Schümann Jan M, Ochmann Lukas, Becker Jonathan, Altun Ahmet, Harden Ingolf, Bistoni Giovanni, Schreiner Peter R
Institute of Organic Chemistry, Justus Liebig University, Heinrich-Buff-Ring 17, 35392 Giessen, Germany.
Institute of Analytical and Inorganic Chemistry, Justus Liebig University, Heinrich-Buff-Ring 17, 35392 Giessen, Germany.
J Am Chem Soc. 2023 Feb 1;145(4):2093-2097. doi: 10.1021/jacs.2c13301. Epub 2023 Jan 23.
We present an experimental study of a cyclooctatetraene-based molecular balance disubstituted with increasingly bulky -butyl (Bu), adamantyl (Ad), and diamantyl (Dia) substituents in the 1,4-/1,6-positions for which we determined the valence-bond shift equilibrium in -hexane (hex), -octane (oct), and -dodecane (dod). Computations including implicit and explicit solvation support our temperature-dependent NMR equilibrium measurements indicating that the more sterically crowded 1,6-isomer is always favored, irrespective of solvent, and that the free energy is quite insensitive to substituent size.
我们展示了一项实验研究，该研究针对在1,4-/1,6-位被体积逐渐增大的丁基（Bu）、金刚烷基（Ad）和二金刚烷基（Dia）取代基双取代的基于环辛四烯的分子天平，我们在正己烷（hex）、正辛烷（oct）和正十二烷（dod）中测定了其价键转移平衡。包括隐式和显式溶剂化的计算支持了我们依赖温度的核磁共振平衡测量结果，表明无论溶剂如何，空间位阻更大的1,6-异构体总是更受青睐，并且自由能对取代基大小相当不敏感。
