Thermochemistry of 1-alkylimidazoles

• The energetics of alkylimidazoles with chain lengths n = (1 to 12) was studied.
• The linear enthalpy of vaporization dependence on n shows a trend shift at n = 4.
• Gas phase enthalpies of formation were obtained from ab initio calculations.
• Experimental and theoretical results led to liquid phase enthalpies of formation.

The standard molar enthalpies of vaporization, ΔvapHmo, of 1-ethyl, 1-butyl, and 1-octylimidazole, at T = 298.15 K, were measured by Calvet-drop microcalorimetry. The values determined, together with results of high-level ab initio   calculations (W1-F12 and CCSD(T)-F12) and published ΔvapHmo data were used to obtain the enthalpies of formation in the gaseous and liquid states of 1-alkylimidazole compounds ranging from 1-methylimidazole to 1-dodecylimidazole. Structure-energetics trends related to the alkyl chain length are discussed.

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