Unit III_Six membered heterocyclic compounds

What is the molecular formula of pyridine?

• C₆H₆

• C₆H₅N

• C₆H₇N

• C₅H₅N

Which property makes pyridine aromatic?

• Presence of a benzene-like ring

• Delocalization of π-electrons

• Presence of a lone pair on nitrogen

• High electronegativity of nitrogen

Which of the following explains why pyridine is less basic than aliphatic amines?

• Lone pair on nitrogen is delocalized

• Pyridine is sp³ hybridized

• Pyridine is highly reactive

• Pyridine lacks resonance

Which reagent is used in the Chichibabin reaction of pyridine?

• NaNH₂

• H₂SO₄

• H₂O₂

• LiAlH₄

Which of the following reactions does pyridine undergo more readily than benzene?

• Electrophilic substitution

• Nucleophilic substitution

• Hydrogenation

• Friedel-Crafts alkylation

Which product is formed when pyridine undergoes catalytic hydrogenation?

• Piperidine

• Aniline

• Quinoline

• Pyrrole

Which of the following reagents can oxidize pyridine to pyridine-N-oxide?

• LiAlH₄

• H₂SO₄

• Peracids (H₂O₂, MCPBA)

• NaBH₄

Why does pyridine prefer substitution at the 3-position?

• Nitrogen increases electron density at the 3-position

• Electrophilic attack at 2- and 4-positions leads to unstable intermediates

• Pyridine does not undergo electrophilic substitution

• Lone pair on nitrogen directs substitution to the 2-position

What is the molecular formula of quinoline?

• C₉H₇N

• C₆H₅N

• C₇H₅N

• C₆H₆N₂

Quinoline is composed of which two fused rings?

• Benzene and pyridine

• Benzene and pyrrole

• Benzene and furan

• Pyrrole and furan