N-[3-(triethoxysilyl)propyl]ethylenediamine

Adsorption / desorption

Link to relevant study record(s)

Reference

Endpoint:

adsorption / desorption: screening

Remarks:

adsorption

Data waiving:

study scientifically not necessary / other information available

Justification for data waiving:

the study does not need to be conducted because the substance has a low octanol water partition coefficient and the adsorption potential of this substance is related to this parameter

Description of key information

Hydrolysis product:, N-[3-(trihydroxysilyl)propyl]ethylenediamine (CAS 68400-08-8):

log Koc at pH 4: 0.45 - 0.47

log Koc at pH 7: 0.67 - 0.77

log Koc at pH 9: 0.96 - 1.09

Key value for chemical safety assessment

Koc at 20 °C:

5.83

Additional information

N-[3-(triethoxysilyl)propyl]ethylenediamine (CAS 5089-72-5) hydrolyses rapidly (165 min at pH 7) in contact with water to the corresponding hydrolysis product N-[3-(trihydroxysilyl)propyl]ethylenediamine (CAS 68400-08-8) and ethanol (CAS 64-17-5). Both parent substance and hydrolysis product have a very low octanol–water partition coefficient (< 3) and thus low potential for adsorption. In accordance with Column 2 of REACH Annex VIII, the adsorption/desorption screening test does not need to be conducted.

Since the parent compound is not stable in the environment further information on the adsorption behavior of the substance was collected by appropriate calculations only for the hydrolysis product N-[3-(trihydroxysilyl)propyl]ethylenediamine (CAS 68400-08-8).  

Considering the ionizing property of N-[3-(trihydroxysilyl)propyl]ethylenediamine, the adsorption potential has been calculated using Franco and Trapp ‘s expressions (2008) on estimation of the organic carbon-water partitioning coefficient of ionisable organic substances. More detail on the derived octanol-water partitioning coefficient of its non-ionised (log Kow) and ionized forms (log D) as well as the pKa values can be found in chapter 4.7.

The following equation was used for koc calculation as suggested by the authors:

Koc =Φn x 10^{0.37xlogPn+1.70}+Φion x 10^{pKa^0.65xf^0.14}

Where:

Φn = 1/(1+10^(pH-pKa))

Pn: Kow of the neutral molecule (EpiWin)

pKa: 8.8 and 9.4 (more information in chapter 4.7)

Φion = 1- Φn

f: Ratio of concentration in octanol to total concentration: Kow (overall)/(Kow (overall) + 1)

The log Koc was calculated to be 0.45 - 0.47 at pH 4; 0.67 - 0.77 at pH 7 and 0.96 - 1.09 at pH 9. These values indicate the low adsorption potential of the substance to organic carbons in soil. According to the Guidance on Information Requirements and Chemical Safety Assessment, Chapter R.7.1.8.5 the log D value for the ionized molecule determined around the default pH of 7 is considered more relevant for chemical safety assessment. On this basis the calculated log Koc of 0.77 (Koc = 5.83 at pH 7) has been used for the chemical safety assessment.

Reference:

Franco A. & Trapp S., 2008: Estimation of the soil-water partition coefficient normalized to organic carbon for ionizable organic chemicals. Environmental Toxicology and Chemistry, Vol. 27, No. 10, pp. 1995–2004.

[LogKoc: 0.77]

[LogKoc: 0.766]