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Environmental fate & pathways

Henry's Law constant

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Description of key information

From the water surface the major components of the reaction mass will not evaporate into the atmosphere.

Key value for chemical safety assessment

Additional information

The Henry's Law constant (HLC) was calculated according to the bond estimation method of the HENRYWIN Program (v3.20) of EPI Suite v4.11 for the three major components of the reaction mass of 2 -piperazin-1 -ylethanol, piperazine-1,4 -diethanol and piperazine (50, 25 and 25%).

These values are representative for the uncharged molecules. At environmental conditions the major components of the reaction mass are expected to be ionised, therefore pH-corrected Koc's were calculated according to the REACH Guidance document (2008). The resulting Henry's Law constants are listed below:

2 -Piperazin-1 -ylethanol (CAS 103 -76 -4):

- uncharged molecule: bond estimation method: 2.37 E-08 Pa*m³/mol

- charged molecule: REACH Guidance R.7, appendix R7.1 -2, p. 189:

pH 5: 6.38 E-13 Pa*m³/mol

pH 7: 6.36 E-11 Pa*m³/mol

pH 9: 5.03 E-09 Pa*m³/mol

Piperazine-1,4-diethanol (CAS 122 -96 -3):

-uncharged molecule: bond estimation method: the substance is not within the applicability domain of the estimation model.

-charged molecule: REACH Guidance R.7, appendix R7.1 -2, p. 189:

pH 5: 8.18 E-13 Pa*m³/mol

pH 7: 7.93 E-11 Pa*m³/mol

pH 9: 1.93 E-09 Pa*m³/mol

Piperazine (CAS 110-85-0):

-uncharged molecule: bond estimation method: the substance is not within the applicability domain of the estimation model.

HLC calculation based on measured data (vapor pressure and water solubility): 2.53E-03 Pa*m³/mol

-charged molecule: REACH Guidance R.7, appendix R7.1 -2, p. 189:

pH 5: 4.15 E-09 Pa*m³/mol

pH 7: 4.14 E-07 Pa*m³/mol

pH 9: 3.50 E-05 Pa*m³/mol

Based on the HLC for the charged molecules, the major components of the reaction mass will not evaporate from the water surface into the atmosphere.