Ultrasonic Absorption Rate Studies of Crown Ether and 222 Cryptate Complexes of Alkali Metal Cations in Nonaqueous Solutions
Technical rept. Sep 1987-Jun 1988
UTAH UNIV SALT LAKE CITY DEPT OF CHEMISTRY
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Sound absorption in liquids in the 0.5 MHz to 400 MHz frequency range can be measured by partially overlapping resonance, laser Debye-Sears, and pulse relaxation techniques. With appropriate precautions ultrasonic relaxation frequencies can be reliably determined in nonaqueous solutions prepared with dry aprotic solvents such as propylene carbonate and 1,3-dioxolane. Mid infrared spectra of counteranions can furnish valuable insights to the reactions responsible for the ultrasonic absorptions. The Eigen-Winkler reaction mechanism, involving several successive stages of desolvation as the metal cation approaches and enters the macrocycle, appears to apply in all cases. In the case of the 222 cryptates the stability of the complex is so great that one does not observe the coming together of the reactants on the ultrasonic time scale but only two intramolecular rearrangements of the cryptates.
- Inorganic Chemistry