Q.

1. Match the pairs
   Column 'A': i. Inductive effect ii. Hyperconjugation iii. Resonance effect
   Column 'B': a. delocalisation of π electrons b. displacement of π electrons c. delocalisation of σ electrons d. displacement of σ electrons

Three of the four options describe how electrons are displaced or delocalised WITHIN a molecule's bonds (electronic effects); distillation is an unrelated laboratory purification technique, making it the odd one out.

Examine each option:

• Inductive effect: the permanent, distance-decaying displacement of sigma-bond electron density along a chain of atoms due to an electronegativity difference (e.g. a Cl atom pulling electron density through sigma bonds) -> a genuine electron displacement effect.
• Resonance effect (mesomeric effect): the delocalisation of pi electrons (or lone pairs) across a conjugated system, described by multiple contributing resonance structures -> a genuine electron displacement effect.
• Hyperconjugation: the delocalisation of electrons from a sigma bond (typically C-H) into an adjacent empty or pi-type orbital, stabilising carbocations/alkenes/radicals -> a genuine electron displacement effect. …

Inductive, resonance, and hyperconjugation are all electronic effects describing how electron density shifts within a molecule; distillation is a purification technique with no connection to electron movement.

Electron displacement effects describe how electron density is distributed or shifted within a covalent molecule, influencing its reactivity:

1. Inductive effect: permanent displacement of sigma-bond electrons due to electronegativity differences, transmitted along a chain.
2. Resonance effect: delocalisation of pi electrons (or lone pairs) across a conjugated system, described by multiple contributing structures. …