The order of dipole moment of the following molecules is

Options

A. `CHCl_3 gt CH_2Cl_2 gt CH_3Cl gt "CC"l_4`
B. `CH_2Cl_2 gt CH_3Cl gt CHCl_3 gt "CC"l_4`
C. `CH_3Cl gt CH_2Cl_2 gt CHCl_3 gt "CC"l_4`
D. `CH_2Cl_2 gt CHCl_3 gt CH_3Cl gt "CC"l_4`

Answer

C

Explanation

Due to symmetrical structure of `"CC"l_4` (tetrahedral) all the vectors of dipole moment cancel each other and the resultant dipole moment is zero.
In `CHCl_3` , 3 dipole moments due to 3 Cl atoms try to cancel each other so the net resultant is a very small quantity. There is a small quantity of dipole moment because of a C - H bond also. Due to high electronegativity generated by 3 Cl - atoms, electrons are pulled towards C atom.
`CH_2Cl_2` has a higher dipole moment because of only 2 Cl atoms and the addition of 2 dipole moments generated by 2 C - H bonds.
In `CHCl_3` there is a net dipole moment in the bond direction of C - Cl and due to addition of 3 dipole moment generated by C - H bonds (towards C - atom).
So the correct order of dipole moments are :
`CH3Cl > CH_2Cl_2 > CHCl_3 > "CC"l_4 . `