Registration Dossier

Administrative data

Endpoint:
vapour pressure
Type of information:
(Q)SAR
Adequacy of study:
key study
Study period:
2018-03-23
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:
1. SOFTWARE
EPIWIN software by US-EPA

2. MODEL (incl. version number)
MPBPVPWIN v1.43

3. SMILES OR OTHER IDENTIFIERS USED AS INPUT FOR THE MODEL
The substance is a organic UVCB manufactured by reaction of butin-2-diol-1,4, sodium hydroxide and propanesultone using water as solvent. The CAS number 90268-78-3 (EC 290-883-0) is associated with the inventory name 2-Butyne-1,4-diol, reaction products with 1,2-oxathiolane 2,2-dioxide and sodium hydroxide (HBOPS-Na), the molecular formula cannot be given. As indicated by the name, there are several reaction products possible, resulting in a variable composition. Below there are the possible individual components with approximate contents listed:

CAS No Content, approx. Name Molecular formula Molecular weight SMILES notation
75032-91-6 48% sodium 3-[(4-hydroxybut-2-yn-1-yl)oxy]propane-1-sulfonate C7H12O5S.Na 230.214 [Na+].OCC#CCOCCCS(=O)(=O)[O-]
3542-44-7 7.6% sodium 3-hydroxypropane-1-sulphonate C3H7O4S.Na 162.14 [Na+].OCCCS(=O)(=O)[O-]
110-65-6 12.6% but-2-yne-1,4-diol C4H6O2 86.0892 OCC#CCO
n/a 31.8% disodium 3-[4-[3-sulfonatopropoxy)but-2-ynox]propane-1-sulfonate (“Dimer”) C10H16Na2O8S2 374.3438 O=S(=O)([O-])CCCOCC#CCOCCCS(=O)(=O)[O-].[Na+].[Na+]

QSAR estimations are performed for all contained structures, weighing will be done using Raoults law using the approximate content of the single substances, estimated as mean of the concentrations ranges of the boundary composition and adjusted to a sum of 100%.

4. SCIENTIFIC VALIDITY OF THE (Q)SAR MODEL
- The complete test sets of experimental data for (melting point, boiling point and) vapour pressure can be downloaded via the Internet at: http://esc.syrres.com/interkow/EpiSuiteData.htm

5. APPLICABILITY DOMAIN
Estimation accuracy: The accuracy of MPBPWIN's "suggested" VP estimate was tested on a dataset of 3037 compounds with known, experimental VP values between 15 and 30 deg C (the vast majority at 25 or 20 deg C). The experimental values were taken from the PHYSPROP Database that is part of the EPI Suite. For this test, the CAS numbers were run through MPBPWIN as a standard batch-mode run (using the default VP estimation temperature of 25 deg C) and the batch estimates were compared to PHYSPROP's experimental VP. The plot clearly indicates that the estimation error increases as the vapour pressure (both experimental and estimated) decreases, especially when the vapour pressure decreases below 1x10-6 mm Hg (0.0001333 Pa).
The estimation methodology uses the normal boil point to estimate the liquid-phase vapour pressure. For solids, the melting point is required to convert the liquid-phase vapour pressure to the solid-phase vapour pressure. VP estimation error can be introduced by:
(1) poor Boiling Point estimates or values
(2) poor Melting Point estimates or values (for solids)

The 3037 compound test set contains 1642 compounds with available experimental Boiling points and Melting points. For this subset of compounds, the estimation accuracy statistics are (based on log VP):

number = 1642
r2 = 0.949
std deviation = 0.59
avg deviation = 0.32

These statistics clearly indicate that VP estimates are more accurate with experimental BP and MP data.

Estimation domain: The intended application domain is organic chemicals. Inorganic and organometallic chemicals generally are outside the domain.
Currently there is no universally accepted definition of model domain. However, users may wish to consider the possibility that property estimates are less accurate for compounds outside the Molecular Weight range of the training set compounds, and/or that have more instances of a given fragment than the maximum for all 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 fragment coefficient was developed. These points should be taken into consideration when interpreting model results.
The complete training sets for MPBPWIN's estimation methodology are not available. Therefore, describing a precise estimation domain for this methodology is not possible. The current applicability of the MPBPWIN methodology is best described by its accuracy in predicting vapour pressure as described above in the accuracy section.

