No abstract

The NMR chemical shift and line width has been measured for 23Na~in tetrahydrofuran (THF), ethylamine (EA), and methylamine (MA), for 87Rb~in THF and EA, and for 133Cs~in THF. In all cases, the counterion was the 2,2,2 cryptate complex of the corresponding cation. The chemical shift of Na~i s, within experimental error, the same as that calculated for the gaseous anion (based upon the measured value for the gaseous atom) and is independent of solvent. Comparison with the solvent-dependent chemical shift of Na+ provides conclusive evidence that Na" is a "genuine" anion with two electrons in a 3s orbital which shield the 2p electrons from the influence of the solvent. The line width increases from THF to EA to MA, suggesting either an increasing exchange rate with the cryptated cation or, more probably, the influence of an increasing concentration of solvated electrons. In the case of sodium solutions in all solvents, both Na+C and Naare detected by their NMR peaks. However, probably because of extreme line broadening, Rb+C and Cs+C are not observed, but only the relatively narrow line of the corresponding anion. The chemical shifts (diamagnetic shift in ppm from the infinitely dilute aqueous ion) are 185 and 197 for Rb" in EA and THF, respectively, and 292 for Cs~in THF, compared with 212 and 344, respectively, for the gaseous Rb and Cs atoms. When 18-crown-6 is used instead of the 2,2,2 cryptand complex, it is still possible to obtain solutions which are about 0.4 M in total metal when methylamine is used as the solvent. However, in this case, both the Naand the Na+C NMR peaks are exchange broadened, even at -50°C, and coalesce as the temperature is raised to about -15 to 0°C, depending upon the concentrations. The variation of the rate of exchange of the sodium nucleus between Na+C and Nawith concentration should permit determination of the exchange mechanism. Possible exchange mechanisms and the information obtainable from them are discussed.

No abstract

Anthracenide radical anions were formed by the reaction of anthracene with potassium or sodium in tetrahydrofuran (THF) and in dimethoxyethane (DME). The rate of reaction of the radical anion with a series of alcohols and with water was followed spectrophotometrically by using a scanning stopped-flow apparatus. The reactions of K+An • -in both solvents and of Na+An• -in THF were essentially second order in (M+An•-) and of variable (0-1) order in the proton donor. The reactions of Na+An •-with ethanol and with water in DME were

Alkali metals can be made to dissolve in solvents in which they are normally insoluble or only slightly soluble, by using cyclic polyethers to complex the cations. Although the use of the cyclic polyether, dicyclohexyl‐18‐crown‐6 results mainly in the formation of M− as the reducing species, the bicyclic polyether, “cryptate” yields in addition, substantial concentrations of solvated electrons. It also increases the solubility compared with the “crown” compound.