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6126
J. Phys. Chem. B 2010, 114, 6126–6133
Measurements and Molecular Interactions for N,N-Dimethylformamide with Ionic Liquid
Mixed Solvents
Pankaj Attri,† P. Madhusudan Reddy,† P. Venkatesu,*,† Anil Kumar,‡ and T. Hofman§
Department of Chemistry, UniVersity of Delhi, Delhi 110 007, India, Physical Chemistry DiVision, National
Chemical Laboratory, Pune 411 008, India, and Faculty of Chemistry, DiVision of Physical Chemistry, Warsaw
UniVersity of Technology, ul. Noakowskiego 3, 00-664 Warszawa, Poland
ReceiVed: February 8, 2010; ReVised Manuscript ReceiVed: April 3, 2010
To understand the molecular interactions between N,N-dimethylformamide (DMF) with two families of ionic
liquids (ILs), we have measured thermophysical properties such as densities (F) and ultrasonic sound velocities
(u) over the whole composition range at 25 °C under atmospheric pressure. The excess molar volume (VE)
and the deviation in isentropic compressibilities (∆Ks) were predicted using these properties as a function of
the concentration of IL. These results are fitted to the Redlich-Kister polynomials. The materials investigated
in the present study included two families of ILs such as ammonium salts and imidazolium salts.
Diethylammonium acetate ([Et2NH][CH3COO], DEAA), triethylammonium actetate ([Et3NH][CH3COO],
TEAA), triethylammonium dihydogen phosphate ([Et3NH][H2PO4], TEAP), and triethylammonium sulfate
([Et3NH][HSO4], TEAS) are ammonium salts and 1-benzyl-3-methylimidazolium chloride ([Bmim][Cl]) belongs
to the imidazolium family. The intermolecular interactions and structural effects were analyzed on the basis
of the measured and the derived properties. A qualitative analysis of the results is discussed in terms of the
ion-dipole, ion-pair interactions, and hydrogen bonding between ILs and DMF molecules and their structural
factors.
Introduction
the chemical nature of the cation or that of the anion. The
enhancement of their characteristics is usually achieved by
slightly changing the cation’s size, typically by altering the alkyl
chain length of its organic residue, while preserving its chemical
nature. It is clear that the availability of the experimental values
of parameters has a crucial significance for finding a quantitative
description or even a prediction of some properties. The ILs
possess many unique properties when compared to ordinary
fluids. On the other hand, their structures vary and their functions
are designable. These properties make them very attractive,
especially in the emerging field of green chemistry. Therefore,
they become the most promising solvents.
Although the number of articles on ILs is increasing
exponentially, there is still a lack of data on their thermophysical
description and molecular modeling properties. Apparently, the
aim is to achieve exactly the desired chemical and physical
properties by a judicious combination of an anion and a cation.
A small number of physicochemical data are presented in the
literature, which mainly characterize ILs after synthesis work.7-11
In this context, our aim is to study closely two key thermo-
physical properties, density and ultrasonic sound velocity, of
the molecular interactions between ILs and polar solvents. To
date, there is no systematic documentation of studies of the
ammonium ILs with other organic molecular solvents. For these
reasons, four ammonium ILs are synthesized in our laboratory
by the simplest methods, which increase their utility. In spite
of their importance and interest, accurate values for many of
the fundamental physical-chemical properties of this class of
ILs are either scarce or even absent. On the other hand, detailed
contributions of ILs with the organic molecular liquids have
been rather scarcely investigated up to now on the basis of
thermophysical properties and remain to be understood.
N,N-Dimethylformamide (DMF) is an industrial solvent and
a polar solvent used widely in a variety of industrial processes,
Virtually, the term ionic liquids (ILs) stands for liquids
composed of anions and cations. ILs are a relatively new class
of compounds that are combinations of different organic salt
ions that are liquid at room temperature. Due to the ionic nature
of the materials, ionic liquids have essentially negligible vapor
pressure and so can be envisioned as being useful in a broad
variety of applications.1,2 The development of neoteric solvents,
i.e., ILs, for chemical synthesis holds great promise for green
chemistry applications.3 ILs were initially synthesized in the
early 20th century. To date, there are over 200 types of ILs
prepared, and some of them have been successfully applied in
organic synthesis and other aspects.4-6 One of the major
objectives of the chemical industry today is to search for safer
alternatives of volatile organic compounds that will minimize
air pollution, climatic changes, and human health-related
problems. ILs exhibit certain desirable physical properties: wide
electrochemical window, wide thermal window, nonflamma-
bility, large range of densities and viscosities, high potential
for recycling, and highly solvating capacity for organic com-
pounds. Their perceived status as “designer”, alternative “green”
solvents has contributed largely to this interest, namely, the
existence of fluids with no measurable volatility that are able
to selectively dissolve different types of solute merely by
exchanging one of the ions that form the IL or, even more subtly,
by altering one of the organic residues within a given ion.1,4,6
However, their properties and behavior with respect to
solvating ability can usually be coarse-tuned either by changing
* Corresponding author. E-mail: venkatesup@hotmail.com; pvenkatesu@
chemistry.du.ac.in. Tel: +91-11-27666646-142. Fax: +91-11-2766 6605.
† University of Delhi.
‡ National Chemical Laboratory.
§ Warsaw University of Technology.
10.1021/jp101209j 2010 American Chemical Society
Published on Web 04/20/2010
Attri, Pankaj
