Question

Explain dipole-dipole interactions.

Answer 1

Dipole-dipole interactions: 

i. When a polar molecule encounters another polar molecule, the positive end of one molecule is attracted to the negative end of another polar molecule. Interaction between such molecules is termed as dipole-dipole interaction. 

ii. These forces are generally weak, with energies of the order of 3-4 kJ mol^-1 and are significant only when molecules are in close contact, i.e., in a solid or a liquid state. 

iii. For example, C₄H₉Cl, (butyl chloride), CH₃ – O – CH₃ (dimethyl ether), ICl (iodine chloride, B.P. 27 °C), are dipolar liquids. 

iv. The molecular orientations due to dipoledipole interaction in ICl liquid is shown in the following figure:

v. More polar the substance, greater the strength of its dipole-dipole interactions.