Reaction products of phosphoryl trichloride and 2-methyloxirane

Phototransformation in air

Link to relevant study record(s)

Reference

Endpoint:

phototransformation in air

Type of information:

(Q)SAR

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

results derived from a valid (Q)SAR model and falling into its applicability domain, with adequate and reliable documentation / justification

Justification for type of information:

The substance Reaction products of phosphoryl trichloride and 2-methyloxirane (TCPP) is an UVCB substance (Substances of Unknown or Variable composition, Complex reaction products or Biological material). Four representative molecular structures of TCPP (constituent groups A – D) were used for the prediction of the rate constant for the atmospheric, gas-phase reaction and atmospheric half-life using the Estimation Program Interface (EPI) Suite version 4.11. These main constituents are present in TCPP in various concentrations. During manufacture of TCPP no stereo chemical control is applied. Therefore all constituent groups are isomer mixtures.

1. SOFTWARE
Individual model AOPWIN included in the Estimation Programs Interface (EPI) Suite.

2. MODEL (incl. version number)
AOPWIN v1.92 included in EPISuite v 4.11, 2000 - 2012

3. SMILES OR OTHER IDENTIFIERS USED AS INPUT FOR THE MODEL
A SMILES notification was entered in the initial data entry screen. In the structure window, the molecular weight, structural formula and the structure of the input SMILES notation is shown. If available, experimental determined values of melting point and boiling point are taken for input.

4. SCIENTIFIC VALIDITY OF THE (Q)SAR MODEL
a. Defined endpoint: Rate constant for the atmospheric, gas-phase reaction between photochemically produced hydroxyl radicals and organic chemicals at 25°C. The rate constant estimated by the program is then be used to calculate the atmospheric half-life for an organic compound based upon an 24h-day average atmospheric concentration of hydroxyl radicals of 0.5E+06 molecules/cm3.

b. Dependent variable: Hydroxyl radical rate constant in units of cm3/molecule sec

c. Estimation methodology: The molecule is separated into distinct fragments. The reaction rate constant for hydroxyl radicals are the summation of the following mechanisms:
TCPP constituent group A:
Hydrogen Abstraction = 44.7631 E-12 cm3/molecule*sec
Reaction with N, S and -OH = 0.0000 E-12 cm3/molecule*sec
Addition to Triple Bonds = 0.0000 E-12 cm3/molecule*sec
Addition to Olefmic Bonds = 0.0000 E-12 cm3/molecule*sec
Addition to Aromatic Rings = 0.0316 E-12 cm3/molecule*sec
Addition to Fused Rings = 0.0000 E-12 cm3/molecule*sec

TCPP constituent group B:
Hydrogen Abstraction = 37.6907 E-12 cm3/molecule*sec
Reaction with N, S and -OH = 0.0000 E-12 cm3/molecule*sec
Addition to Triple Bonds = 0.0000 E-12 cm3/molecule*sec
Addition to Olefmic Bonds = 0.0000 E-12 cm3/molecule*sec
Addition to Aromatic Rings = 0.0316 E-12 cm3/molecule*sec
Addition to Fused Rings = 0.0000 E-12 cm3/molecule*sec

TCPP constituent group C:
Hydrogen Abstraction = 30.6183 E-12 cm3/molecule*sec
Reaction with N, S and -OH = 0.0000 E-12 cm3/molecule*sec
Addition to Triple Bonds = 0.0000 E-12 cm3/molecule*sec
Addition to Olefmic Bonds = 0.0000 E-12 cm3/molecule*sec
Addition to Aromatic Rings = 0.0316 E-12 cm3/molecule*sec
Addition to Fused Rings = 0.0000 E-12 cm3/molecule*sec

