Question

Dipole moment and explain it with reference to alkyl halode

Answer 1

The bond dipole moment (μμ) of a chemical bond is equal to the magnitude of the separation of charge (δδ) times the displacement of the charge (or the distance over which the charges are spearated) dd, or:

μ⃗ =δd⃗ μ→=δd→

Thus, there are two factors controlling dipole moment. The charge separation can be estimated from the electronegativity difference, but not perfectly. Disparities in size and polarizability also effect the separation of charge between two atoms. The displacement is the length of the bond. The C−ClC−Cl bond length (176 pm) is longer than the C−FC−F bond length (134 pm) - data from here.

Thus:

For C−FC−F, the electronegativity difference on the Pauling scale is 1.43, and the bond length is 134 pm: 1.43×134=1911.43×134=191 (ignoring units at the moment).

For C−ClC−Cl, the electronegativity different on the Pauling scale is 0.61, and the bond length is 174 pm: 0.61×174=1060.61×174=106.

So, my quick and dirty method did not work so well. However the disparity between these two bonds by my method (106/191)=0.55)(106/191)=0.55) is smaller than by just comparing electronegativities (0.61/1.43=0.42)(0.61/1.43=0.42) and that is because of the other factor mentioned above: size and polarizability. Chlorine is bigger and more polarizable than fluorine (and carbon). The carbon-chlorine bond is polarized toward chlorine not just because of the electronegativity difference. Chlorine's larger size decreases the effectiveness of orbital overlap in bonding, and chlorine's increase polarizability implies that it can support more partial negative charge than suggested by its electronegativity alone.

mark please

Answer 2

Dipole moment and its relation with alkyl halides are explained below.

• The Dipole moment of any compound occurs when there is a separation of a charge.
• They can occur between two ions in an ionic bond or between atoms in a covalent bond.
• Dipole moments arise from differences in electronegativity; the larger the electronegativity, the larger will be the dipole moment.
• The dipole moment of alkyl halides is higher than their corresponding alkanes which leads to attractive dipole-dipole interactions in liquid alkyl halides.