Thermochemical properties of different 1-(R-phenyl)-1H-imidazoles

• Methyl-, methoxy-, fluoro-, bromo-derivatives of phenyl-1H-imidazole synthesized.
• Vapor pressures measured by the transpiration method.
• Enthalpies of vaporization derived from pressure-temperature dependence.
• Consistency of vaporization enthalpies tested by a group contribution method.
• Gas-phase enthalpies of formation of phenyl-1H-imidazoles calculated by G3MP2.

Phenyl substituted imidazoles exhibit versatile biological activity. 1-(R-phenyl)-1H-imidazoles with different functional groups R provide a convenient suitcase of molecules with tunable physicochemical properties adjustable for many practical applications. In this work, the absolute vapor pressures of 1-(R-phenyl)-1H-imidazoles (with R = H, 2-methyl, 4-methyl, 2-methoxy, 4-methoxy, 2-fluoro, 4-fluoro, 2-bromo and 4-bromo) at different temperatures have been measured by the transpiration method for the first time. The standard enthalpies of vaporization of these compounds were derived from the temperature dependencies of the vapor pressures. An internal consistency of the standard vaporization enthalpies has been proven by comparison with vaporization enthalpies of parent species, as well as by a group contribution method. A system of group-additivity values is suggested for a quick assessment of vaporization enthalpies of different 1-(R-phenyl)-1H-imidazoles. Gas-phase standard molar enthalpies of formation of 1-(R-phenyl)-1H-imidazoles have been calculated using the high-level quantum-chemical method G3MP2. The combination of experimentally determined standard vaporization enthalpies with the G3MP2 results allows for the prediction of the liquid-phase standard enthalpies of formation for the studied compounds.

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