The role of hydrogen bonds in the melting points of sulfonate-based protic organic salts

There are three main types of interactions inside organic salts - electrostatic interaction, hydrogen bonding and van der Waals force [1-4]. While van der Waals force is relatively weak, it is hydrogen bonding and particularly electrostatic interaction that determine the lattice energies of ionic systems and other physicochemical properties like melting points [5]. The hydrogen bond is an attractive interaction between a hydrogen atom from a molecule or a molecular fragment X-H in which X is more electronegative than H, and an atom or a group of atoms in the same or a different molecule, in which there is evidence of bond formation [6]. Hydrogen bonds in the solid state fall into the classification of strong, moderate, and weak hydrogen bonds [7]. In molecular systems like H₂O (vs. H₂S) or NH₃ (vs. PH₃), strong hydrogen bonds lead to higher melting points. However, in organic salts, the situation may be different [8,9].