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Hydrolysis

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Reference
Endpoint:
hydrolysis
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2015-10-09
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study with acceptable restrictions
Remarks:
The study was conducted according to an appropriate OECD test guideline and in compliance with a known quality system (ISO 9001:2008).
Reference:
Composition 0
Qualifier:
according to
Guideline:
EU Method C.7 (Degradation: Abiotic Degradation: Hydrolysis as a Function of pH)
Version / remarks:
In analogy to OECD 111 testing method
GLP compliance:
no
Remarks:
ISO 9001:2008
Test material information:
Composition 1
Radiolabelling:
no
Analytical monitoring:
yes
Details on sampling:
- Sampling method: 2550 µL of the buffer solutions were mixed with 450 µL of deuterated water containing 3-trimethylsilylpropionic acid, sodium salt, 2, 2, 3, 3-tetradeuterated (Na-TSP-d4) , as reference and internal standard. 5 µL of the test substance was then added, mixed and 1 mL of this mixture was filled into a 5 mm NMR sample tube.

Buffers:
Buffer pH4, CertiPur, Citric acid + hydrochloric acid + sodium hydroxide, company Merck
Buffer pH7, Baker Analyzed, Potassium dihydrogen phosphate + disodiumhydrogen phosphate, company J. T. Baker
Buffer pH9, CertiPur, Boronic acid + potassium chloride + sodium hydroxide, company Merck
Details on test conditions:
TEST SYSTEM
- Volume used/treatment : 1 mL of test substance mixed with medium at each pH
- Medium: Water-d2 / Na-TSP-d4 (5014.54 mg D2O + 23.35 mg Na-TSP-d4)
- Type, material and volume of test flasks: 5 mm NMR sample tube

Duration:
50 min
pH:
4
Temp.:
25 °C
Duration:
50 min
pH:
7
Temp.:
25 °C
Duration:
50 min
pH:
9
Temp.:
25 °C
Positive controls:
not specified
Negative controls:
not specified
Transformation products:
yes
No.:
#1
Reference substance:
Composition 1
Key result
pH:
4
Temp.:
25 °C
Half-life:
< 2 min
Type:
not specified
Remarks on result:
other:
Remarks:
a pH value of 4.5 was measured after end of hydrolysis
Key result
pH:
7
Temp.:
25 °C
Half-life:
< 2 min
Type:
not specified
Key result
pH:
9
Temp.:
25 °C
Half-life:
< 2 min
Type:
not specified
Details on results:
At all pH values only signals of sec-butylamine could be observed after the first measurement. There were no signals of aminosilane detectable.
Therefore it was concluded that hydrolysis was already completed when the first spectrum was measured. Because hydrolysis was finished after the first ¹H NMR measurement (about 5 minutes after mixing the test sample), no exact half-life time or reaction rate could be calculated.

Since the signals of the aminosilane should be detectable for at least 3 half-life times (intensity after t1/2: 50%, after 2x t1/2: 25%, after 3x t1/2: 12.5%), the half-life time was estimated for all pH values to be < 2 min (5 min / 3 = 1.7 min ~ 2 min).

The main test showed the following results:

End point Result pH value measured after end of hydrolysis/end of experiments
Half-life time in pH 4 buffer solution  < 2 min 4.5
Half-life time in pH 7 buffer solution < 2 min 7
Half-life time in pH 9 buffer solution < 2 min 9
Conclusions:
A hydrolysis half life value < 2 minutes was determined at pH4, 7 and 9 and at 25 °C in a reliable study conducted according to EU test method C7.

Description of key information

Hydrolysis half-life: < 2 minutes at 25°C and at pH 4, pH 7 and pH 9 (EU test method C7)

Key value for chemical safety assessment

Additional information

The test substance is expected to undergoes very rapid hydrolysis. In a reliable study conducted according to EU test method C7 the hydrolysis half-lives were estimated to be less than 2 minutes at pH 4, pH 7 and pH 9 and 25°C.

At those pH values only signals of sec-butylamine could be observed after the first 1H NMR measurement. There were no signals of aminosilane detectable. Therefore it was concluded that hydrolysis was already completed when the first spectrum of the pH series was measured.

Because hydrolysis was finished after the first 1H NMR measurement (about 5 minutes after mixing the test sample), no exact half-life time or reaction rate could be calculated. Since the signals of the aminosilane should be detectable for at least 3 half-life times (intensity after t1/2: 50%, after 2x t1/2: 25%, after 3x t1/2: 12.5%), the half-life time was estimated for all pH values to be < 2 min (5 min / 3 = 1.7 min ~ 2 min).

The half-lives are for full hydrolysis and formation of the final hydrolysis products.

The final products of hydrolysis are dimethylsilanediol (1 mole, CAS No. 1066-42-8) and sec-butylamine (2 moles, CAS No. 13952-84-6).