4-Ethoxy-2,3-difluorphenylboronic acid

Hydrolysis

Link to relevant study record(s)

Reference

Endpoint:

hydrolysis

Type of information:

experimental study

Adequacy of study:

key study

Study period:

February 12, 2016 - July 27, 2016

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 111 (Hydrolysis as a Function of pH)

Version / remarks:

2004

Deviations:

no

Qualifier:

according to guideline

Guideline:

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

Version / remarks:

2008

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Remarks:

Siemens AG, Prozess-Sicherheit, Industriepark Höchst, B 596 & B 598, 65926 Frankfurt am Main, Germany

Radiolabelling:

no

Analytical monitoring:

yes

Details on sampling:

- Sampling intervals for the parent/transformation products:
- Sampling method: Aliquots of the test item solutions were diluted from 0.1 mL to 1 mL with the eluent of the HPLC measurement.
- Sampling intervals/times for pH measurements: The pH values of the test solutions were measured at the end of the experiments.

Buffers:

pH 4
21.01 g citric acid monohydrate was dissolved in 200 mL sodium hydroxide solution. This solution was filled up to a volume of 1000 mL with demineralized water. 44 mL of hydrochloric acid was added to 560 mL of this solution and filled up to a volume of 1000 mL with demineralized water. The pH value was adjusted to pH 4 for each hydrolysis temperature

pH 7
13.61 g potassium dihydrogen phosphate was dissolved in 1000 mL demineralized water. 30 mL of sodium hydroxide solution was added to 500 mL of this solution and filled up to a volume of 1000 mL with demineralized water. The pH value was adjusted to pH 7 for each hydrolysis temperature

pH 7
7.46 g potassium chloride and 6.18 g boric acid were dissolved in 1000 mL demineralized water. 21 mL of sodium hydroxide solution was added to 500 mL of this solution and filled up to a volume of 1000 mL with demineralized water. The pH value was adjusted to pH 9 for each hydrolysis temperature

The solubility of the test item in the relevant buffer solutions (pH 7 and 9) was lower than the water solubility and too low for the analytical determination. For the performance of the hydrolysis test, however, it is necessary to detect the test item down to 10% of the quantity used in the hydrolysis test. Therefore acetonitrile was used as solubillizer. At pH 4 the solubility in the corresponding buffer was too low even if an organic solvent was used as solubilizer. Therefore the study was only performed at pH 7 and pH 9.

Details on test conditions:

TEST SYSTEM
- Type, material and volume of test flasks, other equipment used: glass flasks
- Measures to exclude oxygen: Flasks were baked out at 110°C and flooded with nitrogen. The standards for calibration and recheck were freshly prepared.




Due to the low solubility of the test item in buffer solutions at pH 4 even in the presence of a solubilizing agent, the performance of this test could not be performed due to the limit of quantification (LOQ: ca 2.36 mg/L) of the applied analytical method.

Duration:

721 h

pH:

7.1

Temp.:

20 °C

Initial conc. measured:

62.48 mg/L

Duration:

720 h

pH:

7.1

Temp.:

20 °C

Initial conc. measured:

62.79 mg/L

Duration:

692 h

pH:

7.2

Temp.:

40 °C

Initial conc. measured:

51.77 mg/L

Duration:

692 h

pH:

7.2

Temp.:

40 °C

Initial conc. measured:

70.77 mg/L

Duration:

189 h

pH:

7.1

Temp.:

50 °C

Initial conc. measured:

55.3 mg/L

Duration:

236 h

pH:

7

Temp.:

50 °C

Initial conc. measured:

60.31 mg/L

Duration:

719 h

pH:

9.2

Temp.:

20 °C

Initial conc. measured:

65.41 mg/L

Duration:

719 h

pH:

9.2

Temp.:

20 °C

Initial conc. measured:

65.68 mg/L

Duration:

692 h

pH:

9.3

Temp.:

40 °C

Initial conc. measured:

51.69 mg/L

Duration:

691 h

pH:

9.3

Temp.:

40 °C

Initial conc. measured:

52.78 mg/L

Duration:

187 h

pH:

9.2

Temp.:

50 °C

Initial conc. measured:

63.15 mg/L

Duration:

187 h

pH:

9.2

Temp.:

50 °C

Initial conc. measured:

61.85 mg/L

Number of replicates:

2

Positive controls:

no

Negative controls:

no

Preliminary study:

In the preliminary tests, the test solutions (pH 7 and pH 9) were kept at 50 +/-0.5°C for 5 days in tightly closed flasks and the per cent abiotic degradation caused by hydrolysis was determined. At pH 7 and pH 9 more than 10% of the test item hydrolyzed within 5 d, therefore the main test had to be conducted.

