Phosphorodithioic acid, mixed O,O-bis(sec-Bu and 1,3-dimethylbutyl) esters, zinc salts

Adsorption / desorption

Administrative data

Endpoint:

adsorption / desorption

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:

See attached justification

Data source

Reference

Reference Type:

other: QSAR

Title:

Unnamed

Year:

2019

Report date:

2019

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

other: EPI Suite version 4.1 MCI method and Kow method were used to predict the log Koc with experimentally derived Kow values inputed into the models

GLP compliance:

no

Type of method:

other: EPI Suite version 4.1 MCI method and Kow method were used to predict the log Koc with experimentally derived Kow values inputed into the models

Test material

Test material information

Constituent 1

Reference substance name:

Phosphorodithioic acid, mixed O,O-bis(sec-Bu and 1,3-dimethylbutyl) esters, zinc salts

EC Number:

272-238-5

EC Name:

Phosphorodithioic acid, mixed O,O-bis(sec-Bu and 1,3-dimethylbutyl) esters, zinc salts

Cas Number:

68784-31-6

Molecular formula:

C(16-24) H(36-42) O4 P2 S4 Zn

IUPAC Name:

Phosphorodithioic acid, mixed O,O-bis(sec-Bu and 1,3-dimethylbutyl) esters, zinc salts

Details on test material:

- Analytical purity: 81%
- Lot/batch No.: 94008624

Study design

Batch equilibrium or other method

Computational methods:

EPI Suite version 4.1 MCI method and Kow method were used to predict the log Koc with experimentally derived Kow values inputed into the models

Results and discussion

Adsorption coefficient

Adsorption coefficient 1

Key result

Type:

log Koc

Value:

2.966 dimensionless

Adsorption coefficient 2

Key result

Type:

log Koc

Value:

3.046 dimensionless

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Executive summary:

EC 272-238-5 is part of the ZDDP chemical category (see section 13 for category assessment). The category is used to support the QSAR prediction for Koc.

 

As outlined in Table 1 below, a similar ZDDP substance has an experimentally derived log Koc of 1.36. A low log Koc is consistent with the general trend in ZDDPs, which typically have a log Kow < 3, which is the cutoff value for adsorption potential per REACH R.7a Guidance. The Log Kow values for the ZDDP category are found in the category document in section 13. Note that the Log Kow for the target (EC 272-238-5) and analog chemical (EC 247-810-2) are higher than other category members based on the methodology differences.

 

However, the critical part is that the Kow studies for EC 272-238-5 and 247-810-2 were conducted by the same method and gave similar values, which demonstrates that direct read across between these two materials is valid because Kow is a key predictor of Koc. In addition, these two materials have comparable water solubility results (Table 1).

 

To further confirm that the QSAR Koc values are accurate, the QSAR Koc values of the analog were also predicted and found to be very similar as the target, even with the MCI method that is not based on Kow.

 

Therefore, it can be concluded that the QSAR model prediction is reasonable and is consistent with the experimental value resulting in an outcome that indicates there is a relatively low adsorption potential. 

 

Table 1. Summary of data for Target and Analog Substances used in Koc prediction

	EC 272-238-5 (Target)	EC 247-810-2 (Analog)
Molecular weight	604	660
Experimentally derived log Koc	NDA	1.36
Log Koc (MCI method)*	2.966	3.536
Log Koc (Kow method)*	3.046	2.991
Log Kow (experimentally derived)	4.0	3.9
Water solubility (mg/L)	617	727
SMILES used for modeling*	CCC(C)OP(S)(=S)OC(C)CC(C)C	CCCCC(CC)COP(S)(=S)OCC(C)C

* Modeling was conducted using the corresponding dialkyldithiophosphate ester part of the molecule that does not contain the zinc.