Molar heat capacities for (2-methyl-2-butanol + heptane) mixtures and cyclopentanol at temperatures from (284 to 353) K

Abstract

Isobaric specific heat capacities were measured for (2-methyl-2-butanol + heptane) mixtures and cyclopentanol within the temperature range from (284 to 353) K, and for 2-methyl-2-butanol in the (284 to 368) K temperature interval by means of a differential scanning calorimeter. The excess molar heat capacities were calculated from the experimental results. For the temperature range from (284 to 287) K, the excess molar heat capacity is S-shaped with negative values in the 2-methyl-2-butanol rich region and with small negative values at low alcohol concentrations at temperatures from (295 to 353) K. The excess molar heat capacities are positive for all compositions under test at temperatures from (288 to 294) K. The results are explained in terms of the influence of the molecular size and configuration of the alkanols on their self-association capability and of the change in molecular structure of the (2-methyl-2-butanol + heptane) mixtures. The differences between the temperature dependences of the heat capacities of the mixtures studied are qualitatively consistent with results obtained by Rappon et al. [M. Rappon, J.M. Greer, J. Mol. Liq. 33 (1987) 227–244; M. Rappon, J.A. Kaukinen, J. Mol. Liq. 38 (1988) 107–133; M. Rappon, R.M. Johns, J. Mol. Liq. 40 (1989) 155–179; M. Rappon, R.T. Syvitski, K.M. Ghazalli, J. Mol. Liq. 62 (1994) 159–179; M. Rappon, R.M. Johns, J. Mol. Liq. 80 (1999) 65–76; M. Rappon, S. Gillson, J. Mol. Liq. 128 (2006) 108–114].