Solved Practice Questions: Inductive, mesomeric and electromeric effects | Organic Chemistry PDF Download

Q.1. Electronegativity is defined as the power of an atom in a molecule to ______
(a) Repel electrons towards itself
(b) Attract electrons towards itself
(c) Expand itself
(d) All of the mentioned

Correct Answer is (b)
Electronegativity is defined as the power of an atom in a molecule to attract electrons towards itself. Fluorine is the most electronegative element. 

Q.2. In mesomeric effect, the electrons are transferred from ______
(a) A multiple bonds to an atom
(b) A multiple bonds to a single covalent bond
(c) An atom with a lone pair to the adjacent single covalent bond
(d) All of the mentioned

Correct Answer is Option (d)
In the mesomeric effect, the electrons are transferred from multiple bonds to an atom, a multiple bond to a single covalent bond and an atom with the lone pair to the adjacent single covalent bond. 

Q.3. Which of the following is a temporary effect brought into play at the requirement of attacking reagent?
(a) Inductive effect
(b) Mesomeric effect
(c) Electromeric effect
d) Inductomeric effect

Correct Answer is Option (c)
Electromeric effect is a temporary effect brought into play at the requirement of attacking reagent. Electromeric effect refers to a molecular polarizability effect occurring by an intra-molecular electron displacement. 

Q.4. The factors on which electronegativity depends upon ______
(a) Valence state of atom
(b) Hybridisation
(c) Both valence state and hybridisation
d) None of the mentioned

Correct Answer is Option (c)
The factors on which electronegativity depends upon is valence state of atom and hybridisation. 

Q.5. Which of the following is a resonance effect?
(a) Inductive effect
(b) Electromeric effect
(c) Mesomeric effect
(d) Inductomeric effect

Correct Answer is Option (c)
Mesomeric effect is also known as the resonance effect. The mesomeric effect is a permanent effect and operates in compounds containing at least one double bond. 

Q.6. Select the correct statement from the following option.
(a) When multiple bonds are present between two different atoms, electromeric shift towards the more electronegative atom takes place
(b) When multiple bonds are present between two similar atoms, the first possibility is symmetric alkenes or alkynes
(c) When multiple bonds are present between two similar atoms, the second possibility is asymmetric alkenes or alkynes
(d) All of the mentioned

Correct Answer is Option (d)
When multiple bonds are present between two different atoms, electromeric shift towards the more electronegative atom takes place. When multiple bonds are present between two similar atoms, the first possibility is symmetric alkenes or alkyne and the second possibility is asymmetric alkenes or alkynes. 

Q.7. How does the electronegativiy get affected with the negative oxidation state?
(a) It decreases
(b) It increases
(c) It remains constant
(d) None of the mentioned

Correct Answer is Option (a)
Electronegativity decreases with the negative oxidation state since the tendency to attract an electron will decrease with the negative charge of the anion. 

Q.8. The phenomenon in which 2 or more structures, involving identical position of atoms can be written for a particular molecule, is called _______
(a) Conjugation
(b) Resonance
(c) Hyperconjugation
(d) Vibration

Correct Answer is Option (b)
The phenomenon in which 2 or more structures, involving the identical position of atoms can be written for a particular molecule, is called resonance. The mesomeric effect is a permanent effect and operates in compounds containing at least one double bond.

Q.9. Select the correct statement from the following option.
(a) Conjugate effect is stronger than (-I) effect
(b) Conjugate effect is weaker than (-I) effect
(c) Conjugate effect is same as (-I) effect
(d) None of the mentioned

Correct Answer is Option (a)
Conjugate effect is stronger than (-I) effect. Conjugate effect (or delocalization) is an effect in which molecular orbitals (MOs) are conjugated to new molecular orbitals that are more delocalized and therefore generally lower in energy. 

Q.10. The electronegativity of sp² hybridised atom will be _______
(a) 3.29
(b) 2.48
(c) 3.69
(d) 2.75

Correct Answer is Option (d)
The electronegativity of sp² hybridised atom will be 2.75. Fluorine is the most electronegative element. 

Q.11. Select the incorrect option from the following option.
(a) Resonating structures have a real existence
(b) The actual structure lies between various possible resonating structures
(c) Resonating structures are useful as they allow us to describe molecules
(d) None of the mentioned

Correct Answer is Option (a)
Resonating structures have no real existence. All the other options are correct. The actual structure lies between various possible resonating structures, resonating structures are useful as they allow us to describe molecules. 

Q.12. The resonance energy is defined as a difference in energy between ______
(a) Two consecutive resonating structures
(b) Resonance hybrid and most unstable resonating structure
(c) Resonance hybrid and most stable resonating structure
(d) First and last resonating structures

Correct Answer is Option (c)
The resonance energy is defined as a difference in energy between resonance hybrid and most stable resonating structure. The resonance energy of a compound is a measure of the extra stability of the conjugated system compared to the corresponding number of isolated double bonds. 

Q.13. When the complete transfer of π-electrons take place away from the atom at the requirement of attacking agent, it is called _______
(a) (-E) effect
(b) (+E) effect
(c) (-I) effect
(d) (+I) effect

Correct Answer is Option (b)
When the complete transfer of π-electrons takes place away from the atom at the requirement of attacking agent, it is called (+E) effect. 

Q.14. Which of the following is a permanent electron displacement effect?
(a) Inductomeric
(b) Electromeric
(c) Inductive
(d) All of the mentioned

Correct Answer is Option (c)
Inductive effect is the permanent electron displacement effect and inductomeric and electromeric are temporary electron displacement effects.

Q.15. The positively charged and electron deficient compounds which have a tendency to form a bond by accepting the electron pair are known as _______
(a) Electrophiles
(b) Nucleophiles
(c) Homophiles
(d) All of the mentioned

Correct Answer is Option (a)
The positively charged and electron deficient compounds which have a tendency to form a bond by accepting the electron pair are known as electrophiles.