Abstract
The heat capacities (C p,m) of 2-amino-5-methylpyridine (AMP) were measured by a precision automated adiabatic calorimeter over the temperature range from 80 to 398 K. A solid-liquid phase transition was found in the range from 336 to 351 K with the peak heat capacity at 350.426 K. The melting temperature (T m), the molar enthalpy (Δfus H 0m ), and the molar entropy (Δfus S 0m ) of fusion were determined to be 350.431±0.018 K, 18.108 kJ mol−1 and 51.676 J K−1 mol−1, respectively. The mole fraction purity of the sample used was determined to be 0.99734 through the Van’t Hoff equation. The thermodynamic functions (H T-H 298.15 and S T-S 298.15) were calculated. The molar energy of combustion and the standard molar enthalpy of combustion were determined, ΔU c(C6H8N2,cr)= −3500.15±1.51 kJ mol−1 and Δc H 0m (C6H8N2,cr)= −3502.64±1.51 kJ mol−1, by means of a precision oxygen-bomb combustion calorimeter at T=298.15 K. The standard molar enthalpy of formation of the crystalline compound was derived, Δr H 0m (C6H8N2,cr)= −1.74±0.57 kJ mol−1.
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Zhang, J.N., Tan, Z.C., Meng, Q.F. et al. Molar heat capacities and standard molar enthalpy of formation of 2-amino-5-methylpyridine. J Therm Anal Calorim 95, 461–467 (2009). https://doi.org/10.1007/s10973-008-9267-9
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DOI: https://doi.org/10.1007/s10973-008-9267-9