Lorazepam contains more ionic groups. These ionic groups can exhibit strong electrostatic interactions, making lorazepam more water-soluble than lipid-soluble.

Lorazepam contains more nonpolar groups than diazepam. These nonpolar groups can form strong London-dispersion forces making lorazepam more water-soluble than lipid soluble.

Lorazepam is a larger molecule with a larger molecular mass. It has a larger size making lorazepam more water-soluble than lipid-soluble.

Lorazepam contains more polar groups than diazepam. The other polar groups can also form additional hydrogen bonds, making lorazepam more water-soluble than less lipid-soluble.