Separation of benzene and deuterium-substituted benzene via potassium reduction

Perdeuteriated benzene can be partially separated from mixtures of perdeuteriated benzene and benzene simply by (1) reducing a mixture of C/sub 6/H/sub 6/ and C/sub 6/D/sub 6/ containing a molar deficient amount of 18-crown-6 (18C6) to the mixture with potassium metal and (2) distillation of the neutral benzenes from the metal-crown-anion radical complex, followed by (3) reoxidation of the anion radical back to the neutral benzenes. These isotopic enrichments are explained in terms of the less-than unity equilibrium constant for the electron transfer (K/sup +/(18C6)C/sub 6/H/sub 6//sup /center dot/-/ + C/sub 6/D/sub 6/ = K/sup +/(18C6)C/sub 6/D/sub 6//sup /center dot/-/ + C/sub 6/H/sub 6/). In this way the differences in the physical properties of an anion radical and a neutral molecule are utilized to separate isotopic mixtures. The differences in the chemical properties can also be used to effect similar separations. This was demonstrated by adding water to a partially reduced mixture of naphthalene and perdeuterionaphthalene. Since the solution electron affinity of the isotopically light material is larger than that of the perdeuteriated material, the water addition results in the formation of dihydronaphthalene and dihydroperdeuterionaphthalene with the ratio (C/sub 10/H/sub 10/)/(C/sub 10/D/sub 8/H/sub 2/) being greater than the ratio (C/submore » 10/H/sub 8/)/(C/sub 10/D/sub 8/) in the original mixture.« less