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![Relative secondary product concentration as a function of photolysis time for di†erent reactant ratios. ( ) ) [Me SiSiMe SiMe ], ( K ) [Me HSiSiMe SiMe ], ( L ) [Me HSiSiMe SiHMe ], reactant concentration as in Fig. 3. 3 2 3 2 2 3 2 2 2](profile/Ines-Lein/publication/250867505/figure/fig4/AS:298067254366216@1448076179749/Relative-secondary-product-concentration-as-a-function-of-photolysis-time-for-dierent.png)
Relative secondary product concentration as a function of photolysis time for di†erent reactant ratios. ( ) ) [Me SiSiMe SiMe ], ( K ) [Me HSiSiMe SiMe ], ( L ) [Me HSiSiMe SiHMe ], reactant concentration as in Fig. 3. 3 2 3 2 2 3 2 2 2
Source publication
Di- and trimethylsilyl radicals, generated by the reaction of H atoms with di- and trimethylsilane, react to produce three main products: 1,1,2,2-tetramethyldisilane, pentamethyldisilane and hexamethyldisilane. These products are formed by both radical combination and radical disproportionation reactions. The disproportionation reactions form Me2Si...
Contexts in source publication
Context 1
... products are rapidly formed in our system. After a conversion of only 0.3% a triplet of peaks is observed in the gas chromatogram. The size of the peaks grows quadratically with photolysis time (Fig. 5 ...
Context 2
... reaction sequence (20)È (25) explains the formation of the secondary trisilane products (Fig. 5). We have also endeav- oured to simulate the formation of secondary products by computer calculations. Rate constants for reaction (21) have been reported for R 4 H18 as well as for R 4 Me 2 SiH, The rate constants for reaction (20) were taken to be Me ...
Citations
Me3Si and C2H5 radicals have been generated by the reaction of H atoms with mixtures of Me3SiH and C2H4 and the subsequent reactions studied by end-product analysis. The primary radicals undergo self- and cross-combination and disproportionation reactions. The Me3Si radical also adds to the C2H4, generating another radical, Me3SiCH2CH2. This radical in turn undergoes a variety of self- and cross-combination as well as disproportionation reactions with all the radicals present, A number of relative rate constants were extracted from the data. In particular the ratio k(H + Me3SiH)/k(H + C2H4) was found to be in good agreement with recent absolute determinations of these two rate constants. For the addition reaction we obtained the relative rate constant k(Me3Si + C2H4)/k(1/2)(2Me(3)Si) = (8.7 +/- 0.2) X 10(-10) cm(3/2) s(-1/2) at room temperature. From studies in the temperature range 300-470 K the following values of the Arrhenius parameters for the addition reaction were obtained: 11.6 less than or equal to E-a/kJ mol(-1) less than or equal to 14.1 and 7.1 x 10(-13) less than or equal to A/cm(3) s(-1) less than or equal to 1.9 X 10(-12). In addition, it was found that alkyl and silyl radicals closely obey the geometric mean rule and that disproportionation reactions between alkyl and silyl radicals are of only minor importance. The reactivity of the silyl radical is much higher than that of the alkyl radical in adding to C2H4, and this can be explained in terms of polar effects.
Introduction
Organosilyl Radical Structure, Reactions and Mechanisms
Organosilanes as Reagents in Radical Chain Reactions
