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Environmental fate & pathways

Hydrolysis

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Description of key information

The substance was found to hydrolyse under environmental conditions. The hydrolysis reaction did not follow pseudo-first order reaction kinetics. The rate of the hydrolysis reaction was dependent on the starting concentration and was decreasing with decreasing concentration.

 

Key value for chemical safety assessment

Additional information

A valid hydrolysis study in accordance with OECD TG 111 was conducted. The results of a preliminary test indicated that further testing is required and the hydrolysis was studied in a main test at pH 4, pH 7 and pH 9 with sample solutions being maintained at 50, 60 or 70 °C at pH 4 and 7 and at 40, 50 and 60 °C at pH 9. It was found that the substance did not follow pseudo-first order reaction kinetics. The substance hydrolysed under all test conditions and the rate of reaction was dependent on the starting concentration. The rate constants for the reaction at 25 °C were estimated by using the Arrhenius relationship and were 15.8 (g/L)^-1.5 per hour at pH 4, 3.45 (g/L)^-1.5 per hour at pH 7 and 0.0154 (g/L)^-0.25 per hour at pH 9. This corresponds to a half-life of 4.49, 20.6 and 6.85 days at an initial concentration of 8 mg/L and of 142, 650 and 12.2 days at an initial concentration of 0.8 mg/L.

The results of the study show that abiotic hydrolysis of 3,5,5-trimethylhexyl acetate may contribute to the degradation of the substance in the environment, but that the importance of the hydrolysis is significantly depending on the starting concentration of the substance and the environmental conditions.