{{chembox | Verifiedfields = changed | verifiedrevid = 433358304 | ImageFile = Quinaldine.png | ImageClass = skin-invert-image | ImageSize = | PIN = 2-Methylquinoline | OtherNames = Quinaldine, α-methylquinoline, chinaldine, khinaldin |Section1={{Chembox Identifiers | CASNo = 91-63-4 | CASNo_Ref = {{cascite|correct|CAS}} | ChEBI = 132813 | ChEMBL_Ref = {{ebicite|correct|EBI}} | ChEMBL = 194931 | ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}} | ChemSpiderID = 13870160 | EINECS = 202-085-1 | PubChem = 7060 | UNII_Ref = {{fdacite|correct|FDA}} | UNII = DVG30M0M87 | SMILES = Cc1nc2ccccc2cc1 | InChI = 1/C10H9N/c1-8-6-7-9-4-2-3-5-10(9)11-8/h2-7H,1H3 | StdInChIKey_Ref = {{stdinchicite|correct|chemspider}} | StdInChIKey = SMUQFGGVLNAIOZ-UHFFFAOYSA-N | StdInChI_Ref = {{stdinchicite|correct|chemspider}} | StdInChI=1S/C10H9N/c1-8-6-7-9-4-2-3-5-10(9)11-8/h2-7H,1H3 }} |Section2={{Chembox Properties | Formula = C<sub>10</sub>H<sub>9</sub>N | MolarMass = 143.19 g/mol | Appearance = colorless oil | Density = 1.058 g/cm<sup>3</sup> | MeltingPtC = -2 | BoilingPtC = 248 | Solubility = Insoluble }} |Section7={{Chembox Hazards | NFPA-H = 2 | NFPA-F = 2 | NFPA-R = 0 | NFPA-S = | GHSPictograms = {{GHS07}} | GHSSignalWord = Warning | HPhrases = {{H-phrases|302|312|319}} | PPhrases = {{P-phrases|264|270|280|301+312|302+352|305+351+338|312|322|330|337+313|363|501}} | FlashPtC = 79 | AutoignitionPtC = }} }}
'''Quinaldine''' or '''2-methylquinoline''' is an organic compound with the formula CH<sub>3</sub>C<sub>9</sub>H<sub>6</sub>N. It is one of the methyl derivatives of the heterocyclic compound quinoline. It is bioactive and is used in the preparation of various dyes. It is a colorless oil but commercial samples can appear colored.<ref name=Hoke>{{Ullmann | author1 = Gerd Collin | author2 = Hartmut Höke | title = Quinoline and Isoquinoline | doi = 10.1002/14356007.a22_465}}</ref>
==Production and reactions== Quinaldine is recovered from coal tar. It can be prepared from aniline and paraldehyde via Skraup synthesis or from aniline and crotonaldehyde via Doebner-von Miller variation of the Skraup reaction.<ref name=Hoke/>
Hydrogenation of quinaldine gives 2-methyltetrahydroquinoline. This reduction can be conducted enantioselectively.<ref>{{Cite journal |first1=Fei|last1=Chen|first2=Zi-Yuan|last2=Ding|first3=Yan-Mei|last3=He|first4=Qing-Hua|last4=Fan| title = Synthesis of Optically Active 1,2,3,4-Tetrahydroquinolines via Asymmetric Hydrogenation Using Iridium-Diamine Catalyst|journal=Org. Synth.|volume = 92 | pages = 213–226 | year = 2015 | doi = 10.15227/orgsyn.092.0213|doi-access=free}}</ref> Oxidation with selenium dioxide give the aldehyde 2-formylquinoline.<ref>{{cite journal |author=H. A. Riley, A. R. Gray|title=Phenylglyoxal |journal=Organic Syntheses |date=1935 |volume=15 |page=67 |doi=10.15227/orgsyn.015.0067}}</ref>
==Properties== Quinaldine has critical point at 787 K and 4.9 MPa and its refractive index is 1.8116.{{cn|date=November 2021}}
==Uses== [[File:Quinoline Yellow SS.svg|thumb|left|124 px|Quinoline Yellow is a popular dye derived from quinaldine.]] [[File:Quinaldine_Red.svg|thumb|left|122px|Quinaldine Red, a pH indicating dye.]] Quinaldine is used in manufacturing anti-malaria drugs, dyes and food colorants (e.g., Quinoline Yellows, pinacyanol). It is the precursor to the pH indicator Quinaldine Red.
Quinaldine sulfate is an anaesthetic used in fish transportation.<ref>{{cite journal | author = Blasiola G. C. Jr. | year = 1977 | title = Quinaldine sulphate, a new anaesthetic formulation for tropical marine fishes | journal = Journal of Fish Biology | volume = 10 | issue = 2 | pages = 113–119(7) | doi = 10.1111/j.1095-8649.1977.tb04048.x }}</ref> In some Caribbean islands it is used to facilitate the collection of tropical fish from reefs.
== See also == * Lepidine, the isomer with the methyl group in position 4.
==References== <references/> {{clear|left}}
==External links== * [http://www.sciencelab.com/msds.php?msdsId=9924783 MSDS at Science Lab] {{Webarchive|url=https://web.archive.org/web/20150909161952/http://www.sciencelab.com/msds.php?msdsId=9924783 |date=2015-09-09 }} * [http://www.freepatentsonline.com/6020494.html Method of purifying quinaldine] * {{cite EB1911 |wstitle=Quinoline |volume=22 |pages=758–760}}
Category:Quinolines Category:Methyl compounds