Test performance:

The recovery of the standards indicated a sufficient accuracy of the analytical method.

Transformation products:

not measured

Remarks:

identification not necessary as the amount of the transformation product was <10% of the applied dose

Key result

pH:

7

Temp.:

25 °C

Hydrolysis rate constant:

0.001 h-1

DT50:

26.4 d

Type:

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

Key result

pH:

9

Temp.:

25 °C

Hydrolysis rate constant:

0.001 h-1

DT50:

26.9 d

Type:

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

Details on results:

Preliminary Test
In the preliminary tests (pH 7 and pH 9; 50 +/-0.5°C), the test item hydrolyzed by more than 10% within 5 d (67-ca. 84%), therefore the main test had to be conducted.

Main Test
Based on the findings of the preliminary test, the abiotic degradation via hydrolysis was investigated at pH 7 and pH 9, at temperatures of 20, 40, and 50°C and a observation period of 30 d at maximum.

Solutions of the test item were prepared by first dissolving approx. 3 mg of the test item in 0.5 mL acetonitrile and filling the solution up with the relevant buffers. The concentrations of the test solutions were <73 mg/L (range: ca. 50-71 mg/L).
At pH 7 and test temperatures of 20, 40, and 50°C, 38.9%, 91.2-92.7, and 91.0-92.6% of the test item hydrolyzed within <= 30 d, respectively. The test item had a half-life of 26.4 d at pH 7 and a temperature of 25°C.
At pH 9 and test temperature sof 20, 40, and 50°C, 31.1-44.9, 92.5-95.1, and 92.7-92.9% of the test item hydrolyzed within <=30 d, respectively. The test item had a half-life of 26.9 d at pH 9 and a temperature of 25°C.

Only one major hydrolysis product was found in tier 1 using a DAD detector. The amount of this major hydrolysis product was evaluated for experiments with a high hydrolysis rate of tier 2. For this purpose the peak areas of the hydrolysis products at the end of the experiment were compared with the peak area of the test item at the beginning of the experiment.
The amount of the hydrolysis product at 50°C and pH 7 was 4.8%. The amount of the hydrolysis product at 50°C and pH 9 was 4.2%. No identification of major hydrolysis products was necessary as no major hydrolysis products (>= 10% of the applied dose) was identified in the experiments of tier 2.

Table 1: Results of preliminary test

pH of buffer solution	pH of test item solution^a	Duration (d)	C0^b(mg/L)	Ct^c(mg/L)	Ct/C0	Decomposition (%)
7	7.1	5	63.31	20.88	0.330	67
7	7.1	5	61.01	16.29	0.267	73.3
9	9.2	5	55.52	11.37	0.205	79.5
9	9.2	5	63.07	10.20	0.162	83.8

a The pH values of the test item solutions were measured at the end of the experiments

Table 2: Measured half-lives at pH 7 and pH 9

pH value	Temperature (°C)	t1/2(h)
7	20 20 40 40 50 50	986 997 186 181 55.5 67.9
9	20 20 40 40 50 50	795 1409 151 178 50.7 49.8

Table 3: Calculated half-lives at 20°C and 25°C

pH value	Temperature (°C)	t1/2(h)	t1/2(d)
7	20 25	1037 633	43 26
9	20 25	1108 645	46 27

Validity criteria fulfilled:

yes

Conclusions:

The abiotic degradation of the test item was determined as a a function of temperature and pH. Based on measured data, half-lives t1/2 of 43 and 26 d at pH 7 and temperatures of 20 and 25°C, respectively, were calculated.

Executive summary:

The object of this study was the determination of the abiotic degradation of the test item, the determination of the hydrolysis rate as a function of the pH value.

For this purpose, the test item was added to the corresponding buffer solutions. Due to the low solubility of the test item in the buffer solutions, acetonitrile was used as solubilizing agent. At pH 4 the solubility in the relevant buffer solution was too low even in the presence of a solubilizing agent. Therefore the study was only performed at pH 7 and pH 9.

