Reaction mass of 3a,4,5,6,7,7a-hexahydro-4,7-methano-1H-inden-5-yl isobutyrate and 3a,4,5,6,7,7a-hexahydro-4,7-methano-1H-inden-6-yl isobutyrate

Hydrolysis

Description of key information

Estimated half-life is derived from the structural analogue Cyclobutanate:
>1 year at pH 4 and 7 at 25°C
13 days at pH 9 at 25°C

Key value for chemical safety assessment

Half-life for hydrolysis:

1 yr

at the temperature of:

25 °C

Additional information

No hydrolysis study is available for Cyclabute and read across from Cyclobutanate is feasible. Firstly, the executive summary of the hydrolysis test of Cyclobutanate will be presented, thereafter a summarised read across justification is presented. A full read across justification was not considered necessary in view of the close similarity in structure and the final conclusion that the substance is stable. For a reference of the chemical structures and physical chemical properties, please see the aquatic toxicity read across documentation in the Aquatic toxicity Endpoint summary.

Cyclobutanate and its hydrolysis

A hydrolysis study with Cyclobutanate was carried out according to EU Method C.7 (Degradation: Abiotic Degradation: Hydrolysis as a Function of pH). Following the testing strategy it was shown that in a preliminary study at pH 4 and at 50°C the substance was hydrolytically stable. At pH 7 and at 50°C, the substance decreased in the solution. Further testing at pH 7 and at 60 and 70°C showed that this loss was not attributed to hydrolysis. The loss may be due to volatilization despite using limited headspace. This study showed an estimated half-life of >1 year for pH 4 and 7 at 25°C and an estimated half-life of 13 days at pH 9 at 25°C. It can be concluded that Cyclabute will be hydrolytically stable under environmental conditions.

Executive summary of Cyclabute and the hydrolysis rate derived by read across from Cyclobutanate

No hydrolysis study is available for Cyclabute. However, an available study on the structural similar substance Cyclobutanate, which has a butanoic ester instead of an isobutanoic ester attached to the tricyclodecenyl ring, could be used for read-across. Cyclabute is considered the target chemical and Cyclobutanate the source chemical. Both chemicals have a tricyclodecenyl backbone with one unsaturated bond in the ring at the 5-yl or 6-yl position and an ester bond. The difference in the molecular structure between the source and the target chemical is a butyl ester, instead of an isobutyl ester attached to the ring. The butyl ester group compared to the isobutyl ester group is expected to be similarly (in) sensitive to hydrolysis, because the straight versus the iso-group to be minimal. Therefore, the same hydrolysis results of Cyclobutanate will be used for Cyclabute. The key study used for read-across was a study for hydrolysis as a function of pH conducted according to OECD TG111. This study showed an estimated half-life of >1 year for pH 4 and 7 at 25°C and an estimated half-life of 13 days at pH 9 at 25°C. It can be concluded that Cyclabute will be hydrolytically stable under environmental conditions.