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Solution conformations for the flexible 1-chloro-1,1-difluoro-2-pentanol unveiled using multinuclear magnetic resonance
Tetrahedron ( IF 2.1 ) Pub Date : 2018-01-08 , DOI: 10.1016/j.tet.2018.01.008
Francisco A. Martins , Lucas A. Zeoly , Rodrigo A. Cormanich , Matheus P. Freitas

The preferred conformations of a small polyfunctional molecule containing fluorine, chlorine and hydroxyl groups, the 1-chloro-1,1-difluoro-2-pentanol (CDP), were completely elucidated using 1H, 13C and 19F NMR in three different solvents. While the Cl-C-C-O dihedral angle was asserted using coupling constant data for the diastereotopic fluorines, the Et-C-C-O torsional angle was analyzed by means of 1H NMR spectra with selective irradiation of the diastereotopic hydrogens and fluorines. In addition, unusual couplings of the hydroxyl hydrogen with a diastereotopic hydrogen and fluorines provided information on the O-H orientation. The behavior of 1JC,F when the solvents varied agrees with a weak F⋅⋅⋅HO intramolecular hydrogen bond. These findings were corroborated, and the governing interactions rationalized with the aid of high level CCSD(T) theoretical calculations. Noteworthy, hyperconjugation involving the electron-acceptor σ*C-Cl orbital drives the conformational equilibrium rather than the fluorine gauche effect.



中文翻译:

利用多核磁共振揭示了柔性1-氯-1,1-二氟-2-戊醇的溶液构象

使用1 H,13 C和19 F NMR在三种不同的条件下完全阐明了含氟,氯和羟基的多官能小分子1-氯-1,1-二氟-2-戊醇(CDP)的优选构象溶剂。尽管使用非对映异构体氟的偶合常数数据确定了Cl-CCO二面角,但通过1 H NMR光谱对非对映异构体中的氢和氟进行了选择性照射,对Et-CCO扭转角进行了分析。另外,羟基氢与非对映体氢和氟的不同寻常的偶联提供了关于OH取向的信息。1 J C,F的行为当溶剂变化时,表明F⋅⋅⋅HO分子内氢键弱。这些发现得到了证实,并借助高级CCSD(T)理论计算使控制相互作用合理化。值得注意的是,涉及电子受体σ* C-Cl轨道的超共轭作用会驱动构象平衡,而不是氟絮凝效应。

更新日期:2018-01-08
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