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Environmental fate & pathways

Adsorption / desorption

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Description of key information

Adsorption to solid soil phase expected.

Key value for chemical safety assessment

Additional information

The Koc value for PACM (4,4'-methylenebis(cyclohexylamine)) was estimated by the Molecular Connectivity Index (MCI) module and the log KOW module. The MCI method is the more reliable of the two calculation methods in the KOCWIN v2.00 model. The molecular weight of PACM (molecular weight = 210.37 g/mol) falls within the molecular weight range of both the training data set (MW range 32.04 g/mol to 665.02 g/mol) and the validation data set (73.14 g/mol to 504.12 g/mol). The correction factor for the nitrogen-to-cycloalkane (aliphatic) structure (-0.861602) was applied twice (-1.7232) to the calculation of the log Koc by the MCI methodology. The MCI method resulted in a Koc of 446 (log Koc = 2.65), while the log KOW method gave a slightly lower Koc of 103 (log Koc = 2.01). Both calculated values refer to the uncharged molecule. However at environmentally relevant conditions (pH 5 to 8), PACM will be present in ionised form (pKa2 = 11.1 at 20 °C; Baltussen, 2010).

Therefore, the Koc was also calculated for the environmetally relevant pH range according to Franco and Trapp (2008, 2009, 2010). This resulted in a log Koc of 4.23 at pH 5 to 8 (Koc = 17047 at pH 5 to Koc = 17034 at pH 8).