Low Temperature Heat Capacities and Thermodynamic Properties of 2‐Methyl‐2‐butanol

The low‐temperature heat capacity C p ,m of 2‐methyl‐2‐butanol was precisely measured in the temperature range from 80 to 305 K by means of a small sample automated adiabatic calorimeter. Three solid‐solid phase transitions and one solid‐liquid phase transition were found at T =146.355, 149.929, 214.395 and 262.706 K from the experimental C p ‐ T curve, respectively. The dependence of heat capacity on temperature was fitted to the following polynomial equations with a least square method. In the temperature range of 80 to 140 K, C p ,m =39.208+8.0724 X −1.9583 X 2 +10.06 X 3 +1.799 X 4 −7.2778 X 5 +1.4919 X 6 , X = ( T −110)/30; in the temperature range of 155 to 210 K, C p ,m =70.701+10.631 X +12.767 X 2 +0.3583 X 3 −22.272 X 4 −0.417 X 5 +12.055 X 6 , X = ( T −182.5)/27.5; in the temperature range of 220 to 250 K, C p ,m =99.176+7.7199 X −26.138 X 2 +28.949 X 3 +0.7599 X 4 −25.823 X 5 +21.131 X 6 , X = ( T −235)/15; and in the temperature range of 270 to 305 K, C p ,m =121.73+16.53 X −1.0732 X 2 −34.937 X 3 −19.865 X 4 +24.324 X 5 +18.544 X 6 , X = ( T −287.5)/17.5. The molar enthalpies of these transitions were determined to be 0.9392, 1.541, 0.6646 and 2.239 kJ·mol −1 , respectively. The molar entropies of these transitions were determined to be 6.417, 10.28, 3.100 and 8.527 J·K −1 ·mol −1 , respectively. The thermodynamic functions [ H T − H 298.15 ] and[ S T − S 298.15 ], were derived from the heat capacity data in the temperature range of 80 to 305 K with an interval of 5 K.