Flaw in PVC repeat unit notation

Steps:

• Identify PVC as poly(vinyl chloride) from monomer CH2=CHCl via addition polymerization.
• Determine repeat unit structure: -CH2-CHCl-, with explicit bond notation.
• Check each statement against chemical properties and standard representations.
• Confirm D's notation omits the structural dash, making it imprecise.

Why D is correct:

• Standard repeat unit notation is -[CH2-CHCl]-, with a dash linking CH2 and CHCl to denote the C-C single bond.

Why the others are wrong:

• A: PVC combustion yields HCl, a highly acidic gas, due to chlorine content.
• B: PVC chain contains only single bonds, classifying it as saturated.
• C: Monomer and repeat unit both have empirical formula C2H3Cl.

Final answer: D