Question

Why is resonance more stable than hyperconjugation?

Answer 1

Resonance:

1. Resonance, also known as mesomerism in chemistry, is a way of describing bonding in certain molecules or polyatomic ions by blending several contributing structures (or forms, also known as resonance structures or canonical structures) into a resonance hybrid (or hybrid structure) in valence bonding.

Reason for Resonance more Stable than Hyperconjugation:

1. Because both approaches allow a molecule to stabilise by delocalizing electrons, hyperconjugation is an extension of resonance; moreover, hyperconjugation requires delocalization of sigma bond electrons as well as pi bond electrons, whereas resonance only induces delocalization of sigma bond electrons.
2. Resonance allows for delocalization, which lowers a molecule's total energy as the electrons inhabit a larger volume, making molecules that undergo resonance more stable than those that do not. These are referred to as stabilised resonance compounds.
3. Hyperconjugation is a stabilising process that occurs when electrons in a -bond (typically C-H or C-C) engage with a p-orbital or a -orbital neighbouring unoccupied or partially filled to produce an extended molecular orbital that improves system stability.