Quinoline molecule
C=black, H=white, N=blue
Quinoline molecule
C=black, H=white, N=blue
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)
ECHA InfoCard 100.001.865 Edit this at Wikidata
EC Number
  • 202-051-6
MeSH Quinolines
RTECS number
  • VA9275000
UN number 2656
  • InChI=1S/C9H7N/c1-2-6-9-8(4-1)5-3-7-10-9/h1-7H checkY
  • InChI=1/C9H7N/c1-2-6-9-8(4-1)5-3-7-10-9/h1-7H
  • n1cccc2ccccc12
  • C1=CC=C2C(=C1)C=CC=N2
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
GHS labelling:
GHS07: Exclamation markGHS08: Health hazardGHS09: Environmental hazard
H302, H312, H315, H319, H341, H350, H411
P201, P202, P264, P270, P273, P280, P281, P301+P312, P302+P352, P305+P351+P338, P308+P313, P312, P321, P322, P330, P332+P313, P337+P313, P362, P363, P391, P405, P501
NFPA 704 (fire diamond)
NFPA 704 four-colored diamondHealth 2: Intense or continued but not chronic exposure could cause temporary incapacitation or possible residual injury. E.g. chloroformFlammability 1: Must be pre-heated before ignition can occur. Flash point over 93 °C (200 °F). E.g. canola oilInstability 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
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).
checkY verify (what is checkY☒N ?)

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.[11]

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.[12]

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.

Going clockwise from top these are:

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

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


Quinolines are used in the manufacture of dyes and 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 were 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.[15] (C.f. Kairine)

Several anti-malarial drugs contain quinoline substituents. These include quinine, chloroquine, amodiaquine, and primaquine.

Quinoline is used as a solvent and reagent in organic synthesis.[16]

Quinolinium compounds (e.g. salts) can also be used as corrosion inhibitors and intensifiers.

See also


  1. ^ "QUINOLINE (BENZOPYRIDINE)". Chemicalland21.com. Retrieved 2012-06-14.
  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. ^ a b c Chisholm, Hugh, ed. (1911). "Quinoline" . Encyclopædia Britannica. Vol. 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; Lee, KH (May 2018). "Biologically active quinoline and quinazoline alkaloids part I." Medicinal Research Reviews. 38 (3): 775–828. doi:10.1002/med.21466. PMC 6421866. 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; Zhang, Ji-Yu; Lee, Kuo-Hsiung (September 2018). "Biologically active quinoline and quinazoline alkaloids part II". Medicinal Research Reviews. 38 (5): 1614–1660. doi:10.1002/med.21492. PMC 6105521. 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. ^ a b c Gerd Collin; Hartmut Höke. "Quinoline and Isoquinoline". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a22_465. ISBN 978-3527306732.
  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. ^ 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.
  12. ^ 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.
  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.
  15. ^ 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.
  16. ^ Sherman, Angela R.; Caron, Antoine; Collins, Shawn K. (2001). "Quinoline". Encyclopedia of Reagents for Organic Synthesis. pp. 1–4. doi:10.1002/047084289X.rq002.pub2. ISBN 9780470842898.