01861nas a2200169 4500008004100000022001400041245006200055210006100117260011000178300001400288490000700302520122500309100002501534700002601559700001601585856009001601 2012 eng d a1463-907600aDo anions influence the polarity of protic ionic liquids?0 aDo anions influence the polarity of protic ionic liquids aTHOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLANDbROYAL SOC CHEMISTRYcDEC a2754-27610 v143 a

Polarity studies in two classes of imidazolium-based protic ionic liquids (PILs) possessing [HSO4](-), [HCOO](-),[CH3COO](-) and [CH3CH2COO](-) anions were carried out using a solvatochromic method from 298.15 to 353.15 K. For 1-methylimidazolium class of PILs, ET(30) was found to be independent over the entire range of temperature, while ET(30) was noted to decrease with a rise in temperature in the case of 1-butylimidazolium class of PILs containing [CH3COO](-) and [CH3CH2COO](-) anions. The ET(30) value decreases in both the classes upon varying the anions ([HSO4](-), [HCOO](-), [CH3COO](-) and [CH3CH2COO](-)). The E-T(30) value is controlled by hydrogen bond acceptor basicity, b, and dipolarity/polarizability, pi*. The E-T(30) value for PILs varies inversely to the strength of the coulombic interaction between ions in PILs. Strong interactions between ions lead to lower E-T(30) values. Unlike the poor thermal effect on E-T(30), the Kamlet-Taft parameters i.e. alpha, beta and pi* have pronounced thermal effect in the imidazolium-based PILs. Variation in the Kamlet-Taft parameters is controlled by the stabilization of ions and the degree of proton transfer from Bronsted acid to Bronsted base.

1 aShukla, Shashi, Kant1 aKhupse, Nageshwar, D.1 aKumar, Anil uhttp://library.ncl.res.in/content/do-anions-influence-polarity-protic-ionic-liquids-001317nas a2200157 4500008004100000022001400041245010300055210006900158260007300227300001000300490000800310520067700318100002500995700001601020856012301036 2013 eng d a0009-261400aDo protic ionic liquids and water display analogous behavior in terms of hammett acidity function?0 aDo protic ionic liquids and water display analogous behavior in  aPO BOX 211, 1000 AE AMSTERDAM, NETHERLANDSbELSEVIER SCIENCE BVcAPR a12-160 v5663 a

We address an issue whether the strength of carboxylic acids in water is linear with respect to that in ionic liquids. Strength of carboxylic acids in water and different PILs using Hammett function (Ho) has revealed interesting linear correlation between the Ho function for all acids in PILs and PIL-water in spite of large structural and electronic differences. These observations suggest that different structural and electronic features of PILs and water behave analogously towards Ho. This linearity in Ho functions between PILs and PIL-water systems can be used to develop predictive method to calculate Ho values. (c) 2013 Elsevier B.V. All rights reserved.

1 aShukla, Shashi, Kant1 aKumar, Anil uhttp://library.ncl.res.in/content/do-protic-ionic-liquids-and-water-display-analogous-behavior-terms-hammett-acidity-002184nas a2200157 4500008004100000022001400041245014000055210006900195260007100264300001400335490000800349520150200357100002501859700001601884856012601900 2013 eng d a1520-610600aProbing the acidity of carboxylic acids in protic ionic liquids, water, and their binary mixtures: activation energy of proton transfer0 aProbing the acidity of carboxylic acids in protic ionic liquids  a1155 16TH ST, NW, WASHINGTON, DC 20036 USAbAMER CHEMICAL SOCcFEB a2456-24650 v1173 a

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.

1 aShukla, Shashi, Kant1 aKumar, Anil uhttp://library.ncl.res.in/content/probing-acidity-carboxylic-acids-protic-ionic-liquids-water-and-their-binary-mixtures-002302nas a2200157 4500008004100000022001400041245011500055210006900170260007100239300001400310490000800324520164600332100002501978700001602003856012502019 2015 eng d a1520-610600aDissociation of equimolar mixtures of aqueous carboxylic acids in ionic liquids: role of specific interactions0 aDissociation of equimolar mixtures of aqueous carboxylic acids i a1155 16TH ST, NW, WASHINGTON, DC 20036 USAbAMER CHEMICAL SOCcAPR a5537-55450 v1193 a

Hammett acidity function observes the effect of protonation/deprotonation on the optical density/absorbance of spectrophotometric indicator. In this work, the Hammett acidity, H-0, of equirriolar mixtures of aqueous HCOQH, CH3COOH, and CH3CH2COOH was measured in 1-methylimidazolium-, 1-methylpyrrolidinium-, and 1-methylpiperidinium-based protic ionic liquids (PILs) and 1-buty1-3-methylimidazolium-based aprotic ionic liquid (AIL), with formate (HCOO-) anion. Higher H-0 values were observed for the equimolar mixtures of aqueous carboxylic acids in protic ionic liquids compared with those of the aprotic ionic liquid because of the involvement of the stronger specific interactions between the conjugate acid of ionic liquid and conjugate base of carboxylic acids as suggested by the hard soft acid base (HSAB) theory. The different Ho values for the equimolar mixtures of aqueous carboxylic acids in protic and aprotic ionic liquids were noted to depend on the activation energy of proton transfer (E-a,H(+)). The higher activation energy of proton transfer was obtained in AIL indicating lower ability to form specific interactions with solute than that of PILs. Thermodynamic parameters determined by the ``indicator overlapping method'' further confirmed the involvement of the secondary interactions in the dissociation of carboxylic acids. On the basis of the thermodynamic parameter values, the potential of different ionic liquids in the dissociation of carboxylic acids was observed to depend on the hydrogen bond donor acidity (alpha) and hydrogen bond acceptor basicity (beta), characteristics of specific interactions.

1 aShukla, Shashi, Kant1 aKumar, Anil uhttp://library.ncl.res.in/content/dissociation-equimolar-mixtures-aqueous-carboxylic-acids-ionic-liquids-role-specific-101242nas a2200157 4500008004100000022001400041245005400055210005400109260005700163300001400220490000700234520071500241100002500956700001600981856008700997 2015 eng d a1618-954X00aPolarity issues in room temperature ionic liquids0 aPolarity issues in room temperature ionic liquids a233 SPRING ST, NEW YORK, NY 10013 USAbSPRINGERcAPR a1111-11160 v173 a

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.

1 aShukla, Shashi, Kant1 aKumar, Anil uhttp://library.ncl.res.in/content/polarity-issues-room-temperature-ionic-liquids-0