6. ADEQUACY OF THE RESULT
The result calculated for the organic substance 2-Butyne-1,4-diol, reaction products with 1,2-oxathiolane 2,2-dioxide and sodium hydroxide respectively its individual constituents seems reasonable. No melting or boiling point has been determined experimentally for the individual constituents, so the estimated results have been used for vapour pressure calculation. Further, due to the magnitude of the result it is considered as adequate.

Data source

Reference
Reference Type:
other: estimation software
Title:
EPI Suite Version 4.10
Year:
2018
Bibliographic source:
MPBPWIN - three separate methods for VP: Antoine method (1990), modified Grain method (1985) and Mackay method (1985)

Materials and methods

Test guideline
Guideline:
other: REACH guidance on QSARs Chapter R.6
Version / remarks:
May 2008
Principles of method if other than guideline:
Vapour Pressure is estimated by three methods; all three methods use the boiling point.  The first is the Antoine method (see Chapter 14 of W.J. Lyman's book "Handbook of Chemical Property Estimation Methods", Washington, DC: American Chemical Society, 1990).  The second is the modified Grain method (see page 31 of Neely and Blau's Environmental Exposure from Chemicals, Volume I, CRC Press, 1985).  The third is the Mackay method (see page 31-2 of Neely and Blau's Environmental Exposure from Chemicals, Volume I, CRC Press, 1985).
As the substance is actually an UVCB, vapour pressure was derived for the single constituents, the vapour pressure of the reaction mass was calculated using Raoult's law.
GLP compliance:
no
Remarks:
not required
Type of method:
other: QSAR calculation

Test material

Reference
Name:
Unnamed
Type:
Constituent
Test material form:
solid

Results and discussion

Vapour pressureopen allclose all
Temp.:
25 °C
Vapour pressure:
0 Pa
Remarks on result:
other: for sodium 3-[(4-hydroxybut-2-yn-1-yl)oxy]propane-1-sulfonate
Temp.:
25 °C
Vapour pressure:
0 Pa
Remarks on result:
other: for sodium 3-hydroxypropane-1-sulphonate
Temp.:
25 °C
Vapour pressure:
0.331 Pa
Remarks on result:
other: for but-2-yne-1,4-diol
Temp.:
25 °C
Vapour pressure:
0 Pa
Remarks on result:
other: for disodium 3-[4-[3-sulfonatopropoxy)but-2-ynox]propane-1-sulfonate (“Dimer”)
Key result
Temp.:
25 °C
Vapour pressure:
0.1 Pa
Remarks on result:
other: for the registered substance, calculated using Raoult's law

Applicant's summary and conclusion

Conclusions:
The study report describes a scientifically accepted calculation method for the vapour pressure using the US-EPA software MPBPWIN v1.43.No GLP criteria are applicable for the usage of this tool and the QSAR estimation is easily repeatable. The result is adequate for the regulatory purpose. As the registered substance is an UVCB consisting of various components which could be rather concretely quantified, the individual vapour pressure values for each of the components was used to estimate the vapour pressure of the mixture by multiplying the predicted value by the mole fraction for each of the components and then summing together, using Raoult’s law.
Executive summary:

The vapour pressure of the substance 2-Butyne-1,4-diol, reaction products with 1,2-oxathiolane 2,2-dioxide and sodium hydroxide (HBOPS-Na) was determined by the computer program MPBPWIN v1.43 (EPIWIN software) by US-EPA (2012). The program calculates the vapour pressure according to three different methods: Antoine, Modified Grain and Mackay. The Modified Grain method is preferentially adopted and therefore the most important one [Lyman, W.J., 1985. In: Environmental Exposure From Chemicals. Volume I., Neely, W.B. and Blau, G.E. (eds), Boca Raton, FL: CRC Press, Inc., Chapter 2]. Therefore, the vapour pressures of the individual constituents were estimated using estimated melting and boiling points, and an ambient temperature of 25 °C is assumed. Then the individual vapour pressures were multiplied by the mole fraction for each of the components and then summing together, using Raoult’s law. The vapour pressure of the registered substance 2-Butyne-1,4-diol, reaction products with 1,2-oxathiolane 2,2-dioxide and sodium hydroxide, was estimated to be 9.95E-02 Pa @25°C.