Editing Quinoline (section)

== Occurrence and isolation ==
Quinoline was first extracted from [[coal tar]] in 1834 by German chemist [[Friedlieb Ferdinand Runge]];<ref name=EB1911/> he called quinoline ''leukol'' ("white oil" in Greek).<ref>F. F. Runge (1834) [https://books.google.com/books?id=wCUAAAAAMAAJ&pg=PA65 "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.)</ref> Coal tar remains the principal source of commercial quinoline.<ref name=Hoke/>  In 1842, French chemist [[Charles Frédéric Gerhardt|Charles Gerhardt]] obtained a compound by dry distilling [[quinine]], [[strychnine]], or [[cinchonine]] with [[potassium hydroxide]];<ref name=EB1911/> he called the compound ''Chinoilin'' or ''Chinolein''.<ref>Gerhardt, Ch. (1842)  [https://babel.hathitrust.org/cgi/pt?id=mdp.39015026322233;view=1up;seq=710 "Untersuchungen über die organischen Basen"] (Investigations of organic bases), ''Annalen der Chemie und Pharmacie'', '''42''' :  310-313.  See also:  (Editor) (1842) [https://babel.hathitrust.org/cgi/pt?id=hvd.hx3bgp;view=1up;seq=675 "Chinolein oder Chinoilin"] (Quinoline or quinoilin), ''Annalen der Chemie und Pharmacie'', '''44''' :  279-280.</ref>  Runge's and Gephardt's compounds seemed to be distinct [[isomers]] because they reacted differently. However, the German chemist [[August Wilhelm von Hofmann|August Hoffmann]] eventually recognized that the differences in behaviors was due to the presence of contaminants and that the two compounds were actually identical.<ref>Initially, Hoffmann thought that Runge's ''Leukol'' and Gerhardt's ''Chinolein'' were distinct. (See:  Hoffmann, August Wilhelm (1843) [https://babel.hathitrust.org/cgi/pt?id=hvd.hx3bgr;view=1up;seq=51 "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) [https://babel.hathitrust.org/cgi/pt?id=uiug.30112025846970;view=1up;seq=442 "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.)</ref> 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.<ref>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.</ref>

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.<ref>{{cite journal | doi = 10.1016/S0964-8305(96)00032-7 | title = Isolation, characterization, and substrate utilization of a quinoline-degrading bacterium | year = 1996 | last1 = O'Loughlin | first1 = Edward J. | last2 = Kehrmeyer | first2 = Staci R. | last3 = Sims | first3 = Gerald K. | journal = International Biodeterioration & Biodegradation | volume = 38 | issue = 2 | pages = 107| bibcode = 1996IBiBi..38..107O }}</ref>

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