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Hydrolysis

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Reference
Endpoint:
hydrolysis
Type of information:
experimental study
Adequacy of study:
key study
Study period:
20 OCT 2004 - 13 OCT 2004
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)
Deviations:
not specified
GLP compliance:
yes (incl. QA statement)
Remarks:
SafePharm Laboratories Ltd., Shardlow, Derbyshire, UK
Specific details on test material used for the study:
Details on properties of test surrogate or analogue material:
No details on properties of test surrogate or analogue material.
PHYSICO-CHEMICAL PROPERTIES
- Vapour pressure:
- Water solubility:
- log Pow:
- pKa:
- Base or acid catalysis of test material:
- UV absorption:
- Stability of test material at room temperature:


OTHER PROPERTIES (if relevant for this endpoint)
Radiolabelling:
not specified
Analytical monitoring:
yes
Details on sampling:
Aliquots of the sample solutions were taken from the flasks at various times and the pH of each solution recorded.
No further details on sampling.
Buffers:
- pH: information not available
- Type and final molarity of buffer: no data
- Composition of buffer:

Buffer sol. Components Concentration (mmol/L)
---------------------------------------------------------
4 Potassium hydrogen phthalate: 2.5
7 Disodium hydrogen orthophosphate (anhydrous): 1.5
Potassium dihydrogen orthophosphate: 1
Sodium chloride: 1
9 Disodium tetraborate: 0.5
Sodium chloride: 1
Details on test conditions:
TEST SYSTEM
- Type, material and volume of test flasks, other equipment used: information not available
- Sterilisation method: filtration through a 0.2 µm membrane filter
- Lighting: no data
- Measures taken to avoid photolytic effects: shielded from light
- Measures to exclude oxygen: ultrasonication and degassing with nitrogen
- Details on test procedure for unstable compounds: no data
- Details of traps for volatile, if any: no data
- If no traps were used, is the test system closed/open: no data
- Is there any indication of the test material adsorbing to the walls of the test apparatus? information not available

TEST MEDIUM
- Volume used/treatment: no data
- Kind and purity of water: information not available
- Preparation of test medium: Sample solutions were prepared in stoppered glass flasks at a nominal concentration of 0.05 g/L in the three buffer
solutions. A 1% co-solvent of acetonitrile was used to aid solubility. The solutions were shielded from light while maintained at the test temperature
- Renewal of test solution: no data
- Identity and concentration of co-solvent: 1% acetonitrile

OTHER TEST CONDITIONS
- Adjustment of pH: no data
- Dissolved oxygen: no data
Duration:
0 h
pH:
7
Initial conc. measured:
0.051 g/L
Duration:
120.5 h
pH:
7
Initial conc. measured:
0.015 g/L
Duration:
0 h
pH:
7
Initial conc. measured:
0.051 g/L
Duration:
47 h
pH:
7
Initial conc. measured:
0.013 g/L
Duration:
0 h
pH:
9
Initial conc. measured:
0.05 g/L
Duration:
120 h
pH:
9
Initial conc. measured:
0.027 g/L
Duration:
0 h
pH:
9
Initial conc. measured:
0.051 g/L
Duration:
48 h
pH:
9
Initial conc. measured:
0.02 g/L
Number of replicates:
1
Positive controls:
not specified
Negative controls:
not specified
Statistical methods:
no data
Preliminary study:
Sample solutions at pH 4 and 7 were maintained at 50.0 ± 0.5°C for a period of 120 and 360 hours, respectively. As rapid hydrolysis was expected at pH 9, no preliminary test was undertaken.
Results:
pH4 - Less than 10% hydrolysis after 5 days at 50°C, equivalent to a half-life greater than 1 year at 25°C.
pH7 - The extent of hydrolysis after 360 hours indicated that a further test was required to estimate the rate constant and half-life [please see also "Remarks on results including tables and figures" - 1) Preliminary test]
Test performance:
Results from the preliminary test showed it was necessary to undertake further testing at pH 7, with solutions being maintained at 60 and 70 ± 0.5°C. This was due to the hydrolysis rate being greater than 10% after 5 days at 50°C. Due to the anticipated rapid hydrolysis at pH 9, solutions were
maintained at 20 and 30 ± 0.5°C.
Graphs of the common logarithm of the concentration (g/L) versus time (hours) were plotted for pH 7 and pH 9 and the rate constant and half-life calculated. By plotting the natural logarithm of the rate constants against the reciprocal of the temperature (K), the rate constant and half-lives at
25°C were obtained by either interpolation or extrapolation.
Transformation products:
not measured
Details on hydrolysis and appearance of transformation product(s):
No details on hydrolysis and appearance of transformation product(s).
% Recovery:
29.7
pH:
7
Temp.:
60 °C
Duration:
120.5 h
% Recovery:
25.3
pH:
7
Temp.:
70 °C
Duration:
47 h
% Recovery:
53.8
pH:
9
Temp.:
20 °C
Duration:
120 h
% Recovery:
39.3
pH:
9
Temp.:
30 °C
Duration:
48 h
pH:
7
Temp.:
60 °C
Hydrolysis rate constant:
86.4 a-1
DT50:
69 h
Type:
(pseudo-)first order (= half-life)
Remarks on result:
other: slope = -4.36 x 10e-3
pH:
7
Temp.:
70 °C
Hydrolysis rate constant:
253.2 a-1
DT50:
23.7 h
Type:
(pseudo-)first order (= half-life)
Remarks on result:
other: slope = -1.27 x 10e-3
pH:
9
Temp.:
20 °C
Hydrolysis rate constant:
45.2 a-1
DT50:
133 h
Type:
(pseudo-)first order (= half-life)
Remarks on result:
other: slope = -2.27 x 10e-3
pH:
9
Temp.:
30 °C
Hydrolysis rate constant:
165.9 a-1
DT50:
36 h
Type:
(pseudo-)first order (= half-life)
Remarks on result:
other: slope = -8.36 x 10e-3
Other kinetic parameters:
none
Details on results:
TEST CONDITIONS
No details on test conditions.


