Quinoline is a colorless liquid with a strong odor that is slightly soluble in water. It has various industrial uses including in the manufacture of dyes, as a precursor to hydroxyquinoline and cyanine dyes, and in the production of herbicides and pesticides. Quinoline undergoes electrophilic substitution on the benzene ring and can be synthesized through the Skraup reaction involving aniline, glycerol, and an oxidizing agent. It is also produced commercially via the Combes quinoline synthesis which condenses anilines with β-diketones.

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Table of Content…………….
Defination…………………………………………………………………..3
Structure of Quinoline………………………………………………..3
Property of Quinoline………………………………………………….4
Sources & Emission of Quinoline…………………………….…..5
Synthesis of Quinoline…………………………………………………5
 Skraup synthesis
 Reaction mechanism
 Combes quinoline synthesis
Reactions of Quinoline………………………………………………7
 Electrophilic substitution
 Nucleophilic substitution
 Reduction
 oxidation
Application of Quinoline……………………………………………9
End of the page…………………………………………………………10

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Defination:
Any of a class of aromatic heterocyclic compounds containing a benzene ring fused with a
ring of five carbon atoms and a nitrogen atom; especially the simplest such compound, C 9H7N.
Quinoline is a heterocyclic aromatic organic compound with the chemical formula C9H7N. It
is a colorless hygroscopic liquid with a strong odor . 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 itself has few application, but
many of its derivatives are useful in diverse applications. A prominent example is quinine, which
is found naturally in plants as alkaloids. 4-Hydroxy-2-alkylquinolines (HAQs) are involved in
antibiotic resistance.
Structure:
I. It has the molecular formula C9H7N .
II. Chemical formula:
III. Resonance structures of Quinoline :

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Property of Quinoline:
Quinoline is a hygroscopic liquid with a penetrating odor. It absorbs as much as 22 percent water and
is volatile with steam. Quinoline is slightly soluble in cold water, more easily in hot water; and miscible
with alcohol, ether, and carbon disulfide. It dissolves sulfur, phosphorus, and arsenic trioxide .
Quinoline is a colourless liquid ,bp238°c,having disagreeaceble, pyridine -like odour.
chemically it gives all the reaction of pyridine and electrophilic substitution reaction of the
benzene ring.
Chemical and physical properties of quinoline :
Property Information Reference
Molecular weight 129.16 HSDB, 1999
Molecular formula C9H7N
Density at 25°C 1.0900
Melting point -15°C
Boiling point (760 mmHg) 237.63°C
Solubility: slightly soluble in water
Appearance: colourless to brown liquid
Density at 30°C 1.08579 g/cm3
Vapor pressure at 25°C 9.10 x 10-3 mm Hg
Henry’s Law constant 2.49 x 10-7 atm-m3mol-2
Water solubility at 25°C 6,110 mg/L
pKa 9.5
Koc 79–205
Bioconcentration factor 21
Log Kow 2.03

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SOURCES AND EMISSIONS
A. Sources :
Sources of quinoline include petroleum, coal processing, wood preservation, production and
use facilities, and shale oil.
Quinoline has been detected in tobacco smoke, emissions from petroleum refining, coal and shale oil
processing, and wood preservation. Quinoline has also been detected in coke oven tars.
B.Emission:
No emissions of quinoline from stationary sources in California were reported, based on data
obtained from the Air Toxics "Hot Spots" Program.
C.Natural occurrance:
Quinoline occurs naturally in small amounts in coal tar and in slightly decomposed sphagnum peats. It
also may be extracted from bone oil
Synthesis of Quinoline:
Skraup reaction:
The Skraup synthesis is a chemical reaction used to synthesize quinolines. It is named after the Czech
chemist Zdenko Hans Skraup (1850-1910). In the archetypal Skraup, aniline is heated with sulfuric acid,
glycerol, and an oxidizing agent, like nitrobenzene to yield quinoline.
In this example, nitrobenzene serves as both the solvent and the oxidizing agent. The reaction,
which otherwise has a reputation for being violent ("the Chemical Inquisition"), is typically
conducted in the presence of ferrous sulfate. Arsenic acid may be used instead of nitrobenzene
and the former is better since the reaction is less violent.

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Reaction mechanism
The reaction mechanism is unclear, yet there is good reason to believe that acrolein (obtained by
dehydration of glycerol in presence of concentrated sulfuric acid) is an intermediate, which then
undergoes 1,4-addition. Acrolein itself is not used since it undergoes polymerisations under the
conditions of the experiment. NOTE: position of hydroxyl group from 6th step forwards is
incorrect and should be move one carbon to the left
H
CH2
CH 2O H O
NH2 CH 2
CH
CHOH
-H2O CH 2
C
CH 2O H N
H O H
Glycerol Acroline
-H2O
C6H 5NO 2
Oxidation
N
Combes quinoline synthesis
N
H
The Combes quinoline synthesis is a chemical reaction involving the condensation of
unsubstituted anilines (1) with β-diketones (2) to form substituted quinolines (4) after an acid-
catalyzed ring closure of an intermediate Schiff base (3).

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Reaction of Quinoline:
1)Electrophilic substitution reaction:
It undergoes electrophilic substitution reaction in the benzene ring and not in the more resistant
piriding ring.the electrophile preferably attacks position 8 and 5.
2) Nucleophilic substitution reaction:
Quinoline radily gives Nucleophilic substitution reaction shown by pyridine.

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3) Reduction of Quinoline:
 The pyridine ring is more easily reduced
 Quinoline can be selectively reduced at 1,2-bond by reaction with lithium aluminium
hydride but the 1,2-dihydro quinolines are unstable and disproportionate easily to give
quinoline and 1,2,3,4-tetrahydroquinoline.
 Quinoline can be converted to 1,2,3,4-tetrahydroquinoline by catalytic hydrogenation or
with tin and hydrochloric acid
4 ) Oxidation:
 Quinoline undergo oxidative cleavage with alkalian potassium permangnate to give
pyridine-2,3-dicarboxylic acid
 However, pyridine-2,3-dicarboxylic acid is not stable and undergoes decarboxylation to
give nicotinic acid. Quinoline form N-oxides when treated with hydrogen peroxide in
acetic acid or with organic peracids.

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Aplication of Quinoline:
Quinoline is used in the manufacture of dyes.Quinoline and quinoline derivative can be used
in manufacturing a wide range of Food Colors, Lake Colors, Salt Free Dyes, etc. which are
extensively used as Dyes in various industries, such as Food, Pharmaceutical and Cosmetic.
Quinoline is used in the preparation of hydroxyquinoline sulfate and niacin. It has also used as
a solvent for resins and terpenes.
Quinoline is mainly used as a feedstock in the production of other specialty chemicals. 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".
Non-Cancer: Quinoline is an irritant of the eye and respiratory tract. Acute inhalation
overexposure to quinoline vapors in humans may cause signs and symptoms such as headaches,
dizziness and nausea, and coma. Quinoline overexposure has also been reported to cause injury
to the cornea, retina, and optic nerve.

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