Registration Dossier

Environmental fate & pathways

Hydrolysis

Currently viewing:

Administrative data

Link to relevant study record(s)

Reference
Endpoint:
hydrolysis
Type of information:
experimental study
Adequacy of study:
key study
Study period:
15 August 2012 - 13 February 2013
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Study conducted in accordance with current Guideline and GLP compliant
Qualifier:
according to
Guideline:
OECD Guideline 111 (Hydrolysis as a Function of pH)
Deviations:
yes
Remarks:
No sterility confirmation tests were conducted at the end of the higher Tier test.
GLP compliance:
yes
Specific details on test material used for the study:
Details on properties of test surrogate or analogue material (migrated information):
PHYSICO-CHEMICAL PROPERTIES
- Water solubility: 1.6 mg/L in water at 25 °C
- log Pow: 4.1 at 25 °C
- Stability of test material at room temperature: stable

Radiolabelling:
no
Analytical monitoring:
yes
Details on sampling:
- Sampling intervals for the parent/transformation products:
pH7 and pH9 Tests (Tier 1 only at 50 °C) = 0, 0.1, 1 and 5 Days
pH4 Test at 15 °C = 0, 3, 7, 11, 16, 23 and 30 Days
pH4 Test at 25 °C = 0, 3, 7, 11, 16, 23 and 30 Days
pH4 Test at 50 °C = 0, 0.1, 1, 3, 5, 7 and 10 Days
The test design was set up so that all test vessels from an individual rate experiment were analysed together (eg staggered introduction of each data time point set)

- Sampling method: Direct transfer to chromatograph
- Sampling intervals/times for pH measurements: At end of test
- Sampling intervals/times for sterility check: No sterility check performed (vessels, caps and buffer solutions were all sterilised)
- Sample storage conditions before analysis: ambient - samples vialled immediately prior to analysis
- Other observation, if any (e.g.: precipitation, color change etc.): None
Buffers:
- pH: 4
- Type, final molarity and composition of buffer: 0.05 M Ammonium Acetate prepared in Milli-Q Water and buffered with Formic Acid

- pH: 7
- Type, final molarity and composition of buffer: 0.05 M Ammonium Hydrogen Carbonate prepared in Milli-Q Water and buffered with Formic Acid

- pH: 9
- Type, final molarity and composition of buffer: 0.05 M Ammonium Hydrogen Carbonate prepared in Milli-Q Water and buffered with conc. Ammonia
Duration:
5 d
Initial conc. measured:
ca. 610 other: ng/mL
Duration:
5 d
Initial conc. measured:
ca. 593 other: ng/mL
Duration:
30 d
Initial conc. measured:
ca. 779 other: ng/mL
Duration:
30 d
Initial conc. measured:
ca. 755 other: ng/mL
Duration:
10 d
Initial conc. measured:
ca. 572 other: ng/mL
Number of replicates:
pH 7 and 9 = 3 replicates at 4 timepoints
pH 4 = 3 replicates at 7 timepoints
Positive controls:
no
Negative controls:
no
Statistical methods:
Mean % recoveries and difference in recovery from T0

Ln recovery regression
Preliminary study:
After 5 days at 50 °C the test item was observed to have hydrolysed less than 10% versus the T0 timepoint in pH 7 and pH 9 buffer. This indicates that the test item is hydrolytically stable at neutral and basic pH, and significant hydrolysis did not occur.

