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Difficulty: HardBiodegradable vs Non-Biodegradable Materials and Recycling

Two synthetic polymers, Polymer X (a polyamide formed by condensation polymerization) and Polymer Y (a polyalkene formed by addition polymerization), are buried in soil at a waste disposal site. Over time, Polymer X undergoes gradual microbial breakdown, whereas Polymer Y remains chemically intact for decades. What is the primary structural reason for this marked difference in biodegradability?

  1. Polymer X contains hydrolyzable polar linkages vulnerable to enzymatic cleavage, whereas Polymer Y possesses a non-polar carbon-carbon backbone resistant to microbial attack.Answer
  2. B
    Polymer Y has a significantly higher average molecular mass than Polymer X, preventing soil bacteria from absorbing its polymer chains.
  3. C
    Polymer Y undergoes spontaneous cross-linking in damp soil, forming a rigid network that repels microbial enzymes.
  4. D
    Polymer X is synthesized from naturally occurring monomers, while Polymer Y is made exclusively from toxic petrochemically derived alkene monomers.

Answer

Polymer X contains hydrolyzable polar linkages vulnerable to enzymatic cleavage, whereas Polymer Y possesses a non-polar carbon-carbon backbone resistant to microbial attack.
Biodegradability depends on the presence of polar functional linkages (such as amide –CO–NH– or ester –CO–O– bonds) within the main chain that soil micro-organisms can cleave via enzymatic hydrolysis. Polymer X (a polyamide) contains these hydrolyzable bonds. In contrast, Polymer Y (an addition polyalkene) has a saturated, non-polar carbon-carbon backbone that micro-organisms lack the specific enzymes to decompose, causing it to persist indefinitely.

Step-by-Step Solution

1
Analyze the backbone chemical structure of Polymer X (condensation polyamide) versus Polymer Y (addition polyalkene).
Polymer X features repeating amide linkages (–CO–NH–), while Polymer Y consists of a continuous chain of single carbon-carbon bonds (–C–C–).
Chemical degradation in nature relies on microbial enzymes recognizing specific functional groups.
2
Evaluate the mechanism of microbial breakdown for these functional groups.
Microbial enzymes secrete hydrolases that break polar amide and ester bonds via hydrolysis, whereas non-polar C-C backbones lack reactive sites for enzymatic cleavage.
Enzymatic hydrolysis requires polar or reactive functional groups embedded within the polymer chain.
3
Select the option that correctly attributes biodegradability to structural functional group susceptibility.
The option stating that Polymer X contains hydrolyzable polar linkages while Polymer Y has a non-polar carbon-carbon backbone is correct.
This represents the fundamental chemical basis of polymer degradation in the environment.

Key Concept

Structural Basis of Polymer Biodegradability
Estimated Time:1m 30s
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Topics

Biodegradable vs Non-Biodegradable Materials and Recycling

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