The equivalent conductance of THF solutions of LiAlH4, NaAlH4, Bu4NA1H4, and LiBH4 were obtained over a wide concentration range, i.e., 0.5 to 1 X 10~7 M. The data are consistent with the presence of free ions and ion pairs in dilute solution and the formation of triple ions as the concentration is increased. The application of the Fuoss treatment to the data, where only free ions and ion pairs are encountered, permits the evaluation of the infinite dilution equivalent conductance ( 0) and the ion-pair dissociation constant (Aa) for each hydride. Utilizing a sphere in a continuum model, the center-to-center distances between the ions in the ion pair calculated from the experimental Ka values indicate that the ion pairs of Bu4NA1H4 and LiBH4 are in intimate contact, whereas the LiAlH4 and NaAlH4 species are solvent-separated ion pairs. Thermodynamic parameters also suggest that LiAlH4 ion pairs are predominantly solvent separated, whereas a substantial fraction of the NaAlH4 ion pairs are are in intimate contact at 25°. The 0 values obtained for these hydrides also support these conclusions. In the region where ion pairs and triple ions are encountered, the triple ion dissociation constants (Kt) have been evaluated from the data using the Fuoss method. Combining the X» and Kt values, the fraction of each species present at any concentration below 0.1 M has been calculated. When these data are used to calculate association i values, good agreement is found between the observed ebullioscopic i values and those calculated from the conductance results. Nmr studies indicate the formation of a 4:1 THF solvate with LiAlH4, Lil, and LiC104 and the formation of a 2:1 THF solvent with LiBH4. Similar studies show no interaction for Bu4NA1H4. The appearance of infrared bands near 420 cm-1 (attributed to the vibration of the lithium ion in a solvent cage) are found for LiAlH4, LiClOi, Lil, and LiBr, but well-defined bands are absent for LiBH4 in THF.

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Die Reduktion zahlreicher Ketone wie 3,3,5‐Trimethyl‐cyclohexanon, Norcampher, Campher, Isopinocampher, 2‐Methyl‐cyclopentanon, 2‐Methylcyclohexanon oder 2‐tert.‐Butyl‐cyclohexanon durch die Hydride (I)‐(V) wird untersucht und die Anteile an den isomeren Carbinolen werden bestimmt.