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Environmental fate & pathways

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Description of key information

Additional information

Reaction mass of DIPE and 2-methylpent-2-ene consists of moderately volatile organic substances (

overall vapour pressure 128 hPa at 20°C and 155 hPa at 25°C, all known constituents in the range of 5 – 250 hPa at 20°C considered as moderately volatile) of relatively low molecular weight (average ca. 93 g/mol). An overall Henry’s law constant (H) calculated from the parameters used for exposure assessment is 420 Pa m3/mol (at 20°C). According to the TGD IR & CSA R7a (p.191), chemicals with H values around 100 Pa m3/mol are considered to volatilise rapidly from the water compartment. At the same time the reaction mass is soluble in water (2.8 g/L). Vapour pressure for the two main components DIPE and 2-methylpent-2-ene are similar (ca. 200 hPa at 25°C). DIPE is soluble in water (ca. 3.1 g/L), but 2-methylpent-2-ene was estimated to be only slightly water soluble (ca. 0.08 g/L). Based on these data, DIPE and 2-methylpent-2-ene are predicted to volatilise rapidly from water based on estimated Henry’s law constants, with a more rapid volatilization of 2-methylpent-2-ene due to lower water solubility. Both compounds will be rapidly oxidized in the atmosphere (estimated atmospheric oxidation half-lives of ca. 1.5 - 5 hours). DIPE is not readily biodegradable, while 2-methylpent-2-ene is predicted to be readily biodegradable. At least inherent biodegradability is supported by conclusions on biodegradability of higher olefins (C6-C18) [1]. DIPE shows a low potential for adsorption as the log Pow value, based on literature data and a measurement with the reaction mass using the HPLC method is below 3. The estimated log Kow for 2-methyl-2-pentene using QSAR is 3.1, the estimated log Koc 2.1 - 2.7. With the HPLC method, the highest determined log Pow was 4.3 with a corresponding highest log Koc of 2.6 (Koc = 362). These values, that may probably be assigned to 2-methylpent-2-ene and/or other methylpentene or methylpentane isomeres, indicate a moderate potential for adsorption. Chemicals with a Koc value between 150 and 500 are likely to move through the soil at a moderate rate [2]. Strong binding to soil particles is only expected for a log Pow > 5 or log Koc > 4 and adsorption to sediment it not expected below a log Koc of 2.7 - 3 (TGD IR & CSA R7 p.154). Overall, other methylpentene isomers and methylpentane [3] are expected to distribute in the environment in a similar way to 2-methylpent-2-ene. None of the constituents of the reaction mass of DIPE and 2-methylpent-2-ene are considered to bioaccumulate (see chapter 8).

[1] OECD SIDS: Higher Olefins-Category, SIDS Initial Assessment Report ForSIAM19; Berlin, Germany, 19-21 October 2004, prepared by the American Chemistry Council, Higher Olefins Panel

[2] Swann RL, Laskowshi DA, McCall PJ, Vander-Kuy K and Disburger HJ (1983). A rapid method for the estimation of the environmental parameters octanol/water partition coefficient, soil sorption constant, water to air ratio and water solubility.Residue Reviews 85, 17-28.

[3] Data for CAS 107-83-5 in HSDB database http://toxnet.nlm.nih.gov/cgi-bin/sis/htmlgen?HSDB, last accessed March 2010.