Q.What are silicones?

Step 1 - Starting material

Silicones are prepared starting from alkyl/aryl substituted chlorosilanes, e.g. $\text{R}_2\text{SiCl}_2$ (such as dimethyldichlorosilane, $R=\text{CH}_3$), obtained by reacting RCl with silicon in the presence of a copper catalyst.

Step 2 - Hydrolysis and condensation

Hydrolysis of $\text{R}_2\text{SiCl}_2$ gives an unstable diol, which undergoes intermolecular condensation (polymerisation), eliminating water and building up long chains with a repeating $-\text{O}-\text{Si(R}_2)-\text{O}-\text{Si(R}_2)-$ backbone:

Step 3 - Range of products and uses …

Recall silicones are organosilicon polymers with a Si-O backbone (not C-C); build them from R2SiCl2 via hydrolysis then condensation polym …

• Confusing silicones (Si-O-Si backbone with organic R groups) with silicates (purely inorganic Si-O network anions).
• Forgetting the organic groups are bonded to Si via a direct Si-C bond, not through oxygen. …