3,7-dimethyloct-1-en-3-yl acetate

Hydrolysis

Link to relevant study record(s)

Reference

Endpoint:

hydrolysis

Type of information:

experimental study

Adequacy of study:

key study

Study period:

From 2014-05-19 to 2014-07

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

test procedure in accordance with generally accepted scientific standards and described in sufficient detail

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 111 (Hydrolysis as a Function of pH)

GLP compliance:

no

Remarks:

The study was not performed according to GLP principles.

Radiolabelling:

yes

Analytical monitoring:

yes

Details on sampling:

- Sampling intervals for the parent/transformation products: In Series 1 samples were taken after 0, 0.5, 1, 1.5, 2, 3, 4 and 6 h at pH 9.2 and after 0, 0.5, 1, 1.5, 2 and 3 h at pH 2.2, in Series 2 samples were taken after 0, 0.5, 1, 1.5, 2, 3.5, 4 and 6 h at pH 9.2, after 0, 0.5, 1, 1.5, 2, 3, 4 and 6 h at pH 7.5, after 0, 0.5, 1, 1.5, 2, 2.5, 3, 4, 5 and 6 h at pH 4.0 and after 0, 0.5, 1, 2, 3, 4 and 6 h at pH 2.2. In Series 2b samples were taken after 0, 0.25, 0.5, 0.75, 1 and 1.25 h at pH 2.2. In Series 3 samples were taken after 0, 0.25, 0.5, 0.75, 1, 1.25, 1.5, 1.75 and 2 h at pH 2.2. In Series 4 samples were taken after 0, 3 and 6 h at pH 9.2 an 4.
- Sampling method: At each sampling time point 20 µL aliquots were removed (one aliquot from a fresh vial) and analyzed by HPLC

Buffers:

pH 2.2: 98.8 % 0.1 mol/L citric acid monohydrate + 1.2 % 0.2 mol/L disodium hydrogen
phosphate
pH 4.5: 56.4 % 0.1 mol/L citric acid monohydrate + 43.6 % 0.2 mol/L disodium hydrogen
phosphate
pH 7.5: 19.0 % 0.1 mol/L citric acid monohydrate + 81 % 0.2 mol/L disodium hydrogen
phosphate
pH 9.2: 10.0 % 0.1 mol/L sodium carbonate + 90.0 % 0.1 mol/L sodium hydrogen carbonate

Details on test conditions:

Stock solution: 50 µL of the test item solution in ethanol was added to 450 µL ethanol. The resulting test item concentration was 3.37 mmol/L. The concentration corresponded to 3.975 MBq/mL or 238500 dpm/ µL.
Series 1
50 µL of the stock solution was added to 450 µL buffer and immediately 50 µL aliquots were distributed into 8 individual conical HPLC vials. The HPLC vials were crimp capped with a PTFE seal and placed into the HPLC autosampler thermostatted at 37 °C.
Series 2 and 3
50 µL of the stock solution was added to 450 µL buffer and immediately about 400 - 450 µL was filled into one conical HPLC vial. The HPLC vials were crimp capped with a PTFE seal and placed into the HPLC autosampler thermostatted at 37 °C.
Series 4
40 µL aliquots of the stock solution were added into 3 20 mL headspace vials containing 960 µL buffer. The HPLC vials were crimp capped with a PTFE seal and placed into the HPLC autosampler thermostatted at 37 °C.

