Thermophysical and spectroscopic studies of room temperature ionic liquid, 1-butyl-3-methylimidazolium hexafluorophosphate in Tritons Ganga Ram Chaudhary a,⇑ , Shafila Bansal b , S.K. Mehta a , A.S. Ahluwalia c a Department of Chemistry & Centre of Advanced Studies in Chemistry, Panjab University, Chandigarh 160014, India b Department of Environment Studies, Panjab University, Chandigarh 160014, India c Department of Botany, Panjab University, Chandigarh 160014, India article info Article history: Received 5 December 2011 Received in revised form 4 January 2012 Accepted 31 January 2012 Available online 14 February 2012 Keywords: Room temperature ionic liquid 1-Butyl-3-methylimidazolium hexafluorophosphate Triton X-45 Triton X-100 abstract The thermophysical properties viz. density q, speed of sound u, and specific conductivity j of pure room temperature ionic liquid (1-butyl-3-methylimidazolium hexafluorophosphate) and its binary formula- tions with Triton X-45 and Triton X-100 have been studied over the entire composition range at different temperatures (293.15 to 323.15) K. Excess molar volume V E , deviation in isentropic compressibility DK S , partial molar excess volume V E i , deviation in partial molar isentropic compressibility DK S;i , deviation in specific conductivity Dj have also been estimated and analysed. Spectroscopic properties (IR, 1 H and 13 C NMR) of these mixtures have been investigated in order to understand the structural and interac- tional behaviour of formulations studied. The magnitude of interactions between the two components increases with addition of number of oxyethylene groups in Tritons and with rise in temperature. Spec- troscopic measurements indicate that interactions are mainly taking place through the five member ring of room temperature ionic liquid and six member ring of Tritons. Ó 2012 Elsevier Ltd. All rights reserved. 1. Introduction Room-temperature ionic liquids (RTILs) are a class of organic salts commonly composed of relatively large organic cations and inorganic or organic anions that cannot form an ordered crystal and thus remain liquid at or near room temperature. Due to an almost unlimited number of potential combinations of cations and anions, RTILs can be tailored to specific applications in many fields, including organic chemistry, electrochemistry, physical chemistry, engineering etc. RTILs can be designed to be flammable, unstable, or even toxic, however, non-flammable, stable, nontoxic and having a non-detectable vapour pressure RTILs can also be designed [1–3]. Due to increasing environmental awareness in our industrialised society, it has become a necessary to develop more environmentally benign ways to manufacture all kinds of chemical based products. Indeed, vapour emissions of organic solvents into the atmosphere have been found to contribute to the increased human exposure to toxic substances, depletion of ozone layer and changes in global climate that create health, envi- ronmental and economic concerns. Volatile organic compound (VOC) based products degrade air quality and interrupt important ecological processes. The non-volatile RTILs results in low impact on the environment and human health hence they have been used extensively as ideal solvents for replacing conventional harmful VOCs in the frame of a ‘‘Green Chemistry’’. The RTILs can be recy- cled after use in organic reactions [4,5]. Many RTILs show an inter- esting mixing behaviour with other liquids, including selective solubility of gases [6]. They are the excellent solvents for organic, inorganic and polymeric materials [7,8]. They are the most inter- esting candidates for separation processes where they could serve as extraction media [9]. RTILs have the potential to provide environmentally friendly solvents for industries ranging from the petrochemical industry [10], via heavy chemicals, fine chemicals, agrochemicals, and pharmaceuticals [11] to the nuclear industry [12]. RTILs open new ways for chemical reactions in homogeneous as well as bipha- sic catalysis including biocatalysis due to their highly polar charac- ter caused by coulomb forces acting between the ions in the liquid state [13–15]. These liquids are used as lubricants, plastisizers, sensing materials for detection of organic vapours, electrolytes, desulphurization and denitrogenation of fuels, capture of toxic gases like carbon dioxide and dioxins, extraction and recovery of dyes, heavy metals and amino acids etc [16–27]. In addition, they are known for their good energy storage properties [28]. A large number of different classes of RTILs have been investi- gated so far. Majority of the research work has been focused on organic synthesis [22,29–33] and on the study of chemical reac- tions in these liquids [34,35]. Systematic investigations of physico- chemical properties of pure RTILs [36,37], in particular mixtures containing RTILs [37,38] are still rare. The objective of the present research work is to provide some new formulations of room temperature ionic liquids based ‘‘green 0021-9614/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved. doi:10.1016/j.jct.2012.01.028 ⇑ Corresponding author. Tel.: +91 172 2534406; fax: +91 172 2545074. E-mail address: grc22@pu.ac.in (G.R. Chaudhary). J. Chem. Thermodynamics 50 (2012) 63–70 Contents lists available at SciVerse ScienceDirect J. Chem. Thermodynamics journal homepage: www.elsevier.com/locate/jct