MAJOR TRANSFORMATION PRODUCTS
No details on major transformation products.


MINOR TRANSFORMATION PRODUCTS
No details on major transformation products.


MINERALISATION (distinguish between dark and irradiated samples)
- % of applied radioactivity present as CO2 at end of study: not applicable


INDICATION OF UNSTABLE TRANSFORMATION PRODUCTS:
no data

VOLATILIZATION (at end of study)
- Evolved CO2 in % of the applied: no data
- Total volatile organics in % of the applied: no data


UNIDENTIFIED RADIOACTIVITY (at end of study)
not applicable


PATHWAYS OF HYDROLYSIS
- Description of pathwayS: no description available
- Figures of chemical structures attached: No

1) Preliminary test

The test material concentrations at the given time points are shown in the following tables:

pH 4 at 50.0 ± 0.5°C

Time (hrs)
  0 24 120
Conc. (g/L) 5.03 x 10-2 4.99 x 10-2 4.97 x 10-2
% of initial - 99.3 98.9

Result: Less than 10% hydrolysis after 5 days at 50°C, equivalent to a half-life greater than 1 year at 25°C.

pH 7 at 50.0 ± 0.5°C

Time (hrs) Conc. (g/L) Log 10 conc. (g/L) % of initial
0 5.03 x 10-2 -1.30 -
24 4.60 x 10-2 -1.34 91.5
96 3.64 x 10-2 -1.44 72.4
192 2.86 x 10-2 -1.54 57.0
264 2.41 x 10-2 -1.62 48.0
360 1.72 x 10-2 -1.76 34.3

Result: Slope = -1.25 x 10-3

kobs = 2.87 x 10-3 hour-1 = 7.97 x 10-7 second-1

t1/2 = 242 hours

The extent of hydrolysis after 360 hours indicated that a further test was required to estimate the rate constant and half-life.

2) Definitive Test

The test material concentrations at the given time points are shown in the following tables:

pH 7 at 60.0 ± 0.5°C

Time (hrs) Conc. (g/L) Log 10 conc. (g/L) % of initial
0 5.15 x 10-2 -1.29 -
23.5 3.98 x 10-2 -1.40 77.3
72.5 2.42 x 10-2 -1.62 47.0
120.5 1.53 x 10-2 -1.82 29.7

Result: Slope = -4.36 x 10-3

kobs = 1.00 x 10-2 hour-1 = 2.79 x 10-6 second-1

t1/2 = 69.0 hours

pH 7 at 70.0 ± 0.5°C

Time (hrs) Conc. (g/L) Log 10 conc. (g/L) % of initial
0 5.13 x 10-2 -1.29 -
23.5 2.55 x 10-2 -1.59 49.6
29.0 2.15 x 10-2 -1.67 41.9
47.0 1.30 x 10-2 -1.87 25.3

