Change of C(2)-Hydrogen–Deuterium Exchange in Mixtures of EMIMAc

  • Caroline Marks
  • Alexander Mitsos
  • Jörn ViellEmail author


1-Ethyl-3-methylimidazolium acetate (EMIMAc) is an ionic liquid (IL) often investigated as a solvent, especially in the context of biopolymers and biomass pretreatment. A reduced solvent efficacy occurs upon the addition even of low amounts of water to EMIMAc. Molecular mechanisms have not yet been fully understood. It is expected that the functionality as hydrogen bond donor and acceptor is key for the solvent–solute interactions. In this work, we analyze the solvent efficacy of EMIMAc in terms of hydrogen–deuterium (H/D) exchange at the C(2)-position in mixtures with water or acetic acid added as proton donors. Low-field NMR spectroscopy and deuterated solvents are used for a time-resolved evaluation of H/D exchange reactions. The H/D exchange is also modeled to explore changes in the reaction kinetics as a function of the mixture composition. The significant difference in calculated rate constant values among the concentration regimes shows that the chosen model equations of a possible pseudo-first-order and second-order reaction mechanism including water dissociation do not cover all interaction phenomena that influence the exchange in the individual concentration ranges. However, the modeling also indicates that the investigated interaction of \(\hbox {EMIM}^+\) and \(\hbox {Ac}^-\) remains constant for concentrated IL mixtures containing \(70\, {\text{mol}}\%\) of EMIMAc in water up to diluted mixtures as low as \(30\, {\text{mol}}\%\) EMIMAc. This exemplifies the change between ions strongly associated in networks in concentrated mixtures suitable for biomass pretreatment and the much less associated anion–cation pairs in diluted mixtures which leads to the decreased efficiency of EMIMAc with increasing water content.


Ionic liquid Interaction Hydrogen–deuterium exchange NMR Water Acetic acid 



This work was funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) under Germany’s Excellence Strategy - Exzellenzcluster 236 “Tailor-Made Fuels from Biomass”. We thank our colleagues Olga Walz and Luisa Brée for their support concerning the modeling part of this study. We would also like to thank Prof. Walter Leitner for fruitful discussions.

Supplementary material

10953_2019_899_MOESM1_ESM.pdf (1.1 mb)
Supplementary material 1 (PDF 1134kb)


