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Water solubility

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Reference
Endpoint:
water solubility
Type of information:
(Q)SAR
Adequacy of study:
key study
Study period:
03 April 2018
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
results derived from a valid (Q)SAR model, but not (completely) falling into its applicability domain, with adequate and reliable documentation / justification
Justification for type of information:
1. SOFTWARE
EPI Suite Version 4.11

2. MODEL (incl. version number)
WSKOW v1.42

3. SMILES OR OTHER IDENTIFIERS USED AS INPUT FOR THE MODEL
CAS: 73246-85-2: CCCCCCCCCCCCOC(=O)CS[Sn](CCCCCCCC)(CCCCCCCC)SCC(=O)OCCCCCCCCCCCC
CAS: 79330-84-0: O=C(CS[Sn](SCC(=O)OCCCCCCCCCCCCCC)(CCCCCCCC)CCCCCCCC)OCCCCCCCCCCCCCC

4. SCIENTIFIC VALIDITY OF THE (Q)SAR MODEL
- Data Collection:
A database of more than 8400 compounds with reliably measured log Kow values had already been compiled from available sources. Most experimental values were taken from a "star-list" compilation of Hansch and Leo (1985) that had already been critically evaluated (see also Hansch et al, 1995) or an extensive compilation by Sangster (1993) that includes many "recommended" values based upon critical evaluation. Other log Kow values were taken from sources located through the Environmental Fate Data Base (EFDB) system (Howard et al, 1982, 1986). A few values were taken from Section 4a, 8d, and 8e submissions the to U.S. EPA under the Toxic Substances Control Act (see http://www.syrres.com/esc/tscats_info.htm).
Water solubilities were collected from the AQUASOL dATAbASETM of the University of Arizona (Yalkowsky and Dannenfelser, 1990), Syracuse Research Corporation's PHYSPROP© Database (SRC,1994), and sources located through the Environmental Fate Data Base (EFDB) system (Howard et al, 1982, 1986). Water solubilities were primarily constrained to the 20-25 °C temperature range with 25 °C being preferred.
Melting points were collected from sources such as AQUASOL dATAbASETM, PHYSPROP©, and EDFB as well as the Handbook of Chemistry and Physics (Lide, 1990) and the Aldrich Catalog (Aldrich, 1992).
- Regression & Results:
A dataset of 1450 compounds (941 solids, 509 liquids) having reliably measured water solubility, log Kow and melting point was used as the training set for developing the new estimation algorithms for water solubility. Standard linear regressions were used to fit water solubility (as log S) with log Kow, melting point and molecular weight.
Residual errors from the initial regression fit were examined for compounds sharing common structural features with relatively consistent errors. On that basis, 12 compound classes were initially identified and added to the regression to comprise a multi-linear regression including log Kow, melting point and/or molecular weight plus 12 correction factors. Each correction factor is counted a maximum of once per structure [if applicable], no matter how many times the applicable fragment occurs. For example, the nitro factor in 1,4-dinitrobenzene is counted just once. A compound either contains a correction factor or it doesn't; therefore, the matrix for the multi-linear regression contained either a 0 or 1 for each correction factor.
WSKOWWIN estimates water solubility for any compound with one of two possible equations. The equations are equations 19 and 20 from Meylan and Howard (1994a) or equations 11 and 12 from the journal article (Meylan et al., 1996). The equations are:
log S (mol/L) = 0.796 - 0.854 log Kow - 0.00728 MW + ΣCorrections
log S (mol/L) = 0.693 - 0.96 log Kow - 0.0092(Tm-25) - 0.00314 MW + ΣCorrections
(where MW is molecular weight, Tm is melting point (MP) in °C [used only for solids]). When a measured MP is available, that equation is used; otherwise, the equation with just MW is used.

