Methyltrimethoxysilane → Methyltrimethoxysilane Isobutyltrimethoxysilane KOH

Beteiligte Stoffe

Reaktionsschritte

A 500 ml 5-neck round-bottom flask rendered inert with nitrogen and equipped with paddle stirrer, dropping funnel, thermometer, and water separator with reflux condenser is charged—in an oil bath at 40° C.—with 77.4 g (0.42 mol) of isobutyltrimethoxysilane (=2-methyl-1-propyltrimethoxysilane, available commercially from abcr GmbH & Co. KG), 25 g (0.18 mol) of methyltrimethoxysilane (available commercially from Wacker Chemie AG), and 78.3 g of Isopar (isoparaffinic hydrocarbon mixture with a boiling range of 113-143° C., available commercially from ExxonMobil). The water separator is filled to the brim with Isopar E. While stirring at 300 rpm, 67.5 g of 50% strength potassium hydroxide solution (0.6 mol KOH) are metered in over 10 minutes. During this addition, the reaction mixture warms up to 63° C. By subsequent heating it is brought to boiling temperature. The distillate separates out as the lower phase in the water separator. It is removed from time to time and replaced each time by Isopar E. Up to a boiling temperature of 118° C., 74 g of clear colorless distillate are collected, which according to analysis by gas chromatography contains 75:5% methanol, 23.6% water, and 0.6% Isopar E. Thus 97% of the methoxy radicals are hydrolyzed. During the distillation, a suspension is formed in the reaction mixture. The volatile constituents are removed by distillation at 70° C./4 hPa. The residue left is 96.5 g of a white, coarse powder whose solids content is 99.4% (determined using the HR73 Halogen Moisture Analyzer solids content balance from Mettler Toledo at 160° C.)

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