A Rational Study of the Origin and Generality of Anti-Enthalpy–Entropy Compensation (AEEC) Phenomenon

Abstract

Abstract In addition to enthalpy–entropy compensation (EEC), anti-enthalpy–entropy compensation (AEEC) phenomenon is also found in literature. The reports on the latter are limited, and analyses and justifications are so far unclear. Herein we present demonstration on the nature and possibility of the AEEC phenomenon. Although literature reports so far have mostly shown linear AEEC, we have found both linear and non-linear dependences. The non-linearity we consider arises from large “free energy window” (FEW) like EEC, recently presented and discussed. Attempts have been made to rationalize the observations in terms of solvation–desolvation phenomenon of the involved processes anticipated in previous studies. We have found that enthalpy and entropy of formation of gaseous and solid materials may also exhibit AEEC, it can be thus classified as a global phenomenon. In addition to AEEC, the phenomenon of no-enthalpy–entropy compensation (NEEC) is also reported. Thus, the phenomena EEC, AEEC and NEEC are thermodynamic puzzles that require close attention and analysis. With the help of wide range of physical chemical processes, an elaborate general understanding of the linear and non-linear AEEC phenomena has been attempted. The experimental data herein used are collected from literature reports, new measurements were not done. A variety of examples have supported possible generality of AEEC.