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REACH

4,4'-methylenebis(cyclohexylamine)

EC number: 217-168-8 | CAS number: 1761-71-3

Life Cycle description
Uses advised against

Environmental fate & pathways

Phototransformation in air

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Administrative data

Link to relevant study record(s)

Reference

Endpoint:: phototransformation in air
Type of information:: (Q)SAR
Adequacy of study:: key study
Reliability:: 2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:: other: validated QSAR model, part of OECD (Q)SAR Toolbox.
Justification for type of information:: QSAR prediction

AOPWIN v1.92a estimated the rate constant for the atmospheric, gas-phase reaction between photochemically produced hydroxyl radicals and organic chemicals. This rate constant was used to calculate atmospheric half-life under two sets of assumptions:
(1). 12-hour daylight and a hydroxyl radical concentration of 1.5 x 106molecules/cm3(default setting recommended by the model User's Guide, Section 1.1; Section 6.2); and
(2). 24 -hour daylight, with a hydroxyl radical concentration of 5 x 105molecules/cm3(the recommended hydroxyl radical concentration for the 24 -hour daylight cycle in the Northern hemisphere, from the model User's Guide, Section 1.1; Section 6.2).

SMILES : NC(CCC(C1)CC(CCC(N)C2)C2)C1
CHEM :
MOL FOR: C13 H26 N2
MOL WT : 210.37

Accuracy & Domain
Estimation Accuracy
Hydroxyl Radical Estimation Accuracy of AOPWIN
Appendix F is a compilation of experimentally determined gas-phase, hydroxyl radical rate constants for more than 660 organic chemicals at room temperatures. Most experimental values were taken from Atkinson (1989, 1994) and Kwok and Atkinson (1995). Appendix F also lists the rate constant estimations made by the Atmospheric Oxidation Program (AOPWIN).

Figure 1 is a graphical representation of the correlation between the experimental OH rate constants and the rate constants estimated by the AOP program. The correlation includes 667 compounds; most experimental values containing a "less than" sign (<) were excluded. Since the range of experimental rate constants spans nearly six orders of magnitude, a statistical correlation was computed on a logarithmic basis ... comparing experimental to estimated values:

AOPWIN

correlation coefficient (r2) 0.963
standard deviation (sd) 0.218
absolute mean error (me) 0.127

For the 667 AOPWIN estimations, 90% are within a factor of two of the experimental value and 95% are within a factor of three.

Ozone Reaction Rate Estimation Accuracy of AOP

Appendix G is a compilation of experimentally determined gas-phase, ozone reaction rate constants for 112 organic chemicals at room temperatures. Figure 2 is a graphical representation of the correlation between the experimental ozone rate constants and the rate constants estimated by the AOPWIN program. Statistical accuracy is:

AOPWIN

correlation coefficient (r2) 0.88
standard deviation (sd) 0.52
absolute mean error (me) 0.35

Estimation Domain
Currently there is no universally accepted definition of model domain. However, users may wish to consider the possibility that property estimates are less accurate for compounds outside the Molecular Weight 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 was developed. These points should be taken into consideration when interpreting model results.

The complete training sets for AOPWIN's estimation methodology are not available. Therefore, describing a precise estimation domain for this methodology is not possible.
The current applicability of the MPBPWIN methodology is best described by its accuracy in predicting available experimental values as described above in the Accuracy section. New experimental data will be compiled into a validation data set and tested in the future.
Principles of method if other than guideline:: Parameter estimation by QSAR, using AOPWIN v1.92a, a QSAR model within Estimation Programs Interface Suite™ for Microsoft® Windows, v4.0, from the United States Environmental Protection Agency (EPA), a validated QSAR program which is also
part of the OECD (Q)SAR Toolbox.
GLP compliance:: no
Remarks:: not applicable
Validity criteria fulfilled:: not applicable
Remarks:: approved QSAR model
Conclusions:: The QSAR model AOPWIN v1.92a, a validated QSAR model part of OECD (Q)SAR Toolbox, was used to estimate the degradation constant of PACM (4,4'-methylenebis(cyclohexylamine)) in the presence of hydroxyl radicals. The degradation rate was estimated as 116.5291 E-12 cm3/molecule-s. The half-life was estimated under two alternate modeling assumptions: a half-life of 0.092 days (1.101 hours) assuming 12-hour daylight cycle with a hydroxyl radical concentration of 1.5E+6 molecules/cm3; and a half-life of 0.138 days (3.304 hours) assuming 24-hour daylight cycle with a hydroxyl radical concentration of 5E+5 molecules/cm3. The model User's Guide states that the 24-hour daylight average hydroxyl radical concentration may be more appropriate for chemicals that react more slowly (i.e., > a few days). Since the modeling results indicate that PACM is a fast-reacting chemical (with a half-life in the scale of hours), the estimated half-life associated with the default hydroxyl radical concentration with 12-hour daylight cycle (i.e., 1.101 hours) is considered the more appropriate of the two half-life values.

Description of key information

The half-life of PACM (4,4'-methylenebis(cyclohexylamine)) and its degradation rate constant in the presence of hydroxyl radicals were predicted by the use of quantitative structural activity relationship modelling, by the use of AOPWIN v1.92a, a model within the EPI Suite v4.00, validated QSAR model, part of OECD (Q)SAR Toolbox.

Key value for chemical safety assessment

Half-life in air:: 1.101 h
Degradation rate constant with OH radicals:: 0 cm³ molecule-1 s-1

Additional information

The photolysis half-life and degradation rate constant of PACM (4,4'-methylenebis(cyclohexylamine)) were estimated, based on QSAR modelling. The degradation constant with hydroxyl radicals was predicted to be 116.5291 x 10^-12cm³/molecule^-1s^-1. Assuming a hydroxyl radical concentration [-OH] of 0.5 x 10⁶molecules/cm³and 24 hours of sunlight, the half-life was predicted as 3.304 hours (0.138 days); assuming a hydroxyl radical concentration [-OH] of 1.5 x 10⁶molecules/cm³and 12 hours of sunlight, the half-life was predicted as 1.101 hours (0.092 days).

The model User's Guide states that the 24-hour daylight average hydroxyl radical concentration may be more appropriate for chemicals that react more slowly (i.e.,> a few days). Since the modelling results indicate that PACM is a fast-reacting chemical (with a half-life in the scale of hours), the estimated half-life associated with the default hydroxyl radical concentration with 12-hour daylight cycle (i.e., 1.101 hours) is considered the more appropriate of the two estimated half-life values.

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