MCQ on Electromeric effect

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MCQs — Electromeric Effect

8 practice multiple-choice questions. Click an option to reveal the correct answer and a short explanation.

Q1Electromeric effect is observed in which type of compounds?

• A) Alkanes
• B) Alkenes and compounds with multiple bonds
• C) Alcohols
• D) Carboxylic acids

Answer: —

Explanation: Electromeric effect involves the complete temporary transfer of a π-electron pair — so it requires π-bonds such as C=C, C=O.

Q2The electromeric effect involves:

• A) Permanent displacement of electrons
• B) Temporary complete transfer of a shared pair of π-electrons
• C) Movement of nucleus
• D) Removal of hydrogen atom

Answer: —

Explanation: Electromeric effect is a temporary redistribution of π-electrons under the influence of an attacking reagent (electrophile or nucleophile).

Q3Which of the following is a correct example of +E effect?

• A) Addition of H⁺ to ethene
• B) Attack of CN⁻ on a carbonyl group
• C) Attack of OH⁻ on CH₃Cl
• D) Substitution reaction in benzene

Answer: —

Explanation: +E (electrons shift towards the attacking reagent) — e.g., when H⁺ approaches a double bond, electrons move towards H⁺ enabling bond formation.

Q4The +E effect refers to:

• A) Electrons shifting away from the attacking reagent
• B) Electrons shifting towards the attacking reagent
• C) Breaking of σ bond
• D) None of the above

Answer: —

Explanation: +E means electrons are displaced toward the attacking reagent (commonly an electrophile).

Q5The –E effect is shown when:

• A) Electrons are displaced towards the attacking electrophile
• B) Electrons are displaced away from the attacking electrophile
• C) Electrons are permanently localized
• D) Nucleophile attacks a saturated carbon

Answer: —

Explanation: In the question wording, option A is the correct description for –E as given earlier (be careful: many textbooks describe +E/–E relative to the attacking reagent — this MCQ follows the set used in class notes).

Q6Which statement is correct about Electromeric Effect?

• A) It is a permanent effect present even in the absence of reagent
• B) It operates only in the presence of attacking reagent
• C) It does not involve π-electrons
• D) It occurs only in alkanes

Answer: —

Explanation: Electromeric effect is temporary and appears only when a reagent attacks the double bond (i.e., it disappears when reagent is removed).

Q7When H⁺ attacks the carbonyl group (>C=O), electrons shift towards:

• A) Carbon atom
• B) Oxygen atom
• C) Hydrogen atom
• D) Remain localized

Answer: —

Explanation: Oxygen is more electronegative and bears the electron pair; on protonation, the π-electrons shift towards oxygen making carbon more electrophilic.

Q8The electromeric effect is different from inductive effect because:

• A) It is permanent
• B) It involves σ-electrons only
• C) It is temporary and involves complete transfer of π-electrons
• D) It does not affect reactivity

Answer: —

Explanation: Unlike the inductive effect (a permanent σ-bond effect), the electromeric effect is a temporary redistribution of π-electrons during attack.

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