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See also: Quinoline Yellow|Quinoline Yellow (disambiguation)|Quinoline Yellow
Quinoline chemical structure.svg
Quinoline molecule
Quinoline molecule
Preferred IUPAC name
Systematic IUPAC name
  • 1-Benzopyridine
  • Benzo[b]pyridine
  • 2-Azabicyclo[4.4.0]deca-1(6),2,4,7,9-pentaene
  • 2-Azabicyclo[4.4.0]deca-1,3,5,7,9-pentaene
  • Benzo[b]azine
  • Benzo[b]azabenzene
Other names
  • 1-Azanaphthalene
  • 1-Benzazine
  • Benzazine
  • Benzazabenzene
  • Benzopyridine
  • 1-Benzine
  • Quinolin
  • Chinoline
  • Chinoleine
  • Chinolin
  • Leucol
  • Leukol
  • Leucoline
3D model (JSmol)
EC Number
  • 202-051-6
MeSH Quinolines
RTECS number
  • VA9275000
UN number 2656
Molar mass 129.16 g/mol
Appearance Colorless oily liquid
Density 1.093 g/mL
Melting point −15 °C (5 °F; 258 K)
Boiling point 237 °C (459 °F; 510 K) , 760 mm Hg; 108–110 °C (226–230 °F), 11 mm Hg
Slightly soluble
Solubility Soluble in alcohol, ether, and carbon disulfide
Acidity (pKa) 4.85 (conjugated acid)[3]
−86.0·10−6 cm3/mol
174.9 kJ·mol−1
R-phrases (outdated) R21, R22
S-phrases (outdated) S26, S27, S28, S29, S30, S31, S32, S33, S34, S35, S36
NFPA 704 (fire diamond)
Flammability code 1: Must be pre-heated before ignition can occur. Flash point over 93 °C (200 °F). E.g. canola oilHealth code 2: Intense or continued but not chronic exposure could cause temporary incapacitation or possible residual injury. E.g. chloroformReactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no codeNFPA 704 four-colored diamond
Flash point 101 °C (214 °F; 374 K)
400 °C (752 °F; 673 K)
Lethal dose or concentration (LD, LC):
331 mg/kg
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
Tracking categories (test):

Quinoline is a heterocyclic aromatic organic compound with the chemical formula C9H7N. It is a colorless hygroscopic liquid with a strong odor. Aged samples, especially if exposed to light, become yellow and later brown. Quinoline is only slightly soluble in cold water but dissolves readily in hot water and most organic solvents.[4] Quinoline itself has few applications, but many of its derivatives are useful in diverse applications. A prominent example is quinine, an alkaloid found in plants. Over 200 biologically active quinoline and quinazoline alkaloids are identified.[5][6] 4-Hydroxy-2-alkylquinolines (HAQs) are involved in antibiotic resistance.

Occurrence and isolation

Quinoline was first extracted from coal tar in 1834 by German chemist Friedlieb Ferdinand Runge;[4] he called quinoline leukol ("white oil" in Greek).[7] Coal tar remains the principal source of commercial quinoline.[8] In 1842, French chemist Charles Gerhardt obtained a compound by dry distilling quinine, strychnine, or cinchonine with potassium hydroxide;[4] he called the compound Chinoilin or Chinolein.[9] Runge's and Gephardt's compounds seemed to be distinct isomers because they reacted differently. However, the German chemist August Hoffmann eventually recognized that the differences in behaviors was due to the presence of contaminants and that the two compounds were actually identical.[10] The only report of quinoline as a natural product is from the Peruvian stick insect Oreophoetes peruana. They have a pair of thoracic glands from which they discharge a malodorous fluid containing quinoline when disturbed. (Eisner, T; Morgan, R.C.; Attygalle A.B., Smedley, S.R.; Herath, K.B., Meinwald, J. (1997) “Defensive Production of quinoline by a phasmid insect (Oreophoetes peruana) J. Exp. Biol. 200, 2493–2500).

Like other nitrogen heterocyclic compounds, such as pyridine derivatives, quinoline is often reported as an environmental contaminant associated with facilities processing oil shale or coal, and has also been found at legacy wood treatment sites. Owing to its relatively high solubility in water quinoline has significant potential for mobility in the environment, which may promote water contamination. Quinoline is readily degradable by certain microorganisms, such as Rhodococcus species Strain Q1, which was isolated from soil and paper mill sludge.[11]

Quinolines are present in small amounts in crude oil within the virgin diesel fraction. It can be removed by the process called hydrodenitrification.


Quinolines are often synthesized from simple anilines using a number of named reactions.

Quinoline from aniline.png

Going clockwise from top these are:

A number of other processes exist, which require specifically substituted anilines or related compounds:


Quinoline is used in the manufacture of dyes, the preparation of hydroxyquinoline sulfate and niacin. It is also used as a solvent for resins and terpenes.

