Pressure–volume–temperature data and dielectric properties of liquid and solid 2,2-dimethylbutan-1-ol up to 300 MPa

DSC studies of neohexanol and its isomers

“…In the case when 2,2-dimethyl-1-butanol sample have been abruptly cooled down to 100 K the DSC curve obtained on slow heating shows different phase transition anomalies, i.e., first an exothermic at 180 K and then an endothermic one at 235 K as presented in figure 2. Taking into account results of neutron scattering results one can presume that at 180 K a supercooled liquid transforms spontaneously to a plastic crystal C2 [23] which melts at 234 K. These phase transitions are not reported in [20]. On the other hand, we have not found the transition registered by means of DTA at 199 K [20] and observed in our neutron experiment recognized as C2 !…”

“…Taking into account results of neutron scattering results one can presume that at 180 K a supercooled liquid transforms spontaneously to a plastic crystal C2 [23] which melts at 234 K. These phase transitions are not reported in [20]. On the other hand, we have not found the transition registered by means of DTA at 199 K [20] and observed in our neutron experiment recognized as C2 ! C3 [23] on slow cooling from 214 K. For 3,3-dimethyl-1-butanol the DSC curve shows three anomalies on heating the sample after cooling (ÁT/Át ¼ 10 K min À1 ) down to liquid nitrogen temperature (see figure 3).…”

“…On cooling an exothermic anomaly due to crystallization at 212 K and on heating two endothermic anomalies due to a solid-solid transition at 234 K and melting at 251 K have been found. In addition, a very slight anomaly at about 160 K has been identified on heating which corresponds to softening of a glassy crystal found by DTA [20,21] and confirmed in neutron studies [23]. On cooling it was impossible to trace a glass formation at all.…”

“…C I (210.4 K), C I ! I (250.6 K) and glass of crystal !C II (158 K)) [19,20]. At higher pressure two additional crystalline phases have been detected.…”

“…Localization of OH group in 1-butanols (in terminal position) and in 2-butanols (in side position) is expected to influence the tendency to form hydrogen bonds between molecules. Investigations of thermal features have been performed for 2,2-DM-1-B (neohexanol) using DTA method [19,20] and for 3,3-DM-1-B using DSC and adiabatic calorimetry [21]. Both compounds have also been studied by dielectric relaxation method and the plastic phases have been found there [13,[19][20][21].…”