@article { ISI:000234066100022, title = {Pressure dependence of the dissociation of acetic, benzoic, mandelic and succinic acids at 298.15 K}, journal = {Thermochimica Acta}, volume = {439}, number = {1-2}, year = {2005}, month = {DEC}, pages = {154-157}, publisher = {ELSEVIER SCIENCE BV}, type = {Article}, address = {PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS}, abstract = {

Dissociation constants for acetic, benzoic, mandelic and succinic acids have been measured at 298.15 K as a function of pressure up to 138.8 MPa. The spectrophotometric technique using Bromocresol Green as the optical indicator was employed up to ionic strength of 0.03 mol kg(-1) in aqueous solution. Thermodynamic dissociation constants were calculated with the Davies activity coefficient equation. The pressure dependences of the ionization constants for the weak acids can be described by the equation of Lown, Thirsk and Wynne-Jones, application of which leads to accurate partial molal volume change on ionization, Delta(V) over bar (o) and compressibility change, Delta(K) over bar (o) at 0.1 MPa. (C) 2005 Elsevier B.V. All rights reserved.

}, keywords = {Acetic acid, benzoic acid, dissociation constants, high pressure, mandelic acid, succinic acid}, issn = {0040-6031}, doi = {10.1016/j.tca.2005.06.045}, author = {Kumar, Anil} } @article { ISI:000295128000013, title = {Protic ionic liquid attenuates the deleterious actions of urea on alpha-chymotrypsin}, journal = {Physical Chemistry Chemical Physics}, volume = {13}, number = {38}, year = {2011}, month = {SEP}, pages = {17023-17026}, publisher = {ROYAL SOC CHEMISTRY}, address = {THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND}, abstract = {

We present a biocompatible ionic liquid, triethyl ammonium acetate (TEAA), that attenuates the denaturation action of a non-ionic chaotrope, urea, on the industrially relevant proteolytic enzyme alpha-chymotrypsin.

}, issn = {1463-9076}, doi = {10.1039/c1cp22195g}, author = {Attri, Pankaj and Venkatesu, Pannuru and Kumar, Anil and Byrne, Nolene} } @article { ISI:000313767800044, title = {Probing the mechanism of baylis-hillman reaction in ionic liquids}, journal = {Journal of Organic Chemistry}, volume = {77}, number = {19}, year = {2012}, month = {OCT}, pages = {8775-8779}, publisher = {AMER CHEMICAL SOC}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {

The kinetic data for a Baylis-Hillman reaction in certain ionic liquids possessing ethylsulfate anion [EtSO4](-) demonstrate that the rate determining step (RIDS) is second order in aldehyde, but first order in acrylate and DABCO. This observation is similar to the one made by McQuade et al., who carried out this reaction in an aprotic polar solvent like DMSO. However, this is in contrast to the general observation that ADS is first order in aldehyde, acrylate, and DABCO in organic solvents.

}, issn = {0022-3263}, doi = {10.1021/jo301348k}, author = {Singh, Anshu and Kumar, Anil} } @article { ISI:000303921600036, title = {Probing thermal interactions of ionic liquids with dimethyl sulfoxide}, journal = {Chemphyschem}, volume = {13}, number = {7, SI}, year = {2012}, month = {MAY}, pages = {1927-1933}, publisher = {WILEY-V C H VERLAG GMBH}, address = {BOSCHSTRASSE 12, D-69469 WEINHEIM, GERMANY}, abstract = {

Interactions between ionic liquids and dimethyl sulfoxide (DMSO) are probed by isothermal titration calorimetry. The excess partial molar enthalpies of ionic liquids H-IL(E) in DMSO are discussed in terms of solutesolvent interactions. The specific interaction theory originally developed by Pitzer is used to analyze the apparent molar enthalpy phi(L) of ionic liquids in DMSO with the help of ion-interaction parameters. Furthermore, quantitative information on solvent reorganization and clathrate formation is obtained and interpreted.

}, keywords = {calorimetry, dimethyl sulfoxide, ionic liquids, solvent effects, thermochemistry}, issn = {1439-4235}, doi = {10.1002/cphc.201100821}, author = {Rai, Gitanjali and Kumar, Anil} } @article { ISI:000315707900026, title = {Probing the acidity of carboxylic acids in protic ionic liquids, water, and their binary mixtures: activation energy of proton transfer}, journal = {Journal of Physical Chemistry B}, volume = {117}, number = {8}, year = {2013}, month = {FEB}, pages = {2456-2465}, publisher = {AMER CHEMICAL SOC}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {

Acidity functions were used to express the ability of a solvent/solution to donate/accept a proton to a solute. The present work accounts for the acidity determination of HCOOH, CH3COOH, and CH3CH2COOH in the alkylimidazolium-based protic ionic liquids (PILs), incorporated with carboxylate anion, water, and in a binary mixture of PIL and water using the Hammett acidity function, H-0. A reversal in the acidity trend was observed, when organic acids were transferred from water to PIL. It was emphasized that an increased stabilization offered by PIL cation toward the more basic conjugate anion of organic acid was responsible for this anomalous change in acidity order in PILs, which was absent in water. The greater stabilization of a basic organic anion by PIL cation is discussed in terms of the stable hard-soft acid base (HSAB) pairing. A change in the H-0 values of these acids was observed with a change in temperature, and a linear correlation between the ln H-0 and 1/T was noted. This relationship points toward the activation energy of proton transfer (E-a,E-H+), a barrier provided by the medium during the proton transfer from Bronsted acid to indicator. The H-0 function in binary mixtures points to the involvement of pseudosolvent, the behavior of which changes with the nature and concentration of acid. The presence of the maxima/minima in the H-0 function is discussed in terms of the synergetic behavior of the pseudosolvent composed of the mixtures of aqueous PILs.

