Which one of the following compounds is used for the synthesis of

Which one of the following compounds is used for the synthesis of silicones?

[amp_mcq option1=”SiCl₄” option2=”(CH₃)₂Si(OH)₂” option3=”SiO₂” option4=”Na₄SiO₄” correct=”option2″]

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UPSC Geoscientist – 2023

The correct answer is (CH₃)₂Si(OH)₂.

Silicones are polymeric organosilicon compounds. They are typically synthesized by the hydrolysis of alkyl or aryl substituted chlorosilanes, such as R₂SiCl₂. The hydrolysis of (CH₃)₂SiCl₂ yields (CH₃)₂Si(OH)₂, which is a silanol. These silanol monomers then undergo condensation polymerization by eliminating water molecules between hydroxyl groups, forming Si-O-Si linkages, which constitute the backbone of silicones.

While chlorosilanes like R₂SiCl₂ are the starting materials for the synthesis of linear silicones, the hydrolysis product, R₂Si(OH)₂, is the intermediate that directly undergoes polymerization. SiCl₄ can be used to produce branched or cross-linked silicones (by yielding Si(OH)₄ upon hydrolysis, which can polymerize in multiple directions), but the simple linear silicones often start from dialkyl dichlorosilanes and their hydrolysis products. SiO₂ (silica) is a natural inorganic compound, not used as a direct monomer for common silicones synthesis. Na₄SiO₄ is sodium orthosilicate, which is a silicate salt, also not a typical monomer for silicone synthesis.

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