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Please be aware that this old REACH registration data factsheet is no longer maintained; it remains frozen as of 19th May 2023.

The new ECHA CHEM database has been released by ECHA, and it now contains all REACH registration data. There are more details on the transition of ECHA's published data to ECHA CHEM here.

Diss Factsheets

Environmental fate & pathways

Phototransformation in air

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Administrative data

Link to relevant study record(s)

Reference
Endpoint:
phototransformation in air
Type of information:
calculation (if not (Q)SAR)
Adequacy of study:
supporting study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Accepted calculation/estimation method, as recommended in ECHA Chapter 7 guidance (May 2008).
Reason / purpose for cross-reference:
reference to same study
Reason / purpose for cross-reference:
reference to other study
Principles of method if other than guideline:
The second-order rate constant for reaction with photochemically-generated hydroxyl radical (indirect photolysis) was estimated using U.S. EPA AOPWIN software v1.92a (June 2008). The associated atmospheric half-life was calculated from an assumed average hydroxyl radical concentration of 500,000 molecules/cm3 and 24 hr. day (ECHA recommended values).
GLP compliance:
no
Specific details on test material used for the study:
Details on properties of test surrogate or analogue material (migrated information):
not applicable
Estimation method (if used):
U.S. EPA AOPWIN software v1.92a (June 2008).
Assumed hydroxyl radical concentration of 500,000 molecules/cm3 and 24 hr photoday
Light source:
other: sunlight irradiance producing default tropospheric hydroxyl radical concentration of 500,000 molecules/cm3
Details on light source:
not applicable
Details on test conditions:
Half-lives calculated from estimated second-order rate constant, default hydroxyl radical concentration of 500,000 molecules/cm3, and 24-hr. photoday.
Preliminary study:
not applicable
Test performance:
not applicable
DT50:
1.6 d
Test condition:
Estimated half-life for reaction with hydroxyl radical (500,000 OH molecules/cm3) over 24 hr photoday
Transformation products:
not measured
Results with reference substance:
Butyric acid (CASRN 107-92-6)
SMILES: O=C(O)CCC
Experimental Rate Constant: 2.4 x 10-12 cm3/molecule*sec
Half-life based on experimental rate constant: 160 hrs (6.7 days)
Predicted Rate Constant: 2.7 x 10-12 cm3/molecule*sec
Half-life based on predicted rate constant: 142 hrs (5.9 days)

The prediction is accurate within a factor of 2 for estimating second-order rate constant of OH radical and organic acids such as butyric acid and 2-ethyl hexanoic acid

The predicted second-order rate constant for reaction of OH radical with Stannous Octoate is 9.9 x 10 -12 cm3/molecule*sec. This rate constant equates to an estimated half-life of 38.9 hrs, or 1.6 days; assuming an OH radical concentration of 500,000 molecules/cm3.

Validity criteria fulfilled:
not applicable
Conclusions:
The estimated atmospheric half-life for Stannous Octoate is 1.6 days, indicating that the substance will not behave as a persistent atmospheric pollutant if emitted to the air. This half-life is < 2 days, and therefore the substance is not regarded as having potential for long-range transport in the atmosphere.

Description of key information

The predicted second-order rate constant for reaction of OH radical with tin bis(2-ethylhexanoate) is 9.9 x 10-12 cm³/molecule*sec. This rate constant equates to an estimated half-life of 38.9 hrs, or 1.6 days; assuming an OH radical concentration of 500,000 molecules/cm3.

Key value for chemical safety assessment

Half-life in air:
38.9 h
Degradation rate constant with OH radicals:
0 cm³ molecule-1 s-1

Additional information

The estimated atmospheric half-life for tin bis (2-ethylhexanoate) is 1.6 days, indicating that the substance will not behave as a persistent atmospheric pollutant if emitted to the air. This half-life is < 2 days, and therefore the substance is not regarded as having potential for long-range transport in the atmosphere.

The training set used to develop the AOPWIN algorithm does not include other Sn(II) organometallic compounds. However, since the mode of reactivity for the tin bis (2-ethylhexanoate) molecule with hydroxyl radical is dominated by reactions with the 2-ethyl hexanoate part (i.e., hydrogen abstraction), the presence of the Sn atom is not expected to result in decreased accuracy of the prediction. The accuracy of this prediction of the second-order rate constant for organic acids was demonstrated by comparing experimental and predicted rate constants for butyric acid. The predicted value deviates from the experimental value by only 12 %.