14.5 : 羧酸衍生物的物理性质

Physical properties depend on the strength of intermolecular forces, with ionic forces being the strongest and dispersion forces the weakest.

Since esters and acid chlorides cannot function as hydrogen bond donors, they fail to engage in intermolecular hydrogen bonding. Consequently, they have the lowest boiling points.

In comparison, acid anhydrides are large polar molecules and experience strong dispersion forces leading to higher boiling points.

Nitriles have even higher boiling points resulting from strong dipolar interactions between the cyano groups.

Among the derivatives, amides have the highest boiling points.

Primary and secondary amides form strong hydrogen bonds and have higher boiling points than tertiary amides, where the primary interaction is the dipole-dipole interaction.

The melting point of amides follows the same trend as their boiling points.  

Esters, amides, and nitriles with less than four carbons are highly polar, making them water-soluble.

However, the water solubility decreases as the length of the non-polar alkyl group increases, making longer chains soluble in less polar solvents.