Dimethoxydiphenylsilane

Endpoint summary

Description of key information

No studies are available. Based on molecular structure, molecular weight, water solubility, and octanol-water partition coefficient it can be expected that the submission substance is likely to be absorbed via the oral and dermal routes rather than via inhalation. Hydrolysis occurs in contact with water and moist air, and systemic exposure is expected to both the parent substance and the hydrolysis product. Based on the water solubility, the registered substance and its silanol-containig hydrolysis product are likely to be distributed in the body, and excretion via the renal pathway can be expected. The bioaccumulation potential is expected to be low.

Key value for chemical safety assessment

Bioaccumulation potential:

low bioaccumulation potential

Additional information

There are no studies available in which the toxicokinetic properties of dimethoxydiphenylsilane have been investigated. Therefore, the toxicokinetic behaviour assessment of the substance and its hydrolysis products was estimated by its physico-chemical properties and the available toxicology studies on the substance itself.

Dimethoxydiphenylsilane hydrolyses in contact with water, generating methanol and diphenylsilanediol. QSAR predictions revealed half-lives at 20-25°C of 0.1 h at pH 4 and pH 5, 0.6 h at pH 7, and 0.0 h at pH 9. As the hydrolysis reaction may be acid or base catalysed, the rate of reaction is slowest at pH 7 and increase as the pH is raised or lowered. This suggests that systemic exposure to both the parent and to the hydrolysis products is possible. Hence, this toxicokinetic behaviour assessment will try to predict the behaviour of these substances. The toxicokinetics of methanol is discussed elsewhere and is not included in this summary. The molecular weight of dimethoxydiphenylsilane is 244 g/mol. In contrast, the molecular weight of diphenylsilanediol is 216 g/mol. The hydrolysis products are smaller in size and are more water soluble and, thereby suggest that it will have greater potential to be absorbed through biological membranes than the parent substance. The water solubility is 3 mg/l and 510 mg/l for dimethoxydiphenylsilane and diphenylsilanediol, respectively. Furthermore, the moderate range of log Kow of 2-4.4 for diphenylsilanediol and dimethoxydiphenylsilane, respectively, indicate that these substances are lipophilic enough to efficiently pass through biological membranes by passive diffusion.

Absorption

Oral:

In an acute oral toxicity study with dimethoxydimethylsilane mortality as well as various clinical signs occurred during the study. Thus, systemic availability was proven for the test substance or the corresponding hydrolysis product. Based on the physical and chemical data absorption of the hydrolysis product seems likely (low molecular weight, moderate log Pow).

Inhalation:

The vapour pressure of the liquid parent substance (0.03 Pa) and the boiling point (300 °C) indicates that inhalation of the registered substance as a vapour is unlikely. If the substances would reach the lower respiratory tract (inhalation by mist or adsorbed to particles), then absorption would be possible (indicated absorption by oral route).

Dermal:

No study results are available for the dermal route. Based on the physical and chemical data for diphenylsilanediol, absorption vie the dermal route is considered to be likely. The molecular weight between 100 and 500 g/mol, the moderate water solubility and log Pow favour the absorption via the skin. Irritant effects on the skin could enhance the possible absorption.

Metabolism:

Dimethoxydiphenylsilane hydrolyses in contact with water, generating methanol and diphenylsilanediol. There are no data regarding the enzymatic metabolism of dimethoxydiphenylsilane. Genetic toxicity tests showed no observable differences with and without metabolic activation.

Excretion:

The low molecular weight and moderate water solubility of the hydrolysis product suggest that it is likely to be excreted by the kidneys into urine.