Electromeric Effect (E-effect)
A temporary effect involving the complete transfer of a shared pair of π electrons to one of the bonded atoms in the presence of an attacking reagent.
What is Electromeric Effect (E-effect)?
A temporary effect in which the π-electron pair of a multiple bond is completely transferred to one of the bonded atoms in the presence of an attacking reagent, where the electron pair shifts towards the atom that is attacked by the reagent.
Key points
- Define the electromeric effect.
- Differentiate between the positive (+E) and negative (-E) electromeric effects.
- Explain the temporary nature of the electromeric effect.
- Identify the conditions under which the electromeric effect occurs.
Common exam trap
Confusing it with the inductive effect (permanent vs. temporary).
Definitions
- Term
Electromeric Effect (+E)
- Meaning
A temporary effect in which the π-electron pair of a multiple bond is completely transferred to one of the bonded atoms in the presence of an attacking reagent, where the electron pair shifts towards the atom that is attacked by the reagent.
- Term
Electromeric Effect (-E)
- Meaning
A temporary effect in which the π-electron pair of a multiple bond is completely transferred to one of the bonded atoms in the presence of an attacking reagent, where the electron pair shifts away from the atom that is attacked by the reagent.
Learning objectives
Define the electromeric effect.
Differentiate between the positive (+E) and negative (-E) electromeric effects.
Explain the temporary nature of the electromeric effect.
Identify the conditions under which the electromeric effect occurs.
Understand its role in the polarization of multiple bonds.
Prerequisites
Basic understanding of chemical bonds (σ and π bonds).
Knowledge of multiple bonds (double and triple bonds).
Familiarity with the concept of electron movement in reactions.
Understanding of electrophiles and nucleophiles.
Common mistakes
Confusing it with the inductive effect (permanent vs. temporary).
Assuming the effect is always present, even without a reagent.
Incorrectly identifying the direction of electron shift (+E vs. -E).
Overlooking its role in reaction mechanisms.
Keywords
Electromeric Effect
E-effect
Π-electron transfer
Multiple bonds
Attacking reagent
Polarization
+E effect
-E effect
Temporary effect
Organic reactions
Practice preview
The electromeric effect is a type of electron displacement that:…
medium
In which of the following molecules can the electromeric effect be observed?…
easy
Which of the following is a characteristic of the electromeric effect?…
easy