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Description of key information

Parent compound pivaloyl chloride (CAS 3282-30-2): Adsorption to the solid soil phase is not expected.


Hydrolysis product pivalic acid (CAS 75-98-9): Adsorption to the solid soil phase is not expected.

Key value for chemical safety assessment

Additional information

QSAR-disclaimer


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 pivaloyl chloride (CAS 3282-30-2) (Q)SAR results were used for the estimation of the adsorption potential. 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 the adsorption potential are not provided.


 


Assessment


Parent compound pivaloyl chloride


In order to assess the adsorption potential of the parent compound pivaloyl chloride (CAS 3282-30-2), the Koc value was estimated using QSAR models (BASF SE, 2019). According to the MCI method of the KOCWIN v2.00 module of EPI Suite v4.11 the substance has a Koc of 3.4 L/kg (log Koc = 0.53). The estimation of the MCI module, which is more reliable than the log Kow method of KOCWIN v2.00, estimates the Koc based on the substance’s n-octanol/water partition coefficient (estimated log Kow = 0.89; KOWWIN v1.68). The latter method resulted in a Koc of 15.42 L/kg (log Koc = 1.19). The substance is within the applicability domain of both estimation models.  


Based on the estimated data, adsorption to the solid soil phase is not to be expected.


 


However, the parent compound pivaloyl chloride (CAS 3282-30-2) rapidly hydrolyses in contact with water and forms pivalic acid (CAS 75-98-9). The adsorption potential will therefore be also assessed based on information available for the hydrolysis product pivalic acid.


 


Hydrolysis product pivalic acid


At environmentally relevant conditions, pivalic acid (CAS 3282-30-2) is present in ionized form (pKa= 5.04 at 25°C, SPARC 4.2; pKa database query; IUPAC 8, 2537). Therefore, the adsorption coefficient was calculated according to Franco & Trapp (2008, 2009, 2010) to correct for the charged molecule at pH 5, 7, and 8. This pH range is representative for 98% of the European soils. The method is based on the dissociation constant pKa and the log Kow for the uncharged molecule (log Kow = 1.8; measured @ pH 2.5; Hexxion, 1983). The substance is slightly out of the applicability domain (AD), since the measured log Kow of pivalic acid is 1.8 and limits for the AD for acids are: ~2.18 < log Kow < 8.50. However, since the low log Kow does not point to any adsorption potential of the substance, the deviation from the AD seems of low relevance. Regarding pKa the substance is completely within the AD. The resulting log Koc is 57 L/Kg (at pH 7 and 25°C). This value was selected as key data.


 


In addition, the adsorption potential of pivalic acid (CAS 75-98-9) was estimated for the uncharged molecule using EPISuite v4.11 (BASF SE, 2018). According to the MCI method of the KOCWIN v2.00 module the substance has a Koc of 3.23L/kg (log Koc = 0.51). The estimation of the MCI module, which is more reliable than the log Kow method of KOCWIN v2.00, estimates the Koc based on the substance’s n-octanol/water partition coefficient (estimated log Kow = 1.8; measured @ pH 2.5, Hexxion, 1983). The latter method resulted in a Koc of 14.17 L/kg (log Koc = 1.15); the substance is within the applicability domain of both estimation models. 


Based on the estimated data, adsorption to the solid soil phase is not to be expected.

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