“…The generation of di-and trimethylsilyl radicals by the reactions of hydrogen atoms with di-and trimethylsilane and their subsequent reactions have been described 23 . Three main products were observed in these reactions: 1,1,2,2-tetramethyldisilane, pentamethyldisilane and hexamethyldisilane which are formed by both radical coupling and disproportionation processes.…”
Section: Si Simentioning
confidence: 99%
“…Three main products were observed in these reactions: 1,1,2,2-tetramethyldisilane, pentamethyldisilane and hexamethyldisilane which are formed by both radical coupling and disproportionation processes. The authors describe a detailed kinetic analysis of the various reactions of interest but have difficulty in providing a mechanistic description that fully fits their observed data 23 Sulkes, Fink and their associates recently investigated the molecular beam photochemistry of oligosilanes and related germanes 24 . In particular, photolysis of compounds 25 -29 in the nozzle region of a supersonic jet by a 193 nm laser and subsequent analysis by 118 nm photoionization followed by time-of-flight mass spectrometry revealed the formation of several products.…”
“…The generation of di-and trimethylsilyl radicals by the reactions of hydrogen atoms with di-and trimethylsilane and their subsequent reactions have been described 23 . Three main products were observed in these reactions: 1,1,2,2-tetramethyldisilane, pentamethyldisilane and hexamethyldisilane which are formed by both radical coupling and disproportionation processes.…”
Section: Si Simentioning
confidence: 99%
“…Three main products were observed in these reactions: 1,1,2,2-tetramethyldisilane, pentamethyldisilane and hexamethyldisilane which are formed by both radical coupling and disproportionation processes. The authors describe a detailed kinetic analysis of the various reactions of interest but have difficulty in providing a mechanistic description that fully fits their observed data 23 Sulkes, Fink and their associates recently investigated the molecular beam photochemistry of oligosilanes and related germanes 24 . In particular, photolysis of compounds 25 -29 in the nozzle region of a supersonic jet by a 193 nm laser and subsequent analysis by 118 nm photoionization followed by time-of-flight mass spectrometry revealed the formation of several products.…”
“…This discrepancy was not the only motivating factor in beginning this work. We have published a number of papers dealing with the mechanistic pathways followed by silyl radicals, and therefore, of at least equal interest to us were the radical−radical reactions which lead to the final products. 1 Dependence of the product quantum yields on ethene concentration for a constant reactant ratio [C 2 H 4 ]/[Me 3 SiH] = 1.02: (○) experimental values; (▾) calculated values.…”
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(2Me3Si) = (8.7 ± 0.2)
× 10-10 cm3/2 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 ≤ E
a/kJ mol-1 ≤ 14.1 and 7.1 × 10-13 ≤ A/cm3 s-1 ≤ 1.9 × 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.
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