Question

How do functional groups affect intermolecular attractions?

Answer 1

Functional groups contribute to dipole-dipole attractions and to hydrogen bonds.

Every functional group is polar. This causes dipole-dipole attractions. If the group contains O-H or N-H bonds, hydrogen bonds are also present.

Common functional groups include

R-X —alkyl halide; R-O-R’ —ether; R-C≡N — nitrile

These all have polar bonds and generate dipole-dipole interactions.

R-CHO —aldehyde; R-COR’ — ketone; R-COOR’ — ester

These have polar C=O groups. They generate stronger dipole-dipole interactions.

R-OH — alcohol; R-NH₂ — amine

These have O-H and N-H bonds. They generate strong hydrogen-bonding interactions.

R-COOH — carboxylic acid; R-CONH₂— amide

These have C=O bonds as well as O-H or N-H groups. They generate the strongest intermolecular forces.