What type of molecules cannot form hydrogen bonds with water?

Nonpolar molecules cannot form hydrogen bonds with water due to their lack of significant electronegativity differences between the atoms involved. Hydrogen bonds occur between polar molecules because these bonds depend on the attraction between the partial positive charge of a hydrogen atom and the partial negative charge of another atom (such as oxygen in water). Nonpolar molecules, by definition, do not possess polar regions; they have an even distribution of electrical charge and thus do not interact well with water, which is a polar solvent.

In contrast, polar molecules can form hydrogen bonds because they have regions of partial positive and partial negative charge that facilitate such interactions. Charged molecules (ions) also interact favorably with water, typically leading to hydration shells. Hydrophilic molecules attract water molecules due to their polar nature and can participate in hydrogen bonding. Therefore, the defining characteristic of nonpolar molecules is what excludes them from forming these hydrogen bonds, making them hydrophobic and resulting in limited solubility in water.