Bis-sec-butyl peroxydicarbonate

Hydrolysis

Administrative data

Endpoint:

hydrolysis

Type of information:

experimental study

Adequacy of study:

key study

Study period:

Study initiation date: 23 January 2012 Study completion date: 16 May 2013

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2013

Report date:

2013

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 111 (Hydrolysis as a Function of pH)

Test guideline 2

Qualifier:

according to guideline

Guideline:

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

Test guideline 3

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)

Test material

Test material information

Constituent 1

Reference substance name:

Bis-sec-butyl peroxydicarbonate

EC Number:

243-424-3

EC Name:

Bis-sec-butyl peroxydicarbonate

Cas Number:

19910-65-7

Molecular formula:

C10H18O6

IUPAC Name:

2-[({[(butan-2-yloxy)carbonyl]peroxy}carbonyl)oxy]butane

Test material form:

liquid

Specific details on test material used for the study:

The specific details on the test material used for this study were as follows:
Description: clear, colourless liquid
Batch number: 08081B1901
Purity: 99.88%
Expiry I Retest Date: 30 May 2012
Storage Conditions: approximately -20 °C, in the dark

Radiolabelling:

not specified

Study design

Analytical monitoring:

yes

Remarks:

HPLC

Details on sampling:

A plastic, 50 m L volumetric flask was partially filled with acetonitrile and 0.5 g of test item added. This was then diluted to volume with acetonitrile to give a stock solution at a concentration of 1 x 10^4 mg/L. An aliquot of stock solution (15 mL) was diluted to a total volume of 50 mL with acetonitrile to prepare a spike solution at a concentration of 3 x 10^3 mg/L.
Aliquots of the spike solution were then diluted by a factor of 100 using the appropriate buffer solutions, such that a sample solution concentration of 30 mg/L (3.0 x 10^-2 g/L) was achieved,
employing 1 % v/v acetonitrile co-solvent. Successful dissolution was confirmed by a Tyndall beam assessment.
The concentration of each solution did not exceed the lesser of 0.0 1 mol/L or half the estimated water solubility of the test item (7.3 x 10^-2 g/L, WSKOWWIN version 1.42, September 2010, ©
2000 U.S. Environmental Protection Agency).
The test solutions were split into multiple, individual vessels, with duplicate independent vessels being analyzed at each data point. The remaining test solution was also analyzed in duplicate to
provide initial timepoint data.
The solutions were shielded from light whilst maintained at the test temperature.

Buffers:

See "Materials and Methods" section below.

Duration of test

Duration of test 1

Duration:

7 h

pH:

4

Temp.:

25 °C

Initial conc. measured:

ca. 0.017 g/L

Duration of test 2

Duration:

7 h

pH:

7

Temp.:

25 °C

Initial conc. measured:

ca. 0.031 g/L

Duration of test 3

Duration:

5 h

pH:

9

Temp.:

25 °C

Initial conc. measured:

ca. 0.016 g/L

Duration of test 4

Duration:

30 h

pH:

4

Temp.:

15 °C

Initial conc. measured:

ca. 0.016 g/L

Duration of test 5

Duration:

30 h

pH:

7

Temp.:

15 °C

Initial conc. measured:

ca. 0.029 g/L

Duration of test 6

Duration:

5 h

pH:

9

Temp.:

15 °C

Initial conc. measured:

ca. 0.026 g/L

Duration of test 7

Duration:

5 h

pH:

1.2

Temp.:

37 °C

Initial conc. measured:

ca. 0.029 g/L

Duration of test 8

Duration:

5 h

pH:

4

Temp.:

37 °C

Initial conc. measured:

ca. 0.015 g/L

Duration of test 9

Duration:

5 h

pH:

7

Temp.:

37 °C

Initial conc. measured:

ca. 0.027 g/L

Duration of test 10

Duration:

2 h

pH:

9

Temp.:

37 °C

Initial conc. measured:

ca. 0.023 g/L

Number of replicates:

2 replicates per pH per temperature

Positive controls:

not specified

Negative controls:

not specified

Results and discussion

Transformation products:

yes

Identity of transformation products

No.:

#1

Reference

Reference substance name:

Unnamed

IUPAC name:

butan-2-ol

Inventory number:

InventoryMultipleMappingImpl [inventoryEntryValue=EC 201-158-5]

CAS number:

78-92-2

Dissipation DT50 of parent compound

Dissipation DT50 of parent compound 1

Key result

pH:

1.2

Temp.:

37 °C

Hydrolysis rate constant:

0 s-1

DT50:

83 min

Type:

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

Dissipation DT50 of parent compound 2

Key result

pH:

4

Temp.:

15 °C

Hydrolysis rate constant:

0 s-1

DT50:

6.22 h

Type:

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

Dissipation DT50 of parent compound 3

Key result

pH:

4

Temp.:

25 °C

Hydrolysis rate constant:

0 s-1

DT50:

2.05 h

Type:

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

Dissipation DT50 of parent compound 4

Key result

pH:

4

Temp.:

37 °C

Hydrolysis rate constant:

0 s-1

DT50:

54 min

Type:

