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Henry's Law constant

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Endpoint:
Henry's law constant
Type of information:
calculation (if not (Q)SAR)
Remarks:
pH correction
Adequacy of study:
weight of evidence
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
accepted calculation method
Qualifier:
no guideline followed
Principles of method if other than guideline:
Correction of pH for partition coefficients for ionisable substances according to REACH Guidance Document R.7a, Appendix R.7.1-2 (p.190).
GLP compliance:
no
H:
0 Pa m³/mol
Remarks on result:
other: pH 5
H:
0 Pa m³/mol
Remarks on result:
other: pH 7
H:
0 Pa m³/mol
Remarks on result:
other: pH 9

The following input parameters were used for the calculation:

1. Test substance is a base

2. HLC of uncharged molecule: 5.67E-04 Pa·m³/mol (as estimated with the Bond Contribution Method (EPI Suite v4.11, 2014))

3. pKa: 12.33 (as estimated with SPARC v4.6).

The pKa of 12.33 indicates that this compound will exist almost entirely in the cation form in the environment.

Endpoint:
Henry's law constant
Type of information:
(Q)SAR
Adequacy of study:
weight of evidence
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
results derived from a valid (Q)SAR model, but not (completely) falling into its applicability domain, with adequate and reliable documentation / justification
Remarks:
No. of instances for the following bonds were exceeded: hydrogen to carbon (aliphatic) bonds (39 identified, 27 in set), carbon to carbon bonds (16 identified, 9 in set) and carbon to nitrogen bonds (4 identified, 3 in set)
Qualifier:
no guideline followed
Principles of method if other than guideline:
Calculation using HENRYWIN (v3.20) Bond Method
GLP compliance:
no
Specific details on test material used for the study:
- Substance name (as in EPISuite CAS inventory): 95-38-5
- SMILES: CCCCCCCCC=CCCCCCCCC1=NCCN1CCO
- The QSAR was performed with the main constituent of this UVCB
Key result
H:
0.001 Pa m³/mol
Temp.:
25 °C

Result table for Bond Contribution Method from HENRYWIN v3.20:

CLASS

BOND CONTRIBUTION DESCRIPTION

COMMENT

VALUE

HYDROGEN

39

Hydrogen to Carbon (aliphatic) Bonds

 

-4.6674

HYDROGEN

2

Hydrogen to Carbon (olefinic) Bonds

 

-0.2010

HYDROGEN

1

Hydrogen to Oxygen Bonds

 

3.2318

FRAGMENT

16

C-C

 

1.8609

FRAGMENT

2

C-Cd

 

0.1269

FRAGMENT

4

C-N

 

5.2040

FRAGMENT

1

C-O

 

1.0855

FRAGMENT

1

C=N

Estimate

0.0000

FRAGMENT

1

Cd=Cd

 

0.0000

RESULT

 

Bond estimation method for LWAPC value

 

6.641

 

HENRYs LAW CONSTANT at 25 °C

5.60E-009 atm·m3/mole

2.29E-007 unitless

5.67E-004 Pa·m3/mole

Executive summary:

QPRF: HENRYWIN v3.20: Bond contribution method

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

Degree of volatilisation of substances from the aquatic environment

Dependent variable

Henry’s Law Constant

3.2

Algorithm
(OECD Principle 2)

Model or submodel name

HENRYWIN: Bond contribution method

Model version

v. 3.20

Reference to QMRF

Henry’s Law constant (HLC) using HENRYWIN v3.2: Estimation Accuracy (QMRF)

Predicted value (model result)

See “Results and discussion: Henry’s Law constant H”

Input for prediction

Chemical structure via CAS number or SMILES

Descriptor values

- Bond contribution values

- Correction factors

3.3

Applicability domain
(OECD principle 3)

Domains:

1) Molecular weight (range of test data set: 26.04 to 451.47 g/mol, mean: 144.64 g/mol) (On-Line HENRYWIN User’s Guide, Ch. 7.4 Estimation Domain and Appendix G)

Substance within range (350.59 g/mol)

