What are silicones ? How are they prepared ?

Explanation

Silicones: Silicones are polymeric compounds containing Si-O-Si linkages. These have general formula `(R_(2)SiO)_(n)`, These may be linear, cyclic or cross linked. Preparation : Silicones are prepared by the reaction of alkyl halides with silicon in the presence of metallic copper.
`2 R Cl + Si underset(570 K)overset("Cu powder") to R_(2)SiCl_(2)`
The polymers are obtained by the hydrolysis of chloro derivatives as follows :
`Cl - underset(R)underset(|)overset(R)overset(|)(Si) -Cl + 2H_(2)O overset(-2HCl) to HO - underset(R)underset(|)overset(R)overset(|)(Si) - OH`
When large number of molecules of dialkylsilional combine , a polymer is formed with the removal of water molecules .