Dynamics of 2-Pyrrolidinone Self-Association by Nonlinear Dielectric Spectroscopy

Abstract

Nonlinear dielectric spectroscopy is used to study the self-association of 2-pyrrolidinone in benzene solutions up to 0.9 mol/L at 25 °C. The nonlinear dielectric spectra below 100 MHz are recorded using an LC-resonant circuit, while above 100 MHz a partial coaxial resonant cavity is used. Both the kinetic and thermodynamic data are very well described by a dimerization mechanism with an equilibrium constant for dimerization K(ε) = 2676 exp[−17.1(ε − 1)/(2ε + 1)] M-1, depending on the permittivity of the solution according to the reaction field theory. At infinite dilution in benzene, K = 53 M-1 and the rate of association is diffusion-controlled with k 1 = 0.87 × 1010 M-1 s-1. The description proposed in the present work is also confirmed by the analysis of (static) linear dielectric data up to 0.9 mol/L and qualitatively predicts the behavior at higher concentrations. The present study has shown that even for high concentrations there is no need to introduce oligomers such as trimers or tetramers in the association model. Both linear and nonlinear dielectric data lead to a dipole moment value of 3.96 D for the monomer and 2.30 D for the dimer. The latter is believed to undergo a rapid interconversion between a closed and a (partially) open form explaining the relatively high dipole moment. As an overall conclusion, it can be stated that the dynamic measurements have proven to be a much more sensitive tool to discriminate between different association models than thermodynamic results.

Thermodynamic, transport, and spectroscopic studies for mixtures of isomeric butanediol and N-methyl-2-pyrrolidinone

“…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][2][3][4][5][6][7][8]. García et al [1] have determined excess volumes, mixing viscosities, and excess 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-pyrrolidinone from density and viscosity measurements.…”

Tautomerism and Regioselectivity of the Protonation of 2-Pyrrolidone. Stereoselectivity of Complexation between Palladium(II), Chloride Ion, and 2-Pyrrolidone

“…The experimental dipole moments of 2-pyrrolidone in cyclohexane, benzene, carbon tetrachloride, and 1,4-dioxane range from 3.1 to 3.96 D [20,21], which suggests its γ -butyrolactam form I .…”

Molecular interactions of α,ω-alkanediols in pyrrolidin-2-one: Thermophysical and spectroscopic measurements

“…The V E values of a,x-alkanediols in DMF are negative for all the mixtures reveal that DMF interacts strongly with the same diols than with PY in which the disruption of PY dimmers [15,23,24] through breaking of hydrogen bonds result in an increase in volume. Volume loss of these a,x-alkanediols in aqueous media [1,3] is larger than that in PY and this reverse trend in aqueous medium is explained on the basis of occupation of free volume, or cavity in the open ice-like structure of water by diol molecules.…”

“…Alkanediols and amides are used in a wide variety of end-use practical and theoretical applications [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15]. In recent papers, we have reported thermophysical and spectroscopic studies for the mixtures of alkanediols (isomeric butanediols and a,x-alkanediols) with amides (N,Ndimethylformamide and pyrrolidin-2-one) [16][17][18].…”