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Environmental fate & pathways

Endpoint summary

Administrative data

Description of key information

Hydrolysis:

Hydrolysis is a reaction in which a water molecule or hydroxide ion substitutes for another atom or group of atoms present in a chemical resulting in a structural change of that chemical. Potentially hydrolyzable groups include alkyl halides, amides, carbamates, carboxylic acid esters and lactones, epoxides, phosphate esters, and sulfonic acid esters (Neely, 1985). The lack of a suitable leaving group renders compounds resistant to hydrolysis.

2,2-dimethylbutane consists entirely of carbon and hydrogen and do not contain hydrolysable groups. As such, they have a very low potential to hydrolyze. Therefore, this degradative process will not contribute to their removal from the environment.

Biodegradation:

There is no key data available for 2,2-dimethylbutane. Key data is available for Hydrocarbons, C6, isoalkanes, <5% n-hexane which have been used to read across to 2,2-dimethylbutane.

An OECD 301F Manometric Respirometry test was conducted using C6-C7, n-alkanes, isoalkanes, cyclics C6 aliphatics (Shell, 1997a). The test substance was 98% degraded at the end of 28 days, and 83% degraded at the end of the 10 -day window, and was determined to be readily biodegradable. Therefore, 2,2-dimethylbutane is also assumed to be readily biodegradable.

Bioaccumulation:

A QSAR prediction for 2,2 -dimethylbutane indicates a bioconcentration factor of 154 L/kg w/w.

This is supported by data available for isohexane, which can be used to read-across to 2,2 -dimethylbutane.

The BCF of Isohexane was calculated using a QSAR (Veith and Broderius, 1987), based on a log Kow of 3.6. The QSAR used to calculated the BCF of Isohexane followed the TGD guideline and so is deemed suitable for the assessment of bioconcentration. The calculated BCF of 501.187 indicates that Isohexane does not greatly bioaccumulate in the lipids of ecological receptors. 

Adsorption / Desorption:

The log Koc for 2,2-dimethylbutane is reported to be 3.15. The bioconcentration potential of 2,2-dimethylbutane was estimated using the Episuite program v 4.11 provided by the US EPA. This QSAR model is well documented and peer reviewed. The input parameters included: CAS Number: 75-83-2 and a log Kow of 3.82.

To support this, data are read-across to n-Hexane, based on an analogue approach.

The log Koc of n-hexane was calculated to be 3.34. 

Additional information