  1. 1.
    Viell, J., Wulfhorst, H., Schmidt, T., Commandeur, U., Fischer, R., Spiess, A., Marquardt, W.: An efficient process for the saccharification of wood chips by combined ionic liquid pretreatment and enzymatic hydrolysis. Bioresour. Technol. 146, 144–151 (2013). CrossRefPubMedGoogle Scholar
  2. 2.
    Swatloski, R.P., Spear, S.K., Holbrey, J.D., Rogers, R.D.: Dissolution of cellose with ionic liquids. J. Am. Chem. Soc. 124(18), 4974–4975 (2002). CrossRefPubMedGoogle Scholar
  3. 3.
    Sun, N., Rahman, M., Qin, Y., Maxim, M.L., Rodríguez, H., Rogers, R.D.: Complete dissolution and partial delignification of wood in the ionic liquid 1-ethyl-3-methylimidazolium acetate. Green Chem. 11(5), 646–655 (2009). CrossRefGoogle Scholar
  4. 4.
    Kilpeläinen, I., Xie, H., King, A., Granstrom, M., Heikkinen, S., Argyropoulos, D.S.: Dissolution of wood in ionic liquids. J. Agric. Food Chem. 55(22), 9142–9148 (2007). CrossRefPubMedGoogle Scholar
  5. 5.
    Viell, J., Inouye, H., Szekely, N.K., Frielinghaus, H., Marks, C., Wang, Y., Anders, N., Spiess, A.C., Makowski, L.: Multi-scale processes of beech wood disintegration and pretreatment with 1-ethyl-3-methylimidazolium acetate/water mixtures. Biotechnol. Biofuels 9, 7 (2016). CrossRefPubMedPubMedCentralGoogle Scholar
  6. 6.
    Lovell, C.S., Walker, A., Damion, R.A., Radhi, A., Tanner, S.F., Budtova, T., Ries, M.E.: Influence of cellulose on ion diffusivity in 1-ethyl-3-methyl-imidazolium acetate cellulose solutions. Biomacromolecules 11(11), 2927–2935 (2010). CrossRefPubMedGoogle Scholar
  7. 7.
    Le, K.A., Rudaz, C., Budtova, T.: Phase diagram, solubility limit and hydrodynamic properties of cellulose in binary solvents with ionic liquid. Carbohydr. Polym. 105, 237–243 (2014). CrossRefPubMedGoogle Scholar
  8. 8.
    Rabideau, B.D., Agarwal, A., Ismail, A.E.: The role of the cation in the solvation of cellulose by imidazolium-based ionic liquids. J. Phys. Chem. B 118(6), 1621–1629 (2014). CrossRefPubMedGoogle Scholar
  9. 9.
    Lu, B., Xu, A., Wang, J.: Cation does matter: how cationic structure affects the dissolution of cellulose in ionic liquids. Green Chem. 16(3), 1326–1335 (2014). CrossRefGoogle Scholar
  10. 10.
    Xu, A., Wang, J., Wang, H.: Effects of anionic structure and lithium salts addition on the dissolution of cellulose in 1-butyl-3-methylimidazolium-based ionic liquid solvent systems. Green Chem. 12(2), 268–275 (2010). CrossRefGoogle Scholar
  11. 11.
    Brandt, A., Hallett, J.P., Leak, D.J., Murphy, R.J., Welton, T.: The effect of the ionic liquid anion in the pretreatment of pine wood chips. Green Chem. 12(4), 672–679 (2010). CrossRefGoogle Scholar
  12. 12.
    Ebner, G., Schiehser, S., Potthast, A., Rosenau, T.: Side reaction of cellulose with common 1-alkyl-3-methylimidazolium-based ionic liquids. Tetrahedron Lett. 49(51), 7322–7324 (2008). CrossRefGoogle Scholar
  13. 13.
    Clough, M.T., Geyer, K., Hunt, P.A., Son, S., Vagt, U., Welton, T.: Ionic liquids-not always innocent solvents for cellulose. Green Chem. 17(1), 231–243 (2015). CrossRefGoogle Scholar
  14. 14.
    Xu, A., Zhang, Y., Zhao, Y., Wang, J.: Cellulose dissolution at ambient temperature: role of preferential solvation of cations of ionic liquids by a cosolvent. Carbohydr. Polym. 92(1), 540–544 (2013). CrossRefPubMedGoogle Scholar
  15. 15.
    Brehm, M., Weber, H., Pensado, A.S., Stark, A., Kirchner, B.: Proton transfer and polarity changes in ionic liquid–water mixtures: a perspective on hydrogen bonds from ab initio molecular dynamics at the example of 1-ethyl-3-methylimidazolium acetate–water mixtures-part 1. Phys. Chem. Chem. Phys. 14(15), 5030–5044 (2012). CrossRefPubMedGoogle Scholar
  16. 16.
    Hollóczki, O., Gerhard, D., Massone, K., Szarvas, L., Németh, B., Veszprémi, T., Nyulászi, L.: Carbenes in ionic liquids. New J. Chem. 34(12), 3004–3009 (2010). CrossRefGoogle Scholar
  17. 17.
    MacFarlane, D.R., Pringle, J.M., Johansson, K.M., Forsyth, S.A., Forsyth, M.: Lewis base ionic liquids. Chem. Commun. 18, 1905–1917 (2006). CrossRefGoogle Scholar
  18. 18.
    Vilarino, T., de Vicente, M.E.S.: Theoretical calculations of the ionic strength dependence of the ionic product of water based on a mean spherical approximation. J. Solution Chem. 26(9), 833–846 (1997). CrossRefGoogle Scholar
