Department of Chemistry and Biochemistry and Center for Nano Science, University of Missouri-St. Louis, St. Louis, Missouri 63121, USA.
J Phys Chem B. 2011 Jul 14;115(27):8785-96. doi: 10.1021/jp2041857. Epub 2011 Jun 20.
The vaporization enthalpies of a series of heterocyclic compounds some suspected of showing evidence of a higher degree of self-association in comparison to many other nitrogen heterocycles have been measured both by correlation gas chromatography (CGC) and for comparison by transpiration. The compounds share some structural similarities. They include 2- and 4-(N,N-dimethylamino)pyridine, 1,5-diazabicyclo[4.3.0]non-5-ene, 1,8-diazabicyclo[5.4.0]undec-7-ene, 1,2,4-triazolo[1,5-a]pyrimidine and imidazo[1,2-a]pyridine. The vaporization enthalpies of the first three of the compounds are well reproduced by a standard series of reference compounds, mainly pyridine derivatives. The latter two compounds and 4-(N,N-dimethylamino)pyridine exhibit vaporization enthalpies approximately 7 kJ·mol(-1) larger. Their values are reproduced by using standards previously shown to exhibit stronger but similar self-association properties. The crystal structure of 1,2,4-triazolo[1,5-a]pyrimidine has been determined in an effort to understand the nature of the self-association. The molecule crystallizes in planar stacks slightly offset with a stacking distance of 3.24 Å.
已经通过相关气相色谱法 (CGC) 和蒸发法测量了一系列杂环化合物的汽化焓，这些化合物中有些被怀疑比许多其他含氮杂环具有更高程度的自缔合证据。这些化合物具有一些结构相似性。它们包括 2- 和 4-(N,N-二甲基氨基)吡啶、1,5-二氮杂双环[4.3.0]壬-5-烯、1,8-二氮杂双环[5.4.0]十一-7-烯、1,2,4-三唑并[1,5-a]嘧啶和咪唑并[1,2-a]吡啶。前三种化合物的汽化焓可以通过一系列标准的参考化合物很好地再现，主要是吡啶衍生物。后两种化合物和 4-(N,N-二甲基氨基)吡啶的汽化焓约大 7 kJ·mol(-1)。通过使用先前显示出更强但类似自缔合性质的标准品来再现它们的值。为了了解自缔合的性质，已经确定了 1,2,4-三唑并[1,5-a]嘧啶的晶体结构。该分子在略微偏移的平面堆积中结晶，堆积距离为 3.24 Å。
