 Solution

ID: past-exam-of-the-chemistry-course-of-the-year-3-of-the-natural-sciences-course-of-the-university-of-cambridge/2022/paper-3/50/c/solution

B contains both

- C H_{2} - CH (Cl) -

and

- C H_{2} - CH (OCOC H_{3}) -

monomeric units distributed along the same carbon backbone: a vinyl chloride-vinyl acetate copolymer. One possible local segment is

\dots - C H_{2} - CH (Cl) - C H_{2} - CH (OAc) - C H_{2} - CH (Cl) - \dots, OAc = OC (O) C H_{3} .

The ester is attached through oxygen to the backbone carbon. A random copolymer should not be drawn as two long homopolymer blocks. The stated

75 : 25

monomer feed is not enough to prove an incorporated

75 : 25

unit ratio: monomer reactivity ratios and conversion affect composition and sequence statistics. Under an explicitly ideal equal-incorporation assumption that ratio could be used as a schematic average, not a periodic repeat.

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