A reaction between xenon and 02BF4 has been observed to liberate oxygen and fluorine at temperatures near 173 °K. A white solid was produced which decomposed at 243 °K into an equimolar mixture of Xe and BF3. On the basis of analytical and vibrational spectroscopic data, it is believed that the structure of this solid is FXe-BF2. This structure is novel in that a covalent xenon-boron bond is assumed.

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A new crystalline compound, NF4-BF4-, has been prepared by exposing the heterogeneous ternary system NF3-BF3-F2 to 3-MeV bremsstrahlung at 77°K. The G value for the reaction (molecules isolated per 100 eV absorbed) is about unity.The compound is stable at room temperature in dry air; it decomposes above 250°to the reactants.It reacts rapidly with moisture and with organic substances. The indicated ionic structure is confirmed by infrared and Raman spectroscopy.The X-ray powder pattern can be indexed on the basis of a tetragonal unit cell with a = 7.01 and c = .22 A. Irradiation of mixtures of nitrogen trifluoride and excess fluorine at 77°K has led to isolation in low yields of a white solid. It decomposes below 143°K to liberate nitrogen trifluoride and reacts with boron trifluoride at low temperature to form NF4BF4.Its most likely identity is perfluoroammonium fluoride.

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The aromatization of 2,4-dimethyl-3-methyl-C14-pentane over "nonacidic" chromia-alumina was studied. The main aromatic products were o-, m-, and p-xylene, with the production of m-xylene dropping rapidly with the time. The radioactivity distribution in the xylenes supports the previously proposed cyclopropane-and cyclobutane-type intermediates for the dehydroisomerization and aromatization of branched hydrocarbons. In addition, this study has indicated that C7-and Cg-membered ring intermediates must play at least a minor role in the aromatization of branched chain hydrocarbons.The aromatization of methylpentanes must be preceded by some rearrangement to at least a Ce-chain intermediate and such a rearrangement presents an interesting mechanistic problem. Studies in our laboratory have shown that alumina has intrinsic acidic properties and that the strength of the acidic sites depends upon the method employed for the preparation of the aluminas.3 It was found that chromia-alumina catalyst containing alumina prepared from aluminum isopropoxide has relatively strong acidic sites and that this catalyst may cause skeletal isomerization of the hydrocarbon via a carbonium ion mechanism.4'5 However, chromia-alumina catalyst containing alumina prepared from potassium alumínate ("nonacidic" chromia-alumina) has relatively weak acidic sites and such cationic skeletal isomerization does not occur.This observation has been subsequently confirmed by others.6 Large membered ring intermediates have been shown for the aromatization of n-heptane and n-octane1'7-8 over "nonacidic" chromia-alumina catalyst. Further studies of the aromatization of branched Cg-Cg hydrocarbons over "nonacidic" chromia -alumina catalyst have shown the existence of adsorbed cyclopropane intermediates and have indicated strongly the possibility of adsorbed cyclobutane intermediates prior to the aromatization reaction.9'10In order to shed more light on the possible existence of cyclobutane intermediates, 2,4-dimethyl-3-methyl-C14-pentane was synthesized and aromatized under conditions described previously.9 The aromatic products of the reaction were mainly o-, m-, and p-xylene. The mechanism involving an adsorbed cyclopropane intermediate would produce 0-and p-xylenes with 100% methyl-labeled o-xylene and 100% ring-labeled pxylene (Scheme I). An adsorbed cyclobutane intermediate would give m-xylene with all the radioactivity in the ring (Scheme II). The production of 0-and pxylene are precluded by this mechanism.