Transport Mechanism of Acetamide in Deep Eutectic Solvents

Abstract

Over the last couple of decades, deep eutectic solvents (DESs) have emerged as novel alternatives to ionic liquids that are extensively used in synthesis of innovative materials, metal processing, catalysis, etc. However, their usage is limited, primarily because of the large viscosity and poor conductivity. Therefore, an understanding of the molecular origin of these properties is essential to improve their industrial applicability. Here, we present the report of the nanoscopic diffusion mechanism of acetamide in a DES synthesized with lithium perchlorate as studied using neutron scattering and molecular dynamics (MD) simulation techniques. Although, the acetamide based DES (ADES) has remarkably lower freezing point compared to pure acetamide, the molecular mobility is found to be enormously restricted in the former. MD simulation indicates a diffusion model with two distinct processes, corresponding to, long range jump diffusion and localised diffusion within a restricted volume. This model is validated by analysis of neutron scattering data in both molten acetamide and ADES. The long range diffusion process of acetamide is slower by a factor of three in ADES in comparison with molten acetamide. MD simulation reveals that the long range diffusion in ADES is restricted mainly due to the formation of hydrogen bond mediated complexes between the ionic species of the salt and acetamide molecules. Hence, the origin of higher viscosity observed in ADES can be attributed to the complexation. The complex formation also explains the inhibition of the crystallisation process while cooling and thereby results in depression of the freezing point of ADES.

Deep eutectics and analogues as electrolytes in batteries

“…120 Alternative Li salts such as lithium triflate (LiTfO), lithium perchlorate (LiClO4) and lithium bromide (LiBr) have been used as well. 11,130,[133][134][135][136][137] It has been shown that mixtures of Li salts (LiClO4, LiBr, and lithium nitrate LiNO3) and AA in a molar ratio of approximately 1:4 form DESs having freezing points below room temperature. 11 Apparently the depression of freezing points in these systems can be ascribed to the ability of these salts to break the interamide hydrogen bonding.…”

“…140 The nanoscale dynamics of some of these AA-based DESs (with LiNO3 or LiClO4) has been investigated by Srinivasan and coworkers using quasielastic neutron scattering (QENS) and MD simulations. [134][135][136] Results indicate that the AA molecules form a hydrogen-bond network with its neighbouring set of molecules resulting in a transient cage and the molecular diffusion of AA involves a combination of localized diffusion and cage-to-cage jump diffusion. 134,135 The localized diffusion process is associated with the dynamics of the molecules while it is trapped by an H-bond with neighbouring AA molecules and ions, whereas the jump diffusion process is associated with the diffusion of the molecule between two transient cage.…”

“…[134][135][136] Results indicate that the AA molecules form a hydrogen-bond network with its neighbouring set of molecules resulting in a transient cage and the molecular diffusion of AA involves a combination of localized diffusion and cage-to-cage jump diffusion. 134,135 The localized diffusion process is associated with the dynamics of the molecules while it is trapped by an H-bond with neighbouring AA molecules and ions, whereas the jump diffusion process is associated with the diffusion of the molecule between two transient cage. 134,135 The dynamics of AA is relevant for the Li + transport, as Li ions are solvated in the DES, with solvation shells predominantly made up of 3-4 AA molecules.…”

Recent investigations into synthesis and pharmacological activities of phenoxy acetamide and its derivatives (chalcone, indole and quinoline) as possible therapeutic candidates

“…Acetamide (also known as ethanamide or acetic acid amide) belongs to the class of organic compounds known as carboxamides acids with the formula CH 3 CONH 2 Fig. 2 [59].…”

“…Further, a novel series of fluoro-substituted chalcone derivatives (62a-i) were prepared by three steps reaction. First phloroglucinol (58) was treated with acetic anhydride in the presence of methane sulfonic acid at 80 °C to achieve compound 1,1′,1′'-(2,4,6-trihydroxybenzene-1,3,5-triyl) triethanone (59). The next step was to obtain compound 1,1′,1′'-(2,4,6-Trimethoxybenzene-1,3,5-triyl)triethanone (60) by the reaction of compound (59) with dimethyl sulphate.…”