}, issn = {1520-6106}, doi = {10.1021/jp310927w}, author = {Shukla, Shashi Kant and Kumar, Anil} } @article { ISI:000348753600040, title = {Phase behavior, diffusion, structural characteristics, and pH of aqueous hydrophobic ionic liquid confined media: insights into microviscosity and microporsity in the [C(4)C(4)im][NTf2] + water system}, journal = {Journal of Physical Chemistry B}, volume = {119}, number = {4}, year = {2015}, month = {JAN}, pages = {1641-1653}, publisher = {AMER CHEMICAL SOC}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {

We present our studies on the physicochemical properties of water confined in Dibutylimidazolium bis(trifluoromethanesulfonylimide) ([C(4)C(4)im][NTf2]) reverse micelles through the NMR relaxation measurements that provide us an understanding of microviscosity and pH in the confined condition. We present experimental results on phase behavior, diffusion, structural characteristics and pH in aqueous ionic liquid-confined media. The ternary phase diagram was constructed by the cloud point measurements and the microheterogeneous regions were detected by the measurement of bulk viscosity and diffusion coefficients of K-4[Fe(CN)(6)] inside the homogeneous microemulsion systems through the cyclic voltammetric (CV) measurements. The size of the microemulsion systems was characterized by the dynamic light scattering (DLS) method. The H-1 NMR spectra of homogeneous microemulsion systems were taken which indicates the presence of bound and free water molecules inside the microemulsion system. The NMR spinlattice relaxation time (T-1) of water molecules in its homogeneous microemulsion systems were measured and the reorientational correlation time (t(c)) of water molecules obtained from it indicates that the fluidity of homogeneous confined media decreases with the decrease in the composition of water. Microviscosity of the aqueous confined media was calculated from the measured T-1 relaxation time values by applying the DebyeStokes equation and correlated with the bulk viscosity of the samples. It was observed that both the microviscosity and bulk viscosity show inverse relationship. The fraction of bound and free water molecules were calculated from the measured T-1 values. NMR spinspin relaxation time (T-2) of water molecules in its homogeneous microemulsion systems were measured with the varying pH of the aqueous core. A change in the T-2 relaxation time of the water proton was observed proposing an exchange of proton between the H2O and -OH group of the TX-100 molecules. Finally, methyl orange (MO) was used as a UVvis spectrophotometric molecular probe and the measured lambda(max) values of the probe were used for the detection of micropolarity of the homogeneous aqueous confined media and was found to be increase with the increase in the size of the confined media.

}, issn = {1520-6106}, doi = {10.1021/jp511318t}, author = {Nanda, Raju and Kumar, Anil} } @article { ISI:000353058700025, title = {Polarity issues in room temperature ionic liquids}, journal = {Clean Technologies and Environmental Policy}, volume = {17}, number = {4}, year = {2015}, month = {APR}, pages = {1111-1116}, publisher = {SPRINGER}, address = {233 SPRING ST, NEW YORK, NY 10013 USA}, abstract = {

The study on ionic liquids has occupied an important place in chemical processes because of several beneficial properties. In order to use these ionic liquids as solvent media in chemical processes, it is essential to know their solvent properties. In this review, an attempt has been made to critically evaluate and discuss the polarity parameters of ionic liquids. The experimental polarity data on ionic liquids are not yet available for numerous ionic liquids. This review will serve as a guideline to investigate polarity issues of these materials and emerge with a simple, but still sound theoretical or semi-empirical models to account for the variation in polarity in the ionic liquid solutions.

}, issn = {1618-954X}, doi = {10.1007/s10098-014-0864-y}, author = {Shukla, Shashi Kant and Kumar, Anil} } @article {43861, title = {Probing the solute-solvent interactions in the binary mixtures of ionic liquids with water and alcohols by conductance, viscosity and IR spectroscopy}, journal = {Journal of Molecular Liquids}, volume = {238}, year = {2017}, month = {JUL}, pages = {270-280}, type = {Article}, abstract = {The molar conductance and viscosities of the bisulfate ([HSO4](-)) and ethylsulfate ([EtSO4](-))-based imidazolium ionic liquids in various molecular solvents have been measured at 298.15 K as a function of concentration of ionic liquids (1 x 10(-4) to 0.1 mol L-1). It is shown that the anions have considerable effect on the molar conductance and association constant of the [HSO4](-) and [EtSO4](-)-based imidazolium ionic liquids. Higher molar conductance of the [HSO4](-)-based imidazolium ionic liquids in polar protic solvents (water and methanol) is noted as compared to the [EtSO4](-)-based imidazolium ionic liquids, though the [HSO4](-)-based imidazolium ionic liquids possess higher association constant in water than in methanol. The intermolecular interactions in the pure and binary mixture of [HSO4](-) and [EtSO4](-)-based imidazolium ionic liquids have been investigated by IR spectroscopy. The C-2-H stretching vibration frequency of the imidazolium ring reveals the H-bonding between cations and anions of pure ionic liquids and their solutions. The transport properties (limiting molar conductance, transport number, ionic mobility and diffusion coefficient) of cations and anions correlate well with the hydrodynamic radius in their aqueous solutions. The study shows that the energy barrier for charge transfer is minimal as compared to the fluidity of the aqueous solution of the studied ionic liquids obtained from the Arrhenius equation. (C) 2017 Elsevier B.V. All rights reserved.}, doi = {10.1016/j.molliq.2017.05.005}, author = {Jain, Preeti and Kumar, Anil} }