The Proton Dissociation of Bio-Protic Ionic Liquids: [AAE]X Amino Acid Ionic Liquids
[AAE]X composed of amino acid ester cations is a sort of typically “bio-based” protic ionic liquids (PILs). They possess potential Brønsted acidity due to the active hydrogens on their cations. The Brønsted acidity of [AAE]X PILs in green solvents (water and ethanol) at room temperature was systemat...
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doaj-caae204fa6ae4b0fb228a58f89c021b12020-12-26T00:00:04ZengMDPI AGMolecules1420-30492021-12-0126626210.3390/molecules26010062The Proton Dissociation of Bio-Protic Ionic Liquids: [AAE]X Amino Acid Ionic LiquidsTing He0Cheng-Bin Hong1Peng-Chong Jiao2Heng Xiang3Yan Zhang4Hua-Qiang Cai5Shuang-Long Wang6Guo-Hong Tao7Institute of Chemical Materials, China Academy of Engineering Physics, Mianyang 621900, ChinaCollege of Chemistry, Sichuan University, Chengdu 610064, ChinaInstitute of Chemical Materials, China Academy of Engineering Physics, Mianyang 621900, ChinaInstitute of Chemical Materials, China Academy of Engineering Physics, Mianyang 621900, ChinaInstitute of Chemical Materials, China Academy of Engineering Physics, Mianyang 621900, ChinaInstitute of Chemical Materials, China Academy of Engineering Physics, Mianyang 621900, ChinaCollege of Chemistry, Sichuan University, Chengdu 610064, ChinaCollege of Chemistry, Sichuan University, Chengdu 610064, China[AAE]X composed of amino acid ester cations is a sort of typically “bio-based” protic ionic liquids (PILs). They possess potential Brønsted acidity due to the active hydrogens on their cations. The Brønsted acidity of [AAE]X PILs in green solvents (water and ethanol) at room temperature was systematically studied. Various frameworks of amino acid ester cations and four anions were investigated in this work from the viewpoint of structure–property relationship. Four different ways were used to study the acidity. Acid dissociation constants (p<i>K</i><sub>a</sub>) of [AAE]X determined by the OIM (overlapping indicator method) were from 7.10 to 7.73 in water and from 8.54 to 9.05 in ethanol. The p<i>K</i><sub>a</sub> values determined by the PTM (potential titration method) were from 7.12 to 7.82 in water. Their Hammett acidity function (<i>H</i><sub>0</sub>) values (0.05 mol·L<sup>−1</sup>) were about 4.6 in water. In addition, the p<i>K</i><sub>a</sub> values obtained by the DFT (proton-transfer reactions) were from 7.11 to 7.83 in water and from 8.54 to 9.34 in ethanol, respectively. The data revealed that the cationic structures of [AAE]X had little effect and the anions had no effect on the acidity of [AAE]X. At the same time, the OIM, PTM, Hammett method and DFT method were reliable for determining the acidic strength of [AAE]X in this study.https://www.mdpi.com/1420-3049/26/1/62protic ionic liquidsBrønsted acidityamino acid ionic liquidsbio-based ionic liquids |
collection |
DOAJ |
language |
English |
format |
Article |
sources |
DOAJ |
author |
Ting He Cheng-Bin Hong Peng-Chong Jiao Heng Xiang Yan Zhang Hua-Qiang Cai Shuang-Long Wang Guo-Hong Tao |
spellingShingle |
Ting He Cheng-Bin Hong Peng-Chong Jiao Heng Xiang Yan Zhang Hua-Qiang Cai Shuang-Long Wang Guo-Hong Tao The Proton Dissociation of Bio-Protic Ionic Liquids: [AAE]X Amino Acid Ionic Liquids Molecules protic ionic liquids Brønsted acidity amino acid ionic liquids bio-based ionic liquids |
author_facet |
Ting He Cheng-Bin Hong Peng-Chong Jiao Heng Xiang Yan Zhang Hua-Qiang Cai Shuang-Long Wang Guo-Hong Tao |
author_sort |
Ting He |
title |
The Proton Dissociation of Bio-Protic Ionic Liquids: [AAE]X Amino Acid Ionic Liquids |
title_short |
The Proton Dissociation of Bio-Protic Ionic Liquids: [AAE]X Amino Acid Ionic Liquids |
title_full |
The Proton Dissociation of Bio-Protic Ionic Liquids: [AAE]X Amino Acid Ionic Liquids |
title_fullStr |
The Proton Dissociation of Bio-Protic Ionic Liquids: [AAE]X Amino Acid Ionic Liquids |
title_full_unstemmed |
The Proton Dissociation of Bio-Protic Ionic Liquids: [AAE]X Amino Acid Ionic Liquids |
title_sort |
proton dissociation of bio-protic ionic liquids: [aae]x amino acid ionic liquids |
publisher |
MDPI AG |
series |
Molecules |
issn |
1420-3049 |
publishDate |
2021-12-01 |
description |
[AAE]X composed of amino acid ester cations is a sort of typically “bio-based” protic ionic liquids (PILs). They possess potential Brønsted acidity due to the active hydrogens on their cations. The Brønsted acidity of [AAE]X PILs in green solvents (water and ethanol) at room temperature was systematically studied. Various frameworks of amino acid ester cations and four anions were investigated in this work from the viewpoint of structure–property relationship. Four different ways were used to study the acidity. Acid dissociation constants (p<i>K</i><sub>a</sub>) of [AAE]X determined by the OIM (overlapping indicator method) were from 7.10 to 7.73 in water and from 8.54 to 9.05 in ethanol. The p<i>K</i><sub>a</sub> values determined by the PTM (potential titration method) were from 7.12 to 7.82 in water. Their Hammett acidity function (<i>H</i><sub>0</sub>) values (0.05 mol·L<sup>−1</sup>) were about 4.6 in water. In addition, the p<i>K</i><sub>a</sub> values obtained by the DFT (proton-transfer reactions) were from 7.11 to 7.83 in water and from 8.54 to 9.34 in ethanol, respectively. The data revealed that the cationic structures of [AAE]X had little effect and the anions had no effect on the acidity of [AAE]X. At the same time, the OIM, PTM, Hammett method and DFT method were reliable for determining the acidic strength of [AAE]X in this study. |
topic |
protic ionic liquids Brønsted acidity amino acid ionic liquids bio-based ionic liquids |
url |
https://www.mdpi.com/1420-3049/26/1/62 |
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