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Environmental fate & pathways

Hydrolysis

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Description of key information

The test substance is stable at pH 4, 7 and 9 at 50 °C: it has a half-life period longer than one year at 25 °C at pH 4, 7 and 9.

Key value for chemical safety assessment

Half-life for hydrolysis:
1 yr
at the temperature of:
25 °C

Additional information

Hydrolysis is a common degradation route in the environment, namely the reaction of a substance with water with a net exchange of the X group with an OH at the reaction centre such that RX + H2O → ROH + HX. Hydrolysis is often dependent upon pH as the reaction is commonly driven by hydrogen or hydroxide ions. Hydrolysis kinetics are usually determined experimentally and should be used to consider the test type and whether parent or degradation product should be tested.

In the case of OB 5 -A, it can be estimated that hydrolysis does not occur because there are not hydrolysable groups in any of the structures; this is also confirmed by calculation with HYDROWIN 2.0.

Hydrolyzable organic groups are in fact those groups that can react with water like Esters, Anhydrides, Amides, Carbammates, Nitriles, Cyanates, Epoxides, Halomethanes, Alkylhalides, Urea and none of these groups are present within the substance or their impurities.

The substance has an amide functionality, but the hydrolysis if this terminal group lead to the acid form with no further degradation and no impact to the environmental fate.

Two reliable studies were performed on two similar substances, OB 2 -A and OB 3a-MSA, belonging the category of Stilbene Fluorescent Whitening Agents. Both the studies (Ciba-Geigy Ltd., 1992 and Ciba-Geigy Ltd., 1992) demonstrate that the tested substances are stable (hydrolysis < 10 %) at pH 4, 7 and 9 at 50 °C and in both the studies the half life for hydrolysis was proved to be greater than 1 year. Since all substances within the category are estimated having the same behaviour regarding hydrolysis property (none of the substances, nor their identified impurity/ies, have in fact hydrolysable organic groups within the molecular structure) the existing data can be assumed as representative for the whole category.