Advanced Topic 762 of 1102 Organic Chemistry
Electromeric Effect
A temporary shift of pi electrons caused by an attacking reagent.
In-depth explanation of Electromeric Effect
The electromeric effect is a temporary and complete shift of the pi electrons of a multiple bond toward one atom, caused by the approach of an attacking reagent. It occurs only while the reagent is present and reverses when the reagent is removed, so it is not a permanent property of the molecule. It is relevant to addition reactions at double and triple bonds, where the attacking species triggers the polarization that makes the reaction possible. The effect is commonly distinguished from the inductive and resonance effects, which are permanent.
Going deeper: Electromeric Effect
Key ideas: A temporary effect in which pi electrons shift entirely to one atom under attack by a reagent, and revert when the reagent is removed. +E when electrons move toward the atom that the attacking reagent bonds to, -E when they move away. Example: C=O polarises with carbon plus and oxygen minus as a nucleophile approaches; for C=C with H+, electrons move to the carbon that bonds H.
Common mistakes and connections: Students confuse it with the permanent resonance effect, which exists without a reagent. It also applies only to multiple bonds, never single bonds. Links to electrophilic addition, nucleophilic addition to carbonyls and the general idea of polarisability.
Visualization of Electromeric Effect
When an attacking reagent approaches, the pi electrons of the multiple bond shift completely onto one atom, a temporary effect leading to addition. The interactive lesson shows this as a live animation or chart.
Worked example and use case
When a nucleophile approaches a carbonyl compound, the pi electrons of the C=O bond shift onto the oxygen temporarily.
Frequently asked questions about Electromeric Effect
What is Electromeric Effect?
A temporary shift of pi electrons caused by an attacking reagent.
Is Electromeric Effect a beginner, intermediate or advanced topic?
Electromeric Effect is a advanced topic in Organic Chemistry. It builds on beginner and intermediate topics, so review those first if needed.
What should I learn before Electromeric Effect?
Study these earlier topics in Organic Chemistry first: Inductive Effect, Resonance Effect, Hyperconjugation.
What comes after Electromeric Effect?
The next topics in Organic Chemistry are Free Radicals and Carbocations.
Can I practise Electromeric Effect with quizzes?
Yes. The interactive lesson includes a self-check question on Electromeric Effect, and the Organic Chemistry quiz draws on every topic in this area.
Where Electromeric Effect fits in Organic Chemistry
Electromeric Effect is topic 34 of 148 in Organic Chemistry.