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Physical Properties of Binary Mixtures of 3-Propylsydnone–Tetrahydrofuran and 1,2-Dimethoxyethane

1993; Oxford University Press; Volume: 66; Issue: 6 Linguagem: Inglês

10.1246/bcsj.66.1608

1348-0634

Yukio Sasaki, Ken-ichi Miyagawa, Nobuyuki Wataru, Hideki Kaido,

Photochemistry and Electron Transfer Studies

Abstract The physical properties of binary mixtures of 3-propylsydnone (3-PSD)–tetrahydrofuran (THF) and 1,2-dimethoxyethane (DME) at various temperatures were investigated in terms of the dielectric constant (ε), refractive index (nD), density (ρ), and viscosity (η) measurements. The dielectric constants of these binary mixtures gradually decrease with increasing THF and DME mole fractions (XTHF and XDME). The dielectric constant data can be described by a cubic equation of the THF and DME mole fractions. The nD of these binary mixtures decreases linearly with increasing temperature. A linear relationship exists between the density and the temperature at each XTHF and XDME. The η of these binary mixtures rapidly decrease with increasing XTHF and XDME at low temperature. The excess viscosity (ηE) of the mixtures is negative over the entire THF and DME mole fractions, and has a maximum value at 0.4 XTHF and XDME. The negative value of ηE may be taken as the formation of weakly associated compounds. It was found from the 1H and 17O NMR spectra that the interaction in a 3-PSD–THF mixture occurs highly between the hydrogen of the 4-position in the sydnone ring and the oxygen of the THF molecule. From the ηE and NMR spectra it seems that one of the associated compounds due to weak hydrogen bonding in these binary mixtures is formed at the 0.4 THF and DME mole fractions. The interactions in these binary mixtures were investigated on the basis of the activation parameters by using the Eyring rate equation. The activation enthalpy (ΔHη*) gradually increases with increasing viscosity of the mixtures. It is considered that the mechanism of viscous flow for these binary mixtures is a thermally activated single process. The activation entropy (ΔSη*) gradually changes from positive to negative with increasing XTHF and XDME. It seems that the change of sign in ΔSη* near to 0.4 THF and DME mole fractions depends on the formation of weakly associated compounds at that mole fraction. The activation Gibbs energy (ΔGη*) with a positive ΔSη* value gradually decreases with increasing temperature. On the contrary, the ΔGη* with a negative ΔSη* value gradually increases with increasing temperature. This means that the change in ΔSη* greatly contributes to that of ΔGη*.