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Environmental fate & pathways

Adsorption / desorption

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Description of key information

This endpoint can be waived on the basis that butenes have a low potential for adsorption, based on a log Kow of less than 3. The calculated adsorption coefficients for butenes range from 97.7 to 117.5. This range was derived from the members of the butenes category: but-1-ene (CAS 106-98-9), 2-butene (CAS 107-01-7) and 2-methylpropene (CAS 115-11-7) using the equation in the TGD (EC 2003).

Key value for chemical safety assessment

Koc at 20 °C:
108.3

Additional information

In accordance with column 2 of REACH Annex VIII, the adsorption/desorption study does not need to be conducted as, based on the physico-chemical properties, the butenes category members can be expected to have a low potential for adsorption (the butenes have a log octanol water partition coefficient less than 3).

However, the adsorption coefficient has been calculated according to the appropriate equation in the TGD (EC 2003) and is considered reliable for this endpoint. The estimated adsorption coefficient, Koc, of 2-butene is 97.7 and the log Koc is 1.99. The estimated adsorption coefficient, Koc, of but-1-ene is 109.6 and the log Koc is 2.04. The estimated adsorption coefficient, Koc, of 2 -methylpropene is 117.5 and the log Koc is 2.07. The mean of the adsorption coefficient values for the butenes is 108.3 (log Koc of 2.03) and this has been used to complete the 'key value for chemical safety assessment'.

[LogKoc: 2.03]