Question

${{\text{(C}{{\text{H}}_{\text{3}}}\text{)}}_{\text{3}}}\text{SiCl}$ is used during polymerization of organosilicons because
(A) The chain length of organosilicon polymers can be controlled by adding ${{\text{(C}{{\text{H}}_{\text{3}}}\text{)}}_{\text{3}}}\text{SiCl}$
(B) ${{\text{(C}{{\text{H}}_{\text{3}}}\text{)}}_{\text{3}}}\text{SiCl}$ improves the quality and yield of the polymer
(C) ${{\text{(C}{{\text{H}}_{\text{3}}}\text{)}}_{\text{3}}}\text{SiCl}$ does not block then end terminal of silicone polymer
(D) ${{\text{(C}{{\text{H}}_{\text{3}}}\text{)}}_{\text{3}}}\text{SiCl}$ acts as a catalyst during polymerization

Answer 1

Hint: The polymerisation of organosilicons cannot be controlled. We need to add a compound that can block the ends of the chain to obtain the required length of organosilicones. ${{\text{(C}{{\text{H}}_{\text{3}}}\text{)}}_{\text{3}}}\text{SiCl}$ can bond to the polymeric chain of organosilicones hence preventing the next molecule of organosilicon to attach.

Complete step by step answer:
Organosilicon compounds are a cateogory of organometallic compounds containing carbon–silicon bonds.
Organosilicon chemistry is the study of their preparation and properties. Most organosilicon compounds are colourless, flammable, hydrophobic, and stable to air.
In most organosilicon compounds, silicon is tetravalent with tetrahedral geometry.
Carbon–silicon bonds compared to carbon–carbon bonds are longer (186 pm vs. 154 pm) and have lower bond dissociation energy (451 kJ/mol vs. 607 kJ/mol).
The carbon-silicon bond is somewhat polarized towards carbon as carbon is more electronegative than silicon on the Pauling scale The Si–C bond can be broken more easily than typical C–C bonds due to polarization.

${{\text{(C}{{\text{H}}_{\text{3}}}\text{)}}_{\text{3}}}\text{SiCl}$ attaches to the terminal of the polymeric chain of organosilicones. ${{\text{(C}{{\text{H}}_{\text{3}}}\text{)}}_{\text{3}}}\text{SiCl}$ blocks the next organosilicon molecule from attaching to the polymeric chain. Hence ${{\text{(C}{{\text{H}}_{\text{3}}}\text{)}}_{\text{3}}}\text{SiCl}$ is used to control the chain length of organosilicon polymers.
So, the correct answer is “Option A”.

Note: Organosilicon compounds are used in the form of resins, elastomers or oils. Resins when mixed with a number of other substances used in the paint industry form very stable layers and are readily applicable even on bases to which others paints do not adhere well. These resins are also used as moulding compounds and used in the manufacture of foams which have high resistance to heat.