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Environmental fate & pathways

Henry's Law constant

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Reference
Endpoint:
Henry's law constant
Type of information:
(Q)SAR
Adequacy of study:
key study
Study period:
2017
Reliability:
2 (reliable with restrictions)
Qualifier:
according to guideline
Guideline:
other: Guidance on information requirements and chemical safety assessment, Chapter R.6: QSARs and grouping of chemicals, ECHA, 2008
GLP compliance:
no
H:
ca. 0 Pa m³/mol
Temp.:
25 °C
Remarks on result:
other: Bond method

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.

The Henry's Law constant (HLC) can be defined as the ratio of the concentration of a compound in the gas-phase to the concentration of the compound in a dilute aqueous solution at equilibrium.  This ratio or partition coefficient is usually known as the unitless HLC.  Most literature reports experimental HLCs as either the unitless value or as a value with units of atm-m3/mole.  The unitless value is converted to units of atm-m3/mole by multiplying it by the gas constant (8.206 X 10-5atm-m3/mole K) and the temperature (in deg K).

HENRYWIN estimates two separate HLC values (one using the group method and one using the bond method).  The bond contribution methodology splits a compound into smaller units (one atom to another atom only).  The bond method includes individual hydrogen bond values; the group method does not. 

Conclusions:
It can be concluded that 1,4-naphthoquinone has a H = 0.000199 Pa-m3/mole. The H values derived with EPISuite™, based on the Bond- Group-Method, can be considered reliable for environmental fate assessments.
Executive summary:

The Henry's law constant of 1,4-naphthoquinone was predicted by a non-experimental calculation method (HENRYWIN).

Description of key information

Key value for chemical safety assessment

Henry's law constant (H) (in Pa m³/mol):
0
at the temperature of:
25 °C

Additional information

It can be concluded that 1,4-naphthoquinone has a H = 0.000199 Pa m3/mole. The H values derived with EPISuite™, based on the Bond- Group-Method, can be considered reliable for environmental fate assessments.