Substituted chlorosilanes, silanols, and siloxanes

Intensive studies of the products of hydrolysis of substituted chloro-silanes and esters have led to an important new branch of chemistry. Many organo-silicon compounds were prepared by Kipping and his school in the early years of this century and it was observed that glue-like products often resulted from the hydrolysis of these compounds, as well as intractable solids of the kinds already mentioned. No study was made of these polymeric products which are now the basis of silicone chemistry. 

By analogy with carbon we might expect mono-, di-, and tri-chloro silanes to hydrolyse to the silicon analogues of alcohols, R3Si. OH, ketones R2Si=0 (by loss 

Silanols R3Si(0H) were obtained in 1911. These compounds tend to condense to the disiloxane  

Silanediols R2Si(OH)2. In the early studies the only diols isolated were those in which R is an aromatic radical, but even these compounds condense to linear and cyclic polysiloxanes. 

All the compounds i, ii, and in were isolated during the years 1912- 1914, the last two being the first cyclic silicon polymers to be characterized. The first dialkylsilanediol was prepared in 1946 by the hydrolysis, by weak alkali, of (C2Hs)2SiCl2 it is a stable crystalline solid. Later, (CH3)2Si(OH)2 was prepared by the hydrolysis of (CH3)2Si(OCH3)2 as a crystalline solid extremely sensitive to acid or alkali, which cause condensation to polysiloxanes, mostly the cyclic tri- and tetra-compounds. Other diols, prepared include the n- and iso-propyl and butyl, and tert-butyl compounds, in addition to tetramethyldisiloxane-l,3-diol (iv). No silanetriol RSi(0H)3 has been isolated. 

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