Reaction products of phosphoryl trichloride and 2-methyloxirane

Adsorption / desorption

Link to relevant study record(s)

Reference

Endpoint:

adsorption / desorption: screening

Remarks:

adsorption

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 organic carbon partition coefficient log Koc 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 KOCWIN included in the Estimation Programs Interface (EPI) Suite.

2. MODEL (incl. version number)
KOCWIN v2.00 included in EPISuite v 4.11, 2000-2012.

3. SMILES OR OTHER IDENTIFIERS USED AS INPUT FOR THE MODEL
A SMILES notation 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.

4. SCIENTIFIC VALIDITY OF THE (Q)SAR MODEL
a. Defined endpoint: Organic carbon partition coefficient, given as log Koc.
b. Dependent variable: KOCWIN estimates log Koc with two separate estimation methodologies:
(1) Estimation using first order Molecular Connecitivity Index (MCI),
(2) Estimation using log Kow (octanol-water partition coefficient)
c. Algorithm:
Log Koc according to MCI method is calculated using the formula:
log Koc = 0.5213 MCI + 0.60 + ΣPfN
(ΣPfN is the sum of all relevant correction factor coefficients multiplied by the number (N) of that factor in each chemical structure)
Log Koc according to the log Kow method is calculated using two formulas (depending on the polarity of the substance):
log Koc = 0.8679 log Kow - 0.0004 (Non-polar substances)
log Koc = 0.55313 log Kow + 0.9251 + ΣPfN (polar substances)

d. Descriptor values:
Log Kow method:
For estimation of log Koc according to log Kow method an experimentally determined log Kow of XY was used (Currenta, 201X).
For estimation of log Koc according to log Kow method the estimated log Kow of XY as calculated by the program was used.

e. Applicability domain: The minimum and maximum values for molecular weight are the following:
Training Set Molecular Weights: 32.04-665.02 g/mol,
Validation Set Molecular Weights: 27.03-991.15 g/mol

f. Statistics for goodness-of-fit:

Statistical accuracy of MCI methodology for training and validation set:
i. Training without corrections:
Number: 69
R^2 correction coefficient: 0.967
Standard deviation (log Koc): 0.247
Average deviation (log Koc): 0.199

ii. Training with corrections:
Number: 447
R^2 correction coefficient: 0.900
Standard deviation (log Koc): 0.340
Average deviation (log Koc): 0.273

iii. Validation data set:
Number: 158
R^2 correction coefficient: 0.850
Standard deviation (log Koc): 0.583
Average deviation (log Koc): 0.459

Statistical accuracy of Log Koc methodology:
i. Training without corrections:
Number: 68
R^2 correction coefficient: 0.877
Standard deviation: 0.478
Average deviation: 0.371

ii. Training with corrections:
Number: 447
R^2 correction coefficient: 0.855
Standard deviation (log Koc): 0.396
Average deviation (log Koc): 0.307

iii. Validation data set:
Number: 150
R^2 correction coefficient: 0.778
Standard deviation (log Koc): 0.679
Average deviation (log Koc): 0.494

g. Mechanistic interpretation: Log Koc is estimated based on the likeliness of a substance for sorption to surfaces of soil/sediment particles. This characteristic is triggered by lipophilic character of substances but may be modified by certain molecular fragments that need to be considered by application of correction factors. The Log Koc is a physical inherent property used extensively to describe a chemical’s likeliness to adsorb to organic carbon.
h. The 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.

5. APPLICABILITY DOMAIN
a. Descriptor domains:
i. Molecular weights: With a molecular weight of 327.57 g/mole the TCPP constituent groups A-D is within the range of the training set (32 - 665 g/mol) as well as in the range of the validation set (27 -– 991 g/mol).
ii. Structural fragment domain: Regarding the structure of the TCPP constituent groups A-D the fragment descriptors found by the program are complete and listed in Appendix D (KOCWIN Fragment and Correction Factor descriptors). For log Koc estimation according to MCI method no fragment descriptors were applied. For estimation of log Koc according to log Kow method the log Kow of 2.68 (experimentally determined, Cuthbert, 2002) was used.
iii. Mechanism domain: No information available.
iv. Metabolic domain: Not relevant.
b. Structural analogues: Noinformation 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, classification and labelling and PBT / vPvB assessment. Further the value is used for other calculations.
c. Outcome: The prediction of organic carbon partition coefficient yields a useful result for further evaluation.
d. Conclusion: The result is considered as useful for regulatory purposes.

Guideline:

other: REACH guidance QSARs R6, May/July 2008

Principles of method if other than guideline:

Estimation Program Interface EPI-Suite version 4.11: KOCWIN (v2.00) for the estimation of the organic carbon-normalized sorption coefficient for soil and sediment (Koc).
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

Type of method:

other: Estimation

Media:

soil

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 organic carbon partition coefficient log Koc 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.