Quinoline is mainly used as in the production of other specialty chemicals. Approximately 4 tonnes are produced annually according to a report published in 2005.[8] Its principal use is as a precursor to 8-hydroxyquinoline, which is a versatile chelating agent and precursor to pesticides. Its 2- and 4-methyl derivatives are precursors to cyanine dyes. Oxidation of quinoline affords quinolinic acid (pyridine-2,3-dicarboxylic acid), a precursor to the herbicide sold under the name "Assert".[8]

The reduction of quinoline with sodium borohydride in the presence of acetic acid is known to produce Kairoline A.[12] (C.f. Kairine)

Quinoline has several anti-malarial derivatives, including quinine, chloroquine, amodiaquine, and primaquine.

Quinolines are reduced to tetrahydroquinolines enantioselectively using several catalyst systems.[13][14]


See also

  • Similar simple aromatic rings
    • Isoquinoline, an analog with the nitrogen atom in position 2
    • Pyridine, an analog without the fused benzene ring
    • Naphthalene, an analog with a carbon instead of the nitrogen
    • Indole, an analog with only a five-membered nitrogen ring


  2. Nomenclature of Organic Chemistry : IUPAC Recommendations and Preferred Names 2013 (Blue Book). Cambridge: The Royal Society of Chemistry. 2014. pp. 4, 211. doi:10.1039/9781849733069-FP001. ISBN 978-0-85404-182-4. "The name ‘quinoline’ is a retained name that is preferred to the alternative systematic fusion names ‘1-benzopyridine’ or ‘benzo[b]pyridine’." 
  3. Brown, H.C., et al., in Baude, E.A. and Nachod, F.C., Determination of Organic Structures by Physical Methods, Academic Press, New York, 1955.
  4. 4.0 4.1 4.2 Chisholm, Hugh, ed (1911). "Quinoline". Encyclopædia Britannica. 22 (11th ed.). Cambridge University Press. p. 759. 
  5. Shang, XF; Morris-Natschke, SL; Liu, YQ; Guo, X; Xu, XS; Goto, M; Li, JC; Yang, GZ et al. (May 2018). "Biologically active quinoline and quinazoline alkaloids part I.". Medicinal Research Reviews 38 (3): 775–828. doi:10.1002/med.21466. PMID 28902434. 
  6. Shang, Xiao-Fei; Morris-Natschke, Susan L.; Yang, Guan-Zhou; Liu, Ying-Qian; Guo, Xiao; Xu, Xiao-Shan; Goto, Masuo; Li, Jun-Cai et al. (September 2018). "Biologically active quinoline and quinazoline alkaloids part II". Medicinal Research Reviews 38 (5): 1614–1660. doi:10.1002/med.21492. PMID 29485730. 
  7. F. F. Runge (1834) "Ueber einige Produkte der Steinkohlendestillation" (On some products of coal distillation), Annalen der Physik und Chemie, 31 (5) : 65–78 ; see especially p. 68: "3. Leukol oder Weissöl" (3. White oil [in Greek] or white oil [in German]). From p. 68: "Diese dritte Basis habe ich Leukol oder Weissöl genannt, weil sie keine farbigen Reactionen zeigt." (This third base I've named leukol or white oil because it shows no color reactions.)
  8. 8.0 8.1 8.2 Gerd Collin; Hartmut Höke. "Ullmann's Encyclopedia of Industrial Chemistry". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a22_465. 
  9. Gerhardt, Ch. (1842) "Untersuchungen über die organischen Basen" (Investigations of organic bases), Annalen der Chemie und Pharmacie, 42 : 310-313. See also: (Editor) (1842) "Chinolein oder Chinoilin" (Quinoline or quinoilin), Annalen der Chemie und Pharmacie, 44 : 279-280.
  10. Initially, Hoffmann thought that Runge's Leukol and Gerhardt's Chinolein were distinct. (See: Hoffmann, August Wilhelm (1843) "Chemische Untersuchungen der organischen Basen im Steinkohlen-Theeröl" (Chemical investigations of organic bases in coal tar oil), Annalen der Chemie und Pharmacie, 47 : 37-87 ; see especially pp. 76-78.) However, after further purification of his Leukol sample, Hoffmann determined that the two were indeed identical. (See: (Editor) (1845) "Vorläufige Notiz über die Identität des Leukols und Chinolins" (Preliminary notice of the identity of leukol and quinoline), Annalen der Chemie und Pharmacie, 53 : 427-428.)
  11. O'Loughlin, Edward J.; Kehrmeyer, Staci R.; Sims, Gerald K. (1996). "Isolation, characterization, and substrate utilization of a quinoline-degrading bacterium". International Biodeterioration & Biodegradation 38 (2): 107. doi:10.1016/S0964-8305(96)00032-7. 
  12. GRIBBLE, Gordon W.; HEALD, Peter W. (1975). "Reactions of Sodium Borohydride in Acidic Media; III. Reduction and Alkylation of Quinoline and Isoquinoline with Carboxylic Acids". Synthesis 1975 (10): 650–652. doi:10.1055/s-1975-23871. ISSN 0039-7881. 
  13. Xu, L.; Lam, K. H.; Ji, J.; Wu, J.; Fan, Q.-H.; Lo, W.-H.; Chan, A. S. C. Chem. Commun. 2005, 1390.
  14. Reetz, M. T.; Li, X. Chem. Commun. 2006, 2159.

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