TCPP constituent group A:
Hydrogen Abstraction = 23.5459 E-12 cm3/molecule*sec
Reaction with N, S and -OH = 0.0000 E-12 cm3/molecule*sec
Addition to Triple Bonds = 0.0000 E-12 cm3/molecule*sec
Addition to Olefmic Bonds = 0.0000 E-12 cm3/molecule*sec
Addition to Aromatic Rings = 0.0316 E-12 cm3/molecule*sec
Addition to Fused Rings = 0.0000 E-12 cm3/molecule*sec

As depending on the structure of the substance, OH-radicals generally react by one or more of the above mentioned pathways, the result of 0.0000 E-12 cm3/molecule¬sec for each mechanism indicate that these mechanisms are not relevant for the substance of interest.
An "assumed value" is applied, showing that a structure fragment that has not been assigned a numeric value by the developer of the estimation methods used by AOPWIN or derived explicitly from experimental values.

TCPP constituent A:
Overall OH Rate Constant = 44.7631 E-12 cm3/molecule-sec
Half-life = 0.358 Days (24-hr day; 0.5E6 OH/cm3)
Half-life = 8.602 Hrs
Hydrogen Abstraction Calculation:
Ktert = 1.94 F(-CH2CL)F(-CH3)F(-OP-) = 1.94(0.360)(1.000)(20.500) = 14.317
Ksec = 0.934 F(-CL)F(>CH-) = 0.934(0.380)(1.230) = 0.437
Kprim = 0.136 F(>CH-) = 0.136(1.230) = 0.167
Ktert = 1.94 F(-CH2CL)F(-CH3)F(-OP-) = 1.94(0.360)(1.000)(20.500) = 14.317
Ksec = 0.934 F(-CL)F(>CH-) = 0.934(0.380)(1.230) = 0.437
Kprim = 0.136 F(>CH-) = 0.136(1.230) = 0.167
Ktert = 1.94 F(-CH2CL)F(-CH3)F(-OP-) = 1.94(0.360)(1.000)(20.500) = 14.317
Ksec = 0.934 F(-CL)F(>CH-) = 0.934(0.380)(1.230) = 0.437
Kprim = 0.136 F(>CH-) = 0.136(1.230) = 0.167
H Abstraction TOTAL = 44.7631 E-12 cm3/molecule sec
Reaction Rates With Nitrogen, Sulfur and -OH:
K(P=O) = 0.0000 E-12 cm3/molecule sec

TCPP constituent B:
Overall OH Rate Constant = 37.6907 E-12 cm3/molecule-sec
Half-life = 0.426 Days (24-hr day; 0.5E6 OH/cm3)
Half-life = 10.216 Hrs
Hydrogen Abstraction Calculation:
Ktert = 1.94 F(-CH3)F(-CL)F(-CH2-) = 1.94(1.000)(0.380)(1.230) = 0.907
Kprim = 0.136 F(-CH-CL) = 0.136(0.360) = 0.049
Ksec = 0.934 F(-OP-)F(-CH-CL)=0.934(20.500)(0.360) = 6.893
Ktert = 1.94 F(-CH3)F(-CH2CL)F(-OP-) = 1.94(1.000)(0.360)(20.500) = 14.317
Kprim = 0.136 F(>CH-) = 0.136(1.230) = 0.167
Ksec = 0.934 F(-CL)F(>CH-) = 0.934(0.380)(1.230) = 0.437
Ktert = 1.94 F(-CH3)F(-CH2CL)F(-OP-) = 1.94(1.000)(0.360)(20.500) = 14.317
Kprim = 0.136 F(>CH-) = 0.136(1.230) = 0.167
Ksec = 0.934 F(-CL)F(>CH-) = 0.934(0.380)(1.230) = 0.437
H Abstraction TOTAL = 37.6907 E-12 cm3/molecule sec
Reaction Rates With Nitrogen, Sulfur and -OH:
K(P=O) = 0.0000 E-12 cm3/molecule sec

