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Difficulty: HardBiodegradable vs Non-Biodegradable Materials and Recycling

A waste management facility evaluates four industrial waste polymers: polyethene, starch, polyvinyl chloride (PVC), and nylon-6,6. Which of the following chemical statements correctly differentiates their biodegradation mechanisms and incineration hazards?

  1. Starch and nylon-6,6 undergo microbial hydrolysis due to polar bonds in their main chains, while PVC releases toxic hydrogen chloride gas upon incineration.Answer
  2. B
    Polyethene degrades rapidly in soil because synthetic addition polymers contain accessible carbon-carbon double bonds along their main chain.
  3. C
    Polyethene and PVC undergo spontaneous bacterial decomposition because saturated aliphatic carbon backbones are easily cleaved by soil enzymes.
  4. D
    Starch and nylon-6,6 resist microbial breakdown because condensation polymerization creates non-polar, hydrophobic polymer chains.

Answer

Starch and nylon-6,6 undergo microbial hydrolysis due to polar bonds in their main chains, while PVC releases toxic hydrogen chloride gas upon incineration.
Natural polymers like starch and condensation polymers like nylon-6,6 contain polar hydrolyzable linkages (ester, amide, glycosidic bonds) that soil micro-organisms readily break down. Additionally, incinerating chlorinated synthetic polymers such as PVC releases toxic and corrosive hydrogen chloride (HClHCl) gas into the environment.

Step-by-Step Solution

1
Analyze the backbone structure of addition polymers versus condensation/natural polymers.
Polyethene and PVC are synthetic addition polymers possessing saturated, non-polar all-carbon (C−CC-C) backbones that lack site-specific functional groups for enzymatic cleavage.
Soil micro-organisms produce hydrolytic enzymes that target polar linkages rather than non-polar carbon-carbon single bonds.
2
Examine the biodegradability of starch and nylon-6,6.
Starch (a polysaccharide) and nylon-6,6 (a polyamide) contain polar linkages (glycosidic and amide bonds) capable of undergoing enzymatic hydrolysis.
Polar functional groups interact with water and microbial enzymes, enabling biodegradation into simpler monomers.
3
Evaluate the incineration behavior of organochlorine polymers like PVC.
Thermal decomposition of polyvinyl chloride ([CH2−CHCl]n[CH_2-CHCl]_n) releases volatile gaseous hydrogen chloride (HClHCl).
Chlorine atoms bound to the polymer backbone undergo elimination as HCl(g)HCl(g) at elevated temperatures during combustion.

Key Concept

Chemical basis of polymer biodegradability and thermal incineration products
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Topics

Biodegradable vs Non-Biodegradable Materials and Recycling

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