Radiolabelling:

no

Key result

Type:

log Koc

Remarks:

calculation (logKow method)

Value:

2.511 dimensionless

Remarks on result:

other: TCPP constituent group A-D: 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)

Type:

log Koc

Remarks:

calculation (MCI method)

Value:

3.205 dimensionless

Remarks on result:

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

Type:

log Koc

Remarks:

calculation (MCI method)

Value:

3.185 dimensionless

Remarks on result:

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

Type:

log Koc

Remarks:

calculation (MCI method)

Value:

3.166 dimensionless

Remarks on result:

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

Type:

log Koc

Remarks:

calculation (MCI method)

Value:

3.146 dimensionless

Remarks on result:

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

Key result

Phase system:

other: Koc

Remarks:

calculation (logKow method)

Type:

other: Koc

Value:

324.2 L/kg

Remarks on result:

other: TCPP constituent group A-D: 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)

Phase system:

other: Koc

Remarks:

calculation (MCI method)

Type:

other: Koc

Value:

1 604 L/kg

Remarks on result:

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

Phase system:

other: Koc

Remarks:

calculation (MCI method)

Type:

other: Koc

Value:

1 532 L/kg

Remarks on result:

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

Phase system:

other: Koc

Remarks:

calculation (MCI method)

Type:

other: Koc

Value:

1 464 L/kg

Remarks on result:

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

Phase system:

other: Koc

Remarks:

calculation (MCI method)

Type:

other: Koc

Value:

1 398 L/kg

Remarks on result:

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

Validity of the model:

1. Defined Endpoint: Organic carbon partition coefficient, given as logarithmic Koc and Koc

2. Unambigous algorithm: The molecule is first classified as a polar substance. Based on structure of the molecule, the following fragment was applied: 1 P=O organo-phosphorus, aliphatic. The number of times of the fragments that occurs in the structure of the substance applied by the program is verified. For estimation of logKoc according to the logKow method an experimentally determined logKow of 2.68 was used.

3. Applicable domain: With a molecular weight of 327.57 g/mol all TCPP constituents A-D are within the range of the training set (32 - 665 g/mol) as well as in the validation set (27 - 991 g/mol). Regarding the structure of the TCPP constituent groups A-D, the fragment descriptors found by the program are complete.

4a. Statistical characteristics (MCI method): N training set without corrections = 69; N training set with correction = 447; N validation set = 158; Correction coefficient of the total training set without corrections r² = 0.967; Correlation coefficient of the total training set with corrections r² = 0.900; Correlation coefficient of the total validation set r² = 0.850.

4b. Statistical characteristics (Kow method): N training set without corrections = 68; N training set with correction = 447; N validation set = 150; Correction coefficient of the total training set without corrections r² = 0.877; Correlation coefficient of the total training set with corrections r² = 0.855; Correlation coefficient of the total validation set r² = 0.778.

5. Mechanistic interpretation: Log Koc is estimated based on the likeliness of a substance for sorption to surfaces of soil/sediment particles. The log Koc is a physical inherent property used extensively to describe a chemical's likeliness to adsorb to organic carbon.

6. Adequacy of prediction: The results for the TCPP constitunet groups A-D fall within the applicability domain described above and the estimation rules applied for the substance appears appropriate.

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 organic carbon partition coefficient log Koc using the Estimation Program Interface (EPI) Suite version 4.11 (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 QSAR determination of the carbon partition coefficient for the TCPP constituent groups A-D using the model KOCWIN included in the Estimation Program Interface (EPI) Suite v4.11 revealed values of 324.2 L/kg (logKow method, TCPP constitent groups A-D) and 1604 L/kg for TCPP constituent group A, 1532 L/kg for TCPP constituent group B, 1464 L/kg for TCPP constituent group C and 1398 L/kg for TCPP constituent group D (MCI method) for the unaffected molecules of the TCPP constituent groups as any decomposition (e.g. hydrolysis) is not taken into account by the program.

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 organic carbon partition coefficient log Koc using the Estimation Program Interface (EPI) Suite version 4.11 (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 organic carbon partition coefficient (Koc) for the TCPP constituent groups A-D was predicted using the QSAR calculation of the Estimation Program Interface (EPI) Suite v 4.11. The Koc was estimated to be 324.2 L/kg (logKow method, TCPP constituent groups A-D) and 1604 L/kg for TCPP constituent group A, 1532 L/kg for TCPP constituent group B, 1464 L/kg for TCPP constituent group C and 1398 L/kg for TCPP constituent group D (MCI method). The results relate to the unaffected molecule of the TCPP constituent groups A-D as any decomposition (e.g. hydrolysis) is not taken into account by the program.

Description of key information

QSAR (KOCWIN) (Heilkenbrinker, 2018): Koc = 324.2
OECD 117 (Cuthbert & Mullee, 2002): Koc = 576

Key value for chemical safety assessment

Koc at 20 °C:

324.2

Additional information

The adsorption coefficient for TCPP has been determined to be 324, logKoc 2.51. This value was determined by a QSAR calculation using the LogKow method for the main constituents of TCPP (using the Estimation Program Interface EPI-Suite version 4.11 (KOCWIN)). This value is in line with the ones selected in the EU RAR document.

The Koc value is supported by a determination carried out using an HPLC screening method according to the EU Method C.19 (Estimation of the Adsorption Coefficient (KOC) on Soil and Sewage Sludge Using High Performance Liquid Chromatography (HPLC)), (Cuthbert and Mullee, 2002) revealing a value of Koc 576, logKoc 2.76.