Excess molar volumes and ultrasonic studies of N-methyl-2-pyrrolidone with ketones at T = 303.15 K

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Abstract

Excess molar volumes (VE) and ultrasonic studies at T = 303.15 K and atmospheric pressure have been measured over the whole composition range for the binary mixtures of N-methyl-2-pyrrolidone (NMP) with ketones. The ketones studied in the present investigation include methyl ethyl ketone (MEK), diethylketone (DEK), methyl propyl ketone (MPK), methyl isobutyl ketone (MIBK), and cyclohexanone (CH). The VE values were measured using a dilatometer and were negative over the entire mole fraction range for NMP with MEK, DEK, MPK, and MIBK and were positive for NMP with CH. The ultrasonic sound velocities for the above systems were measured with a single crystal interferometer at a frequency of 3 MHz. The sound velocity (u) results have been used to calculate isentropic compressibility (Ks) and deviation in isentropic compressibilityKs) over the entire range of volume fraction. The sound velocity results have been predicted in terms of free length theory (FLT), collision factor theory (CFT), and Nomoto relation. The results reveal that all the theories gave a satisfactory estimate of the sound velocity. The deviation values of the isentropic compressibilities (ΔKs) were negative over the entire range of volume fraction in all the binary liquid mixtures except in the binary system NMP with CH, where we observed positive ΔKs values. The results are interpreted on possible molecular interactions between components.

Introduction

The interaction between solvents with polar groups and carbonyl carbon group of ketone plays a crucial role in the structural effects, molecular level and for practical applications [1]. The chemical industries have recognized the importance of the thermodynamic properties in design calculations involving chemical separations, heat transfer, mass transfer and fluid flow. When two or more solvent molecules are associated with one another to form a liquid mixture, it brings about a marked effect on the properties of the resulting system and differences in the intermolecular interactions of the solvents. This fact is well known as the transport phenomenon and thermophysical properties of mixed solvents. Volumetric properties of mixed solvents provided by the intrinsic volume of the molecules have been considered to be a good measure of solute–solvent interactions. The volumetric properties of binary liquid mixtures have been extensively studied [2], [3], [4], [5], as they can contribute to a clarification of the various intermolecular interactions between the different species existing in solution.

N-methyl-2-pyrrolidone (NMP) is a colourless, high-boiling, mobile, characteristic odour, and low viscosity. NMP, known for its low toxicity and solvent power, is rapidly becoming the product of choice for paint strippers, agricultural chemicals, and process solvent applications. As a co-solvent, NMP can improve the gloss of floor polishes and it also has application in the electronic industry as a photo-resist stripper. On the other hand, NMP is a strongly polar liquid and has the potential for use in solvent extraction process for separating polar substances from non-polar substances [6]. It is not on the Hazardous Air Pollutants (HAPs) list of the US 1990 Clean Air Act Amendments. Recently, the demand for NMP is explicitly and incessantly increasing with the research and development of the electronics and chemical industry. It is an aprotic solvent with a large dipole moment and a high dielectric constant (μ = 4.09 Debye and ε = 32.2 at T = 298.15 K) [7]. The NMP is completely soluble with water at all temperatures and also soluble with most organic solvents.

Ketones are also polar and so the dipole–dipole interactions are strong, of course they are weaker hydrogen bonds than in alcohols. Since ketones lack hydroxyl groups, they are incapable to create intermolecular hydrogen bonds, but due to the presence of oxygen, they can form hydrogen bonds with alcohol or water molecules what leads to the complete solubility of low ketones in the former solvents. On the other hand, their boiling points are considerable higher than for ethers or alkanes, indicating the presence of significant intermolecular dipole–dipole forces. The carbonyl group is polar since oxygen is more electronegative than carbon and forms a partially charged dipole. The present study is a continuation of our earlier research [8], [9], [10], [11], [12] on thermodynamic properties of binary liquid mixtures which contains high polar liquids with other solvents. In order to characterize the type and magnitude of the molecular interactions between NMP with ketones, we present here the VE and ultrasonic studies of (NMP) with methyl ethyl ketone (MEK), diethylketone (DEK), methyl propyl ketone (MPK), methyl isobutyl ketone (MIBK), and cyclohexanone (CH) at T = 303.15 K and at atmospheric pressure. However, no effort appears to have been made to collect the molecular interactions between NMP and ketones in terms of VE and ultrasonic studies.

Section snippets

Materials

The pure solvents, of highest purity commercially available were used in the present investigation. NMP (Merck mass fraction purity >0.99) was distilled at low pressure and stored over freshly activated 0.3 nm molecular sieves [13]. Ethyl methyl ketone (BDH Ltd., initial mass fraction purity >0.99), diethyl ketone (Fluka initial mass fraction purity >0.99), methyl propyl ketone (Aldrich, initial mass fraction purity >0.99), methyl isobutyl ketone (BDH Ltd., initial mass fraction purity >0.99),

Results and discussion

The measured VE values of NMP with ketones at T = 303.15 K are summarized as a function of mole fraction of NMP in table 2 and graphically represented in figure 1. The VE results are correlated with the Redlich–Kister type equationVE=x1(1-x1)[a0+a1(2x1-1)+a2(2x1-1)2].

The values of the binary constants, obtained by the above equations are given in table 3 along with the standard deviation σ (VE). The ultrasonic sound velocity (u) of these mixtures has been analyzed in terms of free length theory

Acknowledgment

One of the authors (P. G. K.) is highly thankful to University Grants Commission (UGC), New Delhi, India, for providing a teacher fellowship.

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