5 Questions
What does pyrrole form in dilute acids?
Trimer
Which type of aromatic character do these five-membered heterocycles belong to?
Aromatic character with 4n + 2 = 6 electrons
Which atom in furan and thiophene is sp2 hybridized?
Oxygen atom in furan and sulfur atom in thiophene
What property of pyrrole makes it undergo electrophilic substitution more favorably at the 𝛼- (2- ) position?
Higher stability of the resulting arenium ion from 𝛼-attack
What type of substitution do furan, thiophene, and pyrrole undergo at the 𝛼- (2- ) position?
Electrophilic substitution
Study Notes
Heterocycles
- In dilute acids, pyrrole forms a cation.
Aromatic Character
- Five-membered heterocycles, such as pyrrole, furan, and thiophene, belong to non-benzenoid aromatic compounds.
Hybridization in Furan and Thiophene
- In furan and thiophene, the oxygen and sulfur atoms, respectively, are sp2 hybridized.
Electrophilic Substitution in Pyrrole
- The high electron density at the 𝛂- (2-) position in pyrrole makes it undergo electrophilic substitution more favorably at this position.
Substitution in Furan, Thiophene, and Pyrrole
- Furan, thiophene, and pyrrole undergo electrophilic substitution at the 𝛂- (2-) position.
Test your knowledge on the topic of heterocyclic chemistry, specifically focusing on five-membered heterocycles and their aromatic character. This quiz is based on lecture #7 of the Pharmaceutical Organic Chemistry-3 course for Clinical PharmD students at National Mansoura University.
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