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Environmental fate & pathways

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Due to rapid hydrolysis, stearoyl chloride will not be present in the environment for a significant time. Therefore the fate in the environment is mainly based on the hydrolysis product stearic acid.

 

Adsorption potential

The log Koc of stearyol chloride was calculated to be between 4.1 and 4.8 (Koc = 12250 to 60740; BASF SE, 2009). Therefore adsorption to soil and sediment is expected. However, stearoyl chloride is expected to hydrolyse rapidly and to form stearic acid.

The hydrolysis product stearic acid has a calculated log Koc of 4.1 to 4.7 (uncharged molecule; BASF SE, 2009).

The pH-corrected values for the charged molecule show that with a log Koc of 3.74 at pH 7 adsorption to solid soil phase is expected (BASF SE, 2010).

However, the hydrolysis product is readily biodegradable.

 

 

Henry’s Law Constant

A Henry law constant (HLC) of 6.27E3 Pa*m³/mol was calculated by SRC HENRYWIN v3.20 (BASF SE, 2009). This indicates a volatile character of the test substance. However, stearoyl chloride is expected to rapidly hydrolyse and to form stearic acid. Therefore, this model calculation may be of low relevance.

Stearic acid has a HLC of 0.0904 Pa*m³/mol, which was calculated based on experimental data on vapour pressure and water solubility (BASF SE, 2009). Additionally, most of the stearic acid molecules will be present in dissociated form under environmental relevant pH conditions (pKa = 4.75).

Therefore it may be concluded, that due to rapid hydrolysis, stearoyl chloride will only exist for a short time in water and the hydrolysis product does not evaporate into air.

 

Distribution

Based on the results of the Mackay Level 1 calculation, the substance will over time preferentially distribute into the compartments sediment (43.2%) and soil (42.8%).

Stearoyl chloride (CAS 112 -76 -5) rapidly decomposes in water and forms HCl (CAS 7647-01-0) and stearic acid (CAS 57 -11 -4). Therefore, the model calculation may be of low relevance.

 

The Mackay Level 1 calculation for the hydrolysis product stearic acid indicates that the substance will over time preferentially distribute into the compartments sediment (50.1%) and soil (49.5%). The data refer to the uncharged molecule (calculated pKa value: 4.75).

However, the model does not consider the ionic structure of the molecule at environmentally relevant pH conditions (pH 5 to pH 9). The model may underestimate the distribution into water.