TCPP constituent C:
Overall OH Rate Constant =30.6183 E-12 cm3/molecule-sec
Half-life = 0.524 Days (24-hr day; 0.5E6 OH/cm3)
Half-life = 12.576 Hrs
Hydrogen Abstraction Calculation:
Ktert = 1.94 F(-CH2CL)F(-CH3)F(-OP-) = 1.94(0.360)(1.000)(20.500) = 14.317
Ksec = 0.934 F(-CL)F(>CH-) = 0.934(0.380)(1.230) = 0.437
Kprim = 0.136 F(>CH-) = 0.136(1.230) = 0.167
Ksec = 0.934 F(-CH-CL)F(-OP-) = 0.934(0.360)(20.500) = 6.893
Ktert = 1.94 F(-CH3)F(-CL)F(-CH2-) = 1.94(1.000)(0.380)(1.230) = 0.907
Kprim = 0.136 F(-CH-CL) = 0.136(0.360) = 0.049
Ksec = 0.934 F(-CH-CL)F(-OP-) = 0.934(0.360)(20.500) = 6.893
Ktert = 1.94 F(-CH3)F(-CL)F(-CH2-) = 1.94(1.000)(0.380)(1.230) = 0.907
Kprim = 0.136 F(-CH-CL) = 0.136(0.360) = 0.049
H Abstraction TOTAL = 30.6183 E-12 cm3/molecule sec
Reaction Rates With Nitrogen, Sulfur and -OH:
K(P=O) = 0.0000 E-12 cm3/molecule sec

TCPP constituent D:
Overall OH Rate Constant = 23.5459 E-12 cm3/molecule-sec
Half-life = 0.681 Days (24-hr day; 0.5E6 OH/cm3)
Half-life = 16.353 Hrs
Hydrogen Abstraction Calculation:
Ksec = 0.934 F(-CH-CL)F(-OP-) = 0.934(0.360)(20.500) = 6.893
Ktert = 1.94 F(-CH3)F(-CL)F(-CH2-) = 1.94(1.000)(0.380)(1.230) = 0.907
Kprim = 0.136 F(-CH-CL) = 0.136(0.360) = 0.049
Ksec = 0.934 F(-CH-CL)F(-OP-) = 0.934(0.360)(20.500) = 6.893
Ktert = 1.94 F(-CH3)F(-CL)F(-CH2-) = 1.94(1.000)(0.380)(1.230) = 0.907
Kprim = 0.136 F(-CH-CL) = 0.136(0.360) = 0.049
Ksec = 0.934 F(-CH-CL)F(-OP-) = 0.934(0.360)(20.500) = 6.893
Ktert = 1.94 F(-CH3)F(-CL)F(-CH2-) = 1.94(1.000)(0.380)(1.230) = 0.907
Kprim = 0.136 F(-CH-CL) = 0.136(0.360) = 0.049
H Abstraction TOTAL = 23.5459 E-12 cm3/molecule sec
Reaction Rates With Nitrogen, Sulfur and -OH:
K(P=O) = 0.0000 E-12 cm3/molecule sec

d. Applicability domain: Due to the fragment-based approach of AOPWIN, estimation is adequate as the fragments present in the molecule are available in the list of all fragment and reaction values provided by the program. The AOPWIN program allows the user to select 12 or 24 hour time frames and any average hydroxyl radical concentrations, but the default is originally set at 1.5 × 10^6 molecules (radicals)/cm3 per 12-h of daylight.

