Low‐tmperature Heat Capacities and Standard Molar Enthalpy of Formation of 4‐Nitrobenzyl Alcohol

Abstract

AbstractLow‐temperature heat capacities of 4‐nitrobenzyl alcohol4‐NBAhave been measured by a high precision automated adiabatic calorimeter over the temperature range from 78 to 396 K. The melting temperature, the molar enthalpy and entropy of the phase transition were determined to be (336.426±0.088) K, (20.97±0.13) kJ·mol−1 and (57.24±0.36) J·K−1·mol−1, respectively. The thermodynamic functions [HT−H298.15 K] and [ST−S298.15 K] were calculated in the range from 80 to 400 K at the interval of 5 K. The constant‐volume energy and standard molar enthalpy of combustion have been determined, ΔcU(C7H7NO3, s) =− (3549.11±1.47) kJ·mol−1 and ΔcHm0 (C7H7NO3, s) =− (3548.49±1.47) kJ·mol−1, by means of a precision oxygen‐bomb combustion calorimeter at T=298.15 K. The standard molar enthalpy of formation has been derived, ΔfHm0 (C7H7NO3, s) =− (206.49±2.52) kJ·mol−1, from the standard molar enthalpy of combustion in combination with other auxiliary thermodynamic quantities through a Hess thermochemical cycle.