Thiophene
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Questions and Answers

What is the molecular formula of thiophene?

  • C4H5S
  • C4H4S (correct)
  • C4H3S
  • C4H6S

    • What is the boiling point of thiophene?

  • 90°C
  • 80°C
  • 100°C
  • 84°C (correct)

    • Why is thiophene separated from benzene?

  • Due to its low boiling point
  • Due to its high reactivity towards sulfonation (correct)
  • Due to its low reactivity towards sulfonation
  • Due to its high solubility in water

    • What is the hybridization of the atoms in the thiophene ring?

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

    What is the number of non-bonding electrons in the thiophene ring?

    <p>6</p> Signup and view all the answers

    Why is thiophene aromatic?

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

    What is the solubility of thiophene in water?

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

    What is the reason for the difference in aromaticity between thiophene and furan?

    <p>The electronegativity of the heteroatoms</p> Signup and view all the answers

    What is the electron donating tendency of sulphur compared to nitrogen and oxygen?

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

    What is the product of the condensation reaction between a 1,2-dicarbonyl compound and diethyl thiodiacetate in the presence of a strong base?

    <p>Thiophene 2,5-diacids (-diketone)</p> Signup and view all the answers

    What is the temperature required for the synthesis of thiophene from n-butane?

    <p>650 °C</p> Signup and view all the answers

    In electrophilic substitution reactions, where does the new substituent usually enter on thiophene?

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

    What is the reactant used in the Paal-Knorr synthesis of thiophene?

    <p>1,4-dicarbonyl compounds with sulfur sources</p> Signup and view all the answers

    Why does the new substituent prefer to enter on the 2-position in electrophilic substitution reactions of thiophene?

    <p>C2 attack gives more resonance contributing structures than C3</p> Signup and view all the answers

    What is the catalyst used in the synthesis of thiophene from acetylene?

    <p>Aluminium oxide</p> Signup and view all the answers

    What is the reactant used in the laboratory synthesis of thiophene from sod. succinate?

    <p>Phosphorus trisulfide</p> Signup and view all the answers

    What is the result of treating thiophene with hot phosphoric acid?

    <p>A trimer is formed</p> Signup and view all the answers

    What is the reason for the greater aromaticity of thiophene compared to furan?

    <p>The lower electronegativity of sulphur</p> Signup and view all the answers

    What is the limitation of reducing thiophene using Raney Ni?

    <p>Sulfur poisoning the catalyst and desulfurization occurs with ring opening</p> Signup and view all the answers

    What is the result of partial reduction of thiophene in acidic media?

    <p>Thiophene is partially reduced</p> Signup and view all the answers

    Which reaction does not occur with thiophene?

    <p>Succinyl oxidation</p> Signup and view all the answers

    What happens to thiophene when it undergoes oxidation?

    <p>It does not undergo oxidation</p> Signup and view all the answers

    Which of the following groups makes monosubstituted furan and thiophene less reactive?

    <p>Electron withdrawing groups</p> Signup and view all the answers

    What is the medical use of Sitaxsentan?

    <p>Cardiovascular agent</p> Signup and view all the answers

    What is the characteristic of Cephalothin?

    <p>It is effective against penicillinase-producing staphylococci and other gram-positive and gram-negative organisms</p> Signup and view all the answers

    What is the reaction that does not occur with thiophene?

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

    What is the medical use of Tiagabine?

    <p>Anticonvulsant agent</p> Signup and view all the answers

    Which of the following groups makes monosubstituted furan and thiophene more reactive?

    <p>Electron donating groups</p> Signup and view all the answers

    What is the condition that Sitaxsentan is used to treat?

    <p>Pulmonary artery hypertension</p> Signup and view all the answers

    What is the characteristic of Thiophene electrophilic substitution?

    <p>It is less reactive than unsubstituted compounds</p> Signup and view all the answers

    What is a characteristic of monosubstituted furan and thiophene with electron withdrawing groups?

    <p>They are less reactive than unsubstituted compounds</p> Signup and view all the answers

    Which of the following is NOT a medical use of a heterocyclic compound?

    <p>Pain reliever</p> Signup and view all the answers

    What is the effect of oxidation on tetrahydrothiophene?

    <p>It oxidizes to respective sulphone</p> Signup and view all the answers

    What is the structural relationship between Cephalothin and other antibacterial agents?

