Phase transitions in adamantane derivatives: 1-fluoroadamantane

Abstract

. Can. J. Chem. 69, 1758 (1991).The solid-state phase behaviour of 1-fluoroadamantane (1-CloH15F) has been investigated by differential scanning calorimetry, and by infrared and Rarnan spectroscopy. The phase transition occurs at 227 K on cooling and at 231 K upon heating, with average AHt and ASt of 1.65 kJ mol-' and 7.3 J K-' mol-l. The transition was also apparent in the low-temperature IR and Raman spectra by a sudden line narrowing, and characteristic spectral features of each phase were identified. Both phases I and I1 were disordered, and further cooling of phase I1 resulted in the formation of a glass. Attempts to induce a glass transition (predicted to occur at ~9 0 K) by slow heating were unsuccessful. Vibrational spectroscopic studies at high pressures showed a phase transition at 3.3 f 1.0 kbar, upon compression. The phases formed under pressure were the same as those induced by lowering temperature.

Structure and reorientational dynamics of 1-F-adamantane

“…Based on this, we ascribe the primary α-relaxation to twofold rotations, whereas the faster α' relaxation, that also has lower activation energy, is ascribed to rotations around the threefold axis, as these are characterized by lower steric hindrance in the structure of Phase II. Because 1F-ada is a rigid molecule, 43,44 it cannot exhibit any "internal" relaxation associated with intramolecular dipole moment changes within the analyzed frequency range. This means that the fast β relaxation (whose characteristic relaxation time is plotted in Figure 5) should be ascribed to a Johari-Goldstein (JG) relaxation.…”

Thermodynamic properties of 1-bromoadamantane in the condensed state and molecular disorder in its crystals

“…The number of non-equivalent orientations in plastic crystals of 1-bromoadamantane (n orient ) vs. the mean energy difference between ''plastic'' and ''basic'' orientations (D orient H) for the next conditions: D orient S = 21.4 J AE K À1 AE mol À1 and D orient C p = 44.5 J AE K À1 AE mol À1 at T trs = 309.9 K. FIGURE 7. The schematic diagram presenting phase behaviour of several halohydrocarbons: group of adamantane (Ad [6,33]): 1-FAd, 1-CAd, 1-BAd, and 1-IAd are 1-fluoro- [34], 1-chloro- [30], 1-bromo-(this work), and 1-iodoadamantane [9], respectively; group of cyclohexane (Ch [40]): FCh, CCh, and BCh are fluoro- [41], chloro- [42], and bromocyclohexane [43], respectively; group of methane (CH 4 [44]): CF 4 [45], CCl 4 [46], and CBr 4 [47]. The abbreviation ''p'' means ''plastic''.…”

Six-membered ring aliphatic compounds: A search for regularities in phase transitions

“…For example, different adamantane-based inhibitors were developed as effective drugs against influenza [1]. From a theoretical point of view adamantane derivatives are interesting because they are able to form plastic crystals [2,3]. Compounds composed of approximately spherical molecules like adamantanes easily undergo solid-solid phase transitions.…”

“…It includes uncertainties from the experimental conditions for transpiration, uncertainties in vapor pressure, and uncertainties in the temperature adjustment to T = 298.15 K. literature were adjusted to the reference temperature in a different way using the different values. We treated the literature vapor pressures uniformly using equations(2) and(3)with heat capacity differences listed inTable S5 and calculated…”