Studies of Solvation Phenomena of Ions and Ion Pairs in Dimethoxyethane and Tetrahydrofuran

Abstract

Density, viscosity, and dielectric constant of dimethoxyethane (DME) and tetrahydrofuran (THF) were investigated in the temperature range +25 to -700 and found to be remarkably similar for both solvents. Conductance of tetraphenylboride salts of Nar, C+, and Bu(Am)'iN+ were investigated in both media, down to 5 X 10~6 M concentration and over the whole temperature range of +25 to -70°. The respective 0+, Á+,, and -AHdia showed that Bu(Am)¡N+,BPhr forms contact ion pairs in both solvents and dissociates into free Bu-( )% + and BPhr ions not coordinated with solvent. The simple "sphere in continuum" model accounts for the quantitative behavior of this salt in DME and THF. However, to account for the behavior of Na+,BPhr, it is necessary to assume that in both media the salt forms mainly solvent-separated pairs which dissociate into solvent-coordinated Na+ ions. While the behavior of Bu(Am)¡N+ ,BPhf or Nad,BPhr is similar in THF and DME, that of Cs^,BPhr is different in DME from that in THF. It was shown that the medium-size, free Cs+ ion is coordinated with DME but not with THF, whereas the Cs+,BPhr forms mainly contact ion pairs in both solvents. Therefore, the "sphere in continuum" model ( ) were determined for a temperature range of -70 up to +25°. In addition, the conductance of Na+, Cs+, and (z-Am)sBuN+ (z'-Am = isoamyl) salts of BPh4" was investigated in the same temperature range.

Insight into the Solvation and Isomerization of 3‐Halo‐1‐azaallylic Anions from Ab Initio Metadynamics Calculations and NMR Experiments

“…[29] The performance of the THF model was validated by calculating the radial distribution function (RDF) of the molecular centers, which was found to be in excellent agreement with the benchmark RDF reported in reference [28] (see Supporting Information). Moreover, the MD simulations yielded a conformational distribution of 59 % twisted and 41 % oxygen envelope, indicating a thorough sampling of the system.…”

NMR Stratagems for the Study of Multiple Kinetic Hydrogen/Deuterium Isotope Effectsof Proton Exchange. Example: Di-p-fluorophenylformamidine/THF

“…The proce dure is similar to that described for DPFA [31]. Since the density of THF is temperature dependent, the con centrations C(T) at temperature Twere calculated for each sample using the following equation [52]:…”

Internal rotation in [p-(dialkylamino)benzylidene]malononitriles

“…However, the data given in Table 1 show that the enthalpies and free energies (at the coalescence temperature) of activation are the same for both compounds within experimental error. The use of two solvents with different viscosities can not account for the apparent equality of the barriers to partial rotation in the two compounds because the temperature coefficients of the two solvents are very similar (905 K for THF and 935 K for acetone obtained from the variation of viscosity with temperature (8,9)). Association of solvent-solute molecules could account for the apparent equality of the enthalpies and free energies of activation at TT (10).…”