The thermodynamic properties of 1-bromoadamantane in the gaseous state

Abstract

The saturated vapour pressure over two crystalline phases (crI and crII) of 1-bromoadamantane in the temperature range from 288 to 323 K was measured by the integral Knudsen effusion method with the use of a modified effusion cell with an enlarged surface of sublimation. The temperature dependences of p sat are the following: for crII between T = 288.4 and 309.9 K: ln { p sat ( crII ) ( Pa ) } = ( 30.33 ± 0.44 ) − ( 8608 ± 137 ) ⋅ ( T ( K ) ) − 1 , for crI from 309.9 to 323.0 K: ln { p sat ( crI ) ( Pa ) } = ( 27.07 ± 0.81 ) − ( 7600 ± 252 ) ⋅ ( T ( K ) ) − 1 . The sublimation enthalpy for the compound at T = 303.0 K was measured in a differential heat-conducting microcalorimeter of the Calvet type, Δ sub H m ° ( 303.0 K ) = 71.77 ± 0.31 kJ mo l − 1 , which agrees with the value obtained by the effusion measurements, Δ sub H m ° ( 298.1 K ) = 71.6 ± 1.1 kJ mo l − 1 , within the experimental errors. The molar thermodynamic functions of 1-bromoadamantane in the ideal gaseous state were calculated by the statistical thermodynamic method. The complete set of the fundamentals necessary for the above calculations was made up from the experimental IR and Raman spectral data and the results of DFT calculations (B3LYP/6-31G*). The enthalpy of formation for 1-bromoadamantane was evaluated in terms of three different approaches. The thermodynamic analysis of some reactions with 1-bromoadamantane was performed.