The Effect of C4H and C5H on the Microstructure of Aqueous Solutions of 1‐Alkyl‐3‐methylimidazolium Tetrafluoroborate Ionic Liquids

Abstract

As is well-known, the C2H proton of 1-ethyl-3-methylimidazolium tetrafluoroborate ([Emim]BF ) and 1-butyl-3-methylimidazolium tetrafluoroborate ([Bmim]BF ) has a strong ability to form hydrogen bonds. The purpose of this work is to evaluate the effect of the interactions of the C4H and C5H protons on the microstructure of [Emim]BF and [Bmim]BF with water by using H NMR spectroscopy. The differences between the relative H NMR chemical shifts of C2H, C4H, and C5H and between the interaction-energy parameters obtained from these chemical shifts are minor, thus suggesting that the interactions of C4H and C5H may have a considerable effect on the microstructure. To confirm this, the viscosities of the systems are estimated by using the interaction-energy parameters obtained from the H NMR chemical shifts of the three studied aromatic protons and water, showing that the interactions of C4H and C5H also play an important role in the microstructure.

Changes in microstructure of two ammonium‐based protic ionic liquids proved by in situ variable‐temperature 1H NMR spectroscopy: influence of anion

“…In situ variable‐temperature 1 H NMR spectroscopy of N4Ac and N4NO 3 was recorded on a Bruker AV‐400 MHz spectrometer at 25, 30, 40, 50, 60, 70, 80, 90, 100, and 115 °C, respectively. To avoid the influence of deuterated reagents on the 1 HNMR chemical shifts of PIL sample, the internal reference method was adopted according to previous work . Specific measurement process was as follows: the deuterated dimethyl sulfoxide (DMSO‐ d 6 ) was sealed in a 2‐mm capillary tube, which was placed at the center of a 5‐mm sample tube filled with the sample and chemical shift reference of tetramethylsilane (TMS).…”

“…To avoid the influence of deuterated reagents on the 1 HNMR chemical shifts of PIL sample, the internal reference method was adopted according to previous work. [37][38][39][40][41]44] Specific measurement process was as follows: the deuterated dimethyl sulfoxide (DMSO-d 6 ) was sealed in a 2-mm capillary tube, which was placed at the center of a 5-mm sample tube filled with the sample and chemical shift reference of tetramethylsilane (TMS). It is demanded that the inner capillary tube should be kept parallel with the exterior sample tube.…”

“…In the investigation of the microstructure of pure ILs and their mixtures with solvent, NMR spectroscopy is the commonly used technique and has been frequently utilized to study the interactions between cation and anion, or ILs and solvent, because of its accuracy and sensitivity . Especially for 1 H NMR chemical shifts, which are closely related to chemical environments of protons and could offer us much information about microstructures of mixture conveniently, such as the intermolecular interaction and electronic perturbation caused by hydrogen bonds . Furthermore, the intermolecular interaction obtained from 1 H NMR chemical shifts could be used to predict the thermodynamic and transport properties of the mixtures coupled with certain theoretical models, indicating that 1 H NMR spectroscopy is an invaluable tool in providing benchmark to test theory and in gaining insight into the nature of structure/property relation.…”

“…[32][33][34][35] Especially for 1 H NMR chemical shifts, which are closely related to chemical environments of protons and could offer us much information about microstructures of mixture conveniently, such as the intermolecular interaction and electronic perturbation caused by hydrogen bonds. [36][37][38][39][40][41] Furthermore, the intermolecular interaction obtained from 1 H NMR chemical shifts could be used to predict the thermodynamic and transport properties of the mixtures coupled with certain theoretical models, [41][42][43][44] indicating that 1 H NMR spectroscopy is an invaluable tool in providing benchmark to test theory and in gaining insight into the nature of structure/property relation. In addition, in situ variable-temperature 1 H NMR spectroscopy is often employed to characterize the hydrogen bond strength, [45][46][47] because the intermolecular hydrogen bond is sensitive to the temperature.…”

Insight into the Interactions between Azole-Anion-Based Ionic Liquids and Propargylic Alcohol: Influence on the Carboxylative Cyclization of Propargylic Alcohol with Carbon Dioxide

“…44 The concentration-dependent 1 H NMR chemical shifts of the binary mixtures were measured at 298.15 K with a Bruker spectrometer (400 MHz) using the internal reference method, which was described in our previous works. [43][44][45]51 The specific measurement process was as follows: to avoid the influence of deuterated reagents on the 1 H NMR chemical shifts of the sample, the deuterium oxide (D 2 O) was sealed in a 2 mm capillary tube, which was placed at the center of a 5 mm sample tube filled with the sample and chemical shift reference of tetramethylsilane (TMS). It is necessary to keep the inner capillary tube parallel to the exterior sample tube.…”