Mesophases of Alkylammonium Salts. I. First-Order Transitions

The effect of high external pressures on the infrared and Raman spectra of crystalline tetra-n-propylammonium bromide

“…It is known that for many organic solids, pressure can induce a change in crystal structure, leading to a phase which can be obtained by lowering temperature. However, in the present case, since TPABr already crystallizes in its lowest temperature, ordered phase at [9,10]. Our pressure-tuning infrared data do exhibit some differences from those in Ref.…”

“…The phase transition behavior of tetra-n-propylammonium bromide (TPABr) and molecular motion of TPA + as a function of temperature were previously examined by thermal analysis, 1 H and 13 C solid-state NMR spectroscopy [9][10][11]. TPABr possesses three solid phases with two transition temperatures at 395.8 and 382.2 K. TPABr is a plastic crystal when in its highest temperature phase with orientational disorder.…”

Understanding the Polymorphic Behavior of Sibenadet Hydrochloride through Detailed Studies Integrating Structural and Dynamical Assessment

“…47 Conformationally disordered crystals generally exhibit positional and/or orientational order but are involved in partial or full conformational dynamics. Such behavior has been observed for linear, flexible molecules that exhibit chain mobility involving large amplitude motion about the chain axis resulting in an increase in molecular symmetry.…”

Heat capacities of crystalline tetraalkylammonium salts

“…The most complex behavior was exhibited by Hex 4 NBr, whose molecular packing led to five phase transitions at 145-315 K [10].…”

“…The authors of [10,11] showed that on heating the salts, only orientational disordering was observed for tetraalkylammonium salts with C 1 -C 3 cations, both orientational and conformational changes for salts with C 4 -C 7 cations, and only conformational disordering for salts with larger cations. The most complex behavior was exhibited by Hex 4 NBr, whose molecular packing led to five phase transitions at 145-315 K [10].…”