Di-tert-butyl sec-butylidene diperoxide

Hydrolysis

Link to relevant study record(s)

Reference

Endpoint:

hydrolysis

Type of information:

experimental study

Adequacy of study:

key study

Study period:

Experimental starting date 20-05-2014 Experimental completion date 26-11-2015

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)

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

The details of the test material used for the study were as follows:
Batch/Lot no.: 1211442406
Water solubility: 8.3 mg/L (AkzoNobel, 2013)
Appearance: Colorless, clear liquid
Expiry date: December 1, 2022
Storage: Approx. 5°C

Radiolabelling:

not specified

Analytical monitoring:

yes

Remarks:

HPLC

Buffers:

Sterile test buffer solutions of pH 4, 7 and 9 were prepared in glass bottles according to the description in Annex 3 of OECD 111 and purged with nitrogen for at least 5 minutes.

Details on test conditions:

Chemicals
All chemicals used were of reagent grade, unless stated otherwise. Buffer solutions of different pH values were prepared according to the information as described in Annex 3 of OECD 111.
Materials
Glassware and buffer solutions were sterilised. Test solutions were flushed with nitrogen to minimise oxidation. Test vessels were kept under dark conditions. A temperature-controlled water bath was used; temperature was measured using a calibrated thermometer, pH was measured using a pH meter.

Duration:

120 h

pH:

4

Temp.:

50 °C

Initial conc. measured:

1.9 mg/L

Duration:

120 h

pH:

7

Temp.:

50 °C

Initial conc. measured:

1.8 mg/L

Duration:

120 h

pH:

9

Temp.:

50 °C

Initial conc. measured:

1.7 mg/L

Number of replicates:

For Tier 2 testing, 2 replicates per pH per temperature.

Positive controls:

not specified

Negative controls:

not specified

Preliminary study:

The screening hydrolysis study was performed separately for each pH value tested. Results of the different pH values are displayed below.

pH 4
The pH value at the start of the test was measured to be 4.0. The temperature during the test varied between 49.9 and 50.1°C. It was observed that more than 90% of the test substance was hydrolysed
after 1 hour.

pH 7
The pH value at the start of the test was measured to be 7.1. The temperature during the test varied between 49.9 and 50.1°C. It was observed that 41% of the test substance was hydrolysed after 5 days.

pH 9
The pH value at the start of the test was measured to be 9.1. The temperature during the test varied between 50.0 and 50.1°C. It was observed that less than 10% of the test substance was hydrolysed after 5 days.

As more than 10% of hydrolysis after 5 days was observed for pH values 4 and 7, also Tier 2 had to be performed for these pH values.

Transformation products:

not specified

% Recovery:

>= 90 - < 100

pH:

9

Temp.:

50 °C

Duration:

120 h

Remarks on result:

hydrolytically stable based on preliminary test

Key result

pH:

4

Temp.:

10 °C

Hydrolysis rate constant:

0.026 h-1

DT50:

26 h

Type:

not specified

Key result

pH:

4

Temp.:

30 °C

Hydrolysis rate constant:

0.005 min-1

DT50:

2 h

Type:

not specified

Key result

pH:

4

Temp.:

50 °C

Hydrolysis rate constant:

0.046 min-1

DT50:

0.3 h

Type:

not specified

Key result

pH:

7

Temp.:

10 °C

Hydrolysis rate constant:

>= 0.002 - <= 0.004 d-1

DT50:

>= 167 - <= 430 d

Type:

not specified

Key result

pH:

7

Temp.:

30 °C

Hydrolysis rate constant:

ca. 0.014 d-1

DT50:

ca. 49 d

Type:

not specified

Key result

pH:

7

Temp.:

50 °C

Hydrolysis rate constant:

0.093 d-1

DT50:

7 d

Type:

not specified

Hydrolysis of unstable substances (Tier 2):

pH 4

Temperature 10°C

The temperature throughout the test was measured to be 10.0°C. The pH of the buffer solution was measured at the start of the test and was 4.0. After 77.5 hours more than 85% of hydrolysis was observed.

Time hours	Replicate I			Replicate II
	Concentration (Ct) mg/L	Log Ct	Hydrolysis %	Concentration (Ct) mg/L	Log Ct	Hydrolysis %
0	1.6	0.21	0.0	1.6	0.20	0.0
2	1.4	0.15	13.3	1.5	0.18	5.6
4	1.4	0.15	12.5	1.4	0.15	11.6
6	1.3	0.13	18.2	1.4	0.14	13.5
24	0.8	-0.11	52.0	0.8	-0.10	49.8
30	0.7	-0.18	59.2	0.7	-0.16	57.0
48	0.4	-0.40	75.8	0.4	-0.36	72.4
54	0.3	-0.52	81.3	0.3	-0.50	80.2
77.5	0.2	-0.62	85.3	0.2	-0.65	86.1

The results were used to calculate the half-life (t_0.5), applying the Arrhenius relationship. The average half-life was calculated to be 26 hours.

