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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
Study period:
2001
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 111 (Hydrolysis as a Function of pH)
Principles of method if other than guideline:
The study was conducted at 1.5 °C ± 0.5 °C to slow the hydrolysis reaction rate.
GLP compliance:
no
Radiolabelling:
no
Analytical monitoring:
yes
Buffers:
Buffer solutions of known pH and concentration were prepared by titration of acetic acid, sodium phosphate monobasic and boric acid solution with sodium hydroxide solution. Constant ionic strength of 0.5 M was maintained for buffers by the addition of volumes of 5 M sodium nitrate solution.
Number of replicates:
One replicate per pH level
Transformation products:
not specified
Details on hydrolysis and appearance of transformation product(s):
pH 4: t1/2= 6s, pH 7: t1/2= 10s, pH 9: t1/2= 8s
pH:
4
Temp.:
1.5 °C
DT50:
0.1 min
pH:
7
Temp.:
1.5 °C
DT50:
0.167 min
pH:
9
Temp.:
1.5 °C
DT50:
0.133 min

No rate constant or definative t1/2 determined due to rapidity of hydrolysis (sparse data points for 20-70% hydrolysed). Upper limit t1/2 estimated (assuming first hydrolysis step is rate-limiting). Observation of stable[Cl-] was used to estimate t1/2; assumed 10 half-lives = exhaustive hydrolysis.

Conclusions:
The half life of the test substance was reported to be 6 seconds at pH 4, 10 seconds at pH 7 and 8 seconds at pH 9.

Description of key information

Hydrolysis half-life in water: 10 seconds at pH 7 and 1.5°C

Key value for chemical safety assessment

Half-life for hydrolysis:
0.167 min
at the temperature of:
1.5 °C

Additional information

The test substance hydrolyses very rapidly. The half-life of the test substance was reported to be 6 seconds at pH 4, 10 seconds at pH 7 and 8 seconds at pH 9 (Dow Corning, 2001). This study was conducted according to a standard guideline and is considered reliable for assessment. The hydrolysis products are diphenylsilanediol and hydrochloric acid.