Acceleration of aminolysis of nitrophenyl esters by quaternized modifications of polyethylenimine

Derivatives of polyethylenimine, containing free primary amines but with secondary and tertiary amines fully quaternized, were prepared. The residual primary amines of the polymer markedly accentuated the rates of cleavage of nitrophenyl esters. This modified polymer exhibits a pK_a, determined from kinetics of its reactions, close to that for small molecules with a primary amine adjacent to a charged aminoethyl group. Thus, the primary amine group of the polymer stays relatively distant from all charged nitrogens on the macromolecule except its immediately adjacent neighbor on the chain.