The standard molar enthalpies of vaporization, Delta H-vap(m)o, 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 Delta H-vap(m)o 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. (C) 2014 Elsevier Ltd. All rights reserved.