Thermal Analysis and Calorimetric Study of 4-Dimethylaminopyridine

Abstract

4-dimethylaminopyridine (dmap) is an important catalyst. the thermodynamic properties of dmap were investigated through differential scanning calorimetry, thermogravimetric analysis, adiabatic calorimetry, and combustion calorimetry. the low-temperature heat capacity (c-p,c- m) was measured in the temperature range from (80 to 402) k with a high-precision automated adiabatic calorimeter. the melting temperature (t-m), the molar enthalpy (delta h-fus(m)), and the entropy (delta s-fus(m)) of fusion were determined to be ( 387.094 +/- 0.002) k, ( 21.628 +/- 0.144) kj . mol(-1), and (55.873 +/- 0.372) j . k-1 . mol(-1), respectively. the mole fraction purity of the sample used in the adiabatic calorimetric study was determined to be 0.99964 according to the van't hoff equation. the thermodynamic functions [h-t - h-298.15] and [s-t - s-298.15] were derived in the range from (80 to 400) k with temperature interval of 5 k based on the heat capacity measurements. the constant-volume energy and standard molar enthalpy of combustion have been determined, delta u-c (c7h10n2, cr) = -(4232.20 +/- 0.60) kj.mol(-1) and delta h-c(m)0 (c7h10n2, cr) = -(4235.92 +/- 0.60) kj.mol(-1), by means of a precision oxygen-bomb combustion calorimeter at t = (298.15 +/- 0.001) k. the standard molar enthalpy of formation has been derived, delta h-f(m)0 (c7h10n2, cr) = (52.20 +/- 1.71) kj.mol(-1), from the standard molar enthalpy of combustion in combination with other auxiliary thermodynamic quantities through a hess thermochemical cycle.