Hydrolysis of haloacetonitriles: Linear free energy relationship, kineticsand products

The hydrolysis rates of mono-, di- and trihaioacetonitriles were studied in aqueous buffer solutions at different pH. The stability of haloacetonitril es decreases and the hydrolysis rate increases with increasing pH and numbe r of halogen atoms in the molecule: The monochloroacetonitriles are the mos t stable and are also less affected by pH-changes, while the trihaloacetoni triles are the least stable and most sensitive to pH changes. The stability of haloacetonitriles also increases by substitution of chlorine atoms with bromine atoms. The hydrolysis rates in different buffer solutions follow f irst order kinetics with a minimum hydrolysis rate at intermediate pH. Thus , haloacetonitriles have to be preserved in weakly acid solutions between s ampling and analysis. The corresponding haloacetamides are formed during hy drolysis and in basic solutions they can hydrolyze further to give haloacet ic acids. Linear free energy relationship can be used for prediction of deg radation of haloacetonitriles during hydrolysis in water solutions. (C) 199 9 Elsevier Science Ltd. All rights reserved.