3(5),4-Dimethyl- and 3,4,5-trimethylpyrazole at 200 K. X-ray crystallography and quantum-chemical analysis.
3(5),4-Dimethyl- and 3,4,5-trimethylpyrazole at 200 K. X-ray crystallography and quantum-chemical analysis.
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200 K 下的 3(5),4-二甲基- 和 3,4,5-三甲基吡唑。X 射线晶体学和量子化学分析。
DOI：
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发表时间：
1999
期刊：
影响因子：
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通讯作者：
Elguero
中科院分区：
文献类型：
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作者：
Infantes;Foces;Elguero
在200K下测定了3(5)，4-二甲基吡唑，C(5)H(8)N(2)，(I)和3，4，5-三甲基吡唑C(6)H(10)N(2)，(II)的晶体和分子结构。在(I)中，4，5-二甲基吡唑互变异构体以固态形式存在，不对称单元中的六个独立分子通过NH.N氢键形成三聚体。(II)的不对称单元包含一个半分子：这些分子表现出NH质子无序，并通过各自的NH基团相互氢键形成链。在HF和B3LYP/6-31G**水平下的从头计算表明，3，4-二甲基吡唑互变构体比4，5-二甲基吡唑互变构体稳定约0.5kcal(-1)(1kcal(-1)=4.184 kJ(-1))。
The crystal and molecular structures of 3(5),4-dimethylpyrazole, C(5)H(8)N(2), (I), and of 3,4,5-trimethylpyrazole, C(6)H(10)N(2), (II), have been determined at 200 K. In (I) the 4,5-dimethylpyrazole tautomer is present in the solid state and the six independent molecules in the asymmetric unit form trimers via NH.N hydrogen bonds related by a pseudo centre of symmetry. The asymmetric unit of (II) contains one and a half molecules: these exhibit NH proton disorder and are hydrogen bonded to each other via their respective NH groups to form chains. Ab initio calculations at HF and B3LYP/6-31G** levels indicate that the 3,4-dimethylpyrazole tautomer is more stable than the 4,5-dimethylpyrazole tautomer by only approximately 0.5 kcal mol(-1) (1 kcal mol(-1) = 4.184 kJ mol(-1)).