What is Dipole Moment ?
Dipole Moment
Dipole moment is defined as the product of the magnitude of the charges and the distance between the bonded atoms(i.e. bond length). It is denoted by a symbol μ.
If 'q' be the charge on atom and 'd' be the distance between two atoms then-
μ = q x d
Diploe moment is a vector quantity and it determines the polarity of the bond. Dipole moment is expressed in Debye unit.
If the charge 'q' is 4.8 x 10−10 esu and the bond length 'd' is 1Å (i.e. 10−8 cm) then, the dipole moment-
μ = q x d
μ = 4.8 x 10−10 esu x 10−8 cm
or, μ = 4.8 x 10−18 esu cm
or, μ = 4.8 Debye
or, μ = 4.8 D
[Note: 1.6 x 10−10c = 4.8 x 10−10 esu, 1Debye = 10−18 esu cm and 3.336 × 10−30 coulomb meters]
Example: Bond distance between H and Cl
i.e. bond length 'd' = 1.6 x Å esu.
and charge q = 4.8 x 10−10 esu
thus, μ = 1.26 x 10−8 x 4.8 x 10−10 esu
or, μ = 6.05D
For polyatomic molecules, the dipole moment is due to the vector sum of the dipole moments of the bonds.
Dipole moment is of two types. One is permanent dipole moment which occurs when the partial charges in a molecule are fixed due to the electronegativity difference between the atoms. and the other is induced dipole moment which occurs when a non-polar molecule is placed in an electric field, causing a distortion of the electron cloud and a temporary separation of charges.
Factors Affecting Dipole Moment
Dipole moment of a molecule depends on several factors, some of them are given below-
Electronegativity Difference: Greater the difference in electronegativity between the bonded atoms, larger the dipole moment.
Distance between Charges: Longer the distance between the partial charges, arger the dipole moment.
Bond Polarity: Polarity of a bond directly affects the dipole moment of the molecule. Covalent bonds generally have some degree of polarity due to the unequal sharing of electrons.
Molecular Geometry: Shape and orientation of the atoms in a molecule can affect the dipole moment. For example, molecules with a linear or bent shape tend to have larger dipole moments than molecules with a tetrahedral or octahedral shape.
Applications of Dipole Moments
There are number of applications of dipole moments. Some of them are discussed below-
1. Determination of Bond Moment
2. Determination of % Ionic Character
3. Distinction of cis-trans Isomerism
4. Determination of Structure of Molecules
5. Distribution between ortho, meta and para isomers
Detail Explanation of Applications of Dipole Moments