Preliminary Test

In the preliminary tests (pH 7 and pH 9; 50 +/-0.5°C), the test item hydrolyzed by more than 10% within 5 d (67-ca. 84%), therefore the main test had to be conducted.

Main Test

Based on the findings of the preliminary test, the abiotic degradation via hydrolysis was investigated at pH 7 and pH 9, at temperatures of 20, 40, and 50°C and a observation period of 30 d at maximum.

Solutions of the test item were prepared by first dissolving approx. 3 mg of the test item in 0.5 mL acetonitrile and filling the solution up with the relevant buffers. The concentrations of the test solutions were <73 mg/L (range: ca. 50-71 mg/L).

At pH 7 and test temperatures of 20, 40, and 50°C,  38.9%, 91.2-92.7, and 91.0-92.6% of the test item hydrolyzed within <= 30 d, respectively. The test item had a half-life of 26.4 d at pH 7 and a temperature of 25°C.

At pH 9 and test temperature sof 20, 40, and 50°C, 31.1-44.9, 92.5-95.1, and 92.7-92.9% of the test item hydrolyzed within <=30 d, respectively.  The test item had a half-life of 26.9 d at pH 9 and a temperature of 25°C.

No major hydrolysis products (>=10% of the applied dose) were identified in the experiments. Therefore the identification of major hydrolysis products was not necessary.

Conclusion

The abiotic degradation of the test item was determined as a a function of temperature and pH. Based on measured data, half-lives t1/2 of 43 and 26 d at pH 7 and temperatures of 20 and 25°C, respectively, were calculated.

No major hydrolysis products (>=10% of the applied dose) were identified in the experiments. Therefore the identification of major hydrolysis products was not necessary.

Description of key information

Calculated half-value times were as followed:

pH 7: 43 d at 20°C and 26 d at 25°C

pH 9: 46 d at 20°C and 27 d at 25°C.

Key value for chemical safety assessment

Half-life for hydrolysis:

26 d

at the temperature of:

25 °C

Additional information

The object of this study was the determination of the abiotic degradation of the test item, the determination of the hydrolysis rate as a function of the pH value.

For this purpose, the test item was added to the corresponding buffer solutions. Due to the low solubility of the test item in the buffer solutions, acetonitrile was used as solubilizing agent. At pH 4 the solubility in the relevant buffer solution was too low even in the presence of a solubilizing agent. Therefore the study was only performed at pH 7 and pH 9.

Preliminary Test

In the preliminary tests (pH 7 and pH 9; 50 +/-0.5°C), the test item hydrolyzed by more than 10% within 5 d (67-ca. 84%), therefore the main test had to be conducted.

Main Test

Based on the findings of the preliminary test, the abiotic degradation via hydrolysis was investigated at pH 7 and pH 9, at temperatures of 20, 40, and 50°C and a observation period of 30 d at maximum.

Solutions of the test item were prepared by first dissolving approx. 3 mg of the test item in 0.5 mL acetonitrile and filling the solution up with the relevant buffers. The concentrations of the test solutions were <73 mg/L (range: ca. 50-71 mg/L).

At pH 7 and test temperatures of 20, 40, and 50°C,  38.9%, 91.2-92.7, and 91.0-92.6% of the test item hydrolyzed within <= 30 d, respectively. The test item had a half-life of 26.4 d at pH 7 and a temperature of 25°C.

At pH 9 and test temperature sof 20, 40, and 50°C, 31.1-44.9, 92.5-95.1, and 92.7-92.9% of the test item hydrolyzed within <=30 d, respectively.  The test item had a half-life of 26.9 d at pH 9 and a temperature of 25°C.

No major hydrolysis products (>=10% of the applied dose) were identified in the experiments. Therefore the identification of major hydrolysis products was not necessary.

Conclusion

The abiotic degradation of the test item was determined as a a function of temperature and pH. Based on measured data, half-lives t1/2 of 43 and 26 d at pH 7 and temperatures of 20 and 25°C, respectively, were calculated.

No major hydrolysis products (>=10% of the applied dose) were identified in the experiments. Therefore the identification of major hydrolysis products was not necessary.