The zeroth-order reaction of the hydrolysis of sodium polyphosphate in water at pH = 0 can be explained assuming the formation of a pentacovalent terminal phosphorus intermediate. A terminal unit is activated for hydrolysis by protonation of the double-bond oxygen on that unit followed by a nucleophilic attack of water. Proton transfer from an OH group to a P−O−P bond breaks the bond, thereby shortening the phosphate polymer. A mathematical equation is developed to explain the reaction order of the hydrolysis.

No abstract

Raman spectroscopy is used to monitor hydrolysis of a polyphosphate dissolved in water at pH = 0. It is found that this reaction is of zeroth-order and obeys the Arrhenius equation with Ea = 57 kJ·mole−1. Hydrolysis predominantly takes place at terminal phosphate units, and, although random hydrolysis might be involved in the process, its contribution is shown to be very small with respect to the overall process.