N,N',N''-tricyclohexyl-1-methylsilanetriamine

Hydrolysis

Link to relevant study record(s)

Reference

Endpoint:

hydrolysis

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2015-10-12

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. It was not compliant with GLP.

Qualifier:

according to guideline

Guideline:

EU Method C.7 (Degradation: Abiotic Degradation: Hydrolysis as a Function of pH)

Version / remarks:

In analogy to OECD 111 testing method

Deviations:

no

GLP compliance:

no

Remarks:

ISO 9001:2008

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 (10001.23 mg D2O + 41.91 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

Key result

pH:

4

Temp.:

25 °C

DT50:

< 3 min

Type:

not specified

Remarks on result:

other: pH value measured after end of hydrolysis/end of experiments = 5

Key result

pH:

7

Temp.:

25 °C

DT50:

< 2 min

Type:

not specified

Key result

pH:

9

Temp.:

25 °C

DT50:

5.1 min

Type:

(pseudo-)first order (= half-life)

Details on results:

At pH = 4 and pH = 7 only signals of cyclohexylamine 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 of this pH series was measured.

Because hydrolysis was finished after the first 1H NMR measurement (pH 4: about 10 min after mixing the test sample; pH 7: about 5 min 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 3xt1/2: 12.5%), the half-life time was estimated for pH = 4 to be < 3 min (10 min / 3 = 3.3 min ~ 3 min) and for pH = 7 to be < 2 min (5 min / 3 = 1.7 min ~ 2 min).

At pH = 9 decreasing signals of cyclohexylaminosilyl groups and increasing signals of cyclohexylamine could be observed. Half-life time and reaction rate could be calculated from a (ln c[cHxNHSi] vs. t) plot assuming first-order kinetics and using the Na-TSP-d4 as internal standard (see annex). This
evaluation is based on the sum of the three cyclohexylaminosilyl signals.

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	< 3 min	5
Half-life time in pH 7 buffer solution	< 2 min	7
Half-life time in pH 9 buffer solution	5.1 min	9

Conclusions:

Hydrolysis half-lives of < 3.0, < 2.0 and 5.1 minutes at pH 4, 7 and 9 and at 25 °C were determined in a reliable study conducted according to EU test method C7.

Description of key information

Hydrolysis half-lives of  <3.0 minutes at pH 4, <2.0 minutes at pH 7 and 5.1 minutes at pH 9 and 25°C were determined in a reliable study conducted according to EU test method C7.

Key value for chemical safety assessment

Half-life for hydrolysis:

2 min

at the temperature of:

25 °C

Additional information

The test substance 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 3 minutes at pH 4, less than 2 minutes at pH 7 and 5.1 minutes at pH 9 and 25°C. The study was conducted using ¹H NMR spectroscopy

At pH 4 and pH 7 values, only signals of cyclohexylamine 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 of the pH series was measured. Because hydrolysis was finished after the first 1H NMR measurement (pH 4: about 10 min after mixing the test sample; pH 7: about 5 min after mixing the test sample), no exact half-life time or reaction rate could be calculated due to the analysis time. 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 pH = 4 to be < 3 min (10 min / 3 = 3.3 min ~ 3 min) and for pH = 7 to be < 2 min (5 min / 3 = 1.7 min ~ 2 min).

At pH = 9 decreasing signals of cyclohexylaminosilyl groups and increasing signals of cyclohexylamine could be observed. Half-life time and reaction rate could be calculated from a (ln c[cHxNHSi] vs. t) plot assuming first-order kinetics and using the Na-TSP-d4 as internal standard. A half-life time of 5.1 minutes was calculated from the negative slope of the linear regression in a pH 9 buffer solution.

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

The final hydrolysis products were methylsilanetriol (1 mole, CAS No. 2445-53-6) and cyclohexylamine (3 moles, CAS No. 108-91-8).