SRC's  Hydro Program

The Hydro program calculates the hydrolysis rate constant for esters, carbamates, halomethanes, alkyl halides, and epoxides using a method developed by EPA's Office of Pollution Prevention and Toxics. It calculates a second-order acid- or base-catalyzed hydrolysis rate constant at 25 degrees Centigrade. Acid- and base-catalyzed half-lives are calculated for pH 7 and/or pH 8.

The prediction methodology was developed for EPA and is outlined in the following document: Mill,T., Haag,W., Penwell,P.,Pettit,T. and Johnson, H. "Environmental Fate and Exposure Studies Development of a PC-SAR for Hydrolysis: Esters, Alkyl Halides and Epoxides". EPA Contract No. 68-02-4254. Menlo Park, CA: SRI International (1987).

NOTE: It must be remembered that the overall hydrolysis rate constant is equal to the acid-catalyzed + the base-catalyzed + the neutral hydrolysis rate constants. If the neutral hydrolysis rate constant is the dominant constant, the acid- or base-catalyzed estimate made by HYDROWIN will not give the true indication of the environmental hydrolysis rate! In many instances, the pH of the water will determine which rate constant is dominant. This situation applies especially to epoxides, halomethanes and alkyl halides.

The newest version of Hydro runs under Windows (3.1, 95, 98, NT) making the calculation of hydrolysis rate constants more convenient and accurate. Methods for chemical structure input now support SMILES notations as well as chemical structures produced in popular chemical drawing programs. Enhanced features of the Windows version include batch-mode data entry and user functions.

Example Entry / Results (for Ethyl Acetate)