Organic Chemistry 3 Lecture 8: Fused Heterocyclic Compounds
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Questions and Answers

What type of ring system is formed when a heterocyclic ring is fused with another ring, either carbocyclic or heterocyclic?

  • Fused heterocyclic ring system (correct)
  • Carbocyclic ring system
  • Aromatic ring system
  • Heterocyclic ring system

    • Which of the following is an example of a benzofused heterocyclic compound?

  • Indole (correct)
  • Pyrrole
  • Benzene
  • Naphthalene

    • What is the chemical formula of Quinoline?

  • C8H6N
  • C9H7N (correct)
  • C10H8N
  • C11H9N

    • What is the boiling point of Quinoline?

    <p>237°C</p> Signup and view all the answers

    What is the hybridization of the ring atoms in Quinoline?

    <p>SP2</p> Signup and view all the answers

    What is the systematic IUPAC name of Quinoline?

    <p>All of the above</p> Signup and view all the answers

    What is the orientation of pyrrole fusion that gives Isoindole?

    <p>Para orientation</p> Signup and view all the answers

    What is the characteristic of the nitrogen lone pair electrons in Quinoline?

    <p>They are not involved in the formation of the delocalized π molecular orbital</p> Signup and view all the answers

    What is the number of electrons in the π orbital of Quinoline that satisfies Huckel's rule?

    <p>10</p> Signup and view all the answers

    What is the product of the reaction between glycerol and sulfuric acid in the Skraup synthesis?

    <p>Acrolein</p> Signup and view all the answers

    What is the order of basicity of Quinoline, Aniline, and Pyridine?

    <p>Pyridine &gt; Quinoline &gt; Aniline</p> Signup and view all the answers

    What is the characteristic smell of Quinoline similar to?

    <p>Pyridine</p> Signup and view all the answers

    What is the colour of Quinoline when it is exposed to air?

    <p>Yellow</p> Signup and view all the answers

    What is the resonance energy of Quinoline?

    <p>47.3 kcal/mole</p> Signup and view all the answers

    What is the method of synthesizing Quinoline that involves the condensation of o-amino Benzaldehyde with acetaldehyde?

    <p>Friedlander's synthesis</p> Signup and view all the answers

    What is the precursor of α, β-unsaturated carbonyl compound in the Dobner-Miller synthesis when 2-methylquinoline is formed?

    <p>Acetaldehyde</p> Signup and view all the answers

    What is the reason behind quinoline's basicity?

    <p>Availability of lone pair of electrons on nitrogen</p> Signup and view all the answers

    Where does electrophilic substitution in quinoline take place more readily?

    <p>At the benzene ring</p> Signup and view all the answers

    What is the product of oxidation of quinoline in the presence of KMnO4?

    <p>Pyridine-2,3-dicarboxylic acid</p> Signup and view all the answers

    What is the order of hydrogenation in quinoline during reduction reactions?

    <p>Pyridine ring first, then benzene ring</p> Signup and view all the answers

    Where does nucleophilic substitution in quinoline take place?

    <p>At the pyridine ring</p> Signup and view all the answers

    What is the position of nucleophilic substitution on the pyridine ring if it is not occupied by a substituent?

    <p>Position 2</p> Signup and view all the answers

    What is the condition for the formation of quaternary salts with alkyl halides?

    <p>Availability of lone pair of electrons on nitrogen</p> Signup and view all the answers

    What is the product of the reaction of quinoline with sodium amide in liquid ammonia?

    <p>2-Aminoquinoline</p> Signup and view all the answers

    What is the reagent used for bromination of quinoline?

    <p>Br2 in presence of Ag2SO4 and H2SO4</p> Signup and view all the answers

    What is the IUPAC name of Indole?

    <p>1H-benzo[b]pyrrole</p> Signup and view all the answers

    What is the hybridization of the atoms in the Indole molecule?

    <p>sp2</p> Signup and view all the answers

    What is the number of electrons in the π molecular orbital of Indole?

    <p>10</p> Signup and view all the answers

    Why is Indole considered an aromatic compound?

    <p>It follows the Huckel's rule</p> Signup and view all the answers

    What is the most widely used method for the synthesis of Indole?

    <p>Fisher-Indole synthesis</p> Signup and view all the answers

    What is the reaction involved in the Fisher-Indole synthesis?

    <p>Acid-catalysed rearrangement of a phenylhydrazone</p> Signup and view all the answers

    What is the product formed by the reaction of the phenylhydrazone of acetone?

    <p>2-Methyl indole</p> Signup and view all the answers

    What is the preferred position for electrophilic substitution in Indole?

    <p>C3</p> Signup and view all the answers

    What is the reactant used in the Bischler's synthesis of Indole?

    <p>Both a and b</p> Signup and view all the answers

    What is the characteristic of Indole that makes it susceptible to electrophilic substitution reactions?

    <p>It is a π-excessive aromatic heterocycle</p> Signup and view all the answers

    What is the reagent used in the Bischler-Napieralski reaction for the synthesis of Isoquinoline?

    <p>Phosphoryl chloride</p> Signup and view all the answers

    What is the structural relationship between Isoquinoline and Quinoline?

    <p>They are structural isomers</p> Signup and view all the answers

    What is the starting material used in the Bischler-Napieralski reaction for the synthesis of Isoquinoline?

    <p>β-Phenylethylamine</p> Signup and view all the answers

    What is the result of the electrophilic substitution reaction at the C3 position in Indole?

    <p>A decrease in the energy of activation of the intermediate</p> Signup and view all the answers

    What is the type of reaction that occurs preferentially at the C3 position in Indole?

    <p>Electrophilic substitution reaction</p> Signup and view all the answers

    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).

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    Description

    This quiz covers fused heterocyclic compounds, including their naming conventions and examples such as indole, isoindole, quinoline, and isuquinoline.

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