Result: Slope = -1.27 x 10-2

kobs = 2.93 x 10-2 hour-1 = 8.14 x 10-6 second-1

t 1/2 = 23.7 hours

The Arrhenius plot was constructed using the data shown in the following tables:

pH 7 Arrhenius Data

T (°C) 50 60 70
T (K) 323 333 343
1/T (1/K) 3.10x10-3 3.00 x 10-3 2.91 x 10-3
1 kobs (hr-1) 2.87x10-3 1.00 x 10-2 2.93 x 10-2
ln kobs -5.85 -4.60 -3.53

From the graph of the above data, the rate constant and half-life at 25°C have been estimated to be as follows:

kobs = 1.03 x 10-4 hour-1 = 2.87 x 10-8 second-1

t1/2 = 6.72 x 103 hours = 280 days

pH 9 at 20.0 ± 0.5°C

Time (hrs) Conc. (g/L) Log 10 conc. (g/L) % of initial
0 5.04 x 10-2 -1.30 -
22 4.35 x 10-2 -1.36 86.4
49 3.76 x 10-2 -1.42 74.8
73 3.18 x 10-2 -1.50 63.2
120 2.71 x 10-2 -1.57 34.3

Result: Slope = -2.27 x 10-3

kobs = 5.23 x 10-3 hour-1 = 1.45 x 10-6 second-1

t1/2 = 133 hours

pH 9 at 30.0 ± 0.5°C

Time (hrs) Conc. (g/L) Log 10 conc. (g/L) % of initial
0 5.07 x 10-2 -1.30 -
24 4.80 x 10-2 -1.32 94.5
96 4.40 x 10-2 -1.36 86.8
192 3.10 x 10-2 -1.51 61.1
360 1.99 x 10-2 -1.70 39.3

Result: Slope = -8.36 x 10-3

kobs = 1.92 x 10-2 hour-1 = 5.35 x 10-6 second-1

t1/2 = 36.0 hours

pH 9 Arrhenius Data

T (°C) 20 30
T (K) 293 303
1/T (1/K) 3.41 x 10-3 3.30 x 10-3
1 kobs (hr-1) 5.23 x 10-3 1.92 x 10-2
ln kobs -5.25 -3.95

From the graph of above data, the rate constant and half-life at 25°C have been estimated to be as follows:

kobs = 1.01 x 10-2 hour-1 = 2.82 x 10-6 second-1

t1/2 = 68.4 hours

Validity criteria fulfilled:
not specified
Remarks:
see also "Overall remarks - Validation"
Conclusions:
It has been observed that the rate of hydrolysis increases with an increase in pH. The following half-lives (at 25°C) were obtained for the test
substance:
- t1/2 (pH4) > 1 year
- t1/2 (pH7) = 280 day(s)
- t1/2 (pH9) = 68.4 hour(s)
Executive summary:

The abiotic hydrolysis of the test substance 'Diallyl 2,2'-oxydiethyl dicarbonate' as a function of pH and at a nominal concentration of 0.05g/L was studied. The study was conducted following OECD Guideline111 under GLP.

The test was performed in sterile buffer solutions of pH4 (phthalate buffer), pH7 (phosphate buffer), and pH9 (borate buffer) at different temperatures. Samples of the test substance were analyzed at the start and end of the tests using HPLC with MS detection.

It has been observed that the rate of hydrolysis increases with an increase in pH, whereas the following half-lives (at 25°C) were obtained for the test substance:

- t1/2 (pH4) > 1 year

- t1/2 (pH7) = 280 day(s)

- t1/2 (pH9) = 68.4 hour(s)

Description of key information

The abiotic hydrolysisof the test substance 'Diallyl 2,2'-oxydiethyl dicarbonate'as afunctionofpHand atanominal concentrationof 0.05g/Lwas studied.The study was conductedfollowing OECDGuideline111 under GLP.

The testwas performedin sterile buffer solutions ofpH4(phthalatebuffer), pH7 (phosphatebuffer), and pH9 (borate buffer) at different temperatures. Samples of the test substance were analyzed at the start and end of the tests using HPLC with MS detection.

It has been observed that the rate of hydrolysis increases with an increase in pH, whereas the following half-lives (at 25°C) were obtained for the test substance:

- t1/2(pH4) > 1 year

- t1/2(pH7) = 280 day(s)

- t1/2(pH9) = 68.4 hour(s)

Key value for chemical safety assessment

Half-life for hydrolysis:
280 d
at the temperature of:
25 °C

Additional information