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Environmental fate & pathways

Phototransformation in air

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Administrative data

Endpoint:
phototransformation in air
Type of information:
calculation (if not (Q)SAR)
Remarks:
Migrated phrase: estimated by calculation
Adequacy of study:
supporting study
Reliability:
4 (not assignable)
Rationale for reliability incl. deficiencies:
other: Modeled data

Data source

Referenceopen allclose all

Reference Type:
study report
Title:
Unnamed
Year:
2006
Reference Type:
publication
Title:
No information
Year:
2003
Bibliographic source:
USEPA Estimations Programs Interface (EPI) Suite®.

Materials and methods

Principles of method if other than guideline:
calculated: AOPWIN® ver. 1.91other (calculated)
GLP compliance:
no

Test material

Constituent 1
Chemical structure
Reference substance name:
Trimethoxysilane
EC Number:
219-637-2
EC Name:
Trimethoxysilane
Cas Number:
2487-90-3
Molecular formula:
C3H10O3Si
IUPAC Name:
Trimethoxysilane

Study design

Details on test conditions:
Sensitiser (for indirect photolysis): OH
Sensitiser concentration: 500000 molecule/cm³

Results and discussion

Any other information on results incl. tables

Degradation = 50% after 6.4 Days (indirect photolysis only)

Degradation = 50% after 0.002 Days (indirect photolysis and hydrolysis)

Atmospheric Oxidation (25 deg C) [AOPWIN® ver. 1.91]:

"         Hydroxyl Radical Reaction:

o        Reaction Rate Constant = 2.49E-12 cm3/(mol*sec)

o        OH radical conc (24 h ave) = 5.0E+05 mol/cm3 (EUTGD 2001)

o        Half-Life = 6.4 Days

o        Half-Life = 155 Hrs "        

Overall Reaction Rate:

o        Hydrolysis half-life = 0.005 Hrs at pH 7.0 (Miller and Taylor 2002)

o        OH degradation half-life = 155 Hrs

o        Overall reaction half-life = 0.050 Hrs

Rate constant (for indirect photolysis):  0.00000000000249 cm³/(molecule*sec) Degradation products (CAS No./EC No./EINECS Name): 14044-95-2 Degradation products (CAS No./EC No./EINECS Name): 67-56-1     200-659-6 methanol

Trimethoxysilane in the air compartment is expected to undergo photolytic degradation.  Trimethoxysilane contains
no chromaphors 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 hydroxlyl radicals is expected to
occur.  Because the material is highly reactive and hydrolytically unstable, photolysis itself is not likely to
be the primary degradation process.  Reaction with water vapor is likely to be a predominant degradation process and
the overall reaction half life in air should include both the oxidation half life and the hydrolytic half life.  
         
Because of the decreased activity of water, the rate of hydrolysis in air was assumed to be one tenth (1/10) of the
rate in water or 10 times (10x) the measured half life in water.  Silanetriol generated from hydrolysis of
Trimethoxysilane is not expected to undergo direct photolysis but to further react with hydroxyl radicals.

Applicant's summary and conclusion