2) Maximum number of instances of bond in any of the training set compounds (On-Line HENRYWIN User’s Guide, Appendix D)

Exceeded

3) Maximum number of instances of correction factor in any of the training set compounds (On-Line HENRYWIN User’s Guide, Appendix E)

Not exceeded

3.4

The uncertainty of the prediction
(OECD principle 4)

According to REACH Guidance Document R.7a, Appendix R.7.1-1 (Nov. 2012), measurement of HLC is not highly accurate, especially for very high or very low HLC values. The bond contribution method regarded by Altschuh et al. (1999) to produce the most reliable results with the exception of organochlorine pesticides. However, for some compounds, the method can yield a Henry's Law constant of 1.0x10-12atm*m3/mol or smaller. Numbers which are smaller than this value may be unrealistically low.

3.5

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

The compound is split into a summation of individual bonds which comprise the compound. The summation of these bonds (= bond contribution values) is set equal to LWPAC. Correction factors were developed to correct for polar interactions and other deviations from the regression curve, which are applied to members of some chemical classes.

References:

Altschuh, J.R., Bruggemann, H. Santl, G. Eichinger, and O.G. Piringer.1999. Henry’s law constants for a diverse set of organic chemicals: experimental determination and comparison of estimation methods. Chemosphere 39: 1871-87.

Identified number of bonds and correction factors for the current substance:

HLC Appendix D, Table D-1: Bond Contribution Values Derived by Least-Square Regression Analysis

Bond

Coefficient
Value

No. Compounds
 in Training Set
containing
the Bond

Maximum No.
of instances of
each Bond
occurring in any
single compound

Comment

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

C-H

-0.119677

284

27

Hydrogen bond

39

Cd-H

-0.100481

43

6

Hydrogen bond

2

O-H

3.23177

42

3

Hydrogen bond

1

C-C

0.116304

200

9

 

16

C-Cd

0.063454

27

3

 

2

C-N

1.300997

20

3

 

4

C-O

1.085473

83

4

 

1

Cd-Cd

0.099661

5

1

 

1

HLC Appendix D, Table D-2: Bond Contribution Values from a Subsequent Regression

Not applicable

 

HLC Appendix D, Table D-3: Additional Bond Contribution Values Used HENRYWIN

Bond

Coefficient Value

Source

Bond identified

C=N

0

based on limited pesticide data

1

 

HLC Appendix E, Table E-1: Bond Correction Factors Derived from the Original Regression

Not applicable

 

HLC Appendix E, Table E-2: Bond Correction Factors Derived from the Second Regression

Not applicable

 

HLC Appendix E, Table E-3: Bond Correction Factors Derived Individually

Not applicable

Description of key information

For 2-(2-heptadec-8-enyl-2-imidazolin-1-yl)ethanol (CAS 95-38-5) the Henry's Law constant is calculated to be 5.67E-04 Pa·m³/mole based on the Bond method. The pH-corrected constants (for dissociating substances) are calculated to be 2.65E-11 to 2.65E-07 Pa·m³/mole at pH values from 5 - 9. Substances with a Henry's Law constant of <100 Pa·m³/mole will not evaporate into the atmosphere from the water surface.

Key value for chemical safety assessment

Additional information

QSAR-disclaimer:

In Article 13 of Regulation (EC) No 1907/2006, it is laid down that information on intrinsic properties of substances may be generated by means other than tests, provided that the conditions set out in Annex XI (of the same Regulation) are met.According to Annex XI of Regulation (EC) No 1907/2006 (Q)SAR results can be used if (1) the scientific validity of the (Q)SAR model has been established, (2) the substance falls within the applicability domain of the (Q)SAR model, (3) the results are adequate for the purpose of classification and labeling and/or risk assessment and (4) adequate and reliable documentation of the applied method is provided.

For the assessment of the main constituent of CAS 95-38-5(Q)SAR results were used for Henry's Law constant.The criteria listed in Annex XI of Regulation (EC) No 1907/2006 are considered to be adequately fulfilled and therefore the endpoint(s) sufficiently covered and suitable for risk assessment.