Registration Dossier
Registration Dossier
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EC number: 200-899-1 | CAS number: 75-76-3
Phototransformation in air
Administrative data
Link to relevant study record(s)
Description of key information
Phototransformation in air: Rate constant for reaction with OH radicals:
Measured rate constant for reaction with OH radicals 1.0E-12 cm3 molecule-1 s-1 at 24°C (half-life 16 days)
Key value for chemical safety assessment
- Half-life in air:
- 16 d
- Degradation rate constant with OH radicals:
- 0 cm³ molecule-1 s-1
Additional information
Tetramethylsilane contains no chromophores that would absorb visible or UV radiation so direct photolysis is not likely to be significant. Indirect photolysis resulting from gas-phase reaction with photochemically-produced hydroxyl radicals may occur.
An experimental relative rates study (Atkinson, 1991) found that the NO3 radical and O3 reactions are of no importance as tropospheric removal processes for this compound. The dominant gas-phase chemical loss process is by reaction with the OH radical, with measured rate constant of 1.0E-12 cm³ molecule-1 s-1 at 24°C (calculated half-life 16 days, using tropospheric concentration of OH radicals 5E05 molecule/cm3 over 24 h period (EC, 2003)).
A further experimental relative rates study (Sommerlade et al., 1993) found a reaction with the OH radical rate constant of 1.25E-12 cm³ molecule-1 s-1 at 24°C (calculated half-life 12.5 days, using tropospheric concentration of OH radicals 5E05 molecule/cm3 over 24 h period (EC, 2003)).
In another study (Tuazon, 2000) a reaction with OH radicals resulted in a rate constant of 8.5E-13 cm³ molecule-1 s-1 (calculated half-life 19 days, using tropospheric concentration of OH radicals 5E05 molecule/cm³ over 24 h period (EC, 2003))
Reference:
European Communities, 2003. European Union Technical Guidance Document on Risk Assessment for New and Existing Substances, Part II, Section 2.3.6.3.
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