The dehydration process in the dl ‐phenylglycinium trifluoromethanesulfonate monohydrate crystal revealed by XRD, vibrational and DSC studies

Thermal analysis, X‐ray diffraction and temperature‐dependent IR spectroscopy were used to study the dehydration process of crystalline dl ‐phenylglycinium trifluoromethanesulfonate monohydrate (PGTFH), C 8 H 10 NO 2 + ·CF 3 SO 3 − ·H 2 O. PGTFH dehydrates in one step centred at 353 K and crystallizes in the monoclinic space group C 2/ c , whereas the anhydrous compound (PGTF) crystallizes in the triclinic space group P . The dehydration process in PGTFH is preceded by a weakening of both the noncovalent aromatic–aromatic interactions and the packing contacts. This process is accompanied by the breakage of medium‐strength O—H…O hydrogen bonds between ions inside layers and a reorganization of the ions within the layers. This reorganization results in the formation of two different ion pairs ( dl ‐phenylglycinium trifluoromethanesulfonate) and the formation of a new hydrogen‐bond network. The dehydration process does not destroy the nature of the crystal structure. Both crystals, i.e. hydrated and anhydrous, have a layered structure, although the layers of each crystal are arranged somewhat differently.