Low-temperature heat capacities and thermodynamic properties of n-undecylammonium bromide monohydrate C₁₁H₂₈BrNO(s)

Abstract

Crystal structure of n-undecylammonium bromide monohydrate was determined by X-ray crystallography. Low-temperature heat capacities of the compound were measured by a precision automated adiabatic calorimeter over the temperature range from 78 to 390 K. Two solid–solid phase transitions were observed for the title compound. The temperatures, molar enthalpies, and entropies of the phase transitions were derived based on the analysis of heat–capacity curve. Two polynomial equations of heat capacities as a function of temperature were fitted by least-squares method. Based on the two polynomial equations, smoothed heat capacities and thermodynamic functions of the compound relative to the standard reference temperature 298.15 K were calculated and tabulated at 5 K intervals.

Keywords:

• n-undecylammonium bromide monohydrate
• low-temperature heat capacity
• solid–solid phase transition
• thermodynamic functions

Acknowledgements

This work is financially supported by the National Natural Science Foundations of China under the contract NSFC no. 20673050 and 20973089.