Solvent Effects on the NMR Chemical Shifts of Imidazolium‐Based Ionic Liquids and Cellulose Therein

Abstract

The interactions of ionic liquids (IL) with solvents usually used in liquid‐state nuclear magnetic resonance (NMR) spectroscopy are studied. The 1H‐ and 13C‐NMR chemical shift values of 1‐n‐butyl‐3‐methyl (BM)‐ and 1‐ethyl‐3‐methyl (EM)‐substituted imidazolium (IM) ‐chlorides (Cl) and ‐acetates (Ac) are determined before and after diluting with deuterated solvents (DMSO‐d6, D2O, CD3OD, and CDCl3). The dilution offers structural modifications of the IL due to the solvents capacity to ionization. For further investigation of highly viscous cellulose dopes made of imidazolium‐based IL, solid‐state NMR spectroscopy enables the reproducibility of liquid‐state NMR data of pure IL. The correlation of liquid‐ and solid‐state NMR is shown on EMIM‐Ac and cellulose/EMIM‐Ac dope (10 wt %).

Solution‐State One‐ and Two‐Dimensional NMR Spectroscopy of High‐Molecular‐Weight Cellulose

“…[4] They followed up this study by looking at the relaxation times of 13 C-and supposedly H-bonded 35/37 Cl nuclei involved in the dissolution process. [3] In 2010, Hesse-Ertelt et al [16] studied the effect of solvent concentration on the chemical shifts of imidazolium ionic liquidsa nd compared chemical shifts obtained from an HSQC spectrumo f [emim][OAc]a nd 10 wt %e ucalyptus pre-hydrolysis kraft( PHK) pulp diluted with [D 6 ]DMSO with those from solid-state NMR spectroscopy.H owever,t hey note the difficulty to obtain spectra of undiluted, neat samples and the problem of overlapping resonances with the [emim] + + cation.…”

Comparative Investigation of the Ionicity of Aprotic and Protic Ionic Liquids in Molecular Solvents by using Conductometry and NMR Spectroscopy

“…The upfield shift in δ is a direct consequence of weakening of the hydrogen bond between cations and anions and the interaction with solvent molecules. Figure shows that the δ value of the C‐2 proton is strongly affected by the polarity of the solvent, and it is reported that higher polarity leads to lower δ values of the C‐2 proton . In the case of [HmIm][CH 3 COO], we have explained the solvation of ions on the basis of the δ value of CH 3 ‐ proton of anions [CH 3 COO].…”

“…Figure 8s hows that the d value of the C-2 protoni ss trongly affected by the polarity of the solvent, and it is reported that higher polarity leads to lower d values of the C-2 proton. [38][39][40] In the case of [HmIm][CH 3 COO],w e have explained the solvation of ions on the basis of the d value of CH 3 -p roton of anions[ CH 3 COO].G iven that the N-H proton is more acidic than the C-2 protono fp rotic ionic liquids and that it resonates at am ore downfield position, we consider the CH 3 -p roton of the anion for analysis. The d value of the CH 3 -proton in D 2 O( 1.78 ppm) is lower than that in [D 6 ]DMSO (1.93 ppm).…”

Chemisorption of air CO2 on cellulose: an overlooked feature of the cellulose/NaOH(aq) dissolution system

“…EMIMAc was chosen because it dissolves cellulose and shows no chemical shifts in the region of 60-110 ppm, where the cellulose carbon signals appear. It has been reported that the solvent effect of DMSO on the chemical shifts of EMIMAc is minor (Hesse-Ertelt et al 2010). The chemical structures of cellulose and EMIMAc are shown in Fig.…”