Question

what monomer is used to form the polymer below? chemical structure of polymer four chemical structure options, and none of the answers represent the monomer subunit used.

Explanation:

Step1: Recall Polymerization of Alkenes

Polymers from alkenes (monomers with \( \text{C}=\text{C} \)) form via addition polymerization, where the double bond breaks to form single bonds in the polymer chain. The polymer's repeating unit should match the monomer's structure (with single bonds replacing the double bond in the polymer).

Step2: Analyze the Polymer Structure

The polymer has a repeating unit of \( \text{-C(CH}_3\text{)(Cl)-C(Br)(CN)-} \) (single bonds between carbons). So the monomer should have a \( \text{C}=\text{C} \) double bond, with substituents: \( \text{CH}_3 \), \( \text{Cl} \) on one \( \text{C} \); \( \text{Br} \), \( \text{CN} \) on the other \( \text{C} \) (since addition polymerization preserves substituent positions relative to the double bond).

Step3: Match with Options

• Check the third option: \( \text{CH}_3-\text{C}=\text{C}-\text{Br} \) (with \( \text{Cl} \) on first \( \text{C} \), \( \text{CN} \) on second \( \text{C} \)) → Structure: \( \ce{CH3 - C(Cl)=C(Br) - CN} \)? Wait, no—wait the third option's structure: \( \text{CH}_3 \) on one \( \text{C} \), \( \text{Cl} \) on same \( \text{C} \); \( \text{Br} \) on other \( \text{C} \), \( \text{CN} \) on other \( \text{C} \), with \( \text{C}=\text{C} \). Yes! When the double bond breaks, it forms the polymer's single - bonded chain with those substituents. Let's verify:

Monomer: \( \ce{CH3 - C(Cl)=C(Br) - CN} \) (wait, no, the third option's structure: \( \text{CH}_3 \) attached to a \( \text{C} \) with \( \text{Cl} \), double bond to another \( \text{C} \) with \( \text{Br} \) and \( \text{CN} \)? Wait, looking at the third option: \( \text{CH}_3 \), \( \text{Cl} \) on one \( \text{C} \); \( \text{Br} \), \( \text{CN} \) on the other \( \text{C} \), double bond between them. When polymerized, the double bond becomes a single bond, and the chain extends: \( \text{-C(CH}_3\text{)(Cl)-C(Br)(CN)-} \), which matches the polymer's repeating unit (the polymer has \( \text{CH}_3 \), \( \text{Cl} \) on one \( \text{C} \); \( \text{Br} \), \( \text{CN} \) on adjacent \( \text{C} \), single - bonded).

Other options: First two have single bonds (so not alkenes, can't be monomers for addition polymer here). Fourth option has different substituents ( \( \text{Cl} \) and \( \text{Br} \) positions swapped? Wait no, the polymer has \( \text{Cl} \) with \( \text{CH}_3 \), \( \text{Br} \) with \( \text{CN} \). The third option has \( \text{CH}_3 \), \( \text{Cl} \) on one \( \text{C} \); \( \text{Br} \), \( \text{CN} \) on the other \( \text{C} \) (double bond), which is correct.

Answer:

The third option (the one with \( \text{CH}_3 \), \( \text{Cl} \) on one \( \text{C} \), \( \text{Br} \), \( \text{CN} \) on the other \( \text{C} \) with a \( \text{C}=\text{C} \) double bond)