Factors influencing solvolysis of corticosteroid-21-phosphate esters

The solvolysis of methylprednisolone-21-phosphate in dilute aqueous solution ( 0.02 M), however, there is an acceleration of reaction velocities and marked deviation from the expected pH dependency. This change in chemical behavior is attributed to association coolloid formation. Support for this mechanism is drawn from hydrolysis-rate data obtained as a function of concentration and independently determined critical micelle concentration values.