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Environmental fate & pathways

Phototransformation in air

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Description of key information

Parent compound butyryl chloride and hydrolysis product butyric acid:
After evaporation or exposure to air, the substances will be slowly degraded by photochemical processes.

Key value for chemical safety assessment

Additional information


In Article 13 of Regulation (EC) No 1907/2006, it is laid down that information on intrinsic properties of substances may be generated by means other than tests, provided that the conditions set out in Annex XI (of the same Regulation) are met.

According to Annex XI of Regulation (EC) No 1907/2006 (Q)SAR results can be used if (1) the scientific validity of the (Q)SAR model has been established, (2) the substance falls within the applicability domain of the (Q)SAR model, (3) the results are adequate for the purpose of classification and labeling and/or risk assessment and (4) adequate and reliable documentation of the applied method is provided.

For the assessment of butyryl chloride (CAS 141-75-3) and its hydrolysis product butyric acid (CAS 107-92-6) (Q)SAR results were used for phototransformation in air. The criteria listed in Annex XI of Regulation (EC) No 1907/2006 are considered to be adequately fulfilled and therefore the endpoint(s) sufficiently covered and suitable for risk assessment.

Therefore, further experimental studies on phototransformation in air are not provided.



Parent compound butyryl chloride (CAS 141-75-3):

The phototransformation in air was calculated with the estimation model AOPWIN v1.92. Based on an estimated OH radical rate constant of 3.8869 E-12 cm3/(molecule*sec), the half-life of butyryl chloride was calculated to be 4.1 days (conditions: sensitiser for indirect photolysis: OH; 0.5 E06 OH/cm3, 24-h d; EPISuite v4.11, BASF SE, 2022). Based on this result the substance will be slowly degraded by photochemical processes, after evaporation or exposure to air.

This estimation refers to dry air. In mist, rain, droplets and aerosols hydrolysis will be the major fate process of the acid chloride due to the short half-life in aqueous solutions. Therefore this estimate may be of low relevance.


Hydrolysis product butyric acid (CAS 107-92-6)

Based on an estimated OH-radical rate constant of 2.6977 E-12 cm3/(molecule*sec), a half-life of 5.947 days was calculated for the photochemical degradation by OH-radicals (conditions: sensitiser for indirect photolysis: OH, 0.5 E06 OH/cm³, 24-h d; BASF SE, 2022).

Based on this result the substance will be slowly degraded by photochemical processes, after evaporation or exposure to air.