63is currently being investigated under more conventional catalytic conditions.
Conclusionsperatures. Ethane probably occurs via the coupling of the gasphase methyl radicals, but the conversion of methane is quite small. Acknowledgment. We thank David L. Myers and Han-Fan Liu for their experimental assistance. We also acknowledge the Gas-phase methyl radicals may be produced in a catalytic manner from C H~ Over pure and lithium-doped ~~0 .The suggest that surface 0ions are responsible for hydrogen atom Conceptual contributions Of Dr. John Kolts. The work was SUPported by the Division Of Basic Energy Science, Department Of abstraction, and in the lithium-doped samples the 0is present as a [Li 'O-] center. This center is formed from the interaction of substitutional Lif ions with molecular oxygen at high tem-
Energy.Abstract: Several new p-tert-pentylcalixarenes have been synthesized. These and other calixarenes have been used to study carrier-mediated alkali-metal cation fluxes at 25 OC in H,O-(organic solvent)-H,O liquid membranes. In addition to single cation systems, all possible equimolar, two-, three-, and four-cation mixtures of NaOH, KOH, RbOH, and CsOH were used in the study. In each case, alkali cation transport was coupled with the reverse flux of protons. Selective transport of Cs+ over Rb', K' , and Na' was seen in all mixtures studied. The greatest selectivity for Cs+ was found for calix [4]arenes, but the largest flux of Cs' as well as the other alkali cations was seen with the calix[6]arenes and calix [8]arenes. The greater flux in these latter cases may be a result of each calixarene binding two cations. In experiments at low [Cs+]-to-[Rb'] ratios, p-tert-butylcalix[6]arene transports Rb' over Cs'. As these ratios increase, transport of Cs+ becomes favored over that of Rb+, indicating that the cation flux depends, in part, on the relative concentrations of the cations in the source phase.Calixarenes' are macrocyclic phenol-formaldehyde condensation products similar in structure to certain cyclic polyethers which are noted for their size-related selectivity in binding cations.2 Calixarenes have been suggested as potential enzyme mimics because they possess a toruslike architecture similar to that of cycl~dextrins.~ The appealing features of cyclodextrins (which are naturally occurring macrocyclic glucose polymers containing a minimum of 6-~(+)-glucopyranose units, attached by a-( 1,4) linkages) are their abilities to form host-guest complexes by trapping organic compounds, small ions, and gases in their toruslike cavities and to mimic enzyme function^.^ Registry No.
