Protic ionic liquids based on the dimeric and oligomeric anions: [(AcO)xHx-1]-

Katarina Maria Johansson, Ekaterina Izgorodina, Maria Forsyth, Douglas Robert Macfarlane, Kenneth R Seddon

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Abstract

We describe a fluidity and conductivity study as a function of composition in N-methylpyrrolidine-acetic acid mixtures. The simple 1 : 1 acid-base mixture appears to form an ionic liquid, but its degree of ionicity is quite low and such liquids are better thought of as poorly dissociated mixtures of acid and base. The composition consisting of 3 moles acetic acid and 1 mole N-methylpyrrolidine is shown to form the highest ionicity mixture in this binary due to the presence of oligomeric anionic species [(AcO)(x)H(x-1)](-) stabilised by hydrogen bonds. These oligomeric species, being weaker bases than the acetate anion, shift the proton transfer equilibrium towards formation of ionic species, thus generating a higher degree of ionicity than is present at the 1 : 1 composition. A Walden plot analysis, thermogravimetric behaviour and proton NMR data, as well as ab initio calculations of the oligomeric species, all support this conclusion.
Original languageEnglish
Pages (from-to)2972 - 2978
Number of pages7
JournalPhysical Chemistry Chemical Physics
Volume10
Issue number20
DOIs
Publication statusPublished - 2008

Cite this

Johansson, Katarina Maria ; Izgorodina, Ekaterina ; Forsyth, Maria ; Macfarlane, Douglas Robert ; Seddon, Kenneth R. / Protic ionic liquids based on the dimeric and oligomeric anions: [(AcO)xHx-1]-. In: Physical Chemistry Chemical Physics. 2008 ; Vol. 10, No. 20. pp. 2972 - 2978.
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abstract = "We describe a fluidity and conductivity study as a function of composition in N-methylpyrrolidine-acetic acid mixtures. The simple 1 : 1 acid-base mixture appears to form an ionic liquid, but its degree of ionicity is quite low and such liquids are better thought of as poorly dissociated mixtures of acid and base. The composition consisting of 3 moles acetic acid and 1 mole N-methylpyrrolidine is shown to form the highest ionicity mixture in this binary due to the presence of oligomeric anionic species [(AcO)(x)H(x-1)](-) stabilised by hydrogen bonds. These oligomeric species, being weaker bases than the acetate anion, shift the proton transfer equilibrium towards formation of ionic species, thus generating a higher degree of ionicity than is present at the 1 : 1 composition. A Walden plot analysis, thermogravimetric behaviour and proton NMR data, as well as ab initio calculations of the oligomeric species, all support this conclusion.",
author = "Johansson, {Katarina Maria} and Ekaterina Izgorodina and Maria Forsyth and Macfarlane, {Douglas Robert} and Seddon, {Kenneth R}",
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Protic ionic liquids based on the dimeric and oligomeric anions: [(AcO)xHx-1]-. / Johansson, Katarina Maria; Izgorodina, Ekaterina; Forsyth, Maria; Macfarlane, Douglas Robert; Seddon, Kenneth R.

In: Physical Chemistry Chemical Physics, Vol. 10, No. 20, 2008, p. 2972 - 2978.

Research output: Contribution to journalArticleResearchpeer-review

TY - JOUR

T1 - Protic ionic liquids based on the dimeric and oligomeric anions: [(AcO)xHx-1]-

AU - Johansson, Katarina Maria

AU - Izgorodina, Ekaterina

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AU - Macfarlane, Douglas Robert

AU - Seddon, Kenneth R

PY - 2008

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N2 - We describe a fluidity and conductivity study as a function of composition in N-methylpyrrolidine-acetic acid mixtures. The simple 1 : 1 acid-base mixture appears to form an ionic liquid, but its degree of ionicity is quite low and such liquids are better thought of as poorly dissociated mixtures of acid and base. The composition consisting of 3 moles acetic acid and 1 mole N-methylpyrrolidine is shown to form the highest ionicity mixture in this binary due to the presence of oligomeric anionic species [(AcO)(x)H(x-1)](-) stabilised by hydrogen bonds. These oligomeric species, being weaker bases than the acetate anion, shift the proton transfer equilibrium towards formation of ionic species, thus generating a higher degree of ionicity than is present at the 1 : 1 composition. A Walden plot analysis, thermogravimetric behaviour and proton NMR data, as well as ab initio calculations of the oligomeric species, all support this conclusion.

AB - We describe a fluidity and conductivity study as a function of composition in N-methylpyrrolidine-acetic acid mixtures. The simple 1 : 1 acid-base mixture appears to form an ionic liquid, but its degree of ionicity is quite low and such liquids are better thought of as poorly dissociated mixtures of acid and base. The composition consisting of 3 moles acetic acid and 1 mole N-methylpyrrolidine is shown to form the highest ionicity mixture in this binary due to the presence of oligomeric anionic species [(AcO)(x)H(x-1)](-) stabilised by hydrogen bonds. These oligomeric species, being weaker bases than the acetate anion, shift the proton transfer equilibrium towards formation of ionic species, thus generating a higher degree of ionicity than is present at the 1 : 1 composition. A Walden plot analysis, thermogravimetric behaviour and proton NMR data, as well as ab initio calculations of the oligomeric species, all support this conclusion.

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JO - Physical Chemistry Chemical Physics

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