Deuterated photolysis

Photolysis of Cp2TiAr2 in benzene solution yields titanocene and a variety of aryl products derived both intra- and intermolecularly (293—297). Dimethyl titan ocene photolyzed in hydrocarbons yields methane, but the hydrogen is derived from the other methyl group and from the cyclopentadienyl rings, as demonstrated by deuteration. Photolysis in the presence of diphenylacetylene yields the dimeric titanocycle (28) and a titanomethylation product [65090-11-1]. 

The efficiency of reduction of benzophenone derivatives is greatly diminished when an ortho alkyl substituent is present because a new photoreaction, intramolecular hydrogen-atom abstraction, then becomes the dominant process. The abstraction takes place from the benzylic position on the adjacent alkyl chain, giving an unstable enol that can revert to the original benzophenone without photoreduction. This process is known as photoenolization Photoenolization can be detected, even though no net transformation of the reactant occurs, by photolysis in deuterated hydroxylic solvents. The proton of the enolic hydroxyl is rapidly exchanged with solvent, so deuterium is introduced at the benzylic position. Deuterium is also introduced if the enol is protonated at the benzylic carbon by solvent ... 

Deuteration by cyclopropyl ring opening Ijas been used also for the stmcture elucidation of a photolysis product (241) of cholesta-3,5-diene. This bicyclobutyl derivative is very reactive and readily hydrolyzed by aqueous dioxane. When the ring opening is carried out in the presence of deuterium oxide, a deuterium is incorporated in the 4y -position of the resulting 6jS-hydroxy-3a,5a-cyclocholestane (242). ... 

When similar photolysis of 11 in the presence of MeOD was carried out, again the product whose NMR reveals the resonance due to the Si-H proton was observed. The relative ratio of the Si-H and CH3-0 protons was identical with those of the products obtained in the presence of non-deuterated methanol. The formation of the methoxysilyl group can be understood by the addition of methanol across the silicon-carbon double bonds. H NMR spectra of all photoproducts obtained from the photolyses of 11 in the presence of methanol reveal no resonances attributed to the cyclohexadienyl ring protons. This indicates that the photochemical degradation of the polymer 11 gives no rearranged silene intermediates, but produces... 

That propane is indeed formed by H2 reaction is known by observing the distribution of yields of various isotopic compositions of propane from the radiolysis of an equimolar mixture of cyclopentane and deuterated cyclopentane. Further evidence is provided by the facts that (1) propane is not formed by photolysis below the ionization threshold, and (2) an electric field has no effect on the yield. 

Vinylcarbenes. The use of diazoalkenes as vinylcarbene precursors is often precluded by rapid cyclization, with formation of pyrazoles. However, on photochemical generation of the diazoalkenes in situ, cyclization and nitrogen extrusion can proceed competitively. Photolysis of 1,3-diphenylpropenone to-sylhydrazone sodium salt (5) in MeOD afforded 3,5-diphenylpyrazole (9) and l,3-diphenyl-3-methoxypropene (10) in similar amounts.17 If 10 is formed by way of the 1,3-diphenylallyl cation (8), the deuterium should be distributed between C-l and C-3 of 10 (Scheme 6). The observed ratio of 10a to 10b was 66 34 the methoxy group is bound preferentially to the deuterated site, which originates from the divalent carbon of 7 (for a discussion of this effect, see below). 

Regents which are active upon irradiation with benzene are olefins and dienes None of these react photochemically with borazine. Recently, the photolysis of benzene at X = 184.9 run with D2 has been shown to produce a small amount of CgHsD (4> = 0.01) This is contrast to the very efficient deuteration at the boron site of borazine (4 = 0.90). Hexafluoroacetone as the absorbing species reacts with borazine to produce a B-alkoxyborazine substitution product. Reaction of this reagent with benzene, on the other hand, involves the CF3 radicals and the products are addition rather than substitution products ss)... 

Analysis of the reaction KIE using monodeuterated sulfamate 106 reinforces the proposed rhodium-nitrene model (Eq. 9). The ratio of H/D products 107/108 is a direct measure of the KIE and has been found to equal 1.5 0.2 by integration of the C NMR spectrum. An equivalent value is obtained for nitrene C-H insertion upon photolysis of a carbamoyl azide, and is taken as evidence for a nonlinear transition state. As noted previously, Muller s use of NsN=lPh with partially deuterated adamantane gives... 

The structures and isomerization of C4Hg+ ions in connection with the problem of ethylene clusters has been the subject of many studies. Doepker and Ausloos192 studied the photolysis of cyclobutane, its deuterated isotopomer and mixtures thereof, and in their detailed product analysis they found cA-2-butene, trans-2-butene and 1-butene as major ionic products in the approximate ratio of 1 1 2. Lias and Ausloos193 determined... 

Fig. 8.3 Determination of the pseudofirst rate constant for the photolysis of C60H36 and C60D36 in n-hexane. The difference in photolysis rate constant between the hydrogenated and deuterated fullerene is small kC60H36 = 2.45 x 10-3 s 1 and kC60D36 = 2.27 x 1(T3 s 1. The ratio kjj/kp = 1.08...

Fig. 8.6 The kinetics of photolysis of both C7QH38 and C70D38 can be described by pseudofirst order law. The photolysis rate constant of C7ffH38 is 1.54 x 10 3 s 1 while the photolysis of C7QD38 occurs at a rate of 1.17 x 10 3 s 1. The differences in the two rate constant between the hydrogenated and deuterated molecule can be ascribed to primary isotope effects...

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