GAMMA-RAY INDUCED ADDITION OF TRIPHENYLSILANE TO ALKENES
8 = ; silicon hydrides to alkenes is an important method for preparing certain organo-silicon compounds. Degassed soiutions of triphenylsilane and various alkenes are irradiated at room temperature with gamma rays from a cobalt-60 source. The dose rate is 2 x 10/sup 19/ ev/hr and the dose 7 x 10/sup 21/ ev. Under these conditions, triphenlsilane reacts with 1-hexene, 1-octene, 1-tetradecene, cyclopentene, cyclohexene, and 1-methylcyclohexene to give 1 : 1 addition products. The triphenylsilyl group in these products is bonded to the less hindered carbon of the double bond. For example, triphenylsilane and 1-hexene give 1triphenylsilylhexane. The G value is taken as the number of molecules of pure adduct isolated per 100 ev of radiation energy absorbed by the sample. with 1-hexene G values of 200 are obtained when a 2: 1 mole-ratio of triphenylsilane to alkene is used. The chemical yields in these runs are 60% of theory. Under similar conditions, the naphthenes give poor yields and 2-hexene does not react. The reduced reactivity of triphenylsilane with these olefins is caused by steric effects. The reaction between triphenylsilane and 1-hexene is considered in some detail. The G value seems to be independent of slight changes in the dose rate. For doses up to 7 x 10/sup 21/ ev, the G value rises linearly with the dose. The G value decreases with increase in the concentration of 1-hexene. On varying the 1-hexene- triphenylsilane mole ratios from 0.50 to 2.0, the G values vary from 200 to 70. The magnitudes of these G values are indicative of a chain process for the addition reaction. In searching for solvent effects, benzene or n-hexane is added to solutions of triphenylsilane and 1-hexene. The addition of benzene has no effect on the G value. However, the presence of n-hexane promotes the addition of triphenylsilane to 1hexene. The increase in the G value is thought to be caused by a transfer of energy to triphenylsilane by the n-hexane. This results in an increase in the number of excited triphenylsilane molecules and hence the number of triphenylsilyl radicals. (Dissertation Abstr., 22: No. 7, 1962) both for condensed media and for gas phase irradiations. (2) Reactions which occur after the recoiling tritium atom has reached very low energies, perhaps essentially thermal. The yield of particular products in these very low energy or thermal reactions is dependent upon competitive reactions involving dissolved species as well as the solvent molecules. In the investigations utilizing the irradiated pellets of lithium chloride, it was assumed that a nearly uniform distribution of the tritium produced by the Li/sup 6/(n, alpha )T reaction would be throughout the inonganic lattice. When this lattice is subsequently destroyed by solution of the salt in one of the solvents, this tritium, if not already in stable combination, could be freed to react with molecules of the solvent. Reactions involving free hydrogen atoms or ions could well be expected to account for such reactions. The effects of varying the temperature of irradiation, the solvent temperature, and the dissolved solute were determined. Lithium chloride pellets irradiated at room temperature did not produce non-labile tritium in any of these solvents. Lithium chloride irradiated at -- 196 deg C and maintained at this temperature until they were added to an organic solvent produced non-labile tritium in acetone but not in acetic acid or ethanol. The effect of temperature of the solvent and of added solutes is discussed. A lack of reproducibility occurred both in the activity as labelled acetone and in the total amount of activity in the solution. Some of the possible contributing factors to this irreproducibility are discussed. These experiments indicate that the tritium atoms in the lithium chloride lattice are capable of undergoing at least two reactions upon solution in acetone: (1) T + CH/ sub 3/COCH/sub 3/ yields TCH/sub 2/COCH/sub 3/ + H (2) T + =O yields -O-T. Reaction to form HT is probable but was not verified in these experiments. In solutions containing hydroxyl groups, the reaction (3) T + -OR yields -OT +
- Research Organization:
- Originating Research Org. not identified
- NSA Number:
- NSA-17-001551
- OSTI ID:
- 4771572
- Resource Relation:
- Other Information: Thesis. Orig. Receipt Date: 31-DEC-63
- Country of Publication:
- Country unknown/Code not available
- Language:
- English
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