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Endpoint:
adsorption / desorption
Remarks:
adsorption
Type of information:
(Q)SAR
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: see 'Remark'
Remarks:
The (Q)SAR is an accepted calculation method, therefore generally being considered as reliable study with restrictions. As this approach is taken from (1) ECHA's Guidance on information requirements and chemical safety assessment - Chapter R.7a: Endpoint specific guidance, and from (2) "European Chemical Bureau Technical Guidance Document on Risk Assessment Part III", the computation method is considered a valid.
Justification for type of information:
QSAR prediction: migrated from IUCLID 5.6
Guideline:
other: REACH guidance on QSARs R.6, May/July 2008
Principles of method if other than guideline:
The adsorption coefficient of the substance was estimated using different QSPR estimation methods.
GLP compliance:
no
Type of method:
other: QSPR estimation
Media:
other: QSPR estimation
Test temperature:
Computation referring to a temperature of 20 °C.
Computational methods:
- Adsorption coefficient per organic carbon (Koc):
The adsorption coefficient of the substance (ethoxymethoxy)cyclododecane was estimated with the KOCWIN modelling program (version 2) by using the first-order Molecular Connectivity Index (MCI) and by using the octanol-water partition coefficient (log Kow). Additionally, different equations based on a correlation of the Koc and Kow values were applied (Gerstl 1990, Sabljic and Güsten 1995). The Koc based on MCI was considerably lower than those predicted with the other methods and this value therefore was not considered further.
Type:
Koc
Value:
14 622
Temp.:
20 °C
Remarks on result:
other: Geometric mean of Koc values determined with three approaches
Type:
log Koc
Value:
4.165
Temp.:
20 °C
Remarks on result:
other: Geometric mean of Koc values determined with three approaches
Type:
log Koc
Value:
3.73
Temp.:
20 °C
Remarks on result:
other: PCKOCWIN log KOW
Type:
log Koc
Value:
4.33
Temp.:
20 °C
Remarks on result:
other: Gerstl method
Type:
log Koc
Value:
4.474
Temp.:
20 °C
Remarks on result:
other: Sabljic and Güsten (mainly hydrophobic substances)

SMILES : O(COC(CCCCCCCCCC1)C1)CC

CHEM : Cyclododecane, (ethoxymethoxy)-

MOL FOR: C15 H30 O2

MOL WT : 242.41

--------------------------- KOCWIN v2.00 Results ---------------------------

KOC Estimate from MCI:

---------------------

First Order Molecular Connectivity Index ........... : 8.432

Non-Corrected Log KOC (0.5213 MCI + 0.60) .......... : 4.9953

Fragment Correction(s):

2 Ether, aliphatic (-C-O-C-) .......... : -1.7432

Corrected Log KOC .................................. : 3.2521

Estimated KOC: 1787 L/kg <===========

KOC Estimate from Log KOW:

-------------------------

Log KOW (User entered ) ......................... : 5.40

Non-Corrected Log KOC (0.55313 log KOW + 0.9251) .... : 3.9120

Fragment Correction(s):

2 Ether, aliphatic (-C-O-C-) .......... : -0.1812

Corrected Log KOC .................................. : 3.7308

Estimated KOC: 5380 L/kg <===========

Equation from Gerstl (1990): log KOC = 0.679 · og KOW + 0.663 (n = 419, r2 = 0.831)

Computation for neononyl acetate: log KOC = 0.679 · 5.4 + 0.663

The result for neononyl acetate is: log KOC = 4.33

Equation from Sabljic and Günsten (1995), mainly hydrophobic substances: log KOC = 0.81 · log KOW + 0.10 (n = 81, r2 = 0.89)

Computation for neononyl acetate: log KOC = 0.81 · 5.4 + 0.10

The result for neononyl acetate is: log KOC = 4.474

Validity criteria fulfilled:
yes
Conclusions:
The QSPR-estimated adsorption coefficient of the substance (ethoxymethoxy)cyclododecane is Koc = 14622 L/kg (log Koc = 4.165). It is proposed to use this value further in the chemical safety assessment. Substance (ethoxymethoxy)cyclododecane is to be classified as being "immobile" in soil (acc. to McCall et al. 1981).
Executive summary:

The purpose of this study was to determine the Koc of test item (ethoxymethoxy)cyclododecane by the use of non experimental methods. As no single computational model could be identified which would fit completely to this task, the Koc of (ethoxymethoxy)cyclododecane eventually was being calculated from the geometric mean of the results generated by three individual QSPR approaches.