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

Dissipation DT50 of parent compound 5

Key result

pH:

7

Temp.:

15 °C

Hydrolysis rate constant:

0 s-1

DT50:

8.37 h

Type:

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

Dissipation DT50 of parent compound 6

Key result

pH:

7

Temp.:

25 °C

Hydrolysis rate constant:

0 s-1

DT50:

3.83 h

Type:

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

Dissipation DT50 of parent compound 7

Key result

pH:

7

Temp.:

35 °C

Hydrolysis rate constant:

0 s-1

DT50:

94 min

Type:

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

Dissipation DT50 of parent compound 8

Key result

pH:

9

Temp.:

15 °C

Hydrolysis rate constant:

0 s-1

DT50:

100 min

Type:

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

Dissipation DT50 of parent compound 9

Key result

pH:

9

Temp.:

25 °C

Hydrolysis rate constant:

0 s-1

DT50:

33 min

Type:

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

Dissipation DT50 of parent compound 10

Key result

pH:

9

Temp.:

37 °C

Hydrolysis rate constant:

0.002 s-1

DT50:

7 min

Type:

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

Any other information on results incl. tables

Testing at 25.0± 0.5 °C

Slope = -0. 147

k_obs = 0.338 hour^-1

= 9.38 x 10^-5 second^-1

t_1/2 = 2.05 hours

pH 7 at 25.0 ± 0.5°C

Slope = -7.86 x 10^-2

k_obs= 0. 181 hour^-1

= 5.03 x 10^-5 second^-1

t_1/2 = 3.83 hours

pH 9 at 25.0 ± 0.5°C

Data beyond 1.50 hours incubation has been excluded from calculations due t o excessive fluctuation at the trace concentrations remaining. In addition, the 1.00 hour replicate A sample has been excluded from the final correlation due to inconsistency.

Slope = -0.553

k_obs= 1.27 hour^-1

= 3.54 x 10^-4 second^-1

t_1/2 = 0.544 hours

= 33 minutes

pH 4 at 15.0 ± 0.5°C

Slope = -4.84 x 10^-2

k_obs= 0. 112 hour^-1

= 3.10 x 10^-5 second^-1

t_1/2= 6.22 hours

pH 7 at 15.0 ± 0.5°C

Slope = -3.60 x 10^-2

k_obs= 8.29 x 10^-2 hour^-1

= 2.30 x 10^-5 second^-1

t_1/2= 8.37 hours

pH 9 at 15.0 ± 0.5°C

Slope = -0. 180

k_obs= 0.414 hour^-1

= 1.15 x 10^-4 second^-1

t_1/2= 1.67 hours

= 100 minutes

pH 1.2 at 37.0 ± 0.5°C

Slope = -0.218

k_obs= 0.503 hour^-1

= 1.40 x 10^-4second^-1

t_1/2= 1.38 hours

= 83 minutes

pH 4 at 37.0 ± 0.5°C

Slope = -0.332

k_obs= 0.765 hour^-1

= 2.12 x 10^-4second^-1

t_1/2= 0.907 hours

= 54 minutes

pH 7 at 37.0 ± 0.5°C

Slope = -0.192

k_obs= 0.442 hour^-1

= 1.23 x 10^-4second^-1

t_1/2= 1.57 hours

= 94 minutes

pH 9 at 37.0 ± 0.5°C

Slope = -2.61

k_obs= 6.02 hour^-1

= 1.67 x 10^-3second^-1

t_1/2= 0.115 hours

= 7 minutes

On generation of an Arrhenius plot for each pH where 3 individual temperatures have been employed, a further estimation of the rate constant and estimated half-life at 25 °C of the test item can be obtained from the data set as a whole. This further data evaluation resulted in values as shown in the following table:

pH	Rate constant (s^-1)	Estimated half-life at 25 °C
4	8.22 x 10^-5	2.34 hrs
7	5.06 x 10^-5	3.80 hrs
9	3.89 x 10^-4	30 mins

As the test item could be readily predicted to hydrolyses, and to limit the influence of possible thermal degradation mechanisms, testing was initiated directly at 25 °C as opposed to performing a preliminary test at 50 °C. Testing was then performed at 15 °C, reducing the hydrolysis rate and also generating information beneficial to ecotoxicology assessments. For the final of the total of three individual temperatures differing by at least 10 °C required by the test guidelines, 37 °C was selected (as opposed to 35 °C) due to its value in assessing the influence of hydrolysis on mammalian toxicology studies.

The kinetics of the study have been determined to be consistent with that of a pseudo-first order reaction as the graphs of log₁₀ concentration versus time were straight lines. Over the environmentally relevant pH range of 4 to 9, it was observed that the rate of hydrolysis increased with a move away from a neutral pH, but accelerated significantly under basic conditions.

