4-(1-ethoxyvinyl)-3,3,5,5-tetramethylcyclohexanone

Hydrolysis

Link to relevant study record(s)

Reference

Endpoint:

hydrolysis

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

EU Method C.7 (Degradation: Abiotic Degradation: Hydrolysis as a Function of pH)

Qualifier:

according to guideline

Guideline:

OECD Guideline 111 (Hydrolysis as a Function of pH)

Qualifier:

according to guideline

Guideline:

EPA OPPTS 835.2120 (Hydrolysis of Parent and Degradates as a Function of pH at 25°C)

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

Identification:Kephalis
Chemical Name (IUPAC): 4-(1-ethoxyvinyl)-3,3,5,5,-tetramethylcyclohexanone (main component)
Molecular formula: C14H24O2
Molecular weight: 224.4 g/mol
CAS Number: 36306-87-3
EC Number: 252-961-2
Description: Clear colourless to slightly yellow liquid (determined at WIL Research Europe B.V.)
Batch: PE00097828
Purity/Composition: 85.2% (sum of two peaks, 78.8% and 7.3%)
Test substance storage: In refrigerator (2-8°C) protected from light
Stable under storage conditions until: 14 march 2015 (expiry date)

Analytical monitoring:

yes

Buffers:

Acetate buffer pH 4, 0.01 M: solution of 16.7% 0.01 M sodium acetate in water and 83.3% 0.01 M acetic acid in water. The buffer contains 0.0009% (w/v) sodium azide.
Phosphate buffer pH 7, 0.01 M: solution of 0.01 M potassium di-hydrogenphosphate in water adjusted to pH 7 using 1 N sodium hydroxide. The buffer contains 0.0009% (w/v) sodium azide.
Borate buffer pH 9, 0.01 M: solution of 0.01 M boric acid in water and 0.01 M potassium chloride in water adjusted to pH 9 using 1 N sodium hydroxide. The buffer contains 0.0009% (w/v) sodium azide.

Details on test conditions:

The rate of hydrolysis of the test substance as a function of pH was determined at pH values normally found in the environment (pH 4-9).
All solutions containing the test substance were protected from light.

Preliminary test - Tier 1
The buffer solutions were filter-sterilised through a 0.2 μm FP 30/0.2 CA-S filter (Whatman, Dassel, Germany) and transferred into a sterile vessel. To exclude oxygen, nitrogen gas was purged through the solution for 5 minutes. The test substance was spiked to the solutions at a target concentration of 2 mg/l using a spiking solution in acetone. For each sampling time, duplicate sterile vessels under vacuum were filled with 6 ml test solution and placed in the dark in a temperature controlled environment at 49.9°C ± 0.1°C.
Note: the spiking volume was < 1% of the sample volume. Nominal concentrations were not corrected for the spiking volume.
The concentration of the test substance in the test samples was determined immediately after preparation (t=0) and after 5 days. The samples taken at t=5 days were cooled to room temperature using running tap water. The samples were extracted in a 1:1 (v:v) ratio with n-hexane. The shaking time was 30 seconds. The organic layer was analysed.
Blank buffer solutions containing a similar content of blank spiking solution were treated similarly as the test samples and analysed at t=0.
The pH of each of the test solutions (except for the blanks) was determined at each sampling time.

Main study - Tier 2
Test substance solutions were prepared similarly as during the preliminary test. For each sampling time 2 sterile amber glass vessels were completely filled under a stream of nitrogen and were securely closed to avoid evaporation.
Sample were treated similarly as during the preliminary test. The concentrations of the test substance were determined immediately after preparation (t=0) and at several sampling points after t=0.
The samples not analysed on the sampling day were stored in the freezer. Storage stability under these conditions was determined by the analysis of additional accuracy samples prepared at half the nominal concentration of the test samples. On the day of analysis, the frozen samples were defrosted at room temperature, treated and analysed. The stored samples were found to be stable if the mean accuracy was in the range 70-110%. Based on the results obtained the samples were not stable when stored in the freezer for 15 days (results are archived in the raw data).
Blank buffer solutions were treated similarly as the test samples and analysed at t=0.
The pH of each of the test solutions (except for the blanks) was determined at least at the beginning and at the end of the test.
The study was performed at the following temperatures:

