Association between halothane and oxygenated solvents by 1H NMR spectroscopy

Abstract

Using 1H NMR spectroscopy the complex-formation equilibria between halothane (2-bromo-2-chloro-1,1,1-trifluoroethane) and methyl tert-butyl ether or tetrahydrofuran in various inert solvents (hexane, heptane, decane, cyclohexane) were measured as a function of temperature. For two different association models (ideal solution and athermal solution), assuming only the formation of a 1:1 H-bonded complex, the equilibrium constants and the standard enthalpies of the complex-formation reaction were calculated. The ideal solution model provides values of the equilibrium constant that differ for different inert solvents. The athermal solution model makes this false solvent effect much smaller. For the low halothane concentration used, its dimerization was neglected. This assumption was verified experimentally. Keywords: 1H NMR, association, complex formation, halothane.