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EC number: 204-677-5
CAS number: 124-07-2
Koc values of the category members of fatty acids were calculated
by established calculation interfaces in order to indicate the
adsorption potential of the substances and for the needs of the CSA.
Koc values were calculated with the US EPA EPISuite interface
using QSAR/QSPR predictions (KOCWIN v. 2.00) according to the MCI
method. Based on the neutral chemical form of fatty acids, the estimated
Koc values increase with increasing chain length from 28.95 for octanoic
acid (C8) up to 129,000 for docosanoic acid (C22).
However, since fatty acids (C8 - C22) are weak acids with pKa
between 4.75 – 5.7 and occur in their ionisable form in the environment,
the Koc values were corrected based on the soil-water partitioning
coefficient calculation method for ionizable substances developed by
Franco, Fu & Trapp (2009, ChemProp v6.4). The Koc values were predicted
to be between 111.6 for octanoic acid (C8) and 66,696 for C22, which
reflects a slight decrease of the adsorption potential of fatty acids
when considering the speciation of the molecules in the calculation.
Table 1: Koc and Log Koc values calculated for the fatty acids
with Franco, Fu & Trapp model for ionizable substances at neutral pH.
Franco, Fu & Trapp
Log Pow used
Furthermore, transport and distribution of fatty acids through the
atmospheric compartment is not expected due to their low vapour pressure
values ranging from < 0.0001 Pa to < 5.8 Pa at 25 °C.
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