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Photolysis of mixtures of nitrogen trifluoride with the appropriate ketones (in the temperature range 303-486 K) has enabled the reactions of CH3, CF3, C2H5, i-C3H7 and t-C4H9 radicals with nitrogen trifluoride to be studied. With the smaller radicals only the abstraction of difluoroamino radicals is important, but with i-C3H7 and t-butyl both difluoroamino and fluorine abstraction occur. The Arrhenius parameters are given. The disproportionation-combination ratio for methyl and t-butyl radicals was found to be 0.83 k 0.02.The abstraction of hydrogen atoms by alkyl radicals has been thoroughly investigated and the process and parameters are well established. Little is known, however, about the abstraction of groups by these radicals or about the abstraction of atoms other than h~d r 0 g e n . l~~ In this paper we describe the reactions of methyl, ethyl, isopropyl, t-butyl and trifluoromethyl radicals with nitrogen trifluoride. These reactions involve either group abstraction (difluoroamino) or fluorine atom abstraction about which little is known. The presence of the stable radical difluoroamino in the reacting mixture helps to suppress unwanted side reactions. EXPERIMENTALThe photolyses of ketone+ nitrogen trifluoride mixtures were carried out using a medium pressure mercury lamp in a conventional quartz reaction vessel/high vacuum system equipped with a spiral gauge (for pressure measurements). After photolysis the excess reactants were removed with a LeRoy Still before analysis of the products by gas chromatography. The products were separated by Porapak T, 25 % w]w nitrobenzene on celite or 33 % w/w dimethylsulpholane columns, and detected by a Gow Mac gas density balance using nitrogen as the carrier gas. By this means the molecular weights of measured quantities of products were determined. The detector was calibrated with standard compounds before use. CHEMICALSNitrogen trifluoride was obtained from Air Products and purified by low temperature distillation. The other reactants were obtained from normal sources and also purified by distillation before use. RESULTS REACTION OF ETHYL RADICALS W I T H NITROGEN TRIFLUORIDEMixtures of diethy1 ketone (2-40 Torr) 5 and nitrogen trifluoride (26-1 32 Torr) were photolysed between 410 and 486 K for different periods of time.

Photochemical reduction of Bill' on illuminated TiO, suspensions has been investigated. The photoreduction leads to the formation of metallic Bi on TiO,. Adsorption of Bill' species in the dark was examined. The adsorption parameters were determined using the classical Langmuir adsorption isotherm. The photocatalytic deposition rate was determined under various experimental conditions, such as pH, dissolved oxygen and Bill1 initial concentration. The effect of alcohols as hole-scavengers was also investigated. It was found that addition of hole-scavengers increases the efficiency of the photocatalytic deposition process, by impeding recombination of holes and electrons on the catalyst's surface.

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The vacuum ultraviolet of photolysis of ethylene with argon resonance radiation leads to ion formation with a quantum yield (ionization efficiency) of 0.218±0.015. Ethylene ion immediately forms an adduct with ethylene with an internal energy of 58 kcal/mole above the most stable 2-butene or methylpropene ion configurations. Neutralization of the C.Ha+ ions by charge exchange with toluene, dimethylamine, or trimethylamine yields 2-butene and methylpropene as neutral counterparts to ions assumed to have a similar structure. The relative abundance of the isomers is dependent on the concentrations of charge acceptor and of inert gases. Results are interpreted in terms of an equilibrium between the ionic precursors of 2-butene and methylpropene. A transition state corresponding to a loose methylcylopropane ion structure, with a barrier of about 30 kcal/mole, is postulated for the isomerization. The effects of inert additives and ethylene, which does not react rapidly with C.Ha+ ion, are ascribed to successive energy loss by collision and a resultant change in the equilibrium constant. This model is developed quantitatively and it is shown that, within the framework of some limiting assumptions, energy transfer in nonreactive ion-molecule collisions is considerably less than anticipated on the basis of an intimate complex. This is ascribed to inefficient energy loss for ion-molecule collisions at large impact parameters where redissociation occurs rapidly as a result of small increases in over-all angular momentum.