Hameed Rabia, van Mourik Tanja, Khan Afsar
Department of Chemistry, COMSATS University Islamabad, Abbottabad Campus, Islamabad, 22060, Pakistan.
School of Chemistry, University of St Andrews, North Haugh, St Andrews, KY16 9ST, UK.
J Mol Model. 2018 Oct 26;24(11):324. doi: 10.1007/s00894-018-3866-6.
A complete set of NMR coupling constants (J, J, J, and J) were calculated for the eight stereoisomers of quinic acid, at the B3LYP/6-311G(d,p)/PCM(methanol) level of theory. The Fermi contact term of the coupling constants was computed with a modified, uncontracted, version of the 6-311G(d,p) basis set, with additional tight polarization functions. H and C NMR chemical shifts were determined at the same level using the gauge-invariant atomic orbital (GIAO) method. The magnitude of the spin-spin coupling constants was found to be affected by the orientation (axial or equatorial) of the coupling proton and the orientation of the hydroxy group on the coupling carbon, whereas the chemical shifts depend on the presence or absence of electron-withdrawing hydroxy groups attached to the carbon atoms involved. Graphical Abstract Nuclear magnetic resonance coupling constants, computed with density functional theory, can be used to differentiate and identify the different stereoisomers of quinic acid.
在B3LYP/6 - 311G(d,p)/PCM(甲醇)理论水平下，计算了奎尼酸八种立体异构体的全套核磁共振耦合常数（J、J、J和J）。耦合常数的费米接触项使用经过修改的、未收缩的6 - 311G(d,p)基组并带有额外的紧密极化函数进行计算。使用规范不变原子轨道（GIAO）方法在相同水平下确定了H和C NMR化学位移。发现自旋 - 自旋耦合常数的大小受耦合质子的取向（轴向或赤道向）以及耦合碳上羟基的取向影响，而化学位移则取决于所涉及碳原子上是否连接有吸电子羟基。图形摘要 用密度泛函理论计算的核磁共振耦合常数可用于区分和鉴定奎尼酸的不同立体异构体。
