40 Questions
What is the product of the reaction of pyrrole with CHCl3 and strong alkali?
Formylation at position 2 and formation of 3-chloro pyridine
What is the product of the reaction of pyrrole with aldehydes and ketones in acidic medium?
Dipyrryl methane
What is the order of reactivity in five-membered heterocycles?
Pyrrole > Furan > Thiophene > Benzene
What is the name of the reaction that forms a 3-chloro pyridine from pyrrole?
Riemer Tiemann Reaction
What is the name of the reaction that forms amines from pyrrole?
Hoffmann Martius Rearrangement
What is the structure of the tetramer formed by the reaction of pyrrole with aldehydes and ketones?
A planar, stable structure that can accommodate a wide range of metal ions
What is the condition required for the reaction of pyrrole with aldehydes and ketones?
Acidic medium
Which heterocycle is the most aromatic?
Benzene
Why is pyrrole more reactive towards electrophiles?
Due to the electron releasing ability of trivalent nitrogen
Why is furan less reactive than pyrrole towards electrophiles?
Due to the electronegative nature of oxygen
Why is thiophene less reactive than furan towards electrophiles?
Due to the less effective overlapping of p-orbitals of carbon and sulfur
What is the order of reactivity of heterocycles towards electrophiles?
Pyrrole > Furan > Thiophene
What is the position of nitration in furan when reacted with a mild nitrating agent?
C-2
What is the preferred site of electrophilic attack on furan?
C-2
What is the reason for the lower reactivity of benzene towards electrophiles?
Greater resonance stabilisation energy
What is the order of stability of the transition states in heterocyclic ring reactions?
Furan > Thiophene > Benzene
What is the reason for the lower reactivity of phenol compared to aniline?
Due to the electronegative nature of oxygen
Why does furan tend to give addition products rather than substitution products?
Due to the possibility of forming stable bonds like C-O bonds
What is the main factor that determines the reactivity of heterocycles towards electrophiles?
All of the above
What is the relative reactivity of thiophene and furan towards electrophiles?
Furan is more reactive than thiophene
Why is electrophilic substitution in thiophene much easier than in benzene?
Due to the lower resonance stabilisation energy of thiophene
Which of the following compounds is the most aromatic?
Benzene
What is the correct order of reactivity in electrophilic substitution in comparison to benzene?
Pyrrole > Furan > Thiophene > Benzene
Which positions are more reactive in pyrrole?
2 & 5 positions
Why does the intermediate from electrophilic attack at C2 in pyrrole have more resonance structures?
Due to the ability of the nitrogen atom to donate electrons
Which of the following compounds does not undergo Friedel-Crafts alkylation?
Furan
What is the reason for the acid sensitivity of furan in Friedel-Crafts alkylation?
Due to the formation of polymers
What is the condition required for Friedel-Crafts alkylation of furan substituted with electron-withdrawing substituents at the position-2?
Room temperature
What is the role of mild catalysts such as phosphoric acid or boron trifluoride in Friedel-Crafts alkylation of furan?
They facilitate alkylation at the position-2
What is the major difference between the reactivity of pyrrole and benzene in electrophilic substitution reactions?
Pyrrole is more reactive due to the presence of a nitrogen atom
What is the primary reason for the difference in reactivity between the 2 and 3 positions in pyrrole?
The difference in the number of resonance structures that can stabilize the intermediate
Which of the following heterocycles is least reactive towards electrophiles?
Benzene
What is the role of electron-withdrawing substituents in the Friedel-Crafts alkylation of furan?
They allow furan to undergo Friedel-Crafts alkylation at room temperature
Why does furan not undergo Friedel-Crafts alkylation under normal conditions?
Due to the acid sensitivity of furan
What is the relative order of aromaticity of the five-membered heterocycles?
Benzene > Thiophene > Furan > Pyrrole
What is the primary reason for the difference in reactivity between pyrrole and furan towards electrophiles?
The difference in the number of resonance structures that can stabilize the intermediate
What is the role of mild catalysts in the Friedel-Crafts alkylation of furan?
They allow furan to undergo Friedel-Crafts alkylation at room temperature
Why is pyrrole more reactive than benzene towards electrophiles?
Due to the electron-donating nature of the nitrogen atom
What is the relative order of reactivity of the five-membered heterocycles towards electrophiles?
Pyrrole > Furan > Thiophene > Benzene
What is the primary reason for the difference in reactivity between the 2 and 5 positions in pyrrole?
The difference in the number of resonance structures that can stabilize the intermediate
Test your knowledge of heterocyclic ring reactions, focusing on pyrrole and its reactions with aldehydes and ketones, as well as its resemblance to phenol. Learn about the Riemer Tiemann reaction and more. Assess your understanding of pyrrole's reactivity and comparison with benzene.
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