Registration Dossier

Administrative data

Endpoint:
Henry's law constant
Type of information:
(Q)SAR
Adequacy of study:
supporting study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Scientifically acceptable calculation method
Justification for type of information:
The Henry Law Constant has only been calculated for the PNEC calculation, this endpoint is not a REACH requirement for Annex VIII registration and hence, it is only entered as supporting study with limited documentation.

HENRYWIN estimates the Henry's Law Constant of organic compounds at 25°C using the methodology originally described by Hine and Mookerjee (1975). The original methodology was updated and expanded at Syracuse Research Corporation as described in Meylan and Howard (1991). A subsequent update (HENRYWIN version 2) included additional fragment and correction factors. The current HENRYWIN program (version 3) extends the methodology to allow estimation of Henry's law constant over a temperature range (0 to 50°C). In addition, version 3 includes an experimental Henry's law constant database of 1829 compounds.

HENRYWIN estimates Henry's Law Constant (HLC) by two separate methods that yield two separate estimates. The first method is the Bond Contribution Method and the second is the Group Contribution Method. The Bond Method is able to estimate many more types of structures than the Group Method because it has a more extensive library of bond contribution values.

HENRYWIN requires only a chemical structure to make these predictions. Structures are entered into HENRYWIN by SMILES (Simplified Molecular Input Line Entry System) notations.

The following abstract from the Meylan and Howard (1991) article briefly summarizes the bond methodology:

"Bond contribution values, used to estimate Henry's law constant (HLC)(air-to-water partition coefficient) from chemical structure, have been determined for 59 chemical bonds by a least-square analysis of HLCs for 345 organic compounds. A correlation coefficient (r2) of 0.94 was determined for the relationship between known LWAPCs (log water-to-air partition coefficients) and bond estimated LWAPCs for the 345 compound data set. The correlation increases to 0.97 when quantified correction factors are applied to selected chemical classes. The ability of the bond method to estimate LWAPCs is demonstrated by a validation test set of 74 diverse and structurally complex compounds that were not included in the least-square analysis. The correlation coefficient for the validation set is 0.96." (Note: the bond value and correction factor list has been expanded significantly since the journal article was published).

The bond and group contribution values in HENRYWIN use log units described by either LWAPC (log water-to-air partition coefficient) or Log Gamma. LWAPC and Log Gamma are the same; they reflect the terminology of the respective journal articles. They are the logarithm of the reciprocal unitless HLC. The unitless HLC is converted to units of atm-m3/mole by multiplying it by the gas constant (8.206x10-5 atm-m3/mole K) and the temperature (deg K).

References:

Hine, J. and Mookerjee, P.K. 1975. The intrinsic hydrophilic character of organic compounds. Correlations in terms of structural contributions. J. Org. Chem. 40: 292-298.

Meylan WM, Howard PH. 1991. Bond contribution method for estimating Henry's law constants. Environ Toxicol Chem 10:1283–93.

Data source

Reference
Title:
EPI Suite Version 4.10
Year:
2012
Bibliographic source:
HenryWin v3.20

Materials and methods

Test guideline
Qualifier:
according to guideline
Guideline:
other: REACH guidance on QSARs Chapter R.6 , May 2008
Deviations:
not applicable
Principles of method if other than guideline:
The calculation of the Henry´s Law Constant of the test material was performed with US-EPA software EPIWIN/HENRYWIN v3.20. The Program uses two different models for this approach: Bond Method and Group Method.
GLP compliance:
no
Remarks:
(not applicable)

Test material

Constituent 1
Chemical structure
Reference substance name:
2,3-epoxypropyl isopropyl ether
EC Number:
223-672-9
EC Name:
2,3-epoxypropyl isopropyl ether
Cas Number:
4016-14-2
Molecular formula:
C6H12O2
IUPAC Name:
2-[(propan-2-yloxy)methyl]oxirane
Test material form:
not specified
Details on test material:
- Name of test material (as cited in study report) : Oxirane, (1-methylethoxy)methyl -
- SMILES: O(C1COC(C)C)C1

Results and discussion

Henry's Law constant Hopen allclose all
H:
0.334 Pa m³/mol
Temp.:
25 °C
Remarks on result:
other: Bond method estimation
H:
0.062 Pa m³/mol
Temp.:
25 °C
Remarks on result:
other: Group method estimation

Applicant's summary and conclusion

Conclusions:
The study report describes a scientifically accepted calculation method for the biodegradability prediction using the US-EPA software HENRYWIN v3.20 .No GLP criteria are applicable for the usage of this tool and the QSAR estimation is easily repeatable.
Executive summary:

The prediction for the distribution between aqueous solution and air for the test substance was determined by the computer program HENRYWIN v3.20 (EPIWIN software) by US-EPA . Henry´s law states that the solubility of a gas in a liquid solution at a constant temperature will be proportional to the partial pressure of the gas which is above the solution (Henry, W., 1803). Sometimes, the term “air/water partition coefficient” refers to the dimensionless Henry´s law constant (HLC) and therefore describes the ration of the equilibrium concentration of a dissolved substance in air and water.

The program calculates the Henry´s Law Constant based on the Bond Method of 3.34 E-001 Pa*m³/mol at an ambient temperature of 25 °C. The Group Method shows a value of 6.23 E-002 Pa*m³/mol at an ambient temperature of 25 °C as result .