Several methods are available for the preparation of the three chlorosilanes. In order to obtain SiHCl3 as the principal product, the best way is to
react Si with HCl in the presence of copper.
Si + 3 HC1 = SiHCl 3 + H2
A porcelain boat is filled with finely powdered silicon, which has been purified by boiling with hydrochloric acid and dilute hydrofluoric acid. About
10% CuCl2 is mixed in with the silicon. The boat is placed in a Pyrex glass tube fitted with an adapter and a condenser, as described in the
preparation of SiCl4. In this case, however, the end of the condenser should extend into the middle of the distilling flask. The apparatus is first
carefully heated. Hydrogen chloride gas is produced from NaCl and H2SO4, without addition of hydrochloric acid, since it must be absolutely dry. The
furnace around the tube which contains the boat is heated to 300°C and a slow stream of HC1 is introduced. The receiver is cooled with acetone-Dry
Ice mixture. Finally, the crude product is distilled directly from the receiver. The first fraction is HC1. The SiHCl3 comes over at 36.5°C. With a
careful fractionation of the forerun, SiH3 Cl s may also be recovered. The yield of SiHCl3 is about 50%.
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