Tin bis(2-ethylhexanoate)

Partition coefficient

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

partition coefficient

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Data from published review article of critically-evaluated log Kow values.

Justification for type of information:

Read Across to an analogue based on structural similarity. An analogue justification is attached to section 13 of the dataset.

Reason / purpose for cross-reference:

read-across: supporting information

Principles of method if other than guideline:

details of method not given

GLP compliance:

no

Type of method:

shake-flask method to: flask method

Partition coefficient type:

octanol-water

Type:

log Pow

Partition coefficient:

2.64

Temp.:

25

Remarks on result:

other: pH not reported, however, it is noted that meaurement was performed at pH where substance is not ionized.

Details on results:

The confidence interval around the reported log Kow value is ± 0.25 (log units)

Conclusions:

The log Kow of 2-ethylhexanoic acid is 2.64.

Executive summary:

The log Kow of 2-ethylhexanoic acid is 2.64. Because this value is the preferred/accepted value among those critically reviewed by Sangster (1989) and Hansch et al. (1995), the determination is assumed to be made at 25 °C and pH where the substance is not ionized. The log D for this substance at pH 7 is estimated to be 0.55 (ACD Labs Log D Suite, v5.16). Therefore, at pH encountered in the environment, the substance will have very low potential for adsorption to organic matter of soils/sediments, or to bioaccumulate in aquatic organisms.

Reference 2

Endpoint:

partition coefficient

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Data from published review article of critically-evaluated log Kow values.

Justification for type of information:

REPORTING FORMAT FOR THE ANALOGUE APPROACH
[Please provide information for all of the points below. Indicate if further information is included as attachment to the same record, or elsewhere in the dataset (insert links in 'Cross-reference' table)]

1. HYPOTHESIS FOR THE ANALOGUE APPROACH
Tin bis(2-ethylhexanoate) is an organometallic salt and has a pKa value of 5.09 (please see IUCLID dataset). Under the pH conditions typically occurring in the environment (i.e., pH 6-8), the substance is known to rapidly dissociate into two components, namely 2-ethylhexanoate ion and Sn(II) ion, upon introduction to water. Sn(II) ion is not expected to be stable in water at typical environmental conditions and is likely to be oxidized in the presence of molecular oxygen to form the insoluble inorganic solid Sn(IV)O2 (Pettin et al., 1981; Seby, 2001), which is not expected to be bioavailable to aquatic life (Rudel, 2003).
Tin bis(2-ethylhexanoate) will not exist in any relevant concentrations for a relevant duration in the environment and for a series of endpoints testing of tin bis(2-ethylhexanoate) is technically not feasible due to the rapid dissociation. Where no specific data are available, the assessment of environmental and human health endpoints should be based on its dissociation products. The dissociation products of toxicological relevance are 2-ethylhexanoate and Sn(II) components.
As a result, 2-ethyhexanoic acid and tin(II) chloride shall be used as read-across analogue for tin bis(2-ethylhexanoate) where no specific data are available.

2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES)
2-ethylhexanoic acid (CAS 149-57-5)
Tin(II) chloride (CAS 7772-99-8)

Purity of tin(II) bis(2-ethylhexanoate) is >= 92.5%.
Purity of 2-ethylhexanoic acid is 99.9%.
Purity of tin(II) chloride is 98.5%.


3. ANALOGUE APPROACH JUSTIFICATION
Tin bis(2-ethylhexanoate) is an organometallic salt with a dissociation constant of 5.09 at 20 °C. The dissociation study is included in IUCLID dataset. When introduced to water, more than 99% of tin bis(2-ethylhexanoate) will dissociate into 2-ethylhexanoate and Sn(II) components at pH > 6.8.
At environmentally relevant conditions, Sn(II) ion is not expected to be stable in water and is likely to be oxidized in the presence of molecular oxygen to form the insoluble inorganic solid Sn(IV)O2 (Pettin et al., 1981; Seby, 2001,), which is not expected to be bioavailable to aquatic life (Rudel, 2003).
Since tin bis(2-ethylhexanoate) is primarily in a dissociated form in the environment, the observed toxicity is likely dependent upon the toxicities for the respective acid and metal. Thus, where no specific data are available, the assessment of environmental and human health endpoints should be based on its dissociation components, namely Sn(II) in the form of Tin(II) chloride and 2-ethylhexanoic acid.

4. DATA MATRIX
Please refer to justification, attached to this section.

Reason / purpose for cross-reference:

read-across source

Principles of method if other than guideline:

details of method not given

GLP compliance:

no

Type of method:

shake-flask method to: flask method

Partition coefficient type:

octanol-water

Type:

log Pow

Partition coefficient:

2.64

Temp.:

25 °C

Remarks on result:

other: pH not reported, however, it is noted that meaurement was performed at pH where substance is not ionized.

Details on results:

The confidence interval around the reported log Kow value is ± 0.25 (log units)

Conclusions:

The log Kow of 2-ethylhexanoic acid is 2.64.

Executive summary:

The log Kow of 2-ethylhexanoic acid is 2.64. Because this value is the preferred/accepted value among those critically reviewed by Sangster (1989) and Hansch et al. (1995), the determination is assumed to be made at 25 °C and pH where the substance is not ionized. The log D for this substance at pH 7 is estimated to be 0.55 (ACD Labs Log D Suite, v5.16). Therefore, at pH encountered in the environment, the substance will have very low potential for adsorption to organic matter of soils/sediments, or to bioaccumulate in aquatic organisms.

