Registration Dossier
Registration Dossier
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EC number: 700-567-0 | CAS number: 1231728-34-9
Endpoint summary
Administrative data
Description of key information
Additional information
The test substance hexanoic acid, 3,5,5-trimethyl-, tin (2+)salt (2:1) is a light yellow liquid at room temperature. In a study conducted according to OECD Guideline 102 and EU Method A.1 no melting point could be detected in the DSC measurements. A very small effect was visible that was caused by a glass transition at around -57°C which indicated that the test item had solidified amorphously. In a study conducted according to OECD Guideline 103 and EU Method A.2 and using the DSC method no boiling point was found prior to decomposition which started at 205°C as could be noticed via the DSC measurement. The relative density D(20/4) was found to be 1.205 (OECD Guideline 109 and EU Method A.3: pycnometer method). According to REACH Regulation (Annex VII, column 2, 7.14), the study on the particle size distribution does not need to be conducted if the substance is marketed or used in a non-solid or non-granular form. The test substance is a liquid at standard conditions and therefore the study does not need to be done. In a study conducted according to OECD Guideline 104 and EU Method A.4 a vapour pressure of 0.002 hPa at 20°C was determined. When introduced in water, the tin bis(3,5,5 -trimethylhexanoate) will dissociate, where the Sn(II) will be initially speciated as the Sn(OH)2 substance, which will be oxidised in oxygenated solutions to become the insoluble, separate inorganic Sn(IV)O2 species. According to REACH Regulation (Annex VII, column 2, 7.8), the partition coefficient does not need to be determined if the substance is inorganic and therefore the log Kow for the SnO2 does not need to be determined. The 3,5,5-trimethylhexanoic acid part of the salt has its maximum water solubility at pH values > 6.8 where it exists completely as the 3,5,5 -trimethyl hexanoate anion. The calculation of the n-octanol/water partition coefficient for the 3,5,5 -trimethylhexanoate component via ACD/Labs v.12.01 yielded a value of 2.83 at pH 2.8 (log Kow) and 0.65 at pH 7 (log D; 25°C each). Therefore, the substance will have a low potential for adsorption to organic matter of soils and sediments and for bioaccumulation in aquatic organisms at environmental relevant pH values. The water solubility of the test substance was investigated in a study conducted according to OECD Guideline 105 and EU Method A.6. The Sn(II) component is dissociated and oxidized in oxygenated water to become insoluble Sn(IV)O2. The 3,5,5 -trimethylhexanoate component has a pH-dependent solubility which is ca. 5600 mg/L at pH values >=7 and 20°C (at pH 4: ca. 630 mg/L) . According to the classification scheme, the 3,5,5-trimethylhexanoate component can be considered as soluble in water at pH values >=7. According to REACH Regulation (Annex VII, column 2, 7.6), the study on surface tension has only to be done if based on the structure of the substance surface-active properties are to be expected. The test substance does not contain any chemical groups indicating surface-active properties. The flash point of the test substance was determined to be >100°C at 1013 hPa (ISO 2719: 2002). The auto-ignition temperature of the test substance was determined in a study conducted according to EU Method A.15 and DIN 51 794. The auto-ignition temperature was found to be 515°C at 1036 hPa. According to REACH Annex XI, 1. a test for determination of the flammability of the substance is scientifically not necessary, because according to the TGDs (chapter R.7.1.10), for liquids the primary value for ease of ignition is the flash point. Reliable data on the flash point are available and therefore the study does not need to be done.
According to REACH Regulation (Annex VII, column 2, 7.11), the study on explosiveness does not need to be done if the test substance does not contain chemical groups indicating explosive properties. The test substance does not contain any chemical groups indicating explosive properties. In a study conducted according to EU Method A.21 no oxidising properties of the test substance were found.
The dissociation constant was determined to be pKa = 5.0, in a study conducted according to OECD guideline 112 and DIN EN ISO/IEC, using the titration method.
The dissociation constant of 3,5,5-trimethylhexanoic acid was calculated (ACD/Labs Version 12.01) to be pKa = 4.8 at 25 °C.
The pKs values of the salt and of salt-constituent 3,5,5-trimethylhexanoic acid are almost identical.
This is in accordance with, and a proof of the expected total dissociation of the salt to Tin(2 +)-cation and the 3,5,5-trimethylhexanoat(-)-anion.
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