40 Questions
What type of ring system is formed when a heterocyclic ring is fused with another ring, either carbocyclic or heterocyclic?
Fused heterocyclic ring system
Which of the following is an example of a benzofused heterocyclic compound?
Indole
What is the chemical formula of Quinoline?
C9H7N
What is the boiling point of Quinoline?
237°C
What is the hybridization of the ring atoms in Quinoline?
SP2
What is the systematic IUPAC name of Quinoline?
All of the above
What is the orientation of pyrrole fusion that gives Isoindole?
Para orientation
What is the characteristic of the nitrogen lone pair electrons in Quinoline?
They are not involved in the formation of the delocalized π molecular orbital
What is the number of electrons in the π orbital of Quinoline that satisfies Huckel's rule?
10
What is the product of the reaction between glycerol and sulfuric acid in the Skraup synthesis?
Acrolein
What is the order of basicity of Quinoline, Aniline, and Pyridine?
Pyridine > Quinoline > Aniline
What is the characteristic smell of Quinoline similar to?
Pyridine
What is the colour of Quinoline when it is exposed to air?
Yellow
What is the resonance energy of Quinoline?
47.3 kcal/mole
What is the method of synthesizing Quinoline that involves the condensation of o-amino Benzaldehyde with acetaldehyde?
Friedlander's synthesis
What is the precursor of α, β-unsaturated carbonyl compound in the Dobner-Miller synthesis when 2-methylquinoline is formed?
Acetaldehyde
What is the reason behind quinoline's basicity?
Availability of lone pair of electrons on nitrogen
Where does electrophilic substitution in quinoline take place more readily?
At the benzene ring
What is the product of oxidation of quinoline in the presence of KMnO4?
Pyridine-2,3-dicarboxylic acid
What is the order of hydrogenation in quinoline during reduction reactions?
Pyridine ring first, then benzene ring
Where does nucleophilic substitution in quinoline take place?
At the pyridine ring
What is the position of nucleophilic substitution on the pyridine ring if it is not occupied by a substituent?
Position 2
What is the condition for the formation of quaternary salts with alkyl halides?
Availability of lone pair of electrons on nitrogen
What is the product of the reaction of quinoline with sodium amide in liquid ammonia?
2-Aminoquinoline
What is the reagent used for bromination of quinoline?
Br2 in presence of Ag2SO4 and H2SO4
What is the IUPAC name of Indole?
1H-benzo[b]pyrrole
What is the hybridization of the atoms in the Indole molecule?
sp2
What is the number of electrons in the π molecular orbital of Indole?
10
Why is Indole considered an aromatic compound?
It follows the Huckel's rule
What is the most widely used method for the synthesis of Indole?
Fisher-Indole synthesis
What is the reaction involved in the Fisher-Indole synthesis?
Acid-catalysed rearrangement of a phenylhydrazone
What is the product formed by the reaction of the phenylhydrazone of acetone?
2-Methyl indole
What is the preferred position for electrophilic substitution in Indole?
C3
What is the reactant used in the Bischler's synthesis of Indole?
Both a and b
What is the characteristic of Indole that makes it susceptible to electrophilic substitution reactions?
It is a π-excessive aromatic heterocycle
What is the reagent used in the Bischler-Napieralski reaction for the synthesis of Isoquinoline?
Phosphoryl chloride
What is the structural relationship between Isoquinoline and Quinoline?
They are structural isomers
What is the starting material used in the Bischler-Napieralski reaction for the synthesis of Isoquinoline?
β-Phenylethylamine
What is the result of the electrophilic substitution reaction at the C3 position in Indole?
A decrease in the energy of activation of the intermediate
What is the type of reaction that occurs preferentially at the C3 position in Indole?
Electrophilic substitution reaction
Study Notes
Fused Heterocyclic Compounds
- Heterocyclic rings systems can be formally derived by fusion with other rings, either carbocyclic or heterocyclic.
- Examples of benzofused heterocyclic compounds include Quinoline, Isoquinoline, Benzothiophene, Benzazepine, Dibenzoazepine, Carbazole, Acridine, and Benzofuran.
- Nomenclature for several bicyclic benzo-fused heterocycles permits trivial names.
Quinoline
- Quinoline is a heterocyclic aromatic organic compound with the chemical formula C9H7N.
- It is a fused heterocyclic system consisting of a benzene ring fused with a pyridine cycle.
- Quinoline can be considered as the heterocyclic analogue of naphthalene (1-azanaphthalene).
- Systematic IUPAC names: 1-Benzopyridine; Benzo[b]pyridine; Benzo[b]azine; Benzo[b]azabenzene.
- Other names: Quinolin; Chinoline; 1-Azanaphthalene; 1-Benzazine; Benzazine; Benzazabenzene.
- Quinoline is a colourless liquid with an unpleasant odour and boiling point 237°C.
- It is miscible with water, ethanol, and ether.
- All ring atoms in Quinoline are sp2 hybridized.
Preparation and Reactions of Quinoline
- Quinoline can be synthesized through the Skraup synthesis, Friedlander's synthesis, and Dobner-Miller synthesis.
- Chemical properties of quinoline include:
- Basicity: Quinoline acts as a base and forms salts with acids and quaternary salts with alkyl halides.
- Electrophilic substitution: Quinoline undergoes electrophilic substitution reactions, with the carbocyclic (benzene) ring being more electron-rich and resembling benzene.
- Nucleophilic substitution: Quinoline undergoes nucleophilic substitution reactions on the pyridine ring.
Indole
- Indole is an aromatic heterocyclic organic compound with the formula C8H7N.
- It has a bicyclic structure, consisting of a six-membered benzene ring fused to a five-membered nitrogen-containing pyrrole ring.
- Structure of Indole: the IUPAC name of Indole is 1H-benzo[b]pyrrole.
- All ring atoms in Indole are sp2 hybridized.
- Indole is an aromatic compound since it follows the Huckel's rule (i.e., 4n+2π electron rule) for n=2.
- Indole can be synthesized through the Fisher-Indole synthesis, Madelung synthesis, and Bischler's synthesis.
- Chemical properties of indole include:
- Electrophilic substitution reactions: Indole gives electrophilic substitution reactions, with the characteristic reactions of aromatic compounds.
Isoquinoline
- Isoquinoline is a heterocyclic aromatic organic compound.
- It is a structural isomer of quinoline and is obtained by ring fusion of pyridine with a benzene ring.
- Synthesis of isoquinoline: Isoquinoline can be synthesized through the Bischler-Napieralski reaction.
- Isoquinoline shows aromatic properties because its π orbital contains ten electrons and satisfies the Huckel's rule (n = 2 is 4n+2).
This quiz covers fused heterocyclic compounds, including their naming conventions and examples such as indole, isoindole, quinoline, and isuquinoline.
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