Question

Alkyl substituted chlorosilane, ${{\text{R}}_{\text{n}}}{\text{SiC}}{{\text{l}}_{(4 - {\text{n}})}}$, on hydrolysis and then condensation polymerization yields silicones. What is the value of n in alkyl substitutes chlorosilane used for the preparation of cross-liked silicone?
A.$1$
B.$2$
C.$3$
D.$4$

Answer 1

To answer this question we must know how cross linked silicones are formed from alkyl substituted chlorosilane. There are various types of silicones such as linear silicons, cyclic silicones and cross linked silicones. The difference between them arises from the type of alkyl chlorosilane used for the preparation. They all are obtained by hydrolysis only.

Complete step by step solution:
Chlorosilanes as the name suggests contains chlorine and silicon. Each molecule must contain at least one chlorine silicon bond. The alkyl chlorosilanes are prepared from direct process. They are used as basic reagents in organo-silicon chemistry. Chlorosilane or alkyl chlorosilanes reacts with water and produces hydrochloric acid. They are widely used in coating glass surfaces, in the formation of polymers etc.
Hydrolysis refers to the breaking of bonds in any chemical species due to water. The term hydro means water and lysis mean to break. The process given in the question is also hydrolysis. In which ${\text{RSiC}}{{\text{l}}_3}$ reacts with water to form the cross linked chlorosilane and hydrochloric acid if formed as byproduct.
Comparing the above formula with the general formula given, we will get the value of n equals to 1.

Hence the correct option is A, i.e., 1.

Note: The nature of polymer is determined by the extent of cross linking. They can be oily as well as rubber like. All the silicones are hydrophobic in nature. They are used in making water proof clothes, making insulating material and are also mixed with paint because of their high temperature tolerance.