Test: Inductive, mesomeric and electromeric effects - Chemistry MCQ

The correct order is- C₆H₅O^– > COO^– > CR₃ > CHR₂ > H.

Dipole moment, strength of acids and bases and bond length are some of the applications of the mesomeric effect.

NH₃ is an example of lewis base and ZnCl₂, BF₃ and FeCl₂ are the examples of lewis acid.

The correct order is- CN > COOH > F > Cl > Br > I > H.

All the bond length in the benzene ring is equal due to resonance. All the bond lengths are equal in benzene ring i.e. double bond as well as single bond due to resonance.

Nucleophiles possess an unshared electron pair which is not firmly held to the nucleus. All the other options are correct. They are electron rich and attack on electron deficient centres. Examples are: OH^–, NH₃, H₂O etc.

Bond length, dipole moment and strength of carboxylic acids are some of the applications of inductive effect.

Greater the number of resonating structures for a given intermediate, more will be its stability. More resonating structure increases stability.

Those groups which are electron repelling and have lesser electron attracting power than hydrogen show (+I) effect.

Relative basic strength of amines does not depend upon mesomeric effect. This effect is used in a qualitative way and describes the electron withdrawing or releasing properties of substituents based on relevant resonance structures.

Phenyl group show (-M) effect. The phenyl group or phenyl ring is a cyclic group of atoms with the formula C₆H₅.

Explanation for correct option:

C. CH3Cl

Dipole moment:

• “Dipole moment is defined as the product of the magnitude of the charge and the distance between the centers of positive and negative charge”
• It is expressed as μμμ.

The trend for dipole moment in the case of halogens are:

• Dipole moment depends on charge and distance.
• The difference in electronegativity between carbon and halogen atom decreases on going down the group from Fluorine to Iodine because of the decrease in electronegativity of halogen down the group.
• On the other hand, the distance between carbon and halogen atom increases on going down the group from Fluorine to Iodine because of the increase in size on moving down the group in the halogen family.
• The dipole moment of CH3Cl is greater than that of CH3F as the electron affinity of chlorine is greater than that of fluorine. The charge separation is larger in CH3Cl compared to CH3F. The repulsion between the bond pairs and non–bonded pairs of electrons is greater in CH3Cl than CH3F.
• Thus, the charge and distance factors are opposite to each other, in this case, the charge factor dominates. Therefore, the order will be CH3Cl>CH3F>CH3Br>CH3I.

Explanation for incorrect options:

The order of the dipole moment is CH3Cl>CH3F>CH3Br>CH3I. Thus, CH3Cl will have the maximum dipole moment.

Due to the presence of C – X polar bond in alkyl halide, alkyl halides are more reactive than corresponding alkane.

Dipole moment of CH₃-CH₂-Cl > CH₂=CH-Cl. This is due to resonance in vinyl chloride.

Lewis acids are the examples of electrophilic reagents and Lewis bases are the examples of nucleophilic reagents.