Temperature 30°C

The temperature during the test varied between 29.9 and 30.0°C. The pH of the buffer solution was measured at the start of the test and was 4.0. After 350 minutes between 84 and 89% of hydrolysis was observed.

Time Min.	Replicate I			Replicate II
	Concentration (Ct) mg/L	Log Ct	Hydrolysis %	Concentration (Ct) mg/L	Log Ct	Hydrolysis %
0	1.7	0.22	0.0	1.6	0.21	0.0
25	1.4	0.14	18.1	1.3	0.11	21.0
50	1.2	0.08	27.5	1.1	0.05	31.3
75	1.1	0.04	34.9	1.0	0.00	38.6
100	1.0	-0.02	43.1	0.8	-0.10	51.5
125	0.8	-0.10	52.7	0.7	-0.14	56.0
175	0.6	-0.20	62.5	0.6	-0.25	65.5
250	0.4	-0.38	74.8	0.3	-0.50	80.6
350	0.3	-0.58	84.1	0.2	-0.74	88.8

The results were used to calculate the half-life (t_0.5), applying the Arrhenius relationship. The average half-life was calculated to be 2 hours.

Temperature 50°C

The temperature during the test varied between 50.0 and 50.1°C. The pH of the buffer solution was measuredat the start of the test and was 4.0. After 75 minutes more than 94% of hydrolysis was observed.

Time Min.	Replicate I			Replicate II
	Concentration (Ct) mg/L	Log Ct	Hydrolysis %	Concentration (Ct) mg/L	Log Ct	Hydrolysis %
0	1.7	0.24	0.0	1.7	0.24	0.0
25	0.6	-0.23	65.9	0.6	-0.20	63.8
50	0.2	-0.75	89.7	0.2	-0.75	89.9
75	<LOQ	-1.06	95.0	0.1	-0.98	94.0
100	<LOQ	-1.17	96.1	<LOQ	-1.39	97.7

The results were used to calculate the half-life (t_0.5), applying the Arrhenius relationship. The average half-life was calculated to be 0.3 hours.

Using the determined half-lives at the different test temperatures an interpolation curve was composed. Using the equation of this interpolation curve, the half-life at a temperature of 25°C was interpolated to be 4 hours.

pH 7

Temperature 10°C

The temperature throughout the test varied between 9.9 and 10.0°C. The pH of the buffer solution was measured at the start of the test and was 7.0. After 30 days between 3 and 12% of hydrolysis was observed.

Time days	Replicate I			Replicate II
	Concentration (Ct) mg/L	Log Ct	Hydrolysis %	Concentration (Ct) mg/L	Log Ct	Hydrolysis %
0	1.8	0.24	0.0	1.9	0.27	0.0
3	1.8	0.27	-5.4	1.8	0.26	2.5
6	1.7	0.24	1.4	1.8	0.25	5.1
10	1.7	0.24	1.4	1.7	0.24	7.3
16	1.8	0.25	-2.7	1.8	0.26	3.3
20	1.7	0.23	2.3	1.7	0.24	8.7
24	1.7	0.23	3.0	1.6	0.21	13.9
30	1.7	0.23	3.3	1.7	0.22	11.7

The results were used to calculate the half-life (t_0.5), applying the Arrhenius relationship. As the results of the replicates differ significantly, only a range for the half-life was calculated. The half-lives were calculated to be in the range of 167 to 430 days.

Temperature 30°C

The temperature during the test varied between 29.9 and 30.0°C. The pH of the buffer solution was measured at the start of the test and was 7.0. After 30 days between 38 and 41% of hydrolysis was

observed.

Time days	Replicate I			Replicate II
	Concentration (Ct) mg/L	Log Ct	Hydrolysis %	Concentration (Ct) mg/L	Log Ct	Hydrolysis %
0	1.9	0.27	0.0	1.9	0.28	0.0
3	1.6	0.21	13.5	1.6	0.20	16.5
6	1.4	0.14	25.2	1.6	0.19	18.7
10	1.3	0.12	28.9	1.5	0.18	20.8
16	1.3	0.10	32.4	1.4	0.14	27.8
20	1.2	0.08	35.6	1.3	0.10	34.4
24	1.2	0.08	35.9	1.2	0.08	37.7
30	1.2	0.06	38.4	1.1	0.05	40.9

The results were used to calculate the half-life (t_0.5), applying the Arrhenius relationship. The average half-life was calculated to be 46 days.

