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EC number: 221-975-0 | CAS number: 3302-10-1
Henry's Law constant
Administrative data
Link to relevant study record(s)
- Endpoint:
- Henry's law constant
- Type of information:
- (Q)SAR
- Remarks:
- and calculation from water solubility and vapour pressure.
- Adequacy of study:
- supporting study
- 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 limited documentation / justification
- Qualifier:
- no guideline followed
- Principles of method if other than guideline:
- Modelling with SRC - HENRYWIN v3.10: Bond estimation method
- GLP compliance:
- no
- Key result
- H:
- 0.104 Pa m³/mol
- Temp.:
- 20 °C
- Atm. press.:
- 1 013 hPa
- Remarks on result:
- other: from water solubility and vapour pressure
- H:
- 0.286 Pa m³/mol
- Temp.:
- 20 °C
- Atm. press.:
- 1 013 hPa
- Remarks on result:
- other: QSAR, bond contribution method
- H:
- 0.403 Pa m³/mol
- Temp.:
- 25 °C
- Atm. press.:
- 1 013 hPa
- Remarks on result:
- other: QSAR, bond contribution method
- Conclusions:
- Henry's law constant (HENRYWIN v3.10, bond contribution method): 0.286 Pa*m³/mol at 20 °C.
Henry's law constant (from water solubility and vapour pressure): 0.104 Pa*m^3/mol at 20°C.
Concluding, 3,5,5-trimethylhexanoic acid is expected to have a low potential to volatilise from aqueous solutions. - Executive summary:
Using HENRYWIN v3.10, Henry's law constant was calculated according to the bond contribution method to be 0.403 Pa*m³/mol (25 °C; ECT, 2008). The corresponding value according to HENRYWIN (bond contribution) for 20°C is 0.286 Pa*m^3/mol.
Because the submission substance is an acid (pKa 4.8), this may overestimate Henry's law constant for the dissociated fraction.
Estimating Henry's law constant from vapour pressure (0.46 Pa at 20°C) and water solubility (0.7 g/L at 20°C and pH 3.8) results in a value of 0.104 Pa*m^3/mol at 20°C. Based on a pKa of 4.8 and the pH at which the water solubility had been determined (pH 3.8), this value corresponds to a dissociation degree of 8.5% according to the Henderson-Hasselbach equation. Therefore, at higher environmental pH Henry's law constant will even be lower.
Concluding, 3,5,5-trimethylhexanoic acid is expected to have a low potential to volatilise from aqueous solutions.
Reference
Estimating Henry's law constant from vapour pressure (0.46 Pa at 20°C) and water solubility (0.7 g/L at 20°C and pH 3.8) results in a value of 0.104 Pa*m^3/mol at 20°C. Based on a pKa of 4.8 and the pH at which the water solubility had been determined (pH 3.8), this value corresponds to a dissociation degree of 8.5% according to the Henderson-Hasselbach equation. Therefore, at higher environmental pH Henry's law constant will even be lower.
Description of key information
HLC = 0.104 Pa*m³/mol at 20 °C (calculated from water solubility and vapour pressure)
Key value for chemical safety assessment
- Henry's law constant (H) (in Pa m³/mol):
- 0.104
- at the temperature of:
- 20 °C
Additional information
Using HENRYWIN v3.10 Henry's law constant was calculated according to the bond contribution method to be 0.403 Pa*m³/mol (25 °C; ECT, 2008):
HLC (Pa*m³/mol) |
Temperature (°C) |
Method |
Reliability |
Reference |
0.403 |
25 |
estimated: SRC - HENRYWIN v3.10 |
2 |
ECT (2008) |
The corresponding value according to HENRYWIN (bond contribution) for 20°C is 0.286 Pa*m^3/mol.
Because the submission substance is an acid (pKa 4.8), this may overestimate Henry's law constant for the dissociated fraction.
Estimating Henry's law constant from vapour pressure (0.46 Pa at 20°C) and water solubility (0.7 g/L at 20°C and pH 3.8) results in a value of 0.104 Pa*m^3/mol at 20°C. Based on a pKa of 4.8 and the pH at which the water solubility had been determined (pH 3.8), this value corresponds to a dissociation degree of 8.5% according to the Henderson-Hasselbach equation. Therefore, at higher environmental pH Henry's law constant will even be lower.
Therefore, as a key result for environmental exposure and risk assessment the value derived from water solubility and vapour pressure is used.
Concluding, 3,5,5-trimethylhexanoic acid is expected to have a low potential to volatilise from aqueous solutions.
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