N,N-bis(trimethylsilyl)aminopropylmethyldiethoxysilane

Water solubility

Description of key information

Water solubility [N,N-bis(trimethylsilyl)aminopropylmethyldiethoxysilane]: not determinable due to very rapid hydrolysis in water

 

Water solubility [3-(diethoxy(methyl)silyl)propylamine]: 5900 mg/l at 20°C (QSAR)

 

Water solubility [3-(dihydroxymethylsilyl)propylamine]: Above approximately 1000 mg/l condensation reactions can occur over time, limiting the concentration dissolved in water. The calculated solubility is 1.0E+06 mg/l (QSAR).

 

Water solubility [trimethylsilanol]: Above approximately 1000 mg/l condensation reactions can occur over time, limiting the concentration dissolved in water. The calculated solubility is 1.1E+04 mg/l (QSAR).

 

Water solubility [ethanol]: miscible at 20°C

Additional information

The requirement to test the substance for water solubility is waived on the basis that it hydrolyses rapidly to form 3-(dihydroxymethylsilyl)propylamine, trimethylsilanol and ethanol. However, an attempt was made to conduct a water solubility study for the submission substance using a modified method comparable to OECD Test Guideline 105 and in compliance with GLP. 100 ml water at 20°C was spiked with a solution of the test substance in 100 ml acetone, the solution was shaken, wrapped in aluminium foil to exclude light and sampled prior to placing in a water bath at 20°C. Duplicate samples were performed. Sampling of the test substance was performed at various time intervals of 0, 0.5 and 1 hour for test 1 and 0 hour only for test 2. Sample analysis was performed immediately after preparation using GC-FID. At t=0 h, t=0.5 h and t=1 h solutions, no peaks at the characteristic retention time of the test substance were observed in the chromatograms of the sample solution. This indicate that the test substance undergoes very rapid hydrolysis when in contact with water.

 

N,N-bis(trimethylsilyl)aminopropylmethyldiethoxysilane contains two types of hydrolysable group; one silazane (Si-N-Si) and two ethoxy (Si-OEt) groups. The silazane bond hydrolyses very rapidly in contact with water; hydrolysis half-life of <1 minute at pH 4, pH 7 and pH 9 and 25°C to form an intermediate hydrolysis product of 3-(diethoxy(methyl)silyl)propylamine and trimethylsilanol. The diethoxy group in the intermediate hydrolysis product, 3-(diethoxy(methyl)silyl)propylamine also undergoes further hydrolysis to form 3-(dihydroxymethylsilyl)propylamine and ethanol.

 

The water solubility of 3-(diethoxymethylsilyl)propylamine has been predicted to be 5900 mg/l at 20°C using a validated QSAR estimation method.

The hydrolysis products 3-(dihydroxymethylsilyl)propylamine and trimethylsilanol, may undergo condensation reactions in water; these become important above approximately 1000 mg/l and can limit the concentration dissolved in water. For details, see the overall physicochemical properties discussion.

 

3-(Dihydroxymethylsilyl)propylamine and trimethylsilanol are very hydrophilic and hence the calculated solubilities are 1E+06 mg/l and 1.1E+04 mg/l at 20°C respectively using a QSAR estimation method. This QSAR method for water solubility cannot be validated for silanetriols because the saturation concentration of silanetriols in water is limited by condensation reactions rather than lack of true solubility, as discussed above. A prediction of 1E+06 mg/L is indicative but has no practical meaning. The prediction is however considered valid for use in environmental exposure modelling and toxicokinetics modelling because it is considered to adequately describe the hydrophilicity of the substance and hence the partitioning behaviour.

Ethanol is miscible with water (Riddick J. A 1986).

Reference: 

Riddick, J.A; Bunger,W.B; Sakano,T.K; Organic Solvents: Physical Properties and Methods of Purification. Techniques of Chemistry. 4th ED. New York,NY: Wiley-Interscience. 2:PP.1325 1986.