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Environmental fate & pathways

Hydrolysis

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Reference
Endpoint:
hydrolysis
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Reason / purpose:
reference to same study
Qualifier:
according to
Guideline:
OECD Guideline 111 (Hydrolysis as a Function of pH)
Deviations:
no
GLP compliance:
yes (incl. certificate)
Radiolabelling:
no
Analytical monitoring:
yes
Details on sampling:
Sample solutions were prepared in stoppered glass flasks at a nominal concentration of 0.05 g/L in three buffer solutions at pH 4, 7 and 9; acetonitrile was added at 1% to improve solubility. The solutions were shielded from light during testing. In the preliminary test samples solutions were kept at 50˚C and in the definitive test at 25˚C (tested only at pH=9). Aliquots of the sample solutions were taken at each time point.
Buffers:
pH=4: potassium hydrogen phthalate (0.01 mol/dm³)
pH=7: disodium hydrogen orthophosphate, anhydrous (0.006 mol/dm³); Potassium dihydrogen orthophosphate (0.004 mol/dm³); sodium chloride (0.004 mol/dm³)
pH=9: disodium tetraborate (0.002 mol/dm³); sodium chloride (0.004 mol/dm³)
Estimation method (if used):
From the graph of log10 concentration (g/1) versus time, the rate constant was calculated using Equation kobs =-slope x 2,303 and the half-life wa obtained from the rate constant using Equation t1/2, =- 0.693/kobs.
Duration:
240 h
pH:
9
Temp.:
25
Initial conc. measured:
>= 0.025 - <= 0.053 g/L
Number of replicates:
2
Preliminary study:
Result pH 4 at 50.0 ± 0.5°C: Less than 10% hydrolysis after 5 days, equivalent to a half-life greater than 1 year at 25°C.
Result pH 7 at 50.0 ± 0.5°C: Less than 10% hydrolysis after 5 days, equivalent to a half-life greater than 1 year at 25°C.
Result pH 9 at 50.0 ± 0.5°C: More than 70% hydrolysis within 24 h, Slope  = -2.32 x 10-2.hour-1(see page 23)
At pH=9: Kobs = 5.34E-2.h-1 (= 1.48E-5.s-1); t½ = 13.0 at 50°C.
The extent of hydrolysis at pH=9 after 24 hours at 50°C indicated that further testing was required at 25°C.
Transformation products:
yes
No.:
#1
No.:
#2
Details on hydrolysis and appearance of transformation product(s):
Result pH 9 at 25.0 ± 0.5°C: 53.5 % hydrolysis within 240 h.
Using a combination of HPLC with LCMS and GCMS, the degradation products were determined experimentally.
% Recovery:
46.5
pH:
9
Temp.:
25 °C
Duration:
240 h
pH:
4
Temp.:
25 °C
DT50:
> 1 yr
Type:
not specified
Key result
pH:
7
Temp.:
25 °C
DT50:
> 1 yr
Type:
not specified
pH:
9
Temp.:
25 °C
Hydrolysis rate constant:
0 s-1
DT50:
217 h
Type:
not specified
Other kinetic parameters:
Slope  = -1.39E-3.h (see page 26)
Kobs = 3.20E-3.h-1 (= 8.88E-7.s-1); t½ = 217 h or 9.04 d at 25°C.
Validity criteria fulfilled:
not specified
Conclusions:
The rate constant and estimated half-life at 25°C of diallyl phthalate was > 1 year at and below pH 7, while increasing the pH above 7 decreased the estimated half life to about 217 hours at pH=9 with a rate constant of hydrolysis= 8.88E-7 per second.

Description of key information

Information of the hydrolysis of diallyl phathalate is based on the results of recent experimental testing performed under GLP. The key value is based on data for hydrolysis at pH=7.

Key value for chemical safety assessment

Half-life for hydrolysis:
1 yr
at the temperature of:
25 °C

Additional information

The rate constant and estimated half-life at 25°C of diallyl phthalate was > 1 year at and below pH 7, while increasing the pH above 7 decreased the estimated half life to about 217 hours at pH=9 with a rate constant of hydrolysis= 8.88E-7.