2,2-dimethylpropane-1,3-diyl dibenzoate

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:

other: GLP guideline study without restriction

Qualifier:

according to guideline

Guideline:

OECD Guideline 111 (Hydrolysis as a Function of pH)

Deviations:

no

Qualifier:

equivalent or similar to guideline

Guideline:

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

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Radiolabelling:

no

Analytical monitoring:

yes

Buffers:

- Buffer pH 4 (Fa. Fluka, Citric acid/NaOH/NaCl, Art-Nr.: 33643)
- Buffer pH 7 (Fa. Fluka, KH2PO4/Na2HPO4, Art-Nr.: 33646)
- Buffer pH 9 (Fa. Fluka, Na2B4O7/HCl, Art-Nr.: 33648)

Details on test conditions:

PRE-TEST FOR HYDROLYSIS:
- The test item was applied as an aqueous solution (including 1 % acetonitrile) with a concentration of approx. 0.5 mg/l (0.0018 mol/l) which fulfills the requirements of OECD TG 111.
- No further solubility test with organic solvent additives > 1% v/v was performed.

PREPARATION OF THE 2,2-DIMETHYLPROPANE-1,3-DIYL DIBENZOATE TEST SOLUTION:
- 27.5 mg of the test item 2,2-Dimethylpropane-1,3-diyl dibenzoate were dissolved in 50 ml acetonitrile. These stock solution was 1:1000 diluted with buffer solution pH 7, leading to a test item concentration of 538.5 μg/l.
- Aliquots of the stock solution were taken to obtain individual vials for every test point. Preparation was carried out under nitrogen as flushing gas, to avoid oxygen.
- The vials were closed and incubated at 50, 40 and 20 °C in a heat regulator under dark to avoid any photolytic effects.
- The pH of the blank buffer solution was checked at the beginning of the test. Additionally the pH of the hydrolysis solution was measured at each test point. The temperature during the experiment was also checked at each test point.
- Calibration was done for the analysis of the hydrolysis test solution. The calibration was verified at the level of 433.9 μg/l by using a control calibration solution.
- At each test point the hydrolysis solution was directly led to the chromatographic measurement.

STERILITY TEST:
- A plate count test was performed at the end of the tests.

Duration:

5 d

pH:

4

Temp.:

50 °C

Initial conc. measured:

449.91 µg/L

Duration:

6 d

pH:

7

Temp.:

50 °C

Initial conc. measured:

472.312 µg/L

Duration:

3 d

pH:

9

Temp.:

50 °C

Initial conc. measured:

452.082 µg/L

Duration:

8 d

pH:

9

Temp.:

40 °C

Initial conc. measured:

453.279 µg/L

Duration:

7 d

pH:

9

Temp.:

40 °C

Initial conc. measured:

466.845 µg/L

Duration:

30 d

pH:

9

Temp.:

20 °C

Initial conc. measured:

443.949 µg/L

Duration:

30 d

pH:

9

Temp.:

20 °C

Initial conc. measured:

519.872 µg/L

Positive controls:

no

Negative controls:

no

Transformation products:

yes

No.:

#1

Details on hydrolysis and appearance of transformation product(s):

As main hydrolysis product benzoic acid could be determined in the hydrolysis test solution of 2,2-dimethylpropane-1,3-diyl dibenzoate (hydrolyzed at 50 °C and pH 9). The content of formed benzoic acid is determined using benzoic acid as calibration substance by HPLC with UV-detection and quantification by external standardization.

% Recovery:

80.1

pH:

4

Temp.:

50 °C

Duration:

5 d

% Recovery:

80.1

pH:

7

Temp.:

50 °C

Duration:

6 d

% Recovery:

9.4

pH:

9

Temp.:

50 °C

Duration:

3 d

% Recovery:

8.1

pH:

9

Temp.:

40 °C

Duration:

10 d

% Recovery:

7.6

pH:

9

Temp.:

40 °C

Duration:

10 d

% Recovery:

41.9

pH:

9

Temp.:

20 °C

Duration:

30 d

% Recovery:

40.2

pH:

9

Temp.:

20 °C

Duration:

30 d

pH:

9

Temp.:

40 °C

Hydrolysis rate constant:

0 s-1

DT50:

70.78 h

Type:

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

Remarks on result:

other: Mean value of two determinations

pH:

9

Temp.:

25 °C

Hydrolysis rate constant:

0 s-1

DT50:

394.57 h

Type:

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

Remarks on result:

other: Calculated using the Arrhenius equation, Mean value of two determinations

pH:

9

Temp.:

20 °C

Hydrolysis rate constant:

0 s-1

DT50:

727.85 h

Type:

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

Remarks on result:

other: Mean value of two determinations

pH:

4

Temp.:

50 °C

DT50:

> 5 d

Type:

other: not applicable

pH:

7

Temp.:

50 °C

DT50:

> 6 d

Type:

other: not applicable

Details on results:

2,2-Dimethylpropane-1,3-diyl dibenzoate is found to be stable at 50 °C and pH 4 and 7. Therefore, it can be assumed that 2,2-dimethylpropane-1,3-diyl dibenzoate is also stable at 25 °C and no half-life times and hydrolysis rates were calculated.

