Question

Explain the dipole-dipole interaction energy between stationary polar molecules.

Answer 1

Dipole-dipole interaction

1. Dipole-dipole interactions occur when two dipolar molecules interact with each other in space.
2. When this happens, the partially negative component of one of the polar molecules attracts the partially positive portion of the other polar molecule.
3. This type of molecular interaction can explain a variety of physically and biologically significant phenomena, such as the elevated boiling point of water.
4. Between stationary polar molecules, the energy of dipole-dipole interaction is $\frac{1}{r^3}$
5. Between spinning polar molecules, the energy of dipole-dipole interaction is $\frac{1}{r^6}$
6. The letter 'r' stands for the distance between polar molecules.
7. As the distance between the dipoles grows, the attractive force decreases. The distance between polar molecules has an inverse relationship with their interaction energy.
8. Dipole-dipole interactions occur when partial charges formed within one molecule are pulled to an opposite partial charge in a nearby molecule.
9. Dipole-dipole interactions can occur in polar molecules such as hydrogen chloride (HCl), carboxylic acids (e.g., acetic acid), and amino acids.

Dipole-dipole interaction with the help of an example

Hydrochloric acid that is HCl. Here the positive end is the hydrogen atom and it has a partial positive charge and chlorine atom is the negative end and it has a partial negative charge.

$\stackrel{\delta +}{H}-\stackrel{\delta -}{Cl}\cdots \cdots \stackrel{\delta +}{H}-\stackrel{\delta -}{Cl}$