What is the chemical name and monomer unit of natural rubber before vulcanization?
Answer and explanation
Correct answer: C. cis-1,4-Polyisoprene
- Step 1: Natural rubber is a natural elastomer harvested as latex from the rubber tree (Hevea brasiliensis).
- Step 2: Chemically, natural rubber is a linear addition polymer of isoprene (2-methylbuta-1,3-diene: ).
- Step 3: Crucially, all double bonds along the polymer backbone exist strictly in the cis-configuration: cis-1,4-polyisoprene.
- Step 4: The cis-conformation prevents close chain packing and results in coiled chains held only by weak van der Waals forces, which account for its elasticity.
Answer
cis-1,4-Polyisoprene (monomer: 2-Methylbuta-1,3-diene)
Why not the others: 'trans-1,4-Polyisoprene' is gutta-percha, a hard, non-elastic crystalline polymer; 'Polychloroprene' is synthetic neoprene rubber (monomer: chloroprene); 'Polyacrylonitrile' is a synthetic acrylic fiber (Orlon/Acrilan).
Practise more Biomolecules and Polymers.
Free questions with an explanation for every one, and full timed NEET UG mock tests.
More Biomolecules and Polymers questions
- Why is sucrose classified as a non-reducing disaccharide, whereas maltose and lactose are classified as reducing disaccharides?
- Why is the hydrolysis of dextrorotatory sucrose (+66.5°) into an equimolar mixture of D-(+)-glucose and D-(-)-fructose referred to as the 'i…
- What is the structural difference between α-D-glucopyranose and β-D-glucopyranose, which defines them as anomers?
- Which chemical test confirms that all six carbon atoms in D-glucose are arranged in an unbranched, straight chain?
- Which of the twenty standard biological amino acids is optically inactive (achiral) because its α-carbon is bonded to two identical hydrogen…
- In aqueous solution, amino acids exist predominantly as dipolar internal salts known as zwitterions. What is the electrical net charge of a…