Diacetoxydi-tert-butoxysilane

Endpoint summary

Description of key information

Skin irritation/corrosion: Data waiving (study scientifically not necessary): The substance decomposes very fast in the main hydrolysis product acetic acid which has the harmonized classification of Skin Corr. 1B; H314: 10 % ≤ C < 90 % and thus the substance should be classified in the same category.

Eye irritation: Data waiving (study scientifically not necessary): In accordance with column 2 of REACH Annexes VII and VIII, the study does not need to be conducted since the substance is classified as corrosive to the skin.

Key value for chemical safety assessment

Skin irritation / corrosion

Link to relevant study records

Reference

Endpoint:

skin irritation: in vitro / ex vivo

Data waiving:

study scientifically not necessary / other information available

Justification for data waiving:

other:

Justification for type of information:

JUSTIFICATION FOR DATA WAIVING
The substance decomposes very fast in the main hydrolysis product acetic acid which has the harmonized classification of Skin Corr. 1B; H314: 10 % ≤ C < 90 % and thus the substance should be classified in the same category.

Endpoint conclusion

Endpoint conclusion:

no study available

Eye irritation

Link to relevant study records

Reference

Endpoint:

eye irritation: in vitro / ex vivo

Data waiving:

study scientifically not necessary / other information available

Justification for data waiving:

the study does not need to be conducted because the substance is classified as skin corrosion, leading to classification as serious eye damage (Category 1)

Justification for type of information:

JUSTIFICATION FOR DATA WAIVING
In accordance with column 2 of REACH Annexes VII and VIII, the study does not need to be conducted since the substance is classified as corrosive to the skin.

Endpoint conclusion

Endpoint conclusion:

no study available

Additional information

Skin irritation/corrosion: Data waiving (study scientifically not necessary): In accordance with column 2 of REACH Annexes VII and VIII, the study does not need to be conducted since the substance is classified as corrosive to the skin.

Eye irritation: Data waiving (study scientifically not necessary): In accordance with column 2 of REACH Annexes VII and VIII, the study does not need to be conducted since the substance is classified as corrosive to the skin.

Justification for classification or non-classification

The substance is classified as skin corrosive based on a weight of evidence approach:

 

- pH value: Endpoint record pH.04.20_01. In accordance with the method CIPAC 75.3 and GLP, the pH of diacetoxydi-tert-butoxysilane was measured to be 3.02 and therefore, the substance was determined to be strong acid.

- Worth and Cronin (2001) [1]: The aim of the study conducted by Worth and Cronin was to develop classification models based on pH data for predicting the potential of chemicals to cause skin corrosion, skin irritation and eye irritation based on compilation of data sets of 44 chemicals. According to the predicting model results, if pH <3.9 of if pH > 10.5, then the substance is predicted to be corrosive.

- Acetic acid (CAS No. 64 -19 -7): Diacetoxydi-tert-butoxysilane is an acetoxysilanes and have three acetoxy groups linked to a silicon atom. In contact with water and even in moisture, diacetoxydi-tert-butoxysilane hydrolyses into acetic acid and corresponding trisilanol (1 mole of the test item produces 2 moles of acetic acid). According to Regulation (EC) No. 1272/2008 [2], acetic acid is included in the List of harmonised classification and labelling of hazardous substances (Index No. 607-002-00-6) and it is classified as Skin Corr. 1A, H314 (Skin Corr. 1A; H314: C ≥ 90 %; Skin Corr. 1B; H314: 10 % ≤ C < 90 %).

 

Diacetoxydi-tert-butoxysilane polymerizes triggered by hydrolysis in contact with water and the degradation product acetic acid decreases the pH of the test solution. In fact the pH of the test item was determined to be 3.02 due to the hydrolysis product acetic acid. Taking into account that the substance is a strong acid (pH = 3.02) and the harmonised classification of the hydrolysis product acetic acid according to current regulations, diacetoxydi-tert-butoxysilane is determined to be corrosive to the skin.

 

Therefore, and based on the available information on diacetoxydi-tert-butoxysilane (pH = 3.02, acetic acid = Skin Corr. 1B; H314 when 10% < C < 90%), the substance is classified as Skin Corrosive, hazard category 1B.

 

References:

[1]: Worth, A.P and Cronin, M.T.D. 2001. The use of pH measurements to predict the potential of chemicals to cause acute dermal and ocular toxicity. Toxicology 169 (2001) 119 -131.

[2]: Regulation (EC) No 1272/2008 of the European Parliament and of the Council of 16 December 2008 on classification, labelling and packaging of substances and mixtures, amending and repealing Directives 67/548/EEC and 1999/45/EC, and amending Regulation (EC) No 1907/2006.