Problem1:-
On reaction with acid, 4-pyrone is protonated on the carbonyl group oxygen to give a stable cationic product. Explain why the protonated product is so stable, drawing any resonance structures needed to clarify your explanation.

Answer:- Protonation of the C=O oxygen on 1 produces hydroxy carbocation 2 (as a resonance contributor of C=OH⁺). Thus, if the ring oxygen re-hybridizes to sp², the criteria for aromaticity are met; this is, thus, exactly what happens.

Resonance structure illustrates the delocalization of the positive charge and a more "aromatic-looking" ring, while perspective drawing depicts the p orbitals involved. Note that, despite a similarity to benzene (six ring atoms, six p electrons), one p orbital has zero electrons, while the other has a pair. Still, the aromatic criteria are met, so aromaticity occurs.