= Solution
The difficulty is competing chemistry and isolation selectivity. Alkaline treatment can promote <dehydrohalogenation> at chlorinated backbone units while hydrolysing the acetate side groups. Loss of HCl produces unsaturated segments, potentially followed by further degradation or cross-linking; hydroxyl formation also changes solvent compatibility and intermolecular association. The isolated material can therefore differ from the ideal undegraded C in part (e). <Competing dehydrochlorination during copolymer saponification> explains why selective conditions are needed.
This is not an absolute prohibition on hydroxyl-containing <chloride> copolymers. Analytical work on these copolymers used staged alcoholysis/<saponification> and <polymer> precipitation to restrain dehydrochlorination. The sensible conclusion is that clean, exhaustive conversion and isolation are difficult under unselective conditions, rather than that no suitable treatment can ever preserve <chloride> units.<Determination of vinyl acetate in vinyl chloride-acetate copolymers by Takanori Shimazaki and others>[Abstract, pp. 619–623: staged treatment and precipitation used to restrain competing dehydrochlorination]{ref}
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