Which is more reactive Benzaldehyde or Propanal?

1. Benzaldehyde is an aromatic organic compound whereas Propanal has an aliphatic Carbon chain.
2. The reactivity of aldehyde containing group is based on electrophilicity and the polarity of the carbonyl group.
3. The chemical formula of Benzaldehyde is${\mathrm{C}}_7{\mathrm{H}}_6\mathrm{O}$ and Propanal is ${\mathrm{C}}_3{\mathrm{H}}_6\mathrm{O}$
4. The carbonyl group-containing Oxygen should have a partial negative charge and Carbon have a partial positive charge.
5. If the polarization is high it will be more reactive in nature.
6. In the case of Benzaldehyde the polarity of the molecule will be reduced because carbonyl Carbon is attached to the Benzene ring.
7. Benzene shows resonance and so the positive charge will spread throughout the molecule.
8. Thus, it is less reactive toward nucleophilic reactions.
9. In the case of Propanal no such effect of resonance is encountered rather it is affected by polarity.
10. Therefore, the carbonyl carbon of Benzaldehyde is less electrophilic compared with carbonyl Carbon present in Propanal.
11. Hence Propanal is more reactive than Benzaldehyde.
12.