MHTCET 11 May 2024 Shift 2 Paper

Concept:The $-CO-NH-$ (amide) linkage is formed during condensation polymerisation when an amino group ($-NH_2$) reacts with a carboxyl or related group.Explanation:Urea formaldehyde resin is formed by the condensation polymerisation of urea, $\mathrm{H_2N-CO-NH_2}$, with formaldehyde, $\mathrm{HCHO}$.In this reaction, the hydrogen atoms of the $-NH_2$ groups combine with formaldehyde to form methylene bridges, producing repeating units that contain the $-CO-NH-$ linkage.Hence, urea formaldehyde resin contains amide linkages in its backbone.Glyptal is a polyester formed from glycerol and phthalic anhydride, so it contains ester linkages ($-COO-$), not amide linkages.Polycarbonates contain carbonate linkages ($-O-CO-O-$), not $-CO-NH-$.Thermacol is expanded polystyrene, which has only carbon-carbon bonds in its repeat unit.Thus, only urea formaldehyde resin shows the required $-CO-NH-$ linkage.Answer:Option A: Urea formaldehyde resin.