Question

Arrange the following in the decreasing order of their Dipole moments.

• A. \( d>c>b>a \)
• B. \( c>d>b>a \)
• C. \( a>b>c>d \)
• D. \( b>a>c>d \)

Hint:

The dipole moment of substituted benzenes is heavily influenced by the position of the substituents. Ortho and para substitutions tend to produce higher dipole moments than meta substitutions due to the alignment of the dipoles.

Answer 1

The Correct Option is D

Dipole moment depends on both the electronegativity difference between atoms and the geometry of the molecule. For substituted benzenes, the relative positions of the substituents play an important role in determining the dipole moment. - Chlorobenzene (a): Chlorobenzene has a single chlorine atom attached to the benzene ring. The dipole moment results from the electron-withdrawing nature of chlorine, but due to its symmetric nature, the dipole is relatively small. - 1,4-Dichlorobenzene (d): In this compound, the two chlorine atoms are positioned opposite to each other in the para position. This arrangement allows for the dipole moments to add up, resulting in the highest dipole moment among the given compounds. - 1,3-Dichlorobenzene (c): In this compound, the chlorine atoms are in the meta position. The dipole moments of the two chlorine atoms partially cancel each other out, but it is still higher than chlorobenzene because the chlorine atoms are closer than in 1,4-dichlorobenzene. - 1,2-Dichlorobenzene (b): This compound has chlorine atoms in the ortho position. The dipole moment is the highest among the dichlorobenzenes because the chlorine atoms are in close proximity, causing their individual dipoles to add constructively. Thus, the order of dipole moments is: \[ d>c>b>a \]