Compounds of Silicon


  •  These are organosilicon polymers containing Si-O-Si linkages.
  • These are formed by the hydrolysis of alkyl or aryl substituted chlorosilanes and their subsequent polymerization.
  • The alkyl or aryl substituted chlorosilanes are prepared by the reaction of Grignard reagent and silicon tetrachloride.

    RMgCl + SiCl→ R−SiCl+ MgCl2

    2RMgCl + SiCl→ R2SiCl+ 2MgCl2

    3RMgCl + SiCl→ R3SiCl + 3MgCl2
  • Hydrolysis of substituted chlorosilanes yields corresponding silanols, which undergo polymerization.
  • R3SiCl on hydrolysis forms only a dimer.

    R3SiOH + HOSiR→ R3Si − O − SiR+ H2O

Silicones are of the following types:

  1. Linear silicones
  2. Cyclic silicones
  3. Cross linked silicones

Silicones Types


  • The lower silicones are oily liquids but higher members containing long chains or ring structures are waxy and rubber-like solids.
  • Silicones are stable towards heat.
  • Chemical reagents have no action on silicones.
  • These are non-toxic.
  • Viscosity of silicone oils remains the same at different temperatures.
  • Silicones are good electrical insulators.
  • Silicones are water repellents.


  • Used for high temperature oil baths, high vacuum pumps etc as they are highly stable and non-volatile.
  • Used for low-temperature lubrication.
  • Used in making water-proof cloth and paper as they are water repellent.
  • Used in insulating electric motors.