Quinoline

Quinoline
IUPAC name Quinoline
Other names 1-benzazine, 1-azanaphthalene, benzo[b]pyridine
Identifiers
CAS number	91-22-5 Y
PubChem	7047
ChemSpider	6780 Y
UNII	E66400VT9R Y
KEGG	C06413 Y
ChEBI	CHEBI:17362 Y
ChEMBL	CHEMBL14474 Y
Jmol-3D images	Image 1
SMILES n1cccc2ccccc12
InChI InChI=1S/C9H7N/c1-2-6-9-8(4-1)5-3-7-10-9/h1-7H Y Key: SMWDFEZZVXVKRB-UHFFFAOYSA-N Y InChI=1/C9H7N/c1-2-6-9-8(4-1)5-3-7-10-9/h1-7H Key: SMWDFEZZVXVKRB-UHFFFAOYAU
Properties
Molecular formula	C9H7N
Molar mass	129.16 g/mol
Density	1.093 g/ml
Melting point	−15 °C
Boiling point	237°C/760mm Hg, 108-110 °C/11mm Hg
Solubility in water	Soluble
Basicity (pKb)	4.85
Y (verify) (what is: Y/N?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Quinoline is a heterocyclic aromatic organic compound. It has the formula C₉H₇N and is a colourless hygroscopic liquid with a strong odour. Aged samples, 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 is mainly used as a building block to other specialty chemicals. Approximately 4 tonnes are produced annually according to a report published in 2005.^{[citation needed]} 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".

Like other nitrogen heterocylic 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 high water solubility quinoline has significant potential for mobility in the environment, which may promote water contamination. Fortunately, quinoline is readily degradable by certain microorganisms, such as Rhodococcus species Strain Q1, which was isolated from soil and paper mill sludge.

Isolation and synthesis

Quinoline was first extracted from coal tar in 1834 by Friedlieb Ferdinand Runge. Coal tar remains the principal source of commercial quinoline. It can be synthesized using various methods:

• Combes quinoline synthesis using anilines and β-diketones.
• Conrad-Limpach synthesis using anilines and β-ketoesters.
• Doebner-Miller reaction using anilines and α,β-unsaturated carbonyl compounds.
• Friedländer synthesis using 2-aminobenzaldehyde and acetaldehyde.
• Skraup synthesis using ferrous sulfate, glycerol, aniline, nitrobenzene, and sulfuric acid.
• Povarov reaction using an aniline, a benzaldehyde and an activated alkene.
• Camps quinoline synthesis utilizing an o-acylaminoacetophenone and hydroxide
• Knorr quinoline synthesis, using a β-ketoanilide and sulfuric acid.
• Gould-Jacobs reaction starting from an aniline and ethyl ethoxymethylenemalonate
• Niementowski quinoline synthesis, using anthranilic acid and ketones.

Applications

In manufacturing of dyes, preparation of hydroxyquinoline sulfate and niacin. Solvent for resins and terpenes.

See also

• Isoquinoline, an analog with the nitrogen atom in position 2.
• Pyridine, an analog without the fused benzene ring.
• Naphthalene, an analog without the nitrogen atom.
• 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

External links

• International Chemical Safety Card 0071
• Classical methods of synthesizing quinolines
• New methods of synthesizing quinolines
• Quinoline search by Wolfram|Alpha