Thermodynamic Studies of Two Different Inclusion Compounds with the Same Guest:  Toward a General Understanding of Melting Behavior in Binary Compounds

• Published in: Chemistry of materials Vol. 10; no. 3; pp. 833 - 839
• Main Authors: White, Mary Anne, Harnish, R. Shane
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 16.03.1998
• Subjects: Chemistry; Exact sciences and technology; General and physical chemistry; Liquid-solid equilibria; Phase equilibria; Differential scanning calorimetry; Gibbs free energy; Melting; Hydrocarbon; Phase diagram; Binary system; Heat capacity; Liquid solid equilibrium; Experimental study; Thermal stability; Hexadecane; Urea; Alkane; Inclusion compound; Hot stage microscope; Thermodynamic properties; Phase equilibrium
• ISSN: 0897-4756; 1520-5002
• DOI: 10.1021/cm970578g

Melting behaviors of the hexadecane channel inclusion compounds of urea and of perhydrotriphenylene (PHTP) have been investigated by differential scanning calorimetry and hot-stage microscopy. Urea−hexadecane melts incongruently to give solid urea and liquid hexadecane, whereas PHTP−hexadecane melts congruently, i.e., giving liquid directly. Through examination of Gibbs energies, determined from adiabatic calorimetry, it is concluded that both inclusion compounds are stable with respect to their components, and melting behavior can be considered to be dictated by the stability of the host lattice at the melting point. Generalizations concerning factors influencing congruency of melting behavior in binary systems are presented.