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Environmental fate & pathways

Hydrolysis

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Description of key information

At environmentally relevant pH (pH 5 -9) the substance does not hydrolyse.

Key value for chemical safety assessment

Additional information

A reliable GLP hydrolysis study was conducted to assess the hydrolytic stability of 1,8-Diazabicyclo-5,4,0-undecene-7 at pH 4, 7, and 9. The key study was performed according OECD 111 guideline (BASF SE, 2013; Rep. no. 11L00314). All replicates were kept at 50 ± 0.5°C and samples were taken over a test period of 162 hours after test initiation. Analysis was performed via NMR. It was found that no hydrolysis could be observed at any of the pH values. Therefore, the substance is considered to be hydrolytically stable.

An IR spectroscopy study (BASF SE, 2017, Rep. no. 16N00927) was conducted to assess the hydrolytic stability of 1,8-Diazabicyclo-5,4,0-undecene-7 (DBU) at pH 4, 7, 9, 10 and 14. The replicates were kept at 22 °C and 50 °C. It was found that no hydrolysis could be observed at the pH values from 4 to 9. Moreover, at the pH values of 10 and 14, hydrolysis was detected. With increase of the pH value the ratio of hydrolysis was also faster (pH 10-12.5: 1:0.12 (within 30 min) to 1:1.09 (within 24 hours)/ pH 13.82-14: 1:0.15 (directly) to 1:1 (within 1 hour)).

According to data from San-Abbott (1980), DBU reacts with water to give N-(3 -aminopropyl)-e-caprolactam (4) at pH values >9. The reaction followed 2nd order kinetics and a rate constant of 3x10(-4) mole % (-1) min (-1) was found. The half-life was determined to be 33 min. Namely, a 0.657 molar solution will be 1/2 hydrolysed after 33 min at 35°C. In the case of an equi-molar mixture of DBU and water, no change in hydrolysis within the experimental error was found after 1 hour at 80°C. Then, 12% and 38% of DBU were hydrolyzed after 2 hours and 4 hours, respectively.

According to the reliable key study (BASF SE, 2013; rep. no. 11L00314) and the supporting information from a series of experiments by BASF SE (2017; Rep. no. 16N00927), 1,8-Diazabicyclo-5,4,0-undecene-7 (CAS 6674-22-2) is hydrolytically stable up to pH value of 9. With increase of the pH, the hydrolyses was determined and the ratio was getting faster. However, since the DBU (CAS 6674 -22 -2) is stable under environmentally relevant conditions (pH 4 - 9) the substance is considered to be hydrolytically stable.