e. Estimation accuracy:
i. Hydroxyl radical estimation accuracy of AOPWIN: For the 667 AOPWIN estimations, 90 % are within a factor of two of the experimental value and 95 % are within a factor of three. A correlation between the experimental OH rate constants and the rate constants estimated by the AOP program shows the following statistical accuracy for APOWIN: correlation coefficient (r^2) = 0.963, standard deviation = 0.218, absolute mean error = 0.127
ii. Ozone reaction rate estimation accuracy of AOP: A correlation of experimentally determined gas-phase, ozone reaction rate constants for 112 organic chemicals at room temperature and the rate constants estimated by the APOWIN program shows the following statistical accuracy: correlation coefficient (r^2) = 0.88, standard deviation = 0.52, absolute mean error = 0.35

f. Mechanistic interpretation: The Atmospheric Oxidation Program for Microsoft Windows (AOPWIN) estimates the rate constant for the atmospheric, gas-phase reaction between photochemically produced hydroxyl radicals and organic chemicals. It also estimates the rate constant for the gas-phase reaction between ozone and olefinic/acetylenic compounds. The rate constants estimated by the program are then used to calculate atmospheric half-lives for organic compounds based upon average atmospheric concentrations of hydroxyl radicals and ozone.

g. Uncertainty of the prediction (OECD principle 4): The substance is not highly complex and the rules applied for the substance appear appropriate. An individual uncertainty for the investigated substance is not available.

h. Chemical and biological mechanisms according to the model underpinning the predicted result (OECD principle 5): No information available.

5. APPLICABILITY DOMAIN
a. Despcriptor domains:
i. Molecular weight: Not relevant
ii. Structural fragment domain: Due to the fragment-based approach of AOPWIN, estimation is adequate as the fragments present in the molecule are available in the list of all fragment and reaction values provided by the program.
iii. Mechanism domain: No information available
iv. Metabolic domain: Not relevant
b. Structural analogues: No information available
i. Considerations on structural analogues: No information available

6. ADEQUACY OF THE RESULT
a. Regulatory purpose: The data may be used under any regulatory purpose.
b. Approach for regulatory interpretation of the model result: If no experimental data are available the estimated value may be used to fill data gaps needed for hazard and risk assessment.
c. Outcome: The prediction of the rate constant for the atmospheric, gas-phase reaction between photochemically produced hydroxyl radicals and the TCPP constituent groups A-D and their atmospheric half-life yields useful results for further evaluation.
d. Conclusion: The result is considered as useful for regulatory purposes.

Principles of method if other than guideline:

Estimation Program Interface EPI-Suite version 4.11: AOPWIN (v1.92) for the estimation of the atmospheric half-lives for organic compounds based upon average atmospheric concentrations of hydroxyl radicals and ozone.
The Estimation Program Interface was developed by the US Environmental Agency's Office of Pollution Prevention and Toxics, and Syracuse Research Corporation (SRC). © 2000 - 2012 U.S. Environmental Protection Agency for EPI SuiteTM (Published online in November 2012).

GLP compliance:

no

Specific details on test material used for the study:

The substance Reaction products of phosphoryl trichloride and 2-methyloxirane (TCPP) is an UVCB substance (Substances of Unknown or Variable composition, Complex reaction products or Biological material). Four representative molecular structures of TCPP (constituent groups A – D) were used for the prediction of the rate constant for the atmospheric, gas-phase reaction and atmospheric half-life using the Estimation Program Interface (EPI) Suite version 4.11. These main constituents are present in TCPP in various concentrations (constituent group A: 50-85%, constituent group B: 15-40%, constituent group C: 0-15%, constituent group D: 0-1%). During manufacture of TCPP no stereo chemical control is applied. Therefore all constituent groups are isomer mixtures.

Estimation method (if used):

PHOTOCHEMICAL REACTION WITH OH RADICALS
- sensitiser for indirect photolysis: OH radicals
- Concentration of OH radicals: 0.5 E6 OH/cm³, 24 h/d

Key result

% Degr.:

50

Sampling time:

0.358 d

Remarks on result:

other: TCPP constituent group A: Tris(1-chloroprop-2-yl) phosphate, isomer mixture (CAS no. 13674-84-5)

% Degr.:

50

Sampling time:

0.426 d

Remarks on result:

other: TCPP constituent group B: Bis(1-chloroprop-2-yl) 2-chloropropyl phosphate, isomer mixture (CAS no. 76025-08-6)

