MHTCET 16 Apr 2026 Shift 2 Paper

Concept:Buna-S is a synthetic rubber formed by the copolymerisation of two specific monomers.Explanation:Buna-S is prepared by the copolymerisation of 1,3-butadiene and styrene.The name "Buna" comes from butadiene and sodium, while "S" stands for styrene.The polymerisation reaction is shown below:$$n\,\mathrm{CH}_{2}=\mathrm{CH}-\mathrm{CH}=\mathrm{CH}_{2} + n\,\mathrm{C}_{6}\mathrm{H}_{5}\mathrm{CH}=\mathrm{CH}_{2} \rightarrow \text{Buna-S}$$Here, 1,3-butadiene provides the diene unit, and styrene acts as the co-monomer.The product is a copolymer with good abrasion resistance and elasticity.Option A, which uses vinyl cyanide (acrylonitrile) with 1,3-butadiene, gives Buna-N instead of Buna-S.Options C and D use 1,2-butadiene, which is not used in the industrial preparation of Buna-S.Therefore, the correct pair of monomers is 1,3-butadiene and styrene.Answer:Option B: 1,3-butadiene and styrene