Methoxycarbonyloxycyclooct-4-ene

Hydrolysis

Description of key information

The substance has a half-life at 25°C of >1 year at pH 4 and pH 7, and 30 days at pH 9.

Key value for chemical safety assessment

Half-life for hydrolysis:

1 yr

at the temperature of:

25 °C

Additional information

Hydrolysis of the substance as a function of pH was examined in a study according to OECD TG 111 and in compliance with GLP (Huntingdon, 2005). Sample solutions were prepared in Wheaton vials by adding defined nominal concentrations to sterile buffer solutions with pH4, 7, and 9 and maintained at 50°C for a period of up to 120 hours. The solutions were shielded from light. In the preliminary test, <10% hydrolysis was observed (based on summed peak area) at pH 4 and pH 7 after 5 days at 50°C, and therefore further testing was not required. The half-life time of the test substance at these pH values is concluded to be >1 year under environmental conditions (25°C). It should be noted however, that at these pH values the degree of hydrolysis may be underestimated due to data evaluation based on summed peak areas. From the reported data it cannot be determined if these summed peak areas contain a contribution from degradation products, or if these chromatographs are outside the retention window of the test substance. Furthermore, information on vial headspace and type of vial closure (caps) has not been reported, and although some extent of volatilisation, especially at elevated temperatures, cannot be excluded. 

In the preliminary test 82% was observed at pH 9, also based on summation of peak areas in the retention time range 16-21 minutes. Consequentially, higher tier tests were performed at this pH and the half-life at 25°C determined to be ca. 30 days. Ideally, the decrease of individual peaks and arising of new peaks in the indicated retention time range should have been monitored throughout the tests to exclude the possibility of contribution from degradation products to the summed peak area. However, as such monitoring was not performed in this test, it is not possible to conclude if quantification of test substance concentrations in the samples was performed correctly. As a direct consequence the derived log Ct values may not be correct, leading to potentially different regressions curves (slopes), which in turn were used to derive hydrolysis rate constants and environmental half-life times. Therefore the reported half-life time of approximately 30 days at pH 9 has some uncertainties and should be treated with care. Altogether, based on the previous, the environmental half-life at 25 °C is determined to be >1 year for the substance.