Duration:

6 h

pH:

2.2

Temp.:

37 °C

Initial conc. measured:

0.13 mmol/L

Remarks:

Series 3

Duration:

6 h

pH:

2.2

Temp.:

37 °C

Initial conc. measured:

0.13 mmol/L

Remarks:

Series 2

Duration:

6 h

pH:

4

Temp.:

37 °C

Initial conc. measured:

0.13 mmol/L

Remarks:

Series 2

Duration:

6 h

pH:

7.5

Temp.:

37 °C

Initial conc. measured:

0.13 mmol/L

Remarks:

Series 2

Duration:

6 h

pH:

9.2

Temp.:

37 °C

Initial conc. measured:

0.13 mmol/L

Remarks:

Series 2

Number of replicates:

3 test series at pH 9.2
4 test series at pH 2.2
2 test series at pH 4.0
1 test series at pH 7.5

Transformation products:

yes

No.:

#1

pH:

2.2

Temp.:

37 °C

Hydrolysis rate constant:

2.553 h-1

DT50:

0.27 h

Type:

(pseudo-)first order (= half-life)

pH:

2.2

Temp.:

37 °C

Hydrolysis rate constant:

1.95 h-1

DT50:

0.36 h

Type:

(pseudo-)first order (= half-life)

Key result

pH:

4

Temp.:

37 °C

Hydrolysis rate constant:

0.292 h-1

DT50:

2.37 h

Type:

(pseudo-)first order (= half-life)

Key result

pH:

7.5

Temp.:

37 °C

Hydrolysis rate constant:

0.203 h-1

DT50:

3.41 h

Type:

(pseudo-)first order (= half-life)

Key result

pH:

9.2

Temp.:

37 °C

Hydrolysis rate constant:

0.239 h-1

DT50:

2.9 h

Type:

(pseudo-)first order (= half-life)

Validity criteria fulfilled:

not applicable

Remarks:

Test was not performed according to a test guideline therefore no specific validity criteria were specified. Nevertheless, the test was performed according to generally accepted scientific standards and described in sufficient detail. Therefore, the test

Conclusions:

The substance was hydolysed under all tested pH conditions with a tendency of more rapid hydrolysis at basic and acidic pH values.

Executive summary:

The results from all experiments showed that DMOE Ac was hydrolyzed to DMOE under physiological conditions, i.e. at the pH range of pH 2.2 – 9.2. The hydrolysis rate was lowest at pH 7.5 and higher under basic or acidic conditions: Below pH 7.5 the hydrolysis rate was inversely related to the pH: the lower the pH, the higher the rate. Besides DMOE no other reaction products were detected. Incubations at 37 °C yielded a significant loss of compounds into the gas phase. This loss was dependent on the geometry of the incubation system, e.g. at the ratio of gas to aqueous phase. Even by optimization of this ratio and using a closed system, volatilization could not be completely avoided. Measurement of the two compounds in the gas phase by headspace MS confirmed that DMOE Ac is much more volatile than DMOE in aqueous solutions. The corresponding half-lifes for hydrolysis were determined to be 0.36 h, 2.37 h, 3.41 h and 2.9 h at 37 °C and pH of 2.2, 4, 7.5 and 9.2, respectively.

Description of key information

The substance was hydolysed under all tested pH conditions with a tendency of more rapid hydrolysis at basic and acidic pH values.

Key value for chemical safety assessment

Half-life for hydrolysis:

3.41 h

at the temperature of:

37 °C

Additional information

The results from all experiments showed that DMOE Ac was hydrolyzed to DMOE under physiological conditions, i.e. at the pH range of pH 2.2 – 9.2. The hydrolysis rate was lowest at pH 7.5 and higher under basic or acidic conditions: Below pH 7.5 the hydrolysis rate was inversely related to the pH: the lower the pH, the higher the rate. Besides DMOE no other reaction products were detected. Incubations at 37 °C yielded a significant loss of compounds into the gas phase. This loss was dependent on the geometry of the incubation system, e.g. at the ratio of gas to aqueous phase. Even by optimization of this ratio and using a closed system, volatilization could not be completely avoided. Measurement of the two compounds in the gas phase by headspace MS confirmed that DMOE Ac is much more volatile than DMOE in aqueous solutions. The corresponding half-lifes for hydrolysis were determined to be 0.36 h, 2.37 h, 3.41 h and 2.9 h at 37 °C and pH of 2.2, 4, 7.5 and 9.2, respectively.