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New Insights in the Chemistry of Ionic Alkylorganic Carbonates: A Computational Study

Abstract

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 CO2 via ionic organic alkyl-carbonate (RCO3-) formation. Data are obtained by using density functional theory (DFT) calculations with B3LYP/6-31+G* level of theory and compared with experimental results acquired within the literature using different spectroscopic techniques. It is found that the capturing process has a favourable enthalpic contribution and unfavourable entropic penalty regardless the identity of the base, where the enthalpy values of alcohol/MHs binary mixtures are almost two-folds higher compared to their SBs-based mixtures. The utilization of perfluorinated aliphatic 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 reactivity of phenolic compounds is highly affected by the electronic nature of the substituting groups, in which p-substituted phenols are more reactive towards CO2 capturing when electron releasing groups are utilized. A pronounced solvent effect is observed, in which the alkylcarbonate salts (RCO3- SBH+) are stabilized in solvents with high dielectric constant (e.g., DMSO and MeCN). Simulated NMR and IR spectra of RCO3¯ 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 CO2 sequestration using CO2 binding organic liquid (CO2BOLs) and enabling a fair/quick prediction for potential substrates to be used as CO2 sorbents.

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Publication details

The article was received on 31 Mar 2017, accepted on 13 May 2017 and first published on 17 May 2017


Article type: Paper
DOI: 10.1039/C7CP02087B
Citation: Phys. Chem. Chem. Phys., 2017, Accepted Manuscript
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    New Insights in the Chemistry of Ionic Alkylorganic Carbonates: A Computational Study

    K. I. Assaf, A. K. Qaroush and A. F. Eftaiha, Phys. Chem. Chem. Phys., 2017, Accepted Manuscript , DOI: 10.1039/C7CP02087B

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