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Explain the preparation of silicones. |
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Answer» Solution :Generally silicones are prepared by the HYDROLYSIS of dialkyldichlorosilanes `(R_(2)SiCl_(2))` or diaryldichlorosilanes `Ar_(2)SiCl_(2)`, which are prepared by PASSING vapours of RCl or ArCl over silicon at 570 K with copper as a catalyst. `2RCl+Si overset(Cu//570K)to R_(2)SiCl_(2)` The hydrolysis of dialkylchloro silanes `R_(2)SiCl_(2)` yields to a straight chain polymer which grown from both the sides. `Cl-underset(R)underset(|)overset(R)overset(|)Si-Cl underset(-2HCl)overset(+2H_(2)O)toHO-underset(R)underset(|)overset(R)overset(|)Si-OH` `HO-underset(R)underset(|)overset(R)overset(|)Si-OH+HO-underset(R)underset(|)overset(R)overset(|)Si-OH underset(-H_(2)O)toHO-underset(R)underset(|)overset(R)overset(|)Si-O-underset(R)underset(|)overset(R)overset(|)Si-OH+HO-underset(R)underset(|)overset(R)overset(|)Si-OH` `underset(-H_(2)O) to HO-underset(R)underset(|)overset(R)overset(|)Si-O-underset(R)underset(|)overset(R)overset(|)Si-OH-underset(R)underset(|)overset(R)overset(|)Si-OH underset(-H_(2)O) to Etc` The hydrolysis of monoalkylchloro silanes `RSiCl_(3)` yields to a very COMPLEX cross LINKED polymer. LINEAR silicones can be converted into cyclic or ring silicones when water molecules is removed from the terminal -OH groups. 
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