Question

Which of the following compounds show dipole moment?
This question has multiple correct options.
(A)$1,4 - dichlorobenzene$
(B)$1,2 - dichlorobenzene$
(C)$1,3 - dichlorobenzene$
(D)$trans - 2,3 - dichloro - 2 - butene$

Answer 1

When there is a separation of charge, the dipole moment is noticed. It can be noticed between ions in an ionic bond or between atoms in a covalent bond. Dipole moments arise from the differences in the electronegativity of the atoms. The dipole moment is simply the measure of the polarity of a molecule.

Complete answer: In $1,4 - dichlorobenzene$, all carbons are $s{p^2}$ hybridized. It means all carbons have a double bond in which one bond is a sigma bond and one bond is a pi bond. As the hybridization is $s{p^2}$ it is planar. The two chlorine atoms are in para position. The electronegativity of the carbon hydrogen bond is less and is considered as a non- polar covalent bond. The dipole moment of two carbon and chlorine bonds are in equal and opposite directions. So, the total dipole moment will be zero. The structure of $1,4 - dichlorobenzene$ is given below:

In $1,2 - dichlorobenzene$, dipole moment is present because the two carbon chlorine bonds are at ${60^ \circ }$ to each other. The structure of $1,2 - dichlorobenzene$ is given below:

In $1,3 - dichlorobenzene$, dipole moment is present and the structure of $1,3 - dichlorobenzene$ is given below:

In $trans - 2,3 - dichloro - 2 - butene$, the two chlorine atoms are present on opposite sides. The hybridization is $s{p^2}$.So, it is planar. The total dipole moment is zero as the dipole moment due to two chlorine atoms is equal and opposite in direction.

Therefore, option B and C are the correct options.

Note:
The dipole moment between single bonds of a diatomic molecule is known as bond dipole moment. The total dipole moment in a polyatomic molecule is the vector sum of the bond dipoles. The dipole moment is zero if the two opposite bond dipoles cancel each other.