Concerning the mechanism for bifunctional catalysis in the methanolysis of methoxymethylphenoxyphenylsilane
摘要:
The formic acid-formate-catalyzed methanolysis of methoxy-d3-methylphenoxyphenylsilane (1D) was studied. The formation of phenol and the exchange of the deuterated methoxy group with solvent was studied as a function of total buffer concentration. Both processes show bifunctional catalysis involving a molecule of acid and a molecule of base in the transition state. The observation of bifunctional catalysis suggests a mechanism in which formation of the silicon-solvent bond is concerted with breaking of the silicon-leaving group bond (-OC6H5 or -OCD3). From analysis of the kinetic data it is concluded that the concerted bond-forming and bond-breaking processes do not occur on a pentavalent silicon species formed by a preequilibrium addition of solvent or formate anion to ID. The results are interpreted in terms of a mechanism in which solvent attack occurs on a tetravalent silicon center with simultaneous breaking of the silicon leaving group bond.
Concerning the mechanism for bifunctional catalysis in the methanolysis of methoxymethylphenoxyphenylsilane
摘要:
The formic acid-formate-catalyzed methanolysis of methoxy-d3-methylphenoxyphenylsilane (1D) was studied. The formation of phenol and the exchange of the deuterated methoxy group with solvent was studied as a function of total buffer concentration. Both processes show bifunctional catalysis involving a molecule of acid and a molecule of base in the transition state. The observation of bifunctional catalysis suggests a mechanism in which formation of the silicon-solvent bond is concerted with breaking of the silicon-leaving group bond (-OC6H5 or -OCD3). From analysis of the kinetic data it is concluded that the concerted bond-forming and bond-breaking processes do not occur on a pentavalent silicon species formed by a preequilibrium addition of solvent or formate anion to ID. The results are interpreted in terms of a mechanism in which solvent attack occurs on a tetravalent silicon center with simultaneous breaking of the silicon leaving group bond.