pH code Temperature I Temperature II Temperature III
pH 4 21.0°C ± 0.4°C 49.9°C ± 0.1°C 40.0°C ± 0.1°C
pH 7 20.2°C ± 2.3°C 49.9°C ± 0.2°C 60.0°C ± 0.2°C
pH 9 - 49.9°C ± 0.5°C -

Identification of hydrolysis products – Tier 3
Research to investigate the identity or nature and rates of formation and decline of hydrolysis products was not performed. Based on information supplied by the sponsor, acid hydrolysis of the main component of Kephalis most likely occurs (i.e. hydrolysis of the enol ether function). This supports the shorter half-life at pH 4 compared to those at pH 7 and pH 11.

Preliminary study:

A degree of hydrolysis of ≥ 10% was observed at pH 4, pH 7 and pH 9 after 5 days. According to the guideline, the higher Tier test was required to determine the half-life time of the test substance.
No test substance was detected in the blank buffer solutions.
The mean recoveries of the of the test substance containing buffer solutions at t=0 fell within the criterion range of 90-110%. It demonstrated that the analytical method was adequate to support the hydrolysis study on the test substance.

Transformation products:

not measured

% Recovery:

85

pH:

4

Temp.:

21 °C

% Recovery:

84

pH:

4

Temp.:

40 °C

% Recovery:

80

pH:

4

Temp.:

50 °C

% Recovery:

99

pH:

7

Temp.:

20 °C

% Recovery:

96

pH:

7

Temp.:

50 °C

% Recovery:

85

pH:

7

Temp.:

60 °C

% Recovery:

98

pH:

9

Temp.:

50 °C

pH:

4

Temp.:

20 °C

DT50:

1.5 h

pH:

4

Temp.:

25 °C

DT50:

1.1 h

pH:

4

Temp.:

40 °C

DT50:

0.49 h

pH:

4

Temp.:

50 °C

DT50:

0.26 h

pH:

7

Temp.:

20 °C

DT50:

64 d

pH:

7

Temp.:

25 °C

DT50:

44 d

pH:

7

Temp.:

50 °C

DT50:

8.2 d

pH:

7

Temp.:

60 °C

DT50:

4.9 d

pH:

9

Temp.:

25 °C

DT50:

> 1 yr

Validity criteria fulfilled:

yes

Executive summary:

The preliminary test (Tier 1) and main study (Tier 2) were performed for the determination of the rate of hydrolysis of Kephalis at pH values normally found in the environment (pH 4-9).

The half-life times of the test substance were:

pH 4		pH 7		pH 9
Temperature [°C]	t1/2	Temperature [°C]	t1/2	Temperature [°C]	t1/2
20	1.5 hours	20	64 days
25	1.1 hours	25	44 days	25	> 1 year
40	0.49 hours
50	0.26 hours	50	8.2 days
60		60	4.9 days

 

Description of key information

The test item was found to be hydrolytically unstable at pH 4 and, to a certain extent, at pH7 (OECD 111, GLP study). The worst-case half-life of >1 year at pH 9 has been used as the key value for chemical safety assessment.

Key value for chemical safety assessment

Half-life for hydrolysis:

1 yr

at the temperature of:

25 °C

Additional information

The rate of hydrolysis of the test substance as a function of pH was determined at pH values normally found in the environment (pH 4-9). The half-life times of the test substance were determined according to the model for pseudo-first order reactions. Research to investigate the identity or nature and rates of formation and decline of hydrolysis products was not performed. Based on information supplied by the sponsor, acid hydrolysis of the main component of Kephalis most likely occurs (i.e. hydrolysis of the enol ether function). This supports the shorter half-life at pH 4 compared to those at pH 7 and pH 9.