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Environmental fate & pathways

Phototransformation in air

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Description of key information

The hydroxyl radical degradation half-life of butenes range from 7.5 to 12 hours. This range was derived from two members of the butenes category: but-1-ene (CAS 106-98-9) and 2-methylpropene (CAS 115-11-7).

Key value for chemical safety assessment

Half-life in air:
12 h

Additional information

Atkinson (1985) is a review article with no data reported on the test methods or conditions of the original data source. Never-the-less, the data are taken from a published, peer-reviewed journal article and are considered to be suitable for this endpoint. Measured data from author and other investigators were quality assessed and then used to develop rate constants for different chemicals. Therefore, this value represents a valid rate constant for the substances based on all valid studies at the time of publication.

Atkinson (1985) recommended a rate constant with hydroxyl radicals of 3.14 E-11 cm3/mol/sec for but-1-ene and 5.14 E-11 cm3/mol/sec for 2-methylpropene. These rate constants equate to half-lives of 12 and 7.5 hours respectively. These data indicate that indirect photolysis is expected to contribute significantly to degradation of butenes in the environment. The 'key value for chemical safety assessment' has been completed using the most conservative of the available data.