The adsorption coefficient of the substance was estimated with the KOCWIN program using the Molecular Connectivity Index and the octanol-water partition coefficient of the substance. Further, two equations were used for the computation of the adsorption coefficient that were derived from the regression of experimental log Koc and log Kow values (Gerstl 1990, Sabljic and Günsten 1995). The approaches gave a coherent set of three data points for the log Koc value. The geometric mean log Koc value calculated from these three data points was 4.165. It is proposed to use this value further in the chemical safety assessment.

According to the testing strategy as shown in ECHA "Guidance on information requirements and chemical safety assessment - Chapter R.7a: Endpoint specific guidance", if the QSPR result is considered as reliable, but tonnage supply is > 100 tpa, then the QSPR-derived value shall be used for CSA. This QSPR is considered reliable as it is supported from several, different QSPR models, which mostly are based on real phys.-chem. properties of the test item (i.e. robustness of the approach can be assumed).

Finally, based on the classification of soil mobility potential as given in McCall et al.1981, with a Koc within the range > 5000 substance (ethoxymethoxy)cyclododecane is to be classified as being "immobile" in soil (McCall P.J., Laskowski D.A., Swann R.L., and Dishburger H.J., (1981), “Measurement of sorption coefficients of organic chemicals and their use, in environmental fate analysis”, in Test Protocols for Environmental Fate and Movement of Toxicants. Proceedings of AOAC Symposium, AOAC, Washington DC).

Endpoint:
adsorption / desorption
Data waiving:
other justification
Justification for data waiving:
other:
Justification for type of information:
It is being proposed to waive further studies on adsorption/desorption, as is basically would be requested by REACH Annex IX. According to ECHA guidance documents a strong justification needs to be provided for avoiding experimental confirmation of the computed Koc data, as basically being requested by REACH Annex IX. The justification arguments for supporting the robustness of this QSPR-derived Koc result reads as follows: 1. For final computation four individual Koc values were being used which were all based on the log Kow of (ethoxymethoxy)cyclododecane; the high log Kow of (ethoxymethoxy)cyclododecane of 5.4 is considered to have significant impact on Koc computation. 2. While one of these QSPR methods is a statistical method (KOCWIN), the Koc computations of other three methods all are based on real physical properties 3. The three individual Koc data points represent a coherent data set without outliers 4. The log Koc of (ethoxymethoxy)cyclododecane resulting from the geometric mean of these three values therefore is being supported by four different QSPR models Furthermore, concerning data interpretation of the resulting Koc of (ethoxymethoxy)cyclododecane, all available data uniformly are pointing in one direction and clearly indicate that the substance has to be considered as immobile in sediments and soil. For these reasons additional adsorption/desorption testing cannot be expected to reveal new results with any added value concerning the risk assessment of this substance, thus additional Annex IX studies on adsorption/desorption shall be waived.

Description of key information

The log Koc value was predicted with the program KOCWIN and with three QSPR methods. The log Koc = 4.165 indicates that the substance is immobile in soil and sediment according to the classification scheme of McCall et al. (1981).

Key value for chemical safety assessment

Koc at 20 °C:
14 622

Additional information

Discussion of results

As no single computational model could be identified which would fit completely to this task, the Koc of (ethoxymethoxy)cyclododecane eventually was being calculated from the geometric mean of the data generated by five individual QSPR approaches.The five different ways of QSPR computations mostly were based on the experimentally derived log Kow of the test item of 5.4.

Method

Log KOC

PCKOCWIN log KOW

3.73

Gerstl method

4.33

Sabljic and Güsten (mainly hydrophobic)

4.474

Geometric mean

4.165

The resulting geometric mean of log Koc = 4.165 (Koc = 14622 L/kg) is considered as valid as it is being supported by several different QSPR approaches. It is proposed to use the predicted value for the adsorption coefficient of log Koc = 4.165 in the chemical safety assessment. The substance is considered to be immobile in sediments and soil (McCall et al. 1981).

Waiving of further adsorption/desorption studies

As additional adsorption/desorption testing cannot be expected to reveal new results with any added value concerning the risk assessment of this substance, additional Annex IX studies on adsorption/desorption shall be waived (for more details see "waiver_further studies on adsorption/desorption").

[LogKoc: 4.165]