Electrical conductance and ultrasonic relaxation for lithium perchlorate in tetrahydrofuran

Abstract

Electrical conductance (10"5 to 1 M) at 25, -15, and -30°and ultrasonic absorption (0.05-0.5 M) in the frequency range 5-330 MHz at 25, -15, and -30°have been measured for L1CIO4 in tetrahydrofuran (THF). The electrical conductance data reveal the presence of a minimum that can be interpreted and evaluated by the Fuoss-Kraus theory of triple ion formation (up to ~0.1 M). Numerical evaluation of ion pair and triple ion pair constants were made. The ultrasonic relaxation data are interpreted as due to the process of formation of triple ions, the barrier of activation energy for the process being comparable to the one for viscous flow.

Characterization of Tetrahydrofuran as a Solvent for Proton Transfer Reactions

“…Systematic attempts to characterize the solvent properties of THF so far have been based mainly on measurements of conductivities of salts, particularly alkali metal and quarternary ammonium perchlorates and tetraphenylborates (2)(3)(4)(5)(6)(7)(8)(9), as well as such other lithium salts as tetrafluoroborate, hexafluorophosphate, hexafluoroarsenate, and hexafluoroantimonate (10). The study by Barthel (10) was particularly thorough, involving a wide concentration range of 10 -6 to above 1 molal and a temperature range of -45 ~ to +25~ the applicability of various conductance equations to dilute solutions was evaluated, and formation constants for ion pairs and ion triplets were calculated.…”

“…The formation of contact and solvent separated ion pairs could be distinguished (2). In some cases the conductivity data could be supplemented by ultrasonic relaxation measurements, providing information on the dynamics of the association processes (6,7,11).…”

Structural Effect of Formic Acid in Electrolytic Solutions of Lithium Perchlorate in Tetrahydrofuran, at 298.15 K

“…In the present work, the concentration of HCOOH in the THF did not exceed 15%, and the value of the dielectric constant laid between 7.39 and 9.75. The ionic equivalent conductivity for Li + and C104-are known from the literature: ~aCLi+ = 36.6 S cm 2 eq -I (17) and ~,~clo4-----119.5 S cm 2 eq -1 (18), giving A~LiC~O4 = 156.1 S cm2 eq-1, in TH'F (6). The results in Table IV were obtained with this value for A OoLiC104.…”

“…A Sargent oscillometer Model V, calibrated with standards of known dielectric constant, was used. The expression, e ----2.107 ~-2.646 10-4S, obtained by the least squares method, relates the dielectric constant c, with the scale reading of the instrument S. Two Ostwald viscosimeters were used, calibrated with conductivity water ~H2O = 0.8903 cp (5) and THF, ~THF = 0.4583 cp (6), as standards and utilizing the Jones and Stauffer equation (7), ~ ----Apt-B (p/t). All calibrations and measurements were carried out at 298.15 (___0.02) K. The chemicals used were: tetrahydrofuran (THF), Merck p.a., density at 298.15 K, pTHF = 0.8820 (+__.0.001) g cm -3, measured with a 25 cm -~ picnometer and a Metler balance Model H20-T, compares well with the values found in the literature: 0.880 and 0.883 (8,9).…”

“…= constant, wherein e is the dielectric constant of the solvent ( Table V) . The presence of triple ions rather than the slope of a Fuoss-Kraus plot seems to affect the intercept and therefore the determination of A~ (6).…”