DOI: 10.1002/open.201300022
Efficient Sustainable Tool for Monitoring Chemical
Reactions and Structure Determination in Ionic Liquids by
ESI-MS
[
a]
Levon L. Khemchyan, Elena A. Khokhlova, Marina M. Seitkalieva, and Valentine P. Ananikov*
An easy and convenient procedure is described for monitoring
chemical reactions and characterization of compounds dis-
solved in ionic liquids using the well-known tandem mass
spectrometry (MS/MS) technique. Generation of wastes was
avoided by utilizing an easy procedure for analysis of ionic
liquid systems without preliminary isolation and purification.
The described procedure also decreased the risk of plausible
contamination and damage of the ESI-MS hardware and in-
creased sensitivity and accuracy of the measurements. ESI-MS
detection in MS/MS mode was shown to be efficient in ionic
liquids systems for structural and mechanistic studies, which
are rather difficult otherwise. The developed ESI-MS/MS ap-
proach was applied to study samples corresponding to pep-
tide systems in ionic liquids and to platform chemical directed
biomass conversion in ionic liquids.
Introduction
Electrospray ionization mass spectrometry (ESI-MS) is a well-
become attractive and promising reaction media for different
[
1]
known method widely used in polymer science, carbohy-
chemical transformations ranging from fine organic synthesis
[
2]
[3]
[7–10]
drate and peptide analysis, protein structure determina-
to processes of industrial importance.
Ionic liquids showed
[
4]
[5]
[11]
tion, catalysis, and several other areas of practical applica-
excellent results and recyclability for Heck reactions, Friedel–
[
6]
[12]
[13]
tions. From the discovery in the 1980s to today, ESI-MS dis-
closed plenty of opportunities for analysis of natural substan-
ces within molecular weight determinations, structural investi-
gations and reaction mechanism studies. ESI is a “soft”
ionization method that works with solutions at atmospheric
pressure without or with negligible fragmentation of “parent”
ions for many organic compounds. There are only few steps in
sample preparation procedure, thus, making ESI-MS a quick an-
alytical tool for obtaining qualitative and quantitative informa-
tion about compounds and mixtures of interest.
Crafts-type transformations, Michael additions, hydroami-
[14]
[15]
nations of alkenes,
ring-closing metatheses
and many
[
16]
other important organic synthesis procedures. Important to
note, ionic liquids were proposed to be well-suitable “green”
[17]
[10]
solvents for peptide synthesis and biomass conversion.
In spite of several promises and expectations concerning
ionic liquids, recent studies have clearly shown that ionic liq-
uids by no means are “intrinsically green”. Important issues to
consider in this regard are toxicity of ionic liquids and environ-
[18]
mental impact. Ionic liquids can only become “green” if used
appropriately, which takes into account the overall impact of
the chemical process and environmental persistence. This chal-
lenge facilitates development of new, more sophisticated tools
dealing with ionic liquid research.
Rapid development of modern chemistry in recent years has
revealed the importance of new reaction media in addition to
well-known organic solvents. One of the most fascinating find-
ings concerns the outstanding scope of ionic liquids as reac-
tion media, which showed tremendous growth in recent de-
The properties of ionic liquids that are advantageous for
practical applications made it difficult to analyze these reaction
mixtures by conventional analytical methods. High viscosity,
conductive ionic character and absorption of radiofrequencies
deteriorate the quality of high-resolution NMR spectra in ionic
[
7,8,9,10]
cades.
Due to their unique properties—virtually no vapor
pressure, nonflammable, excellent thermal, mechanical and
electrochemical stability, electrical conductivity, high polarity
and exceptional dissolution properties—ionic liquids have
[19,9]
liquids.
Recently, our group has reported a special NMR ap-
[
a] Dr. L. L. Khemchyan, E. A. Khokhlova, M. M. Seitkalieva, Prof. V. P. Ananikov
Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences
Leninsky Prospect 47, Moscow 119991 (Russia)
proach for the determination of molecular structures and mon-
[20]
itoring of chemical reactions directly in ionic liquids.
In the case of mass spectrometry the problem appears to be
even more complicated. On the one hand, mass spectrometry
with different ionization techniques (e.g., fast atom bombard-
ment (FAB), electron ionization (EI), atmospheric-pressure
chemical ionization (APCI), electrospray ionization (ESI)) provid-
ed a wealth of valuable information about ionic liquids itself,
and their applications for example for the detection of reaction
E-mail: val@ioc.ac.ru
Supporting information for this article is available on the WWW under
http://dx.doi.org/10.1002/open.201300022.
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distribution in any medium, provided the original work is properly cited,
the use is non-commercial and no modifications or adaptations are
made.
[21,22]
intermediates.
For instance, ionic liquids were used as an
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2013 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ChemistryOpen 2013, 00, 1 – 8
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