According to OECD 111 Guideline a sterility test was conducted at the end of the hydrolysis test.

High microbes (colonies) were found at 20 °C and pH 9. However, biotic degradation can be excluded, because abiotic degradation was observed at 50 °C and pH 9 and at 40 °C and pH 9, where no microbes were found.

Validity criteria fulfilled:

yes

Conclusions:

2,2-Dimethylpropane-1,3-diyl dibenzoate is found to be stable at 50 °C and pH 4 and 7. Therefore, it can be assumed that 2,2-dimethylpropane-1,3-diyl dibenzoate is also stable at 25 °C and no half-life times and hydrolysis rates were calculated.
At 50 °C and pH 9 abiotic degradation of 2,2-dimethylpropane-1,3-diyl dibenzoate was observed. Benzoic acid could be identified as the main hydrolysis product (hydrolyzed at 50 °C and pH 9). 2,2-Dimethylpropane-1,3-diyl dibenzoate can be considered as hydrolytically unstable at 50 °C and pH 9.
The calculated mean value of half-life time and hydrolysis rate at 25 °C and pH 9 using the Arrhenius equation are 394.57 hours and 4.8958E-07 1/s, respectively.

Executive summary:

The hydrolysis behaviour of 2,2-Dimethylpropane-1,3-diyl dibenzoate was investigated at 50 °C and at pH 4, pH 7 and pH 9 over a period of five days according to OECD TG 111.

The stability was monitored after 2,2-dimethylpropane-1,3-diyl dibenzoate extraction by HPLC analysis using UV detection.

At 50 °C and pH 4 and 7 no abiotic degradation of 2,2-dimethylpropane-1,3-diyl dibenzoate was observed. Consequently, it can be assumed that 2,2-dimethylpropane-1,3-diyl dibenzoate is also stable at 25 °C and therefore, no half-life times and hydrolysis rates were calculated.

Abiotic degradation of 2,2-dimethylpropane-1,3-diyl dibenzoate was observed at 50 °C and pH 9. Benzoic acid could be identified as the main hydrolysis product. 2,2-Dimethylpropane-1,3-diyl dibenzoate can be considered as hydrolytically unstable at 50 °C and pH 9. The calculated mean value of half-life time and hydrolysis rate at 25 °C and pH 9 using the Arrhenius equation are 394.57 hours and 4.8958E-07 1/s, respectively.

According to OECD 111 Guideline a sterility test was conducted at the end of the hydrolysis test. High microbes (colonies) were found at 20 °C and pH 9. However, biotic degradation can be excluded, because abiotic degradation was observed at 50 °C and pH 9 and at 40 °C and pH 9, where no microbes were found.

Description of key information

2,2-Dimethylpropane-1,3-diyl dibenzoate is found to be stable at 50 °C and pH 4 and 7.

Therefore, it can be assumed that 2,2-dimethylpropane-1,3-diyl dibenzoate is also stable at 25 °C and no half-life times and hydrolysis rates were calculated.
At 50 °C and pH 9 abiotic degradation of 2,2-dimethylpropane-1,3-diyl dibenzoate was observed. Benzoic acid could be identified as the main hydrolysis product (hydrolyzed at 50 °C and pH 9).
The calculated mean value of half-life time and hydrolysis rate at 25 °C and pH 9 using the Arrhenius equation are 394.57 hours (16.4 days) and 4.8958E-07 1/s, respectively.

Key value for chemical safety assessment

Half-life for hydrolysis:

6 d

at the temperature of:

50 °C

Additional information

Should read >6 days at 50°C and pH 4 and 7.

According to OECD 111 Guideline a sterility test was conducted at the end of the hydrolysis test. High microbes (colonies) were found at 20 °C and pH 9. However, biotic degradation can be excluded, because abiotic degradation was observed at 50 °C and pH 9 and at 40 °C and pH 9, where no microbes were found.