5. APPLICABILITY DOMAIN
- The WSKOWWIN program applies an individual correction factor only once per structure [if at all] regardless of how many instances of the applicable structural feature occur in the structure. The minimum number of instances is zero and the maximum is one.
- Range of water solubilities in the Training set:
Minimum = 4 x 10^-7 mg/L (octachlorodibenzo-p-dioxin)
Maximum = completely soluble (various)
- Range of Molecular Weights in the Training set:
Minimum = 27.03 (hydrocyanic acid)
Maximum = 627.62 (hexabromobiphenyl)
- Range of Log Kow values in the Training set:
Minimum = -3.89 (aspartic acid)
Maximum = 8.27 (decachlorobiphenyl)
- Currently there is no universally accepted definition of model domain. However, users may wish to consider the possibility that water solubility estimates are less accurate for compounds outside the MW range, water solubility range and log Kow range of the training set compounds. It is also possible that a compound may have a functional group(s) or other structural features not represented in the training set, and for which no correction factor was developed. These points should be taken into consideration when interpreting model results.

6. ADEQUACY OF THE RESULT
- Given that the substance is an organic molecule the prediction is considered to be acceptable, however the molecular weight of the substance is slightly greater than the molecular weights in the training set and as a result the water solubility estimate is less accurate.
Qualifier:
according to guideline
Guideline:
other: REACH guidance on QSARs R.6
Version / remarks:
May/July 2008
Deviations:
no
GLP compliance:
no
Type of method:
other: calculation
Specific details on test material used for the study:
- Molecular weight
CAS: 73246-85-2: 864.02
CAS: 79330-84-0: 920.13
Key result
Water solubility:
0 mg/L
Temp.:
25 °C
Remarks on result:
other: CAS 73246-85-2
Key result
Water solubility:
0 mg/L
Temp.:
25 °C
Remarks on result:
other: CAS 79330-84-0

CAS 79330-84-0

WSKOW v1.42 Results

Log Kow (estimated) : 21.39

Log Kow (experimental): not available from database

Log Kow used by Water solubility estimates: 21.39

Equation Used to Make Water Sol estimate:

Log S (mol/L) = 0.796 - 0.854 log Kow - 0.00728 MW + Correction (used when Melting Point NOT available).

Correction(s): No Applicable Correction Factors

Log Water Solubility (in moles/L) : -24.173

Water Solubility at 25 deg C (mg/L): 6.173e-019

CAS 73246-85-2

WSKOW v1.42 Results

Log Kow (estimated) : 19.43

Log Kow (experimental): not available from database

Log Kow used by Water solubility estimates: 19.43

Equation Used to Make Water Sol estimate: Log S (mol/L) = 0.796 - 0.854 log Kow - 0.00728 MW + Correction (used when Melting Point NOT available). Correction(s): No Applicable Correction Factors

Log Water Solubility (in moles/L) : -22.087

Water Solubility at 25 deg C (mg/L): 7.067e-017

Conclusions:
The water solubility of the test material components were calculated to be 7.067e-017 mg/L and 6.173e-019 mg/L at 25 °C.
Executive summary:

The water solubility of the test material was calculated using WSKOW v1.42 2000 U.S. Environmental Protection Agency.

The molecular weight of the substance components are slightly greater than the molecular weights in the training set and as a result the water solubility estimate is less accurate.

The water solubility of the test material components were calculated to be 7.067e-017 mg/L and 6.173e-019 mg/L at 25 °C.

Description of key information

The water solubility of the test material components were calculated to be 7.067e-017 mg/L and 6.173e-019 mg/L at 25 °C.

Key value for chemical safety assessment

Additional information

The water solubility of the test material was calculated using WSKOW v1.42 2000 U.S. Environmental Protection Agency.

The molecular weight of the substance components are slightly greater than the molecular weights in the training set and as a result the water solubility estimate is less accurate.

The water solubility of the test material components were calculated to be 7.067e-017 mg/L and 6.173e-019 mg/L at 25 °C.