Wilczek Marcin, Jackowski Karol
Laboratory of NMR Spectroscopy, Faculty of Chemistry, University of Warsaw, Pasteura 1, 02-093 Warsaw, Poland.
Molecules. 2024 Sep 20;29(18):4460. doi: 10.3390/molecules29184460.
C and H NMR spectra were observed as the function of density in 1,2-C-enriched ethane and ethylene for the pure gaseous compounds and their binary mixtures with xenon and carbon dioxide gases as the solvents. All the chemical shifts and indirect spin-spin couplings were linearly dependent on the solvent density. The appropriate NMR parameters (σ and J) in isolated CH and CH molecules and the coefficients responsible for the binary molecular interactions were determined and compared with previous similar measurements and selected calculated shielding data. The newly obtained C shielding values in the isolated ethane and ethylene molecules suggest visible secondary isotope effects due to the additional carbon-13 atom. All the investigated shielding parameters depend on intermolecular interactions, and the dependence of C shielding is much more marked. In contrast, the indirect spin-spin couplings in CH and CH molecules are almost independent of solvent molecules. Their J values determined in liquids over sixty years ago are generally consistent with the same J parameters in isolated CH and CH molecules.
在富含1,2 - C的乙烷和乙烯中，以纯气态化合物及其与氙气和二氧化碳气体的二元混合物作为溶剂，观察了碳核磁共振（C NMR）谱和氢核磁共振（H NMR）谱随密度的变化情况。所有化学位移和间接自旋 - 自旋耦合都与溶剂密度呈线性相关。确定了孤立CH和CH₂分子中的合适核磁共振参数（σ和J）以及负责二元分子相互作用的系数，并与先前类似的测量结果和选定的计算屏蔽数据进行了比较。在孤立的乙烷和乙烯分子中新获得的碳屏蔽值表明，由于额外的碳 - 13原子存在明显的二级同位素效应。所有研究的屏蔽参数都取决于分子间相互作用，并且碳屏蔽的依赖性更为显著。相比之下，CH和CH₂分子中的间接自旋 - 自旋耦合几乎与溶剂分子无关。六十多年前在液体中测定的它们的J值通常与孤立CH和CH₂分子中的相同J参数一致。
