Michael M. Farrow

Ultrasonic absorption kinetic studies of the complexation of aqueous potassium and cesium ions by 18-crown-6

Abstract : Reaction rate constants for a rapid conformational rearrangement of aqueous 18-crown-6 (1,4,7,10,13,16-hexaoxacyclooctadecane) and its slower complexation of potassium ions at 25C in aqueous solutions have been determined from ultrasonic absorption data covering the 9-340 MHz frequency range. A concentration independent absorption with a maximum at about 100 MHz occurs in aqueous solutions of 18-crown-6 with no alkali metal cations present. This relaxation was attributed to a conformational rearrangement of the crown ether. Complexation of aqueous potassium ion by the polyether was then investigated kinetically at various polyether and potassium ion concentrations. These data, together with the conformational rearrangement data, were analyzed in terms of two step mechanism.

Titanium Corrosion by a Hot Perfluoropolyether

Abstract The kinetics and mechanism of titanium corrosion by Krytox MLO-71-6 are reported. The rate of corrosion is found to be dependent on the presence of molecular oxygen in the environment. For...

The conductance of lanthanide (III) sulfate solutions in D2O

The formation constants of the LnSO4+ complexes are reported for La3+, Pr3+, Sm3+, Dy3+, Yb3+, and Lu3+ in D2O and for Sm3+ and Lu3+ in water at 25°C. Formation constants which were calculated from conductance data are identical with those obtained in H2O within the limits of the assumptions made in the mathematical analysis.

Ultrasonic absorption in aqueous salts of the lanthanides. IV. Sulfates in D2O

The rates of formation of the monosulfate complexes of the trivalent rare earth ions of Pr, Sm, Gd, and Dy have been measured at 25°C in D2O and additional measurements made on Pr, Sm, Gd, Tb, and Ho in water. Using formation constants recently calculated from conductance measurements in D2O, the rate data were compared to our reevaluated data in water to establish if a solvent isotope effect was present, which may contribute to our understanding of the mechanism of complexation. Contrary to previous reports, none is observed, the rate constants being in agreement within experimental error and within the limits of the assumptions used in the mathematical interpretation. Evidence therefore points to a dissociative mechanism in which the rate of exchange of the solvent from the primary hydration sphere of the cation is rate-determining.

Calorimetric determination of the heats of formation of lanthanide monosulfate complexes in D2O1

Heats of formation of rate-earth monosulfate complexes have been measured calorimetrically for the ions La3+, Sm3+, Tb3+, and Er3+, in D2O and H2O solvents. Within the limits of experimental error there is no evidence for a solvent isotope effect on the heat and entropy changes of these complexation reactions.