In pH 4 buffer after 5 days at 50 °C the test item was observed to have hydrolysed greater than 10% versus the T0 timepoint. This indicates that the test item is not hydrolytically stable at acidic pH, and significant hydrolysis did occur.
Test performance:
After further testing at pH4 it was demonstrated that the rate of degradation was proportionally slower at 25ºC and 15ºC than at 50 ºC. At the termination of the test, the concentration of the parent compound decreased from 71.5% at day 0, to 4.4% of the initial at 50ºC after 10 days, from 94.5% to 25.7% of the initial at 25ºC after 30 days, and from 97.5% to 53.8% of the initial at 15ºC after 30 days. The Kobs (hydrolysis rate constant), half life and activation energy values were calculated using non-linear regression and pseudo first-order kinetics.
Transformation products:
yes
No.:
#1
No.:
#1
Details on hydrolysis and appearance of transformation product(s):
- Pathways for transformation: protonation of oxime nitrogen followed by nucleophilic addition of water. Protonation of hydroxylamine followed by formation of ketone and loss of hydroxylamine group.
% Recovery:
ca. 55.2
St. dev.:
0.723
pH:
4
Temp.:
15 °C
Duration:
ca. 30 d
% Recovery:
ca. 27.2
St. dev.:
0.723
pH:
4
Temp.:
25 °C
Duration:
ca. 30 d
% Recovery:
ca. 6.2
St. dev.:
0.3
pH:
4
Temp.:
50 °C
Duration:
ca. 10 d
pH:
4
Temp.:
15 °C
Hydrolysis rate constant:
ca. 0.02 d-1
DT50:
ca. 35.3 d
Type:
(pseudo-)first order (= half-life)
pH:
4
Temp.:
25 °C
Hydrolysis rate constant:
ca. 0.044 d-1
DT50:
ca. 15.9 d
Type:
(pseudo-)first order (= half-life)
pH:
4
Temp.:
50 °C
Hydrolysis rate constant:
ca. 0.282 d-1
DT50:
ca. 2.45 d
Type:
(pseudo-)first order (= half-life)
Details on results:
TEST CONDITIONS
- pH, sterility, temperature, and other experimental conditions maintained throughout the study: Yes (sterility not checked at end of study)
- Anomalies or problems encountered (if yes):Sterility not checked at end of study

MAJOR TRANSFORMATION PRODUCTS
At pH4: 9- (dichloromethylidene)-2,3,4,6,7,8-hexahydro-1,4-methanonaphthalen-5(1H)-one)

At pH7: Hydrolytically stable

At pH9: Hydrolytically stable

PATHWAYS OF HYDROLYSIS
- Description of pathway: protonation of oxime nitrogen followed by nucleophilic addition of water. Protonation of hydroxylamine followed by formation of ketone and loss of hydroxylamine group.
- Figures of chemical structures attached: Yes
Validity criteria fulfilled:
yes
Conclusions:
The substance was applied to sterile aqueous buffers at pH 4, 7 and 9 and the buffers were incubated in the dark at 50 ± 0.5C for up to 5 days. No degradation was observed in two of the buffers (pH 7 and 9) and, therefore, CA4920 was considered hydrolytically stable under basic and neutral conditions at environmentally relevant temperatures.

At pH 4, degradation was observed. In the subsequent main tests, degradation rate constants of 0.01962, 0.04369 and 0.2824 with associated t1/2 values of 35.3, 15.9 and 2.45 days for incubation temperatures of 15oC, 25oC and 50oC respectively were seen. the substance was considered hydrolytically unstable under acidic conditions at environmentally relevant temperatures.
Executive summary:

During initial testing the test item degraded relatively rapidly at pH 4 at 50ºC but there was no degradation observed at pH 7 or pH 9 at 50ºC.

After further testing at pH4 it was demonstrated that the rate of degradation was proportionally slower at 25ºC and 15ºC than at 50 ºC. At the termination of the test, the concentration of the parent compound decreased from 71.5% at day 0, to 4.4% of the initial at 50ºC after 10 days, from 94.5% to 25.7% of the initial at 25ºC after 30 days, and from 97.5% to 53.8% of the initial at 15ºC after 30 days. The Kobs (hydrolysis rate constant), half life and activation energy values were calculated using non-linear regression and pseudo first-order kinetics.

LC-MS analysis of the terminal samples of hydrolysis of the test item at all temperatures showed the presence of the test item and one major hydrolysis product. In this study, the major degradate of CA4920 was found to be the ketone, 11- (dichloromethylidene)tricyclo [6.2.1.02,7] undec-2(7)-en-3-one (synonym: 9- (dichloromethylidene)-2,3,4,6,7,8-hexahydro-1,4-methanonaphthalen-5(1H)-one)

Description of key information

No degradation was observed in two of the buffers (pH 7 and 9) and, therefore, the test item was considered hydrolytically stable under basic and neutral conditions at environmentally relevant temperatures.

At pH 4, degradation was observed. In the subsequent main tests, degradation rate constants of 0.01962, 0.04369 and 0.2824 with associated t1/2 values of 35.3, 15.9 and 2.45 days for incubation temperatures of 15°C, 25°C and 50°C respectively were seen. The test item was considered hydrolytically unstable under acidic conditions at environmentally relevant temperatures.

Key value for chemical safety assessment

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

Additional information