    <p>It is structurally related to Pencillins</p> Signup and view all the answers

    Which of the following groups makes monosubstituted furan and thiophene more reactive?

    <p>Electron donating groups</p> Signup and view all the answers

    What is the medical condition that Sitaxsentan is used to treat?

    <p>Pulmonary artery hypertension</p> Signup and view all the answers

    What is the effect of partial reduction on thiophene in acidic medium?

    <p>It reduces to tetrahydrothiophene</p> Signup and view all the answers

    What is the characteristic of electrophilic substitution reactions in monosubstituted furan and thiophene?

    <p>The new substituent usually enters on the 2-position</p> Signup and view all the answers

    What is the similarity between the medical uses of Sitaxsentan and Tiagabine?

    <p>They are both used to treat nervous system disorders</p> Signup and view all the answers

    What is the effect of oxidation on thiophene?

    <p>It remains unchanged</p> Signup and view all the answers

    Study Notes

    Thiophene

    • Thiophene is a heterocyclic compound with the formula C4H4S, consisting of a flat five-membered ring.
    • It is aromatic, as indicated by its extensive substitution reactions.

    Properties of Thiophene

    • At room temperature, thiophene is a colorless liquid with a mildly pleasant odor reminiscent of benzene.
    • Its boiling point is 84°C.
    • It is insoluble in water but freely soluble in ethanol, ether, and acetone.
    • The high reactivity of thiophene towards sulfonation is the basis for the separation of thiophene from benzene.

    Thiophene Aromaticity

    • Thiophene has 4C and 1S, all of which are sp2 hybridized.
    • sp² hybridization is planar, making a planar thiophene ring structure.
    • Each ring atom also contains an unhybridized p orbital that is perpendicular to the plane of σ bonds (plane of ring).
    • The total number of non-bonding electrons is 6 (4 from four C, 2 from one S).
    • The resonance of 6 electrons follows the Hückel's rule.
    • Thiophene is more aromatic than furan due to the less electronegative sulfur atom, which has a greater electron donating tendency.
    • The donated electrons take part in delocalization in the ring.

    Synthesis of Thiophene

    • Commercial method: By reaction of sulphur with n-butane in the gas phase at 650 °C.
    • From Acetylene: By passing a mixture of acetylene and hydrogen sulphide through a tube containing aluminium oxide at 600°C.
    • Paal-Knorr synthesis: The condensation of 1,4-dicarbonyl compounds with sulfur sources gives thiophene.
    • From sod.Succinate: Laboratory synthesis by heating a mix of sod.succinate and phosphorus trisulfide.
    • Hinsberg Synthesis: Condensation between a 1,2-dicarbonyl compound and diethyl thiodiacetate in the presence of a strong base gives thiophene 2,5- diacids (-diketone).

    Reactions of Thiophene

    • Electrophilic substitution: Thiophene is more easily substituted than benzene but less vigorously than furan and pyrrole.
    • The new substituent usually enters on the 2-position. If the 2-positions are occupied, then on the 3-position.
    • Thiophene undergoes electrophilic substitution reaction at 2nd position due to two reasons: C2 attack gives more resonance contributing structures than C3, and an extra stable contributing structure generates upon C2 attack.
    • Very strongly acidic conditions lead to acid-catalyzed polymerization.
    • The action of hot phosphoric acid on thiophene leads to a trimer.
    • Friedel-crafts acylation and Chloromethylation reactions are possible.
    • Reaction with organolithium or 2- lithiumthiophene is also possible.
    • Reduction: Partial reduction in acidic media, but thiophene cannot be reduced under the same conditions as in furan due to sulfur poisoning the catalyst and desulphurization occurs with ring opening.

    Medical uses of Thiophene

    • Sitaxsentan: Cardiovascular Agent, used in pulmonary artery hypertension.
    • Tiagabine: Anticonvulsant Agent, used in the treatment of epilepsy.
    • Cephalothin: New semisynthetic antibacterial agent structurally related to Pencillins, effective against penicillinase-producing staphylococci as well as other gram-positive and gram-negative organisms.

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    Description

    This quiz covers the properties, synthesis, reactions, and medical uses of Thiophene, a heterocyclic compound with a flat five-membered ring. Test your knowledge of Thiophene's aromaticity and its applications in organic chemistry.

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