|Systematic IUPAC name
|Molar mass||129.16 g/mol|
|Appearance||yellowish oily liquid|
|Melting point||−15 °C (5 °F; 258 K)|
|Boiling point||237 °C (459 °F; 510 K) /760 mm Hg, 108 to 110 °C/11 mm Hg|
|Solubility||Soluble in alcohol, ether, and carbon disulfide|
Std enthalpy of
|174.9 kJ mol−1|
|S-phrases||S26, S27, S28, S29, S30, Template:S31, Template:S32, S33, Template:S34, S35, S36|
|Flash point||101 °C (214 °F; 374 K)|
|400 °C (752 °F; 673 K)|
LD50 (Lethal dose)
Except where noted otherwise, data is given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
|what is: / ?)(|
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. 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. 4-Hydroxy-2-alkylquinolines (HAQs) are involved in antibiotic resistance.
Occurrence and isolation
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 it 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.
Quinolines are often synthesized from simple anilines using a number of named reactions.
Going clockwise from top these are:
- Combes quinoline synthesis using anilines and β-diketones.
- Conrad-Limpach synthesis using anilines and β-ketoesters.
- Doebner reaction using anilines with an aldehyde and pyruvic acid to form quinoline-4-carboxylic acids
- Doebner-Miller reaction using anilines and α,β-unsaturated carbonyl compounds.
- Gould-Jacobs reaction starting from an aniline and ethyl ethoxymethylenemalonate
- Skraup synthesis using ferrous sulfate, glycerol, aniline, nitrobenzene, and sulfuric acid.
A number of other processes exist, which require specifically substituted anilines or related compounds:
- Camps quinoline synthesis utilizing an o-acylaminoacetophenone and hydroxide
- Friedländer synthesis using 2-aminobenzaldehyde and acetaldehyde.
- Knorr quinoline synthesis, using a β-ketoanilide and sulfuric acid.
- Niementowski quinoline synthesis, using anthranilic acid and ketones.
- Pfitzinger reaction using an isatin with base and a carbonyl compound to yield substituted quinoline-4-carboxylic acids
- Povarov reaction using an aniline, a benzaldehyde and an activated alkene.
Quinoline is mainly used as a feedstock in the production of other specialty chemicals. Approximately 4 tonnes are produced annually according to a report published in 2005. 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".
- 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.
- Simple aromatic rings
- Niementowski quinoline synthesis, quinoline derivative synthesis
- Lindlar catalyst, quinoline prevents formation of alkanes
- "QUINOLINE (BENZOPYRIDINE)". Chemicalland21.com. Retrieved 2012-06-14.
- 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.
- "Quinoline". Encyclopædia Britannica. 1911.
- Gerd Collin; Hartmut Höke (2005), "Quinoline and Isoquinoline", Ullmann's Encyclopedia of Industrial Chemistry, Weinheim: Wiley-VCH, doi:10.1002/14356007.a22_465
- 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.