Identification of Hydrolysis Products: Results

The sec-butanol concentrations are shown in the following table:

Sample	Concentration (M)
Hydrolyzed pH 4 sample solution	2.52 x 10^-4
Hydrolyzed pH 7 sample solution	2.55 x 10^-4
Hydrolyzed pH 9 sample solution	2.53 x 10^-4

Based on the test item molecular weight of 234.25 and an initial sample solution concentration of 3.00 x 10^-2 g/L, this equates to an initial test item concentration of 1.27 x 10^-4 M. The conversion rate for each hydrolyzed sample from test item to sec-butanol is subsequently summarized in the following table:

Sample	Sec-Butanol Generation (M per M of test item)
pH 4	1.97
pH 7	1.99
pH 9	1.97

This therefore confirmed hydrolysis of the test item to sec-butanol by both acidic and basic mechanisms, with essentially 100% mass balance for the initial sample solution concentration achieved.

The remaining central peroxydicarbonic acid was considered to degrade further, possibly through a series of highly unstable intermediates, to carbon dioxide under acidic conditions and potentially a mixture of carbon dioxide and oxygen under basic conditions.

Analysis was performed on completely hydrolyzed samples, as sec-butanol may potentially have been generated from any residual parent test item present by thermal decomposition during the

analytical technique employed.

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Conclusions:

The hydrolysis characteristics of the test item at pH 4, pH 7 and pH 9 have been evaluated at temperatures of 15.0± 0.5 °C, 25.0± 0.5 °C and 37.0± 0.5 °C. In addition, the hydrolysis characteristics of the test item under the physiologically relevant conditions of pH 1.2 at 37.0± 0.5 °C have also been evaluated. The results are summarized below:
At 15 ± 0.5 °C:
pH Rate constant (s^-1) Half-life
1.2 - -
4 3.10 x 10^-5 6.22 hrs
7 2.30 x 10^-5 8.37 hrs
9 1.15 x 10^-4 100 mins

At 25 ± 0.5 °C:
pH Rate constant (s^-1) Half-life
1.2 - -
4 9.38 x 10^-5 2.05 hrs
7 5.03 x 10^-5 3.83 hrs
9 3.54 x 10^-4 33 mins

At 37 ± 0.5 °C:
pH Rate constant (s^-1) Half-life
1.2 1.40 x 10^-4 83 mins
4 2.12 x 10^-4 54 mins
7 1.23 x 10^-4 94 mins
9 1.67 x 10^-3 7 mins

On generation of an Arrhenius plot for each pH where 3 individual temperatures have been employed, a further estimation of the rate constant and estimated half-life at 25 °C of the test item can be obtained from the data set as a whole. This further data evaluation resulted in values as shown below:
pH Rate constant (s^-1) Half-life
4 8.22 x 10^-5 2.34 hrs
7 5.06 x 10^-5 3.80 hrs
9 3.89 x 10^-4 30 mins

The test item has been positively identified to hydrolyze to sec-butanol by both acidic and basic mechanisms, with a mass balance/conversion factor of 2 moles of sec-butanol (actual experimental range 1.97 to 1.99) per mol of initial parent test item. The remaining central peroxydicarbonic acid was considered to degrade further, possibly through a series of highly
unstable intermediates, to carbon dioxide under acidic conditions and potentially a mixture of carbon dioxide and oxygen under basic conditions.

Executive summary:

The hydrolysis characteristics of Di-sec-butyl Peroxydicarbonate (CAS# 199 10-65-7), as a function of pH, have been determined.

Assessment of hydrolytic stability was carried out using a procedure designed to be compatible with Method C7 Abiotic Degradation, Hydrolysis as a Function of pH of Commission Regulation (EC) No 440/2008 of 30 May 2008, Method 1 1 1 of the OECD Guidelines for Testing of Chemicals, 13 April 2004 and Method 835.2 120 of the OPPTS Guidelines. The results of individual tests and specified test temperatures and pH's were as follows:

pH	15±0.5 °C		25.0±0.5 °C		37.0±0.5 °C
	Rate constant (s^-1)	Half-life	Rate constant (s^-1)	Half-life	Rate constant (s^-1)	Half-life
1.2	-	-	-	-	1.40 x 10^-4	83 mins
4	3.10 x 10^-5	6.22 hrs	9.38 x 10^-5	2.05 hrs	2.12 x 10^-4	54 mins
7	2.30 x 10^-5	8.37 hrs	5.03 x 10^-5	3.83 hrs	1.23 x 10^-4	94 mins
9	1.15 x 10^-4	100 mins	3.54 x 10^-4	33 mins	1.67 x 10^-3	7 mins

On generation of an Arrhenius plot for each pH where 3 individual temperatures have been employed, a further estimation of the rate constant and estimated half-life at 25 °C of the test item can be obtained from the data set as a whole. This further data evaluation resulted in values as shown in the following table:

pH	Rate constant (s^-1)	Estimated half-life at 25 °C
4	8.22 x 10-5	2.34 hrs
7	5.06 x 10-5	3.80 hrs
9	3.89 x 10-4	30 mins

The test item has been positively identified to hydrolyze to sec-butanol by both acidic and basic mechanisms, with a mass balance/conversion factor of 2 moles of sec-butanol (actual experimental range 1.97 to 1.99) per mol of initial parent test item. The remaining central peroxydicarbonic acid was considered to degrade further, possibly through a series of highly unstable intermediates, to carbon dioxide under acidic conditions and potentially a mixture of carbon dioxide and oxygen under basic conditions.