% Degr.:

50

Sampling time:

0.524 d

Remarks on result:

other: TCPP constituent group C: 1-Chloroprop-2-yl bis(2-chloropropyl) phosphate, isomer mixture (CAS no. 76649-15-5)

% Degr.:

50

Sampling time:

0.681 d

Remarks on result:

other: TCPP constituent group D: Tris(2-chloropropyl) phosphate, isomer mixture (CAS no. 6145-73-9)

DT50:

8.602 h

Remarks on result:

other: TCPP constituent group A: Tris(1-chloroprop-2-yl) phosphate, isomer mixture (CAS no. 13674-84-5)

DT50:

10.216 h

Remarks on result:

other: TCPP constituent group B: Bis(1-chloroprop-2-yl) 2-chloropropyl phosphate, isomer mixture (CAS no. 76025-08-6)

DT50:

12.576 h

Remarks on result:

other: TCPP constituent group C: 1-Chloroprop-2-yl bis(2-chloropropyl) phosphate, isomer mixture (CAS no. 76649-15-5)

DT50:

16.353 h

Remarks on result:

other: TCPP constituent group D: Tris(2-chloropropyl) phosphate, isomer mixture (CAS no. 6145-73-9)

1) Defined Endpoint: Rate constant for the atmospheric, gas-phase reaction between photochemically produced hydroxyl radicals and organic chemicals at 25°C.

2) Unambiguous algorithm: The molecule is separated into distinct fragments. The reaction rate constant for hydroxyl radicals are the summation of the following mechanisms:

Hydrogen Abstraction = 0.0000 E-12 cm3/molecule-sec

Reaction with N, S and -OH =0.0000 E-12 cm3/molecule-sec

Addition to Triple Bonds =0.0000 E-12 cm3/molecule-sec

Addition to Olefinic Bonds = 0.0000 E-12 cm3/molecule-sec

**Addition to Aromatic Rings = 0.0316 E-12 cm3/molecule-sec

Addition to Fused Rings = 0.0000 E-12 cm3/molecule-sec

** Designates Estimation(s) Using ASSUMED Value(s)

As depending on the structure of the substance, OH-radicals generally react by one or more of the above mentioned pathways, the result of 0.0000 E-12 cm3/molecule-sec for each mechanism indicate that these mechanisms are not relevant for the substance of interest. An "assumed value" is applied, showing that a structure fragment that has not been assigned a numeric value by the developer of the estimation methods used by AOPWIN or derived explicitly from experimental values.

3) Applicability domain:

Currently there is no universally accepted definition of model domain.

Due to the fragment-based approach of AOPWIN, estimation is adequate as the fragments present in the molecule are available in the list of all fragment and reaction values provided by the program.

4) Statistical characteristics:

The correlation includes 667 compounds; most experimental values containing a "less than" sign (<) were excluded.

correlation coefficient (r²) 0.963; standard deviation (sd in log units) 0.218; absolute mean error (me) 0.127

5) Mechanistic interpretation:

The reaction values and fragments for the reaction with OH-radicals used as descriptors reflect the most important mechanisms of indirect phototransformation processes possible in the troposphere.

Adequacy of prediction:

The estimation rules applied for the substance appears appropriate.

The predicted result for the TCPP constituent groups A-D can be considered reliable yielding a useful result for further assessment.

