletal formula of 8-hydroxyquinoline
Ball-and-stick model of the 8-hydroxyquinoline molecule
Names
IUPAC name
Quinolin-8-ol, 8-Quinolinol
Other names
1-azanaphthalene-8-ol, Fennosan H 30, hydroxybenzopyridine, hoxybenzopyridine, oxychinolin, oxyquinoline, phenopyridine, quinophenol, oxine
Identifiers
3D model (JSmol)
ChEBI
ChemSpider
ECHA InfoCard 100.005.193
KEGG
UNII
Properties
C9H7NO
Molar mass 145.16 g/mol
Appearance White crystalline needles
Density 1.034 g/cm3
Melting point 76 °C (169 °F; 349 K)
Boiling point 276 °C (529 °F; 549 K)
Pharmacology
G01AC30 (WHO) A01AB07 (WHO) D08AH03 (WHO) R02AA14 (WHO)
Hazards
Main hazards flammable
Safety data sheet External MSDS
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

8-Hydroxyquinoline is an organic compound with the formula C9H7NO. It is a derivative of the heterocycle quinoline by placement of an OH group on carbon number 8. This light yellow compound is widely used commercially, although under a variety of names.[2][3]

Synthesis

It is usually prepared from quinoline-8-sulfonic acid and from Skraup synthesis from 2-aminophenol.[4]

As a chelating agent

8-Hydroxyquinoline is a monoprotic bidentate chelating agent. In neutral solution, the hydroxyl is in the protonated form (pKa=9.89) and the nitrogen is not protonated (pKa=5.13).[5] However, transient, photochemically induced excited-state zwitterionic isomer exists in which H+ is transferred from the oxygen (giving an oxygen anion) to the nitrogen (giving a protonated nitrogen cation).[6]

Applications

The complexes as well as the heterocycle itself exhibit antiseptic, disinfectant, and pesticide properties,[7][8] functioning as a transcription inhibitor.[9] Its solution in alcohol is used in liquid bandages. It once was of interest as an anti-cancer drug.[10]

The reaction of 8-hydroxyquinoline with aluminium(III)[11] results in Alq3, a common component of organic light-emitting diodes (OLEDs). Variations in the substituents on the quinoline rings affect its luminescence properties.[12]

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.[13]

Hydroxyquinoline was used as a stabilizer of hydrogen peroxide in a rocket fuel oxidizer (T-Stoff) for the German Messerschmitt Me 163 Komet in World War 2.

Related ligands include the Schiff bases derived from salicylaldehyde, such as salicylaldoxime, salen, and salicylaldehyde isonicotinoylhydrazone (SIH). 8-Mercaptoquinoline is the thiol analogue of 8-hydroxyquinoline.

References

  1. ↑ Nanjing Odyssey Chemicals Archived September 28, 2007, at the Wayback Machine.
  2. ↑ "8-Hydroxyquinoline Safety Data". Oxford University.
  3. ↑ "8-Hydroxyquinoline". PAN Pesticides Database.
  4. ↑ Collin, G.; Höke, H. (2005), "Quinoline and Isoquinoline", Ullmann's Encyclopedia of Industrial Chemistry, Weinheim: Wiley-VCH, doi:10.1002/14356007.a22_465
  5. ↑ 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.
  6. ↑ 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.
  7. ↑ Phillips, J. P. (1956). "The Reactions of 8-Quinolinol". Chemical Reviews. 56 (2): 271–297. doi:10.1021/cr50008a003.
  8. ↑ "8-Hydroxyquinoline". Medical Dictionary Online.
  9. ↑ "8-Hydroxyquinoline". Sigma-Aldrich. Retrieved 2012-05-23.
  10. ↑ 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. PMID 10411213. doi:10.1211/0022357991772826.
  11. ↑ 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. PMID 16841973. doi:10.1021/ic060594s.
  12. ↑ 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. PMID 16619313. doi:10.1002/chem.200501403.
  13. ↑ 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. doi:10.1111/j.1461-0248.2004.00576.x.
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