The Reaction of the Hydroxamic Acid Group in Polymer with p-Nitrophenyl Acetate

Water-soluble copolymers containing protected hydroxamate groups were prepared by radical copolymerization of acetyl N-phenylacrylohydroxamate and acrylamide, and the hydroxamic acid group (PHA) was unmasked by treating it with hydroxylamine. In acetylation with p-nitrophenyl acetate (1.4 v/v% CH3CN–H2O, 30 °C) the PHA unit was less reactive than the corresponding monomeric compound. When the PHA content was low (3 mol%), the reactivity of a given PHA anion (true reacting species) was invariant (9.1 M−1 S−1) over a wide range of the dissociation of the PHA unit. However, in the case of the copolymer of a higher PHA content (11 mol%) the reactivity decreased as the neutralization of the PHA anion progressed. This phenomenon was attributed to the intramolecular aggregation of the undissociated PHA side chain. The deacylation rate of the acetylated PHA unit was comparable to those of the monomeric counterparts, in contrast with the acylation process. Finally, the probable role of the PHA unit as catalyst for the ester hydrolysis was discussed.