Thermodynamic and spectroscopic interpretation of molecular interactions of nicotine + alcohol binary mixtures

Highlights

• Densities, viscosities and refractive indices of nicotine + alcohol mixtures are determined in wide temperature range.

• Thermodynamic analysis of four investigated mixtures is performed in order to analyze non-ideal behavior of mixtures.

• FT-IR analysis confirms the presence of hydrogen bonding between unlike compounds, except nicotine + 1-butanol system.

• Stronger interactions take place in the mixtures of nicotine and propanediols comparing to butanols.

Abstract

Density ρ, viscosity η and refractive index n_D have been experimentally measured for four binary mixtures nicotine + 1-butanol, nicotine + 2-butanol, nicotine + 1,2-propanediol and nicotine + 1,3-propanediol over the temperature range T = (293.15–323.15) K with temperature step 5 K and at atmospheric pressure. Excess molar volumes V^E, viscosity deviations Δη, deviations in refractive index Δn_D, excess Gibbs free energy of activation of viscous flow ΔG^∗E, thermal expansion coefficients $\alpha$, excess thermal expansion coefficients ${\alpha }^E$, partial molar volumes ${\bar{V}}_i$, excess partial molar volumes ${\bar{V}}_i^E$ and it’s values at infinite dilutions ${\bar{V}}_i^{E\text{,}\infty }$ were calculated from experimental data and used to analyze non-ideal behavior of mixtures. Fourier-transform infrared analysis of binary mixtures and corresponding pure components was performed at 298.15 K in order to gain insight into the molecular structure of mixtures and possible intermolecular interactions. Performed infra-red analysis confirms the presence of hydrogen bonding between unlike compounds, except for the system nicotine + 1-butanol. Here, the non-ideal behavior of mixtures is contributed to strong intermolecular interaction or in the case of nicotine + 1-butanol due to geometrical packing or dispersion forces of different species.

Introduction

Nicotine is a highly toxic alkaloid, natural product of tobacco and consequently widely present in tobacco industry [1]. Its role as a pharmacological drug against some diseases has been recently demonstrated [2], [3]. Nicotine was found to exhibit highly selective insecticidal activity as well [4]. One of the major concerns related to a wide application of this highly hazardous substance is its removal from waste industrial streams. The goal is to use less volatile and less toxic solvent for nicotine removal as well as for its extraction and purification from natural resources. Many efforts have been undertaken to find environmentally friendly solvents which can be applied for nicotine processing [5], [6], [7]. Nicotine possesses interesting structure with lone electron pairs in nitrogen atoms, two aromatic rings with their π-electron system, high polarity [8], [9] and hydrogen bond basicity (nucleophilicity) [10], disposed to (single or double) protonation [11]. Furthermore, nicotine molecule has two different rings-one aromatic (pyridine) and one aliphatic (pyrrolidine). These show diverse rotation ability [12] and appear in different, non-planar, spatial conformations, both in the gas phase and in (water) solutions [12], [13], [14]. This work suggests new compounds of low toxicity with a potential role in various chemical processes including nicotine treatment and these are alcohols 1-butanol, 2-butanol, 1,2-propanediol and 1,3-propanediol. As it is expected from molecular structures of individual components these solutions are completely miscible having in mind that four of investigated alcohols are polar as well, having OH groups capable of hydrogen bonding. Extraction ability of butanol alcohols is already proven in literature [15], [16]. Propanediols, although mainly produced by chemical synthesis, can be obtained from natural sources via microbial fermentation which make them attractive as renewable [17], [18] and they are also widely used in industrial processes [19], [20]. For the design of industrial process it is necessary to know thermophysical properties of pure components and their solutions. So in this work properties such as density ρ, viscosity η and refractive index n_D have been experimentally measured for four binary mixtures nicotine + 1-butanol, nicotine + 2-butanol, nicotine + 1,2-propanediol, nicotine + 1,3-propanediol in the temperature range T = (293.15–323.15) K with temperature step 5 K and at atmospheric pressure. From the experimental data excess molar volumes V^E, viscosity deviations Δη, deviations in refractive index Δn_D, excess Gibbs free energy of activation of viscous flow ΔG^∗E, thermal expansion coefficients $\alpha$, excess thermal expansion coefficients ${\alpha }^E$, partial molar volumes ${\bar{V}}_i$, excess partial molar volumes ${\bar{V}}_i^E$ and it’s values at infinite dilutions ${\bar{V}}_i^{E\text{,}\infty }$ were calculated from experimental data. V^E, Δη, Δn_D and ΔG^∗E values were fitted using Redlich-Kister polynomial. According to these calculations it can be assumed what molecular interactions contribute to the complete miscibility of investigated binary mixtures, as well as the presence of geometrical effects between component’s molecules. In order to prove the assumptions Fourier-transform infrared analysis of binary mixtures and corresponding pure components was performed at 298.15 K.