Thermodynamic, transport, and spectroscopic studies for mixtures of isomeric butanediol and N-methyl-2-pyrrolidinone S.K. Mehta * , Ganga Ram, Rajat Chauhan, K.K. Bhasin Department of Chemistry and Centre of Advanced Studies in Chemistry, Panjab University, Chandigarh 160 014, India article info Article history: Received 12 January 2009 Received in revised form 4 June 2009 Accepted 6 June 2009 Available online 11 June 2009 Keywords: Thermodynamic characterization Spectroscopic measurements Isomeric butanediol N-methyl-2-pyrrolidinone abstract The thermodynamic parameters viz. excess molar volume V E and speed of sound u, transport parameter viscosity g, and spectroscopic parameters viz. IR, 1 H, 13 C NMR have been measured for the mixtures of isomeric butanediol (1,2-, 1,3-, 1,4-, and 2,3-butanediol) and N-methyl-2-pyrrolidinone over the whole composition range at 308.15 K. The partial molar quantities Q E i , isentropic compressibility K E S , viscosity deviation Dg, deviation in Gibbs free energies of activation for viscous flow g(x), and excess NMR chemical shift d E have been estimated and analyzed. Results show that the interaction between unlike molecules takes place through hydroxyl groups of isomeric butanediol and CO group of N-methyl-2- pyrrolidinone. Excellent agreement between thermodynamic and spectroscopic measurements is observed. Ó 2009 Elsevier Ltd. All rights reserved. 1. Introduction Amide association constitutes a simple model system for base pairing in nucleic acids as well as for peptide bond interactions in polypeptides and proteins. Particularly interesting are cyclic amides (lactams) in which the nitrogen and carbon atoms of the peptide bond are composed by a ring composed of methylene groups. Cyclic amides in general are high density, high boiling point, and high polarity solvents. They are completely miscible over the entire composition range with water. 2-Pyrrolidinone and its methyl derivative, that is, N-methyl-2-pyrrolidinone have been used as cosolvent in the petroleum industry to increase the selectivity and solvent power for extracting aromatic hydrocarbons and have excellent thermal and chemical stability [1–8]. García et al. [1] have determined excess volumes, mixing viscosities, and ex- cess Gibbs free energies of activation of viscous flow of the aqueous binary mixtures of the amides formamide, N-methylformamide, N,N-dimethylformamide, pyrrolidin-2-one, and N-methyl-2-pyrro- lidinone from density and viscosity measurements. The values of these functions point to strong amide–water interaction with the formation of a variety of aggregates, the nature of which depends on the extent of substitution of the amides. George and Sastry [3] reported experimental densities, viscosities, speeds of sound, and relative permittivities, for three binary mixtures of (water + 2-pyr- rolidinone, +N-methyl-2-pyrrolidinone, and +N-vinyl-2-pyrrolidi- none) over the entire composition range and at different temperatures. The analysis revealed that both hydrophobic and hydrophilic hydrations are responsible for the complex nature of the thermophysical behavior in these mixtures. Densities and vis- cosities for binary mixtures of N-methyl-2-pyrrolidinone with cyclohexane, benzene, toluene, p-xylene, and ethylbenzene at dif- ferent temperatures and atmospheric pressure have been reported by Yang et al. [7–9]. The molecular interactions between N-methyl- 2-pyrrolidinone and aromatic hydrocarbons have been analysed by Liu and coworkers [10]. Recently, Dávila and Trusler [11] reported thermodynamic properties of mixtures of N-methyl-2-pyrrolidi- none and methanol. It is anticipated that there is a propensity to form hydrogen bonds between each lone pair of electrons on the oxygen atom in the N-methyl-2-pyrrolidinone molecules and a methanol molecule. Alkanediols are the simplest and model structural units for polyhydroxy compounds. These compounds play a significant role in industry due to their wide range of practical applications, such as antifreezes, coolants, aircraft deicing fluids, heat transfer fluids, hydraulic fluids, solvents, food, flavor and fragrances, pharmaceu- ticals, chemical intermediates, plasticizers, thermoset plastic for- mulations, petroleum, textile, and other industries. The structural and interactional analysis of alkanediols in water mixtures has been extensively studied [12–18]. Nakanishi et al. [12] obtained ex- cess molar volume of aqueous solutions of different diols and it has been found that the volumetric behavior of a,x-alkanediols is al- most same, although their V E slightly increases with molecular size. However, if one of –OH group is not located at the end of diol molecule, the interstitial contribution due to possible cavity occu- pation by methyl group result in a large volume loss. Palepu and coworkers [16,17] have reported various thermophysical proper- ties of aqueous solutions of isomeric butanediol to study the 0021-9614/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.jct.2009.06.006 * Corresponding author. Tel.: +91 172 2534423; fax: +91 172 2545074. E-mail address: skmehta@pu.ac.in (S.K. Mehta). J. Chem. Thermodynamics 41 (2009) 1329–1338 Contents lists available at ScienceDirect J. Chem. Thermodynamics journal homepage: www.elsevier.com/locate/jct