Identifying PVC from the −CH2−CHCl− segment

Steps:

• Examine the given segment: −CH2−CHCl−, a linear unit with chlorine on the second carbon.
• Match to known polymers: This structure is the backbone repeat unit in poly(vinyl chloride).
• Eliminate branched or unsubstituted options: No methyl branch rules out propene-based polymers.
• Confirm via monomer: Derived from CH2=CHCl (vinyl chloride), forming long chains with this segment repeating.

Why C is correct:

• PVC's constitutional formula is −(CH2−CHCl)n−, exactly matching the given segment as its core repeating structure.

Why the others are wrong:

• A: Poly(2-chloropropene) has repeat unit −CH2−CCl(CH3)−, with a methyl branch not present.
• B: Poly(chloroethene) is synonymous with PVC, but C directly names it; B is a redundant distractor.
• D: Poly(propene) has repeat unit −CH2−CH(CH3)−, lacking chlorine.

Final answer: C