Assaf Khaleel I, Qaroush Abdussalam K, Eftaiha Ala'a F
Department of Life Sciences and Chemistry, Jacobs University Bremen, Campus Ring 1, 28759 Bremen, Germany.
Phys Chem Chem Phys. 2017 Jun 14;19(23):15403-15411. doi: 10.1039/c7cp02087b.
A library of hydrogenated, perfluorinated aliphatic and aromatic (p-substituted) alcohols are selected together with a combination of superbases (SBs) and metal hydrides (MHs) to understand the thermodynamic parameters of the binary mixtures once serving as sorbents for the capture of COvia ionic organic alkyl-carbonate (RCO) formation. Data are obtained using density functional theory (DFT) calculations with the B3LYP/6-31+G* level of theory and compared with the experimental results acquired from the literature using different spectroscopic techniques. It is found that the capturing process has a favourable enthalpic contribution and an unfavourable entropic penalty regardless the identity of the base, where the enthalpy values of alcohol/MH binary mixtures are almost two-fold higher compared to their SB-based mixtures. The utilisation of perfluorinated aliphatic alcohols instead of hydrogenated alcohols shows a negative impact on the formation of carbonate adducts, due to the less reactive alkoxide anion along the carbon skeleton, which is attributed to the low charge density of the nucleophilic oxygen atom. While perfluorinated phenol shows a higher reactivity than the parent phenol. The calculations indicate that the reactivity of phenolic compounds is highly affected by the electronic nature of the substituting groups, in which p-substituted phenols are more reactive towards CO capturing when electron releasing groups are utilised. A pronounced solvent effect is observed, in which the alkylcarbonate salts (RCO SBH) are stabilized in solvents with high dielectric constant (e.g., DMSO and MeCN). Simulated NMR and IR spectra of RCO are consistent with those reported for the affiliated systems, which fortifies the results obtained for the unexplored substrate/MH mixtures, filling a gap in the literature of CO sequestration using CO binding organic liquids (COBOLs) and enabling a fair/quick prediction of potential substrates to be used as CO sorbents.
选择了一系列氢化、全氟脂肪族和芳香族（对位取代）醇，以及超强碱（SBs）和金属氢化物（MHs）的组合，以了解二元混合物的热力学参数，这些二元混合物曾作为通过离子有机碳酸烷基酯（RCO）形成来捕获CO的吸附剂。使用密度泛函理论（DFT）计算，在B3LYP/6-31+G*理论水平下获得数据，并与使用不同光谱技术从文献中获得的实验结果进行比较。结果发现，无论碱的种类如何，捕获过程都有有利的焓贡献和不利的熵惩罚，其中醇/MH二元混合物的焓值几乎是基于SB的混合物的两倍。与氢化醇相比，使用全氟脂肪族醇对碳酸酯加合物的形成有负面影响，这是由于沿碳骨架的醇盐阴离子反应性较低，这归因于亲核氧原子的低电荷密度。而全氟苯酚显示出比母体苯酚更高的反应性。计算表明，酚类化合物的反应性受取代基电子性质的高度影响，其中当使用给电子基团时，对位取代的酚对CO捕获更具反应性。观察到明显的溶剂效应，其中碳酸烷基酯盐（RCO SBH）在高介电常数的溶剂（如DMSO和MeCN）中稳定。RCO的模拟NMR和IR光谱与相关体系报道的光谱一致，这加强了未探索的底物/MH混合物所获得的结果，填补了使用CO结合有机液体（COBOLs）进行CO封存文献中的空白，并能够对用作CO吸附剂的潜在底物进行合理/快速预测。
