(2E)-1,1,1,4,4,4-hexafluoro-2-butene

Phototransformation in air

Description of key information

The half-life for the notified substance in the atmosphere was estimated to be 62 days using the EPA OH concentration default of 1.5E+06 OH molecules/cm³and a 12 hour day for reaction to occur (daylight).

Key value for chemical safety assessment

Half-life in air:

62 d

Degradation rate constant with OH radicals:

0 cm³ molecule-1 s-1

Additional information

In the atmosphere the substance is expected to react with OH radicals in the atmosphere.  Baasandorj et al measured the reaction rates of cis-1,1,1,4,4,4-hexafluorobut-2-ene (Z isomer) with tropospheric OH radicals and the resulting half-life was approximately 20 days.  The final atmospheric degradation products for the cis isomer are HF and CO₂which are also expected for the notified substance.  The reaction rates of the notified substance with Cl atoms and OH radicals were reported (Osterstrom, 2017). The reaction rate with chlorine atoms was 1.36E-11 cm³molecule^-1sec^-1and the reaction rate with OH radicals was 1.72E-13 cm³molecule^-1sec^-1.  Osterstrom reported a global warming potential (GWP) for the notified substance of 7. The half-life for the notified substance in the atmosphere was estimated to be 62 days using the EPA OH concentration default of 1.5E+06 OH molecules/cm³and a 12 hour day for reaction to occur (daylight).

t ½ (sec) =      ln2x2                                             =      0.693x2             =     5.4E+06 sec (62 days)   

                 kOH x1.5E+06 OH molecules/cm3    1.72E-13 x 1.5E+06