  19. 19.
    McCune, J.A., He, P., Petkovic, M., Coleman, F., Estager, J., Holbrey, J.D., Seddon, K.R., Swadźba-Kwaśny, M.: Brønsted acids in ionic liquids: how acidity depends on the liquid structure. Phys. Chem. Chem. Phys. 16(42), 23233–23243 (2014). CrossRefPubMedGoogle Scholar
  20. 20.
    MacFarlane, D.R., Chong, A.L., Forsyth, M., Kar, M., Vijayaraghavan, R., Somers, A., Pringle, J.M.: New dimensions in salt–solvent mixtures: a 4th evolution of ionic liquids. Faraday Discuss. 206, 9–28 (2018). CrossRefGoogle Scholar
  21. 21.
    Baek, C.S., Lee, Y.J., Lee, S.J., Kim, H.C., Jeong, S.W.: C2-Functionalized 1,3-dialkylimidazolium ionic liquids for efficient cellulose dissolution. J. Mol. Liq. 234, 111–116 (2017). CrossRefGoogle Scholar
  22. 22.
    Yoshimura, Y., Hatano, N., Takekiyo, T., Abe, H.: Direct correlation between the H/D exchange reaction and conformational changes of the cation in imidazolium-based ionic liquid-D\(_2\)O mixtures. J. Solution Chem. 43(9–10), 1509–1518 (2014). CrossRefGoogle Scholar
  23. 23.
    Cha, S., Ao, M., Sung, W., Moon, B., Ahlström, B., Johansson, P., Ouchi, Y., Kim, D.: Structures of ionic liquid–water mixtures investigated by IR and NMR spectroscopy. Phys. Chem. Chem. Phys. 16(20), 9591–9601 (2014). CrossRefPubMedGoogle Scholar
  24. 24.
    Yasaka, Y., Wakai, C., Matubayasi, N., Nakahara, M.: Slowdown of H/D exchange reaction rate and water dynamics in ionic liquids: deactivation of solitary water solvated by small anions in 1-butyl-3-methyl-imidazolium chloride. J. Phys. Chem. A 111(4), 541–543 (2007). CrossRefPubMedGoogle Scholar
  25. 25.
    Rico Del Cerro, D., Mera-Adasme, R., King, A.W.T., Perea-Buceta, J.E., Heikkinen, S., Hase, T., Sundholm, D., Wähälä, K.: On the mechanism of the reactivity of 1,3-dialkylimidazolium salts under basic to acidic conditions: a combined kinetic and computational study. Angew. Chem. Int. Ed. 57(36), 11613–11617 (2018). CrossRefGoogle Scholar
  26. 26.
    Ohta, S., Shimizu, A., Imai, Y., Abe, H., Hatano, N., Yoshimura, Y.: Peculiar concentration dependence of H/D exchange reaction in 1-butyl-3-methylimidazolium tetrafluoroborate-D\(_2\)O mixtures. Open J. Phys. Chem. 01(03), 70–76 (2011). CrossRefGoogle Scholar
  27. 27.
    Allen, J.J., Bowser, S.R., Damodaran, K.: Molecular interactions in the ionic liquid emim acetate and water binary mixtures probed via NMR spin relaxation and exchange spectroscopy. Phys. Chem. Chem. Phys. 16(17), 8078–8085 (2014). CrossRefPubMedGoogle Scholar
  28. 28.
    Horikawa, Y., Sugiyama, J.: Accessibility and size of Valonia cellulose microfibril studied by combined deuteration/rehydrogenation and FTIR technique. Cellulose 15(3), 419–424 (2008). CrossRefGoogle Scholar
  29. 29.
    Reishofer, D., Spirk, S.: Deuterium and cellulose: A comprehensive review. Adv. Polym. Sci. 271, 93–114 (2016). CrossRefGoogle Scholar
  30. 30.
    Pönni, R., Rautkari, L., Hill, C.A.S., Vuorinen, T.: Accessibility of hydroxyl groups in birch kraft pulps quantified by deuterium exchange in D\(_2\)O vapor. Cellulose 21(3), 1217–1226 (2014). CrossRefGoogle Scholar
  31. 31.
    Suchy, M., Kontturi, E., Vuorinen, T.: Impact of drying on wood ultrastructure: similarities in cell wall alteration between native wood and isolated wood-based fibers. Biomacromolecules 11(8), 2161–2168 (2010). CrossRefPubMedGoogle Scholar
  32. 32.
    Jiang, Z., Fan, J., Budarin, V.L., Macquarrie, D.J., Gao, Y., Li, T., Hu, C., Clark, J.H.: Mechanistic understanding of salt-assisted autocatalytic hydrolysis of cellulose. Sustain. Energy Fuels 2(5), 936–940 (2018). CrossRefGoogle Scholar
  33. 33.
    Hishikawa, Y., Togawa, E., Kataoka, Y., Kondo, T.: Characterization of amorphous domains in cellulosic materials using a FTIR deuteration monitoring analysis. Polymer 40(25), 7117–7124 (1999). CrossRefGoogle Scholar
  34. 34.
    Wahba, M.: Kinetics of the deuteration of cellulose: An infrafred study with D\(_2\)O–H\(_2\)O vapours. Chem. Scr. 11(4–5), 158–163 (1977)Google Scholar
  35. 35.