Temperature 50°C

The temperature during the test was measured to be 50.0°C. The pH of the buffer solution was measured at the start of the test and was 7.0. After 18 days between 83 and 85% of hydrolysis was

observed.

Time days	Replicate I			Replicate II
	Concentration (Ct) mg/L	Log Ct	Hydrolysis %	Concentration (Ct) mg/L	Log Ct	Hydrolysis %
0	1.7	0.23	0.0	2.0	0.30	0.0
1	1.0	0.00	40.5	1.3	0.12	34.7
4	0.9	-0.07	49.7	1.2	0.07	40.8
5	0.8	-0.09	52.5	0.9	-0.07	57.2
7	0.6	-0.21	63.9	0.9	-0.03	53.7
8	0.6	-0.24	66.0	0.8	-0.09	59.3
11	0.5	-0.31	71.2	0.7	-0.16	65.6
15	0.3	-0.50	81.2	0.5	-0.33	76.6
18.1	0.3	-0.59	84.8	0.3	-0.48	83.3

The results were used to calculate the half-life (t_0.5), applying the Arrhenius relationship. The average half-life was calculated to be 8 days.

Using the determined half-lives at the different test temperatures, including the range as calculated for 10°C, interpolation curves were composed. Using the equations of this interpolation curves, the half-lives at a temperature of 25°C was interpolated to be in the range of 58 to 89 days.

Additional experiment

The additional experiment was carried out for pH value 1.2 at 37°C. Results are described below.

Time hours	Concentration mg/L	Hydrolysis* %
0	<LOQ	>95%
0.5	<LOQ	>95%
1	<LOQ	>95%

* Hydrolysis calculated from nominal concentration

The temperature during the test was measured to be 37.0°C. The pH of the buffer solution was measured at the start of the test and was 1.2. From the start of the test up to 1 hour a remaining

concentration of less than limit of quantification was detected and the testing was stopped. Hydrolysis was calculated using the nominal initial concentration and was calculated to be more than 95% from the beginning of the test onwards.

Validity criteria fulfilled:

not specified

Conclusions:

The speed of hydrolysis differs significantly per pH level.
At pH 9 the substance is stable with a half-life > 1 year
at pH 7 half-life is between 58 and 89 days at 25 °C
at pH 4 half-life is 4 hours at 25 °C
at pH 1.2 hydrolysis is instantly at 37 °C.

Executive summary:

The purpose of this study was to determine if the test substance would hydrolyze at environmentally relevant pH values, complying with the OECD Guideline No. 111.

In a preliminary phase of the study (Tier 1) it was observed that the test substance did not hydrolyze significantly at pH 9; less than 10% hydrolysis at 50°C in 5 days was observed. Therefore Tier 2 of the

study was carried out only for the pH values 4 and 7.

An overview of the calculated half-lives of the test substance at the different pH values and tested temperatures is displayed in the table below. Also the interpolated half-lives for the temperature of 25°C

are displayed.

pH value	Temperature °C	Replicate	t1/2 hours
pH 4	10	I	26
		II	26
		Mean	26
	30	I	2
		II	2
		Mean	2
	50	I	0.3
		II	0.3
		Mean	0.3
	25	Interpolated	4
			t1/2days
pH 7	10	I	430
		II	167
		Mean
	30	I	49
		II	44
		Mean	46
	50	I	7
		II	8
		Mean	8
	25	Interpolated	58-89

An additional hydrolysis experiment was carried out for pH value 1.2 at 37°C. Hydrolysis results are displayed in the table below.

Time hours	Concentration mg/L	Hydrolysis* %
0	<LOQ	>95%
0.5	<LOQ	>95%
1	<LOQ	>95%

* Hydrolysis calculated from nominal concentration

Description of key information

The speed of hydrolysis differs significantly per pH level.

At pH 9 the substance is stable with a half-life > 1 year

at pH 7 half-life is between 58 and 89 days at 25 °C

at pH 4 half-life is 4 hours at 25 °C

at pH 1.2 hydrolysis is instantly at 37 °C.

Key value for chemical safety assessment

Half-life for hydrolysis:

89 d

at the temperature of:

25 °C

Additional information

One study is available conducted in compliance with agreed protocols and guidelines (OECD 111). The study report was conclusive, done to a valid guideline and the study was conducted under GLP conditions. The substance was stable at pH 9, rather stale at pH 7 and hydrolytically instable at pH 4.