Registration Dossier
Registration Dossier
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EC number: 806-451-7 | CAS number: 42532-60-5
Phototransformation in air
Administrative data
Link to relevant study record(s)
Description of key information
The atmospheric lifetime (1/pseudo-first order rate constant) for C4 fluorinated isonitrile is 30 years by a weight of evidence. The corresponding half-life is 20.8 years.
Key value for chemical safety assessment
- Half-life in air:
- 20.8 yr
Additional information
Phototransformation was examined by the registrant and in two publications in the open literature. All studies were considered reliable with restrictions and none were GLP compliant. However, all were conducted in accord with scientifically sound principles. The registrant's study and the first publication used a relative rate method, while the second publication used an absolute rate method. The registrant study reported only an atmospheric lifetime (1/rate constant) while the two literature studies reported both rate constants and lifetime. Each report used a different method to calculate lifetime from experimental data. To allow comparability, published rate constants measured at 25 °C were compared to data for the standard reference substance methyl chloroform, for which there is a comprehensive analysis of abundance in the atmosphere as well as rate of emission and removal. For both publications, the calculated atmospheric lifetime was ca. 32 years. The first publication indicates that the degradation products are carbonyl difluoride and trifluoroacetyl fluoride, which are subject to hydrolysis to hydrogen fluoride. The second publication provides a temperature relationship for the reaction with hydroxyl radical. The relationship had considerable variability (defined as 2σ) in its preexponential and activation energy terms. The overall range for calculated rate constant at, e.g. 272K, was 6.4 (1.6 - 18) E-16 cm³/(molecule*sec). However, the rate constant directly measured at 298 K was in excellent agreement with the first publication. Because the greatest amount of study information is available for the registrants own study, it is given more weight than the other two and its results are reported as such.
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