Why is hyperconjugation called no bond resonance?

Hyperconjugation is sometimes referred to as "no bond resonance" because it involves the delocalization or sharing of electrons in a molecule without the formation of new chemical bonds. In other words, it is a type of resonance phenomenon that does not involve the movement of electrons between atoms to form new covalent bonds, as is the case in traditional resonance structures.

In resonance, you typically have different Lewis structures or resonance forms that depict the distribution of electrons in a molecule. These resonance forms involve the shifting of electron pairs and the rearrangement of bonds, resulting in a set of structures that collectively describe the true electronic structure of the molecule. This process usually involves the movement of π (pi) electrons in double bonds or lone pairs of electrons.

Hyperconjugation, on the other hand, specifically refers to the interaction between a σ (sigma) bond and adjacent π electrons or vacant p orbitals in an adjacent atom or group. It occurs in molecules with σ bonds adjacent to double bonds or carbocations (positively charged carbon atoms). The σ bond electrons in the molecule interact with the π electrons or vacant p orbitals, leading to stabilization of the molecule. This interaction does not result in the creation of new bonds or movement of electrons between atoms, as seen in traditional resonance structures. Instead, it redistributes electron density within the molecule, leading to a stabilizing effect.

So, hyperconjugation is called "no bond resonance" because it represents a type of resonance that involves the redistribution of electron density without the formation or breaking of chemical bonds, in contrast to the more typical resonance structures where electron pairs move between atoms to create new resonance forms.