Understanding chemical reactions of CO2 and its isoelectronic molecules with 1-butyl-3-methylimidazolium acetate by changing the nature of the cation: The case of CS2 in 1-butyl-1-methylpyrrolidinium acetate studied by NMR spectroscopy and density functional theory calculations

Abstract

NMR spectroscopy ( 1 H, 13 C, 15 N) shows that carbon disulfide reacts spontaneously with 1-butyl-1-methylpyrrolidinium acetate ([BmPyrro][Ac]) in the liquid phase. It is found that the acetate anions play an important role in conditioning chemical reactions with CS 2 leading, via coupled complex reactions, to the degradation of this molecule to form thioacetate anion (CH 3 COS − ), CO 2 , OCS, and trithiocarbonate (CS 3 2− ). In marked contrast, the cation does not lead to the formation of any adducts allowing to conclude that, at most, its role consists in assisting indirectly these reactions. The choice of the [BmPyrro] + cation in the present study allows disentangling the role of the anion and the cation in the reactions. As a consequence, the ensemble of results already reported on (2), and CO 2 - [Bmim][Ac] (3) systems can be consistently rationalized. It is argued that in system (1) both anion and cation play a role. The CS 2 reacts with the acetate anion leading to the formation of CH 3 COS − , CO 2 , and OCS. After these reactions have proceeded the nascent CO 2 and OCS interact with the cation to form imidazolium-carboxylate ([Bmim] CO 2 ) and imidazoliumthiocarboxylate ([Bmim] COS). The same scenario also applies to system (2). In contrast, in the CO 2 - [Bmim] [Ac] system a concerted cooperative process between the cation, the anion, and the CO 2 molecule takes place. A carbene issued from the cation reacts to form the [Bmim] CO 2 , whereas the proton released by the ring interacts with the anion to produce acetic acid. In all these systems, the formation of adduct resulting from the reaction between the solute molecule and the carbene species originating from the cation is expected. However, this species was only observed in systems (2) and (3). The absence of such an adduct in system (1) has been theoretically investigated using DFT calculations. The values of the energetic barrier of the reactions show that the formation of [Bmim] CS 2 is unfavoured and that the anion offers a competitive reactive channel via an oxygensulphur exchange mechanism with the solute in systems (1) and (2). © 2014 AIP Publishing LLC.

Copper-Tin Alloys for the Electrocatalytic Reduction of CO2 in an Imidazolium-Based Non-Aqueous Electrolyte

“…However, as shown in Figure 4, a product formed from the [BMIM] + cation was observed by 1 H NMR. In particular, the analysis of the post electrolysis solution showed both distinct peaks for the starting [BMIM] + cation as well as peaks corresponding to the zwitterionic [BMIM]-CO 2 adduct, as characterized by the diagnostic signals at 7.16 ppm in the 1 H NMR spectra [26][27][28]. The structure of the [BMIM]-CO 2 adduct is shown in Figure 5.…”

BmmimOAc-Catalyzed Direct Condensation of 2-(Arylamino) Alcohols to Synthesize 3-Arylthiazolidine-2-thiones

“…The reason was that CS2 can react spontaneously with BmimOAc in the liquid phase to form a stable inner-salt compound 1-butyl-3methylimidazolium-2-thiocarboxylate (Bmim + -COS − ) which was got by chromatography on silica gel and structurally characterized by NMR spectra (see Supporting Information). Danten and coworkers 33,34 have reported the same result, and in their studies on chemical reactions of CS2 with ionic liquids, they confirmed that CS2 can undergo degradation to form such compounds. Gao, Mu and coworkers 35 also have summarized some reactions of imidazolium-based ionic liquid with inorganic electrophiles (such as CO2, CS2 and OCS) under alkaline conditions.…”

“…6 completely agreed with the 1 H NMR and 13 C NMR spectra of BmmimCOS. In addition, Danten and coworkers 34,35 also have reported that CS2 can react spontaneously with acetate anion of ionic liquid 1-butyl-1-methylpyrrolidinium acetate ([BmPyrro][OAc]) in the liquid phase. All of the results indicated that the acetate anion of BmmimOAc could react spontaneously with CS2 to form CH3COS − anion.…”

Encapsulated Amino‐Acid‐Based Ionic Liquids for CO2 Capture

“…Acetate‐based ILs are known to play an important role in conditioning chemical reactions with CO 2 with reaction products with low viscosity, compared to most chemisorption solvents . Although most of the work focus on the imidazolium cation, with the sorption mechanism well described and accepted,, Shi et al have shown that for the tetrabutylphosphonium acetate IL the anion controls the large CO 2 solubility by chemisorption, with the cation contributing mostly for the physisorption regime.…”