Vaporization, Sublimation Enthalpy, and Crystal Structures of Imidazo[1,2-a]pyrazine and Phthalazine

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• 作者：Massiel Mori ; Nigam Rath ; Chase Gobble ; James Chickos ; Artemiy A. Samarov ; Sergey P. Verevkin
• 刊名：Journal of Chemical & Engineering Data
• 出版年：2016
• 出版时间：January 14, 2016
• 年：2016
• 卷：61
• 期：1
• 页码：370-379
• 全文大小：483K
• ISSN：1520-5134

文摘

The vaporization enthalpy of imidazo[1,2-a]pyrazine is evaluated by correlation gas chromatography using two sets of standards and by transpiration. Vaporization enthalpies were evaluated using heterocyclic standards with dipole moments that vary from 0 to 3.0 D and using standards with dipole moments > 3.0 D. A value of (70.7 ± 1.0) kJ·molp>–1p> measured by transpiration compares to (67.9 ± 1.4) kJ·molp>–1p> measured by correlation gas chromatography using standards characterized by dipole moments > 3.0 D. The results suggest that imidazo[1,2-a]pyrazine is a member of this series of compounds whose vaporization enthalpies exceed those less polar heterocycles by a fairly constant amount, (6.9 ± 0.3) kJ·molp>–1p>, in this case by (5.9 ± 3.0) kJ·molp>–1p> using the less polar heterocycles. The crystal structures of phthalazine, another member of the polar series, and of imidazo[1,2-a]pyrazine were determined to examine whether π–π stacking, present in the solid state of two other members of the polar series, was a characteristic of this series. If present in the liquid, π–π stacking could offer a possible explanation for the vaporization enthalpy differences observed. The sublimation enthalpy of imidazo[1,2-a]pyrazine was also evaluated.