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Adsorption / desorption

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Endpoint:
adsorption / desorption
Remarks:
adsorption
Type of information:
calculation (if not (Q)SAR)
Remarks:
Migrated phrase: estimated by calculation
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Scientifically acceptable calculation method
Principles of method if other than guideline:
Calculation method determining the Koc for charged molecules
GLP compliance:
no
Type of method:
other: calculation of log Koc for ionized molecule
Media:
soil
Test temperature:
25 °C
Type:
Koc
Value:
17 034 - 17 047
Temp.:
25 °C
Remarks on result:
other: pH 5 - 8
Type:
log Koc
Value:
4.23
Temp.:
25 °C
Remarks on result:
other: pH 5 - 8

The data refer to the charged molecule.

pH-corrected Koc

pH 5: 17047

pH 7: 17045

pH 8: 17034

Endpoint:
adsorption / desorption
Remarks:
adsorption
Type of information:
calculation (if not (Q)SAR)
Adequacy of study:
supporting study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Accepted calculation method
Justification for type of information:

Estimation Programs Interface Suite™ for Microsoft® Windows v 4.10. US EPA, United States Environmental Protection Agency, Washington, DC, USA.

KOCWIN v2.00


SMILES used as identifier

The following journal article explains the MCI prediction methodology and its use:
(1) Meylan, W., P.H. Howard and R.S. Boethling, "Molecular Topology/Fragment Contribution Method for Predicting Soil Sorption Coefficients", Environ. Sci. Technol. 26: 1560-7 (1992).


Currently there is no universally accepted definition of model domain.  However, users may wish to consider the possibility that log Koc estimates are less accurate for compounds outside the MW range of the training set compounds, and/or that have more instances of a given fragment than the maximum for all training set compounds.  It is also possible that a compound may have a functional group(s) or other structural features not represented in the training set, and for which no fragment coefficient or correction factor was developed.  These points should be taken into consideration when interpreting model results.
The minimum and maximum values for molecular weight are the following:

 
Training Set Molecular Weights:

Minimum MW:  32.04

Maximum MW:  665.02

Average MW:  224.4

 
Validation Molecular Weights:

Minimum MW:  73.14

Maximum MW:  504.12

Average MW:  277.8

 

Principles of method if other than guideline:
KOCWIN (v2.00): estimation using log Kow
GLP compliance:
no
Type of method:
other: QSAR estimation: KOCWIN v2.00: Koc estimate from log Kow
Media:
soil
Test temperature:
25 °C
Type:
Koc
Remarks:
Estimate from Log Kow
Value:
103.1 L/kg
Temp.:
25 °C
Type:
log Koc
Remarks:
Estimate from Log Kow
Value:
2.013 L/kg
Temp.:
25 °C
Type:
Koc
Remarks:
Estimate from MCI
Value:
446 L/kg
Temp.:
25 °C
Type:
log Koc
Remarks:
Estimate from MCI
Value:
2.649 L/kg
Temp.:
25 °C

Koc Estimate from MCI:

 

First Order Molecular Connectivity Index

7.237

Non-Corrected Log Koc (0.5231 MCI + 0.60)

4.3725

Fragment Correction(s)

 

2   Nitrogen-to-Cycloalkane (aliphatic)

-1.7232

Corrected Log Koc

2.6493

Estimated Koc: 

 446.1 L/kg

Koc Estimate from Log Kow:

 

Log Kow  (calculated)

3.26

Non-Corrected Log Koc (0.55313 logKow + 0.9251)

2.7283

Fragment Correction(s)

 

2   Nitrogen-to-Cycloalkane (aliphatic)

-0.7151

Corrected Log Koc

2.0132

Estimated Koc: 

 103.1 L/kg

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).