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Alkaline conditions that hydrolyse acetate side groups can also promote elimination from chlorinated backbone units. Dechlorination, unsaturation, changed solubility and possible subsequent cross-linking complicate isolation of an ideal vinyl chloride-vinyl alcohol copolymer. The competition is condition-dependent: analytical work used staged treatment and precipitation to restrain dehydrochlorination, so difficulty under generic conditions is not a proof that every hydroxyl-containing chloride copolymer is impossible.^[ref]

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.^[ref]