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Henry's Law constant

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Reference
Endpoint:
Henry's law constant
Type of information:
(Q)SAR
Remarks:
Migrated phrase: estimated by calculation
Adequacy of study:
key study
Study period:
2017-02-20
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
results derived from a valid (Q)SAR model and falling into its applicability domain, with adequate and reliable documentation / justification
Qualifier:
no guideline followed
Principles of method if other than guideline:
Calculation of Henry's Law Constant. Software used: SRC HENRYWIN v3.20: Bond estimation method
GLP compliance:
no
Key result
H:
234 Pa m³/mol
Temp.:
25 °C
Remarks on result:
other: The substance is within the applicability domain of the model.

Result table for Bond Contribution method from HENRYWIN v3.20

Class

 Bond Contribution Description

Comment

 Value

Hydrogen

5 Hydrogen to Carbon (aliphatic) Bonds

 

-0.5984

Hydrogen

4 Hydrogen to Carbon (aromatic) Bonds

 

-0.6172

Fragment

2 C-Car

 

0.3239

Fragment

1 C-CL

 

0.3335

FragmentT

6 Car-Car

 

1.5828

Result

BOND ESTIMATION METHOD for LWAPC VALUE

 Total

1.025

Henry’s Law Constant at 25 °C

= 2.31E-003 atm-m3/mole

= 9.45E-002 unitless

= 2.34E+002 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 (140.61  g/mol)

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

Not 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.

On-Line HENRYWINUser's Guide:

-      Appendix D: Bond Method Contribution Values used by HENRYWIN.

-      Appendix E: Bond Method Correction Factors Used by HENRYWIN.

-      Appendix G. Chemicals Used to Derive Bond Contribution Values & Correction Factors.

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

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

Not applicable

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

The Henry's Law Constant of the test item is 2.34E+002 Pa m3/mole at the temperature of 25 °C.

Key value for chemical safety assessment

Henry's law constant (H) (in Pa m³/mol):
234
at the temperature of:
25 °C

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. Furthermore according to Article 25 of the same Regulation testing on vertebrate animals shall be undertaken only as a last resort.

 

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 2 -Methylbenzylchloride (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.

 

Therefore, further experimental studies on Henry's Law Constantare not provided.