Thermodynamic Study of N -Methylformamide and N , N -Dimethyl-Formamide.

An extensive thermodynamic study of N -methylformamide (CAS RN: 123-39-7) and N , N -dimethylformamide (CAS RN: 68-12-2), is presented in this work. The liquid heat capacities of N -methylformamide were measured by Tian-Calvet calorimetry in the temperature interval (250-300) K. The vapor pressures for N -methylformamide and N , N -dimethylformamide were measured using static method in the temperature range 238 K to 308 K. The ideal-gas thermodynamic properties were calculated using a combination of the density functional theory (DFT) and statistical thermodynamics. A consistent thermodynamic description was developed using the method of simultaneous correlation, where the experimental and selected literature data for vapor pressures, vaporization enthalpies, and liquid phase heat capacities and the calculated ideal-gas heat capacities were treated together to ensure overall thermodynamic consistency of the results. The resulting vapor pressure equation is valid from the triple point to the normal boiling point temperature.