Abstract
1H, 19F, and 14N NMR, powder X-ray diffraction, and differential scanning calorimetry (DSC) were studied for trimethylethylammonium tetrafluoroborate, (CH3)3NC2H5BF4. Five solid phases, named I, II, III, IV, and V in the order of decreasing temperature, were obtained in the temperature range 77-630 K. The transition temperatures and the corresponding enthalpy changes determined by DSC were 222K (0.16kj moi-1), 239K (1.8 kJ mol-1), 293 K (2.1 kJ mol-1), and 362 K (4.5 kJ mol-1). X-ray powder patterns showed that Phase I and II form an NaCl-type cubic lattice (a = 10.14 Å, Z = 4) and a tetragonal lattice (a = 8.59, c = 6,24 Å, Z = 2), respectively. The NMR study revealed that the canonic orientation in Phase I and II is dynamically disordered. Moreover, since the self-diffusion of anions and the Isotropie rotation of cations were observed in Phase I, this phase can be considered as a mesophase very close to the plastic phase. In Phases II, III, IV, and V we have detected the isotropic reorientation of anions, the anisotropic tumbling of cations, the C′3 reorientation of the whoie (CH3)3N group about C-N bond axis, and the C3 reorientation of the CH3 groups. The motional parameters were evaluated for these cationic and anionic motions.
Original language | English |
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Pages (from-to) | 1833-1838 |
Number of pages | 6 |
Journal | Berichte der Bunsengesellschaft/Physical Chemistry Chemical Physics |
Volume | 100 |
Issue number | 11 |
Publication status | Published - Dec 1 1996 |
Externally published | Yes |
Keywords
- Crystal structure
- Diffusion
- Nuclear magnetic resonance
- Phase transitions
- Speciroscopy
ASJC Scopus subject areas
- Chemical Engineering(all)