[3-(trimethoxysilyl)propyl]urea

Phototransformation in air

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

phototransformation in air

Type of information:

(Q)SAR

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: The result was obtained using an appropriate QSAR method (see attached QMRF and QPRF for details).

Qualifier:

according to guideline

Guideline:

other:

Version / remarks:

REACH Guidance on QSARs R.6

Principles of method if other than guideline:

1. SOFTWARE
EPI Suite v4.11 Estimation Programs Interface Suite™ for Microsoft® Windows v 4.11. US EPA, United States Environmental Protection Agency, Washington, DC, USA.

2. MODEL (incl. version number)
AOPWIN v1.92, Estimation Programs Interface Suite™ for Microsoft® Windows v 4.11. US EPA, United States Environmental Protection Agency, Washington, DC, USA

3. SMILES OR OTHER IDENTIFIERS USED AS INPUT FOR THE MODEL
See test material information

4. SCIENTIFIC VALIDITY OF THE (Q)SAR MODEL
See attached information on the model provided by the developer. Further information on the OECD criteria as outlined by the applicant is provided below under "Any other information of materials and methods incl. tables"

5. APPLICABILITY DOMAIN
See attached information and information as provided in "Any other information on results incl. tables".

6. ADEQUACY OF THE RESULT
See assessment of adequacy as outlined in the "Overall remarks, attachments" section.

GLP compliance:

no

Estimation method (if used):

PHOTOCHEMICAL REACTION WITH OH RADICALS
- Concentration of OH radicals: 0.5E+06 radicals/cm3
- Degradation rate constant: 11.8757 E-12 cm3/molecule-sec
- Temperature for which rate constant was calculated: 25 °C
- Computer programme: AOPWIN v1.92

DT50:

32.42 h

Test condition:

calculation based on a 24 h day

Conclusions:

Half-life of [3-(trimethoxysilyl)propyl]urea (CAS 23843-64-3) in the air is calculated as 32.4 hours.

Reference 2

Endpoint:

phototransformation in air

Type of information:

(Q)SAR

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: The result was obtained using an appropriate QSAR method (see attached QMRF and QPRF for details).

Qualifier:

according to guideline

Guideline:

other: REACH Guidance on QSARs R.6

Principles of method if other than guideline:

1. SOFTWARE
EPI Suite v4.11 Estimation Programs Interface Suite™ for Microsoft® Windows v 4.11. US EPA, United States Environmental Protection Agency, Washington, DC, USA.

2. MODEL (incl. version number)
AOPWIN v1.92, Estimation Programs Interface Suite™ for Microsoft® Windows v 4.11. US EPA, United States Environmental Protection Agency, Washington, DC, USA

3. SMILES OR OTHER IDENTIFIERS USED AS INPUT FOR THE MODEL
See test material information

4. SCIENTIFIC VALIDITY OF THE (Q)SAR MODEL
See attached information on the model provided by the developer. Further information on the OECD criteria as outlined by the applicant is provided below under "Any other information of materials and methods incl. tables"

5. APPLICABILITY DOMAIN
See attached information and information as provided in "Any other information on results incl. tables".

6. ADEQUACY OF THE RESULT
See assessment of adequacy as outlined in the "Overall remarks, attachments" section.

GLP compliance:

no

Estimation method (if used):

PHOTOCHEMICAL REACTION WITH OH RADICALS
- Concentration of OH radicals: 0.5E+06 radicals/cm3
- Degradation rate constant: 19.7369 E-12 cm3/molecule-sec
- Temperature for which rate constant was calculated: 25 °C
- Computer programme: AOPWIN v1.92

DT50:

19.5 h

Test condition:

calculation based on a 24 h day

Conclusions:

The half-life of the hydrolysis product [3-(trihydroxysilyl)propyl]urea in the air is calculated to be 19.5 hours.

Description of key information

DT50air (parent substance) = 32.4 h (QSAR)

DT50air (silanol hydrolysis product) = 19.7 h (QSAR)

Additional information

1-[3-(trimethoxysilyl)propyl]urea (CAS No. 23843-64-3) and its hydrolysis product [3-(trihydroxysilyl)propyl]urea contain 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.

The AOPWIN program (v1.92a) has been used to obtain values of the rate constant kOH for reaction of [3-(trimethoxysilyl)propyl]urea (CAS 23843-64-3) and its hydrolysis product [3-(trihydroxysilyl)propyl]urea with hydroxyl radicals. This prediction method has not been validated to assess applicability to silanes and silanols, therefore, there is uncertainty associated with the calculated values obtained.

The overall half-life in air under default conditions of hydroxyl radical concentration was calculated using the following expressions:

kdegair(d^-1) = k_OH(cm³/molecule. sec) x OH Conc_air(molecules/cm³) x 24 x 3600

DT₅₀(d) = ln 2/ kdeg_air(d^-1)

Where:

kdeg_air= total rate constant for degradation in air

k_OH= rate constant for reaction with hydroxyl radicals

OH Conc_air= concentration of hydroxyl radicals in air = 5 x 10⁵OH molecules/ cm³

DT₅₀= half-life

The results are given in table below:

 

 Table 4.1.2 Results of photodegradation in air calculations. 

Parameter	1-[3-(trimethoxysilyl)propyl]urea	[3-(trihydroxysilyl)propyl]urea
kOH(cm3/molecule. sec)	11.8757E-12	19.7369E-12
kdegair (d-1)	0.0214	0.0355
DT50(days)	32.4 hours (24-hr day; 0.5E6 OH/cm3)	19.7 hours (24-hr day; 0.5E6 OH/cm3)