Registration Dossier

Administrative data

Endpoint:
adsorption / desorption
Remarks:
adsorption
Type of information:
(Q)SAR
Adequacy of study:
supporting study
Study period:
2014-07-31
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Accepted calculation method, substance within applicability domain
Justification for type of information:
QSAR prediction: migrated from IUCLID 5.6

Data source

Referenceopen allclose all

Reference Type:
other: EPIWIN calculation
Title:
Unnamed
Year:
2014
Report date:
2014
Reference Type:
other: Estimation software
Title:
Estimation Programs Interface Suite for Microsoft Windows, v4.10
Author:
US-EPA
Year:
2012
Bibliographic source:
United States Environmental Protection Agency, Washington, DC, USA

Materials and methods

Principles of method if other than guideline:
KOCWIN (v2.00): estimation using first-order Molecular Connectivity Index (MCI)
GLP compliance:
no
Type of method:
other: QSAR estimation: KOCWIN v2.00: Koc estimate from MCI

Test material

Constituent 1
Chemical structure
Reference substance name:
2,5-xylenol
EC Number:
202-461-5
EC Name:
2,5-xylenol
Cas Number:
95-87-4
Molecular formula:
C8H10O
IUPAC Name:
2,5-dimethylphenol
Constituent 2
Reference substance name:
Reference substance 001

Study design

Test temperature:
25 °C

Results and discussion

Adsorption coefficientopen allclose all
Type:
Koc
Value:
491.8
Temp.:
25 °C
Remarks on result:
other: The substance is within the applicability domain of the model.
Type:
log Koc
Value:
2.692
Temp.:
25 °C
Remarks on result:
other: The substance is within the applicability domain of the model.

Any other information on results incl. tables

KOCWIN Program (v2.00) Results:

==============================

SMILES : Oc(c(ccc1C)C)c1

CHEM  : 2,5-DIMETHYLPHENOL

MOL FOR: C8 H10 O1

MOL WT : 122.17

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

 

Koc Estimate from MCI

 

First Order Molecular Connectivity Index

4.198

Non-Corrected Log Koc (0.5213 MCI + 0.60)

2.7884

Fragment Correction(s)

 

1 Aromatic Hydroxy (aromatic-OH).

 -0.0966

Corrected Log Koc

2.6918

Estimated Koc

491.8L/kg

Applicant's summary and conclusion

Executive summary:

QPRF: KOCWIN v2.00 (18 Nov. 2013)

 

1.

Substance

See “Test material identity”

2.

General information

 

2.1

Date of QPRF

See “Data Source (Reference)”

2.2

QPRF author and contact details

See “Data Source (Reference)”

3.

Prediction

3.1

Endpoint
(OECD Principle 1)

Endpoint

Adsorption to solid phase of soils etc.

Dependent variable

Organic carbon normalised adsorption coefficient (Koc)

3.2

Algorithm
(OECD Principle 2)

Model or submodel name

KOCWIN

Model version

v. 2.00

Reference to QMRF

QMRF: Estimation of Soil Adsorption Coefficient using KOCWIN v2.00 (EPI Suite v4.11): MCI methodology

Predicted value (model result)

See “Results and discussion”

Input for prediction

- Chemical structure via CAS number or SMILES

Descriptor values

- MCI (first order molecular connectivity index)

- Correction factors

3.3

Applicability domain
(OECD principle 3)

Domains:

1) Molecular weight
(range of test data set: 32.04 to 665.02 g/mol; On-Line KOCWIN User’s Guide, Ch. 6.2.4 Domain)

Substance within range (122.17 g/mol)

2) Correction factors: Number of instances of the identified correction factor does not exceed the maximum number as listed in Appendix D (On-Line KOCWIN User’s Guide)

fulfilled.

3.4

The uncertainty of the prediction
(OECD principle 4)

Statistical accuracy for training dataset:

n = 516, r² = 0.916, std. dev. = 0.330, average dev. = 0.263

3.5

The chemical mechanisms according to the model underpinning the predicted result
(OECD principle 5)

Adsorption is caused by temporary (reversible) or permanent bonding between the substance and a surface (e.g. due to van der Waals interactions, hydrogen bonding to hydroxyl groups, ionic interactions, covalent bonding, etc.). The organic carbon normalized adsorption coefficient (Koc) is the ratio of a substance concentration sorbed in the organic matter component of soil or sediment to that in the aqueous phase at equilibrium.

MCI methodology: The first-order molecular connectivity index is a measure to describe a variety of properties of chemicals. According to Sabljic (1984; cited in Meylan et al., 1992), the soil sorption potential is highly correlated with the first order MCI. Therefore, it has been used to derive the adsorption coefficient.

 

References

- US EPA (2012). On-Line KOCWIN User’s Guide.

- Meylan, W., P.H. Howard and R.S. Boethling. 1992. Molecular topology/fragment contribution method for predicting soil sorption coefficients. Environ. Sci. Technol. 26: 1560-1567.

 

 

Assessment of estimation domain (molecular weight, fragments, correction factors):

 

Model:

KOCWIN v2.00

MCI & Log Kow method

Substance:

2,5-DIMETHYLPHENOL

CAS-#:

95-87-4

SMILES:

Oc(c(ccc1C)C)c1

Molecular weight (g/mol):

122.17

Log Kow (experimental data):

2.34

 

 

 

 

 

 

 

Molecular weight (g/mol)

 

log Kow

Minimum

Maximum

Average

 

Minimum

Maximum

Training set

32.04

665.02

224.4

 

-2.11

8.12

Validation set

73.14

504.12

277.8

 

-5.98

8.68

Assessment of molecular weight

Molecular weight within range of training and validation set.

 

 

 

 

 

 

 

 

Assessment of log Kow (only relevant for log Kow method)

Log Kow within range of training and validation set.

 

 

 

 

 

 

 

Appendix D. MCI & Log Kow Correction Factors for 447 Compound Training Set

 

 

Correction Factor Descriptor

Coefficient for Molecular Connectivity Index (MCI) Regression Methodology

Coefficient for log Kow Regression Methodology

Occurrence

No. of instances
of each bond
found for the
current substance

(new model)

 Remark

(number of compounds

(max per structure)

 

Aromatic Hydroxy (aromatic-OH)

-0.09661

 

0.166847

27

1

1

.

(a) Counted up to twice per structure. regardless of number of occurrences..

(b) Either one or both carbons aromatic; if both carbons aromatic. can not be cyclic.

(c) Any nitrogen attached to double bond isnotcounted; also. carbonyl and thiocarbonyl arenotcounted as carbons.

(d) This is theonlyfragment counted. even if other fragments occur.

(e) Not included in regression derivation; estimated from other carbonyl fragments.

(f) Counted only once per structure. regardless of number of occurrences.