2,6-dibromo-4-cyanophenyl heptanoate

Hydrolysis

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

hydrolysis

Type of information:

experimental study

Adequacy of study:

key study

Study period:

12 Nov 1985 - 21 Jan 1986

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Qualifier:

according to guideline

Guideline:

EPA Guideline Subdivision N 161-1 (Hydrolysis)

GLP compliance:

no

Radiolabelling:

yes

Analytical monitoring:

yes

Details on sampling:

- Sampling intervals for the parent/transformation products: One sample from each pH level was removed from the constant temperature bath for analysis at the following times: initial or 0 time, 4, 24 and 48 hours, 3, 6, 14, 21 and 30 days.
- Sampling intervals/times for pH measurements: Throughout this study, the pH levels of the samples were monitored with a pH meter and adjusted if deemed necessary.

Buffers:

- pH: 5, 7 and 9
- Type and final molarity of buffer:
pH 5: A 500 ml portion of 0.05 M potassium hydrogen phthalate solution and a 113 mL portion of 0.1 M sodium hydroxide solution were placed into a 1000 mL volumetric flask and diluted to volume with deionized water. The pH was checked on a pH meter and adjusted if necessary.
pH 7: A 500 mL portion of 0.05 M potassium hydrogen phosphate solution and a 145 mL portion of 0.1 M sodium hydroxide solution were placed into a 1000 mL volumetric flask and diluted to volume with deionized water. The pH was checked on a pH meter and adjusted if necessary.
pH 9: A 500 ml portion of 0.05 M sodium borate solution and a 69 mL portion of 0.1 M hydrochloric acid solution were placed into a 1000 mL volumetric flask and diluted to volume with deionized water. The pH was checked with a pH meter and adjusted if necessary.
- Other: All freshly prepared buffer solutions were sterilized by filtering through a sterilized Millipore filtering system with a 0.45 µm aqueous filter disk into sterilized filter flasks under reduced pressure.

Details on test conditions:

TEST SYSTEM
- Type, material and volume of test flasks, other equipment used: Culture tubes with 50 mL capacity with Teflon-lined plastic caps.
- Sterilisation method: Twenty-seven (27) culture tubes, a glass Millipore filtration system and several 500 mL filter flasks were sterilized in a pressure cooker for 20 minutes at 20 psi. Teflon lined plastic caps and several pipets were sterilized overnight in a 1:3 deionized water:ethanol solution.
- Measures to exclude oxygen: The culture tubes were then capped with Teflon-lined plastic caps, thoroughly mixed and placed in a constant temperature bath at 25 ± 1° C and covered to eliminate light.

TEST MEDIUM
- Volume used/treatment: 30 mL
- Kind and purity of water: Deionized water
- Preparation of test medium: The contents of a vial containing 19.92 mg of 14-C Bromoxynil Heptanoate equal to 1.0 mCi were transferred to a 100 mL volumetric flask with several small portions of hexane; the sample was diluted to volume with hexane and thoroughly mixed. Aliquots of this solution were removed for analysis by TLC, LSC and GLC for the determination of radiopurity and specific activity. The resulting concentration of this final solution was 201.2 µg/mL with a specific activity of approximately 95,313 dpm/µg and a radiopurity of 99.6%.

Duration:

30 d

pH:

5

Temp.:

25 °C

Initial conc. measured:

0.067 other: ppm

Duration:

30 d

pH:

7

Temp.:

25 °C

Initial conc. measured:

0.067 other: ppm

Duration:

30 d

pH:

9

Temp.:

25 °C

Initial conc. measured:

0.067 other: ppm

Transformation products:

yes

No.:

#1

No.:

#2

No.:

#3

No.:

#4

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

- Formation and decline of each transformation product during test: The majority of the radioactivity at the beginning of the study is in the form of Bromoxynil Heptanoate. At the conclusion of the study (day 30), the radioactivity is in the form of bromoxynil (87.9% at pH5, 95.5% at pH7, 92.6% at pH9). It must be noted that these radioactive components, determined by thin layer chromatography, comprise >98.6% of the total radioactivity in every case. The existence of the only major radioactive species found in this study was confirmed by two-dimensional TLC autoradiography and also by HPLC with a radiometric detector.

% Recovery:

93.4

pH:

5

Temp.:

25 °C

Duration:

30 d

Remarks on result:

other:

Remarks:

% Recovery of initially applied radioactivity.

% Recovery:

93.5

pH:

7

Temp.:

25 °C

Duration:

30 d

Remarks on result:

other:

Remarks:

% Recovery of initially applied radioactivity.

% Recovery:

97.3

pH:

9

Temp.:

25 °C

Duration:

30 d

Remarks on result:

other:

Remarks:

% Recovery of initially applied radioactivity.

pH:

9

Temp.:

25 °C

DT50:

4.1 d

Type:

other: linear regression analysis

pH:

9

Temp.:

12 °C

DT50:

13.7 d

Remarks on result:

other:

Remarks:

Calculated DT50 at 12 °C

pH:

7

Temp.:

25 °C

DT50:

5.3 d

Type:

other: linear regression analysis

pH:

7

Temp.:

12 °C

DT50:

17.7 d

Remarks on result:

other:

Remarks:

Calculated DT50 at 12 °C

pH:

5

Temp.:

25 °C

DT50:

11.7 d

Type:

other: linear regression analysis

pH:

5

Temp.:

12 °C

DT50:

39 d

Remarks on result:

other:

Remarks:

Calculated DT50 at 12 °C

Details on results:

TEST CONDITIONS
- pH, sterility, temperature, and other experimental conditions maintained throughout the study: Yes. pH remained constant throughout the study, in all three treaments.
- Anomalies or problems encountered (if yes): The accountability of radioactivity is generally well over 100%; the radioactivity extracted is greater than the initial radioactivity because the culture tubes were rinsed with ethyl acetate solublizing the remaining undissolved test chemical. Even though the concentration of the test chemical was very low at 0.067 ppm, a slight problem existed in maintaining dissolution in the glass containers.

