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Difficulty: Very hardBiodegradable vs Non-Biodegradable Materials and Recycling

A waste management facility categorizes organic polymers into synthetic addition polymers, such as polyethene, and natural or condensation polymers, such as starch and nylon-6,6. Upon microbial action, polyethene exhibits extreme resistance to decomposition. Which of the following statements correctly explains the chemical basis for the non-biodegradability of synthetic addition polymers compared to biodegradable natural polymers?

  1. Synthetic addition polymers consist of long, non-polar carbon-carbon single bond chains lacking hydrolyzable functional groups necessary for microbial enzymatic cleavage.Answer
  2. B
    Synthetic addition polymers readily undergo microbial oxidation because their backbone contains highly reactive ester linkages that release methane gas upon bacterial action.
  3. C
    Synthetic addition polymers resist biodegradation solely because they are thermosetting plastics with extensive cross-linking that prevents soil water absorption.
  4. D
    Synthetic addition polymers decompose into toxic chlorofluorocarbons during bacterial degradation, which inhibits further microbial activity in the soil.

Answer

Synthetic addition polymers consist of long, non-polar carbon-carbon single bond chains lacking hydrolyzable functional groups necessary for microbial enzymatic cleavage.
The correct answer highlights that microbial biodegradation depends on enzymatic hydrolysis of functional groups. Natural polymers (like starch) and synthetic condensation polymers (like nylon) possess ester, amide, or glycosidic linkages that enzymes recognize and break. Synthetic addition polymers like polyethene consist of long, non-polar carbon-carbon (C−C\text{C}-\text{C}) chains without hydrolyzable functional groups, making them highly resistant to microbial decay.

Step-by-Step Solution

1
Identify the structural differences between addition polymers and natural/condensation polymers.
Addition polymers like polyethene feature a continuous backbone of non-polar carbon-carbon single bonds (C−C\text{C}-\text{C}), whereas condensation polymers contain functional linkages such as esters, amides, or glycosidic bonds.
Enzymatic breakdown requires specific structural motifs for substrate-enzyme binding.
2
Analyze microbial enzymatic mechanisms of degradation.
Soil micro-organisms produce enzymes (e.g., esterases, peptidases, glucosidases) specialized in hydrolyzing polar functional groups containing heteroatoms (O\text{O}, N\text{N}).
Hydrolysis converts polymers into soluble monomers or oligomers that microbes can metabolize.
3
Evaluate why addition polymers resist enzymatic attack.
The high molecular weight, hydrophobic nature, and inert C−C\text{C}-\text{C} single-bonded backbone of polyethene lack target sites for hydrolytic cleavage by microbial enzymes.
Without active hydrolyzable sites, microbial breakdown is extremely slow, leading to environmental accumulation.

Key Concept

Chemical basis of polymer biodegradability and structural enzymatic specificity
Estimated Time:1m 30s
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Topics

Biodegradable vs Non-Biodegradable Materials and Recycling

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