31 Year NEET Previous Year Questions: Polymers

• A Natural polymer that controls various life processes in the body of an organism is called a natural biopolymer.
• DNA is a natural biopolymer that is the main constituent of chromosomes.
• Starch, proteins and peptides, DNA, and RNA are all examples of biopolymers, in which the monomer units, respectively, are sugars, amino acids, and nucleotides.
• However, Rubber is a natural polymer but not a natural biopolymer.
• Teflon and Nylon-6,6 both are synthetic polymers.

Therefore, the correct answer is DNA. 

Phenol and formaldehyde undergo condensation polymerization under two different conditions to give a cross-linked polymer called Bakelite.

Reaction Mechanism for preparation of Bakelite:

• Rubber-like solids with elastic properties are called elastomers. 
• Polymer chains are held together in these materials by relatively weak intermolecular bonds i.e. weak Van-der Waals interaction, which permit the polymers to stretch in response to macroscopic stresses.

Therefore, the correct answer is B. 

We know that polytetrafluoroethylene or Teflon is a tough material, resistant to heat, and a bad conductor of electricity.

Thus, it is used for coating the cookware to make them non-sticky.

Natural rubber is a polymer of isoprene, [CH₂ =C(CH₃)CH=CH₂] i.e. 2-methylbutadiene

CF₂ = CF₂ is a unit of Teflon. 

Terylene is prepared by condensing dimethyl terephthalate and ethylene glycol in presence of a weak base, (calcium acetate). Methanol is eliminated during condensation.

2-methylpropene is the monomer of 

• Vitamin B₁₂ is a water-soluble vitamin that is naturally present in some foods, added to others, and available as a dietary supplement and a prescription medication.
• Because vitamin B₁₂ contains the mineral cobalt, compounds with vitamin B₁₂ activity are collectively called “cobalamins”.

Additional Information: 

• Methylcobalamin and 5-deoxyadenosylcobalamin are metabolically active forms of vitamin B12. However, two other forms, hydroxocobalamin and cyanocobalamin, become biologically active after they are converted to methylcobalamin or 5-deoxyadenosylcobalamin. 
• It is an anti pernicious anemia vitamin and its chemical formula is C₆₃H₈₈CoN₁₄O₁₄P.

Acrylon is also called as orlon or polyacrylonitrile and is formed by the given reaction.

Chloroprene or 2-chloro-1,3-butadiene on addition polymerisation gives neoprene.

• Polystyrene is a chain-growth polymer.
• Polystyrene results when styrene monomers interconnect.
• In the polymerization, the carbon-carbon pi bond is broken and a new carbon-carbon single bond is formed, attaching another styrene monomer to the chain.
• The newly formed sigma bond is much stronger than the pi bond that was broken, thus it is very difficult to depolymerize polystyrene.

Addition of monomers follows isoprene rule.

The given compound is a co-polymer of hexamethylene diamine and adipic acid. It is actually Nylon-6,6.

Additional Information: A co-polymer is a polymer that is made up of two or more monomer species. Many commercially important polymers are copolymers. Examples include polyethylene-vinyl acetate (PEVA), nitrile rubber, and acrylonitrile butadiene styrene (ABS).

• The copolymer of adipic acid (6C) and hexamethylene diamine (6C) is Nylon-6,6.
• It has high tenacity and elasticity. It is resistant to abrasion and not affected by seawater.
• It is used for the reinforcement of rubber tires, the manufacture of parachutes, safety belts, carpets, and fabrics.

The natural rubber has a 'cis' configuration at every double bond. It is a linear 1,4 polymer of isoprene. In other words, natural rubber is cis-polyisoprene.

Therefore, All statements except (b) are correct

Neoprene is a polymer of chloroprene.
Hence, The correct representation will be:

Neoprene is a polymer of chloroprene (2 – chloro – 1, 3 – butadiene).

Polyesters are condensation polymers of diabasic acid and diol.
Example: Terylene

Neoprene is an addition polymer of isoprene.

Nylon-66 is an example of the first synthetic fibers produced from simple molecules. It is prepared by condensation polymerization of adipic acid and hexamethylenediamine.

Biodegradable polymer is Nylon-2- Nylon-6 which is copolymer of glycine  (H₂N – CH₂– COOH) and amino caproic acid (H₂N–(CH₂)₅ – COOH).

Chloroprene is the monomer of neoprene.

Naturally occurring polyamides are proteins, such as wool and silk.
Artificially made polyamides can be made through step-growth polymerization or solid-phase synthesis yielding materials such as nylons, aramids, and sodium poly(aspartate).