    Mullangi, V., Zhou, X., Ball, D.W., Anderson, D.J., Miyagi, M.: Quantitative measurement of the solvent accessibility of histidine imidazole groups in proteins. Biochemistry 51(36), 7202–7208 (2012). CrossRefPubMedPubMedCentralGoogle Scholar
  36. 36.
    Amyes, T.L., Diver, S.T., Richard, J.P., Rivas, F.M., Toth, K.: Formation and stability of n-heterocyclic carbenes in water: the carbon acid pK\(_a\) of imidazolium cations in aqueous solution. J. Am. Chem. Soc. 126(13), 4366–4374 (2004). CrossRefPubMedGoogle Scholar
  37. 37.
    Bai, Y., Milne, John S., Mayne, Leland, Englander, S.W.: Primary structure effects on peptide group hydrogen exchange. Proteins 17, 75–88 (1993). CrossRefPubMedPubMedCentralGoogle Scholar
  38. 38.
    Amyes, T.L., Richard, J.P.: Determination of the pK \(_a\) of ethyl acetate: Brønsted correlation for deprotonation of a simple oxygen ester in aqueous solution. J. Am. Chem. Soc. 118, 3129–3141 (1996). CrossRefGoogle Scholar
  39. 39.
    Walz, O., Marks, C., Viell, J., Mitsos, A.: Systematic approach for modeling reaction networks involving equilibrium and kinetically-limited reaction steps. Comput. Chem. Eng. 98, 143–153 (2017). CrossRefGoogle Scholar
  40. 40.
    Khan, I., Kurnia, K.A., Mutelet, F., Pinho, S.P., Coutinho, J.A.P.: Probing the interactions between ionic liquids and water: experimental and quantum chemical approach. J. Phys. Chem. B 118(7), 1848–1860 (2014). CrossRefPubMedGoogle Scholar
  41. 41.
    Simoni, L.D., Brennecke, J.F., Stadtherr, M.A.: Asymmetric framework for predicting liquid\(-\)liquid equilibrium of ionic liquid–mixed-solvent systems. 1. Theory, phase stability analysis, and parameter estimation. Ind. Eng. Chem. Res 48(15), 7246–7256 (2009). CrossRefGoogle Scholar
  42. 42.
    Chen, Y., Li, S., Xue, Z., Hao, M., Mu, T.: Quantifying the hydrogen-bonding interaction between cation and anion of pure [EMIM][Ac] and evidencing the ion pairs existence in its extremely diluted water solution: Via \(^{13}\)C, \(^1\)H, \(^{15}\)N and 2D NMR. J. Mol. Struct. 1079, 120–129 (2015). CrossRefGoogle Scholar
  43. 43.
    Hall, C.A., Le, K.A., Rudaz, C., Radhi, A., Lovell, C.S., Damion, R.A., Budtova, T., Ries, M.E.: Macroscopic and microscopic study of 1-ethyl-3-methyl-imidazolium acetate–water mixtures. J. Phys. Chem. B 116(42), 12810–12818 (2012). CrossRefPubMedGoogle Scholar
  44. 44.
    Chen, Y., Cao, Y., Sun, X., Mu, T.: Hydrogen bonding interaction between acetate-based ionic liquid 1-ethyl-3-methylimidazolium acetate and common solvents. J. Mol. Liq. 190, 151–158 (2014). CrossRefGoogle Scholar
  45. 45.
    Wong, J.L., Keck, J.H.: Positional reactivities and mechanisms of deuteration of 1-methylimidazole in pD and -D\(_0\) regions. Reinvestigation of the kinetics of 2-hydrogen exchange in imidazole. J. Org. Chem 39(16), 2398–2403 (1974). CrossRefGoogle Scholar
  46. 46.
    Hatano, N., Watanabe, M., Takekiyo, T., Abe, H., Yoshimura, Y.: Anomalous conformational change in 1-butyl-3-methylimidazolium tetrafluoroborate–D\(_2\)O mixtures. J. Phys. Chem. A 116(4), 1208–1212 (2012). CrossRefPubMedGoogle Scholar
  47. 47.
    Chen, Y., Cao, Y., Zhang, Y., Mu, T.: Hydrogen bonding between acetate-based ionic liquids and water: three types of IR absorption peaks and NMR chemical shifts change upon dilution. J. Mol. Struct. 1058, 244–251 (2014). CrossRefGoogle Scholar
  48. 48.
    Kar, M., Plechkova, N.V., Seddon, K.R., Pringle, J.M., MacFarlane, D.R.: Ionic liquids: further progress on the fundamental issues. Aust. J. Chem. 72(2), 3 (2019). CrossRefGoogle Scholar
  49. 49.
    Armand, M., Endres, F., MacFarlane, D.R., Ohno, H., Scrosati, B.: Ionic-liquid materials for the electrochemical challenges of the future. Nat. Mater. 8(8), 621–629 (2009). CrossRefPubMedGoogle Scholar
  50. 50.
    MacFarlane, D.R., Tachikawa, N., Forsyth, M., Pringle, J.M., Howlett, P.C., Elliott, G.D., Davis, J.H., Watanabe, M., Simon, P., Angell, C.A.: Energy applications of ionic liquids. Energy Environ. Sci. 7(1), 232–250 (2014). CrossRefGoogle Scholar

Copyright information

© Springer Science+Business Media, LLC, part of Springer Nature 2019

Authors and Affiliations

  1. 1.Aachener Verfahrenstechnik - Process Systems EngineeringRWTH Aachen UniversityAachenGermany

Personalised recommendations