Among the following, the molecule with the highest dipole moment is\

Question

Professor PC Thomas Classes · Answer

(a) : The dipole moment of a polar molecule depends on its geometry and shape. A symmetrical molecule is non-polar even though it contains polar bonds. $\mathrm{CCl}_{4}$ being symmetrical molecule has zero resultant dipole moment. We know that the bond dipole moment of $\mathrm{C}-\mathrm{H}$ bond and that of $\mathrm{C}-\mathrm{Cl}$ bond reinforce one-another.\ In $\mathrm{CHCl}_{3}$, the resultant of $\mathrm{C}-\mathrm{H}$ and $\mathrm{C}-\mathrm{Cl}$ dipoles opposes the resultant of two $\mathrm{C}-\mathrm{Cl}$ dipoles while in $\mathrm{CH}_{2} \mathrm{Cl}_{2}$, the resultant of $\mathrm{C}-\mathrm{H}$ dipoles add to the resultant of two $\mathrm{C}-\mathrm{Cl}$ dipoles. In case of $\mathrm{CH}_{3} \mathrm{Cl}$, the resultant of two $\mathrm{C}-\mathrm{H}$ dipoles add to the resultant of $\mathrm{C}-\mathrm{H}$ and $\mathrm{C}-\mathrm{Cl}$ dipoles. Thus, dipole moment of $\mathrm{CH}_{3} \mathrm{Cl}$ is highest among the given compounds. The molecule $\left(\mathrm{CCl}_{4}ight)$ again becomes symmetrical and dipole moment reduces to zero.\