14857-34-2Relevant articles and documents
Substituent effects on the reactivity of the silicon-carbon double bond. Resonance, inductive, and steric effects of substituents at silicon on the reactivity of simple 1-methylsilenes
Leigh, William J.,Boukherroub, Rabah,Kerst, Corinna
, p. 9504 - 9512 (1998)
The reactivities of a series of substituted 1-methylsilenes RMeSi=CH2 (R = H, methyl, ethyl, t-butyl, vinyl, ethynyl, phenyl, trimethylsilyl, and trimethylsilymethyl) in hydrocarbon solvents have been investigated by far- UV (193-nm) laser flash photolysis techniques, using the corresponding 1- methylsilacyclobutane derivatives as silene precursors. Each of these silacyclobutanes yields ethylene and the corresponding silene, which can be trapped as the alkoxysilane RSiMe2OR' cleanly upon 193- or 214-nm photolysis in solution in the presence of aliphatic alcohols. UV absorption spectra and absolute rate constants for reaction of the silenes with methanol, ethanol, and t-butyl alcohol have been determined in hexane solution at 23°C. The rate constants vary from a low 3 x 107 M-1 s-1 for reaction of 1- methyl-1-trimethylsilylsilene with t-BuOH to a high of 1 x 1010 M-1 s- 1 for reaction of 1-ethynyl-1-methylsilene with MeOH. In several cases, rate constants have been determined for addition of the deuterated alcohols, and for addition of methanol over the 0-55°C range. Invariably, small primary deuterium kinetic isotope effects and negative Arrhenius activation energies are observed. These characteristics are consistent with a mechanism involving reversible formation of a silene-alcohol complex which collapses to alkoxysilane by unimolecular proton transfer from oxygen to carbon. Silene reactivity increases with increasing resonance electron-donating and inductive electron-withdrawing ability of the substituents at silicon and is significantly affected by steric effects within this series of compounds. This is suggested to be due to a combination of effects on both the degree of electrophilicity at silicon (affecting the rate constants for formation and reversion of the complex) and nucleophilicity at carbon (affecting the partitioning of the complex between product and free reactants). Two 1- methyl-1-alkoxysilacyclobutanes were also investigated, but proved to be inert to 193-nm photolysis.
A (-)-Menthyl Bonded Silica Phase for Chiral Separations: Synthesis and Solid State NMR Characterization
Lynch, Bernard,Glennon, Jeremy D.,Troeltzsch, Christof,Menyes, Ulf,Pursch, Matthias,Albert, Klaus
, p. 1756 - 1762 (2007/10/03)
A new (-)-menthyl bonded silica phase has been prepared by hydrosilation of a hydride silica intermediate. The hydride silica intermediate was synthesized by the reaction of a monoalkoxysilane (CH3)2SiH(OEt) with silica gel, yielding a relatively high surface coverage (4.4 μmol/m2) of SiH groups. This intermediate was then used successfully in the preparation of a monomeric (-)-menthyl bonded silica phase. The bonded phase produced has been used for the Chromatographic separation of enantiomers in a reversed phase mode (chiral separations). Solid state 13C and 29Si CP-MAS NMR spectroscopy and DRIFT spectroscopy provides valuable information on the structure of the different surface species formed on silica after modification. The surface coverage of the hydride silica intermediate and of the final bonded silica phase produced are also determined. It is found that this modification procedure can exclusively produce a monomeric coverage of SiH groups on the silica surface and can further produce a final monomeric bonded organic silica phase for the separation of enantiomers.
γ-Induced Generation of Dimethylsilylene from Dodecamethylcyclohexasilane
Oka, Kunio,Nakao, Ren,Nagata, Yoshio,Dohmaru, Takaaki
, p. 337 - 340 (2007/10/02)
γ-Irradiation of dodecamethylcyclohexasilane (I) generates dimethylsilylene in 65percent yield when benzene is used as a solvent.Kinetic studies using anthracene as quencher are consistent with a mechanism proposed for the generation of dimethylsilylene, Benzene is first excited by γ-rays and energy is transferred to (I).Excited (I) decomposes to give dimethylsilylene presumably in a way similar to (I) excited by u.v. light.The ratio of the rate constant for self-deactivation of benzene to that for energy transfer from benzene to (I), k2/k3, is 5.1 x 1E-2 mol l-1 at room temperature.Energy transfer to (I) is hindered by added anthracene.The ratio of the rate constant for energy transfer to anthracene to that for energy transfer to (I), k6/k3, is ca. 6 at room temperature.A similar energy transfer is possible in the case of u.v. irradiation.
A Thermochemical Study of Liquid Organosilicon Compounds
Gadzhiev, S. N.,Gubareva, A. I.,Fedotov, N. S.,Sheludyakov, V. D.
, p. 764 - 765 (2007/10/02)
A thermochemical study of liquid organosilicon compounds by an improved method is reported.
Solvent Modified Reactivity of Dimethylsilylene
Steele, Kent P.,Weber, William P.
, p. 6095 - 6097 (2007/10/02)
The insertion of dimethylsilylene into the oxygen-hydrogen single bond of alcohols to yield alkoxydimethylsilanes has been used to probe the effect of solvent on dimethylsilylene reactivity.Competition reactions between pairs of alcohols for dimethylsilylene in various solvents have been carried out.The selectivity of dimethylsilylene is influenced by solvent.Dimethylsilylene is more selective in ether than in hydrocarbon solvents.This difference may result from the formation of complexes between donor solvents and dimethylsilylene.These complexes can deliver dimethylsilylene which is less reactive and more selective than free dimethylsilylene.
INSERTION OF DIMETHYLSILYLENE INTO O-H AND N-H SINGLE BONDS
Gu, Tai-Yin Yang,Weber, William P.
, p. 7 - 11 (2007/10/02)
Dimethylsilylene, generated by photolysis of dodecamethylcyclohexasilane, inserts efficiently into O-H single bonds of alcohols to yield alkoxydimethyl-silanes.Use of ethanol-O-d1 yields ethoxydimethylsilane-Si-d1.Dimethylsilylene also inserts into O-H single bonds of water or D2O to yield respectively tetramethyldisiloxane or tetramethyldisiloxane-Si2-d2.Dimethylsilylene also inserts into N-H bonds of primary and secondary amines to yield aminodimethylsilanes.This reaction provides an efficient route to difunctional silanes.