MAJOR TRANSFORMATION PRODUCTS
At pH5, pH7 and pH9:
- Range of maximum concentrations in % of the applied amount and day(s) of incubation when observed: The majority of the radioactivity at the beginning of the study is in the form of Bromoxynil Heptanoate. At the conclusion of the study (day 30), the radioactivity is in the form of bromoxynil (87.9% at pH5, 95.5% at pH7, 92.6% at pH9). It must be noted that these radioactive components, determined by thin layer chromatography, comprise >98.6% of the total radioactivity in every case. The existence of the only major radioactive species found in this study was confirmed by two-dimensional TLC autoradiography and also by HPLC with a radiometric detector.

MINOR TRANSFORMATION PRODUCTS
Maximum concentrations in % of the applied amount
- at pH5: 0.41% at day 30
- at pH7: 2.55% at day 14
- at pH9: 3.90% at day 14

Validity criteria fulfilled:

not applicable

Reference 2

Endpoint:

hydrolysis

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Qualifier:

according to guideline

Guideline:

EPA Guideline Subdivision N 161-1 (Hydrolysis)

GLP compliance:

no

Radiolabelling:

yes

Duration:

31 d

pH:

9

Temp.:

25 °C

Initial conc. measured:

13.8 mg/L

Duration:

31 d

pH:

7

Temp.:

25 °C

Initial conc. measured:

13.8 mg/L

Duration:

31 d

pH:

5

Temp.:

25 °C

Initial conc. measured:

13.8 mg/L

pH:

9

Temp.:

25 °C

DT50:

> 1 yr

pH:

9

Temp.:

25 °C

DT50:

> 1 yr

Remarks on result:

other:

Remarks:

Calculated DT50 at 12 °C

pH:

7

Temp.:

25 °C

DT50:

> 1 yr

pH:

7

Temp.:

12 °C

DT50:

> 1 yr

Remarks on result:

other:

Remarks:

Calculated DT50 at 12 °C

pH:

5

Temp.:

25 °C

DT50:

> 1 yr

pH:

5

Temp.:

12 °C

DT50:

> 1 yr

Remarks on result:

other:

Remarks:

Calculated DT50 at 12 °C

Conclusions:

Radiolabeled 14-C Bromoxynil was subjected to a 31 day hydrolysis study at 3 pH levels. Bromoxynil remains unchanged in aqueous systems at pH levels of 5, 7 and 3 for at least one month of incubation under sterile conditions at 25 ± 1 °C.

Reference 3

Endpoint:

hydrolysis

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

supporting study

Justification for type of information:

Please refer to the Analogue Justification provided in IUCLID section 13.

Reason / purpose for cross-reference:

read-across source

pH:

9

Temp.:

25 °C

DT50:

> 1 yr

pH:

9

Temp.:

12 °C

DT50:

> 1 yr

Remarks on result:

other:

Remarks:

Calculated DT50 at 12 °C

pH:

7

Temp.:

25 °C

DT50:

> 1 yr

pH:

7

Temp.:

12 °C

DT50:

> 1 yr

Remarks on result:

other:

Remarks:

Calculated DT50 at 12 °C

pH:

5

Temp.:

25 °C

DT50:

> 1 yr

pH:

5

Temp.:

12 °C

DT50:

> 1 yr

Remarks on result:

other:

Remarks:

Calculated DT50 at 12 °C

Description of key information

Half-life at 25°C: 4.1 days at pH 9, 5.3 days at pH 7 and 11.7 days at pH 5 (13.7, 17.7 and 39 days, recalculated to 12 °C; EPA Guideline N161-1).

Key value for chemical safety assessment

Half-life for hydrolysis:

17.7 d

at the temperature of:

12 °C

Additional information

The hydrolysis of radiolabelled 2,6-dibromo-4-cyanophenyl heptanoate was tested in a study following EPA Guideline N 161-1. The rate of hydrolysis was determined under alkaline (pH 9), neutral (pH 7) and acidic (pH 5) conditions. The DT50 of the test substance was estimated to be 4.1 days at pH 9, 5.3 days at pH 7 and 11.7 days at pH 5 (13.7, 17.7 and 39 days, recalculated to 12 °C).

 

One more study on the degradation of 2,6-dibromo-4-cyanophenyl heptanoate is available. This position paper provides an overview of the hydrolysis products of 3,5-dibromo-4-hydroxybenzonitrile (CAS 1689-84-5) and its esters. The only hydrolysis product of bromoxynil esters that is relevant to the environment is 3,5-dibromo-4-hydroxybenzonitrile (bromoxynil phenol), which itself is resistant to hydrolysis.

 

In accordance with Regulation (EC) No 1907/2006 Annex XI, 1.5 “Grouping of substances and read-across” and in accordance with the read across assessment framework (RAAF, ECHA 2017) a read-across from the hydrolysis of 3,5-dibromo-4-hydroxybenzonitrile has been applied to support the environmental hazard assessment of 2,6-dibromo-4-cyanophenyl heptanoate.

In the supporting study, 3,5-dibromo-4-hydroxybenzonitrile was stable at 12 °C and under alkaline (pH 9), neutral (pH 7) and acidic (pH 5) conditions with a half-life of >1 year.