Reference 3

Endpoint:

partition coefficient

Data waiving:

study technically not feasible

Justification for data waiving:

the study does not need to be conducted because the substance is inorganic

Justification for type of information:

REPORTING FORMAT FOR THE ANALOGUE APPROACH
[Please provide information for all of the points below. Indicate if further information is included as attachment to the same record, or elsewhere in the dataset (insert links in 'Cross-reference' table)]

1. HYPOTHESIS FOR THE ANALOGUE APPROACH
Tin bis(2-ethylhexanoate) is an organometallic salt and has a pKa value of 5.09 (please see IUCLID dataset). Under the pH conditions typically occurring in the environment (i.e., pH 6-8), the substance is known to rapidly dissociate into two components, namely 2-ethylhexanoate ion and Sn(II) ion, upon introduction to water. Sn(II) ion is not expected to be stable in water at typical environmental conditions and is likely to be oxidized in the presence of molecular oxygen to form the insoluble inorganic solid Sn(IV)O2 (Pettin et al., 1981; Seby, 2001), which is not expected to be bioavailable to aquatic life (Rudel, 2003).
Tin bis(2-ethylhexanoate) will not exist in any relevant concentrations for a relevant duration in the environment and for a series of endpoints testing of tin bis(2-ethylhexanoate) is technically not feasible due to the rapid dissociation. Where no specific data are available, the assessment of environmental and human health endpoints should be based on its dissociation products. The dissociation products of toxicological relevance are 2-ethylhexanoate and Sn(II) components.
As a result, 2-ethyhexanoic acid and tin(II) chloride shall be used as read-across analogue for tin bis(2-ethylhexanoate) where no specific data are available.

2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES)
2-ethylhexanoic acid (CAS 149-57-5)
Tin(II) chloride (CAS 7772-99-8)

Purity of tin(II) bis(2-ethylhexanoate) is >= 92.5%.
Purity of 2-ethylhexanoic acid is 99.9%.
Purity of tin(II) chloride is 98.5%.


3. ANALOGUE APPROACH JUSTIFICATION
Tin bis(2-ethylhexanoate) is an organometallic salt with a dissociation constant of 5.09 at 20 °C. The dissociation study is included in IUCLID dataset. When introduced to water, more than 99% of tin bis(2-ethylhexanoate) will dissociate into 2-ethylhexanoate and Sn(II) components at pH > 6.8.
At environmentally relevant conditions, Sn(II) ion is not expected to be stable in water and is likely to be oxidized in the presence of molecular oxygen to form the insoluble inorganic solid Sn(IV)O2 (Pettin et al., 1981; Seby, 2001,), which is not expected to be bioavailable to aquatic life (Rudel, 2003).
Since tin bis(2-ethylhexanoate) is primarily in a dissociated form in the environment, the observed toxicity is likely dependent upon the toxicities for the respective acid and metal. Thus, where no specific data are available, the assessment of environmental and human health endpoints should be based on its dissociation components, namely Sn(II) in the form of Tin(II) chloride and 2-ethylhexanoic acid.

4. DATA MATRIX
Please refer to justification, attached to this section.

Description of key information

The substance decomposes when coming into contact with water. Therefore the decomposition products Sn(II)O and 2 -ethylhexanoic acid have to be adressed:

1. 2 -ethylhexanoic acid:

The log Kow of 2-ethylhexanoic acid is 2.64. Because this value is the preferred/accepted value among those critically reviewed by Sangster (1989) and Hansch et al. (1995), the determination is assumed to be made at 25 °C and pH where the substance is not ionized. The log D for this substance at pH 7 is estimated to be 0.55 (ACD Labs Log D Suite, v5.16). Therefore, at pH encountered in the environment, the substance will have very low potential for adsorption to organic matter of soils/sediments, or to bioaccumulate in aquatic organisms.

2. Partition Coefficient for Sn(II) part of salt:

Waived, as this property is not required nor relevant for an insoluble inorganic species.

Key value for chemical safety assessment

Log Kow (Log Pow):

2.64

at the temperature of:

25 °C

Additional information

When introduced to water, the Tin bis(2-ethylhexanoate) substance will dissociate (99% dissociated at pH > 6.8), where the Sn(II) will be initially speciated as the Sn(OH)₂ substance, which will be oxidized in oxygenated solutions to become the insoluble solid SnO₂. The 2-ethyl hexanoic acid part of the salt has its maximum water solubility at pH > 6.8, where it exists completely as the ethyl hexanoate anion. By definition, log Kow must be determined at pH where an ionizable substance is fully neutralized, in this case, pH < 2.8. The reported log Kow of 2-ethylhexanoic acid is 2.64. Because this value is the preferred/accepted value among those critically reviewed by Sangster (1989) and Hansch et al. (1995), the determination is assumed to be made at 25 °C and pH where the substance is not ionized. The distribution coefficient log D for this substance at pH 7 is estimated to be 0.55 (ACD Labs Log D Suite, v5.16). Therefore, at pH encountered in the environment, the substance will have very low potential for adsorption to organic matter of soils/sediments, or to bioaccumulate in aquatic organisms.