Validity criteria fulfilled:

not applicable

Conclusions:

The substance Reaction products of phosphoryl trichloride and 2-methyloxirane (TCPP) is an UVCB substance (Substances of Unknown or Variable composition, Complex reaction products or Biological material). Four representative molecular structures of TCPP (constituent groups A – D) were used for the prediction of the rate constant for the atmospheric, gas-phase reaction and atmospheric half-life (constituent group A: CAS no. 13674-84-5, constituent group B: CAS no. 76025-08-6, constituent group C: CAS no. 76649-15-5, constituent group D, CAS no. 6145-73-9). These main constituents are present in TCPP in various concentrations. During manufacture of TCPP no stereo chemical control is applied. Therefore all constituent groups are isomer mixtures.
The calculated half-life of the TCPP constituent groups A-D by photodegradation in air was 0.358 days (constituent group A), 0.426 days (constituent group B), 0.524 days (constituent group C) and 0.681 days (constituent group D) with an Overall OH rate constant of 44.7631 E-12 m³/molecule-sec (constituent group A), 37.6907 E-12 cm3/molecule sec (constituent group B), 30.6183 E-12 cm3/molecule sec (constituent group C) and 23.5459 E-12 cm3/molecule sec (constituent group D).

Executive summary:

The substance Reaction products of phosphoryl trichloride and 2-methyloxirane (TCPP) is an UVCB substance (Substances of Unknown or Variable composition, Complex reaction products or Biological material). Four representative molecular structures of TCPP (constituent groups A – D) were used for the prediction of the rate constant for the atmospheric, gas-phase reaction and atmospheric half-life (constituent group A: CAS no. 13674-84-5, constituent group B: CAS no. 76025-08-6, constituent group C: CAS no. 76649-15-5, constituent group D, CAS no. 6145-73-9). These main constituents are present in TCPP in various concentrations. During manufacture of TCPP no stereo chemical control is applied. Therefore all constituent groups are isomer mixtures.

The indirect photodegradation in air was calculated with the Estimation Program Interface EPI-Suite version 4.11.The estimated half-life of the TCPP constituent gruops A-D was 0.358 days (constituent group A), 0.426 days (constituent group B), 0.524 days (constituent group C) and 0.681 days (constituent group D) with an Overall OH rate constant of 44.7631 E-12 m³/molecule-sec (constituent group A), 37.6907 E-12 cm3/molecule sec (constituent group B), 30.6183 E-12 cm3/molecule sec (constituent group C) and 23.5459 E-12 cm3/molecule sec (constituent group D).

The estimation rules applied for the substance appears appropriate.

The predicted results for the TCPP constituent groups A-D can be considered reliable yielding a useful result for further assessment.

The calculated value refers to the unaffected molecule. Any decomposition (e.g. hydrolysis) of the substance is not taken into account by the program.

Description of key information

The substance Reaction products of phosphoryl trichloride and 2-methyloxirane (TCPP) is an UVCB substance (Substances of Unknown or Variable composition, Complex reaction products or Biological material). Four representative molecular structures of TCPP (constituent groups A – D) were used for the prediction of the rate constant for the atmospheric, gas-phase reaction and atmospheric half-life (constituent group A: CAS no. 13674-84-5, constituent group B: CAS no. 76025-08-6, constituent group C: CAS no. 76649-15-5, constituent group D, CAS no. 6145-73-9). These main constituents are present in TCPP in various concentrations. During manufacture of TCPP no stereo chemical control is applied. Therefore all constituent groups are isomer mixtures.

The calculated half-life of the TCPP constituent groups A-D by photodegradation in air was 0.358 days (constituent group A), 0.426 days (constituent group B), 0.524 days (constituent group C) and 0.681 days (constituent group D) with an Overall OH rate constant of 44.7631 E-12 m³/molecule-sec (constituent group A), 37.6907 E-12 cm3/molecule sec (constituent group B), 30.6183 E-12 cm3/molecule sec (constituent group C) and 23.5459 E-12 cm3/molecule sec (constituent group D).

Key value for chemical safety assessment

Half-life in air:

0.358 d

Degradation rate constant with OH radicals:

0 cm³ molecule-1 s-1

Additional information

As the constituent group A exhibits the highest concentration within the substance Reaction products of phosphoryl trichloride and 2-methyloxirane (TCPP) in comparison to the other TCPP constituent groups (B-D), the calculated result for constituent group A is used as key result for chemical safety assessment.