why does chlorobenzoic acid have a lower freezing point than benzoic acid explain?

would this have something to do with the intermolecular forces or polarity. I know that the chlorobenzoic acid a Cl atom in the molecule which would create for a stronger intermolecular force but I'm not to sure how this could account for a lower freezing point?

Hmmmm. Please examine the fp for benzoic acid and chlorobenzoic acid.

You're on the right track! The difference in freezing points between chlorobenzoic acid and benzoic acid can indeed be attributed to intermolecular forces and polarity. Let me explain in more detail.

The freezing point of a substance is determined by the strength of the forces holding its molecules together. In general, substances with stronger intermolecular forces tend to have higher freezing points.

In the case of chlorobenzoic acid and benzoic acid, both molecules are composed of a benzene ring with a carboxylic acid group (-COOH) attached. However, chlorobenzoic acid has a chlorine atom (Cl) substituted for one of the hydrogen atoms in the benzene ring. This substitution introduces an electronegative atom (chlorine) into the molecule, resulting in a polar covalent bond.

The presence of the chlorine atom increases the polarity of chlorobenzoic acid compared to benzoic acid. The polar covalent bond between chlorine and carbon creates partial positive and partial negative charges in the molecule. This polarity leads to stronger dipole-dipole interactions between neighboring chlorobenzoic acid molecules.

In contrast, benzoic acid lacks such a polar substituent and exhibits weaker intermolecular forces primarily due to van der Waals forces, specifically London dispersion forces.

The stronger dipole-dipole interactions in chlorobenzoic acid make it more difficult for the molecules to align in the solid state, resulting in weaker intermolecular forces overall. Weaker intermolecular forces mean that less energy is required to break these forces during freezing. Therefore, chlorobenzoic acid has a lower freezing point compared to benzoic acid.

In summary, the lower freezing point of chlorobenzoic acid compared to benzoic acid can be attributed to the stronger dipole-dipole interactions resulting from the presence of the electronegative chlorine atom.