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vapour pressure
Type of information:
Adequacy of study:
key study
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:
EPI Suite™ (2012)

2. MODEL (incl. version number)

CAS-No: 10128-55-9
SMILES: O=C(OC(=Nc1cccc2)c(c(NS(=O)(=O)c(ccc(c3ccc4)c4)c3)ccc5)c5)c12

MPBPWIN estimates vapor pressure (VP) by three separate methods: (1) the Antoine method, (2) the modified Grain method, and (3) the Mackay method. All three use the normal boiling point to estimate VP.
(1) Antoine Method: Chapter 14 of Lyman et al (1990) includes the description of the Antoine method used by MPBPWIN. It was developed for gases and liquids.
MPBPWIN has extended the Antoine method to make it applicable to solids by using the same methodology as the modified Grain method to convert a super-cooled liquid VP to a solid-phase VP.

(2) Modified Grain Method: Chapter 2 of Lyman (1985) describes the modified Grain method used by MPBPWIN. This method is a modification and significant improvement of the modified Watson method. It is applicable to solids, liquids and gases.
The KF structural factors are available in chapter 14 of Lyman et al (1990); the variation of this parameter is related to chemical class and is small (roughly 0.99 to 1.2), so large errors in its selection are unlikely (Lyman, 1985). The modified Grain method may be the best all-around VP estimation method currently available

(3) Mackay Method: Mackay derived the following equation to estimate VP (Lyman, 1985):  ln P  =  -(4.4 + ln Tb)[1.803(Tb/T - 1) - 0.803 ln(Tb/T)] - 6.8(Tm/T - 1)
where Tb is the normal boiling pt (K), T is the VP temperature (K) and Tm is the melting pt (K). The melting point term is ignored for liquids. It was derived from two chemical classes: hydrocarbons (aliphatic and aromatic) and halogenated compounds (again aliphatic and aromatic).

MPBPWIN reports the VP estimate from all three methods. It then reports a "suggested" VP. For solids, the modified Grain estimate is the suggested VP. For liquids and gases, the suggested VP is the average of the Antoine and the modified Grain estimates. The Mackay method is not used in the suggested VP because its application is currently limited to its derivation classes.

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 °C (the vast majority at 25 or 20 °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°C) and the batch estimates were compared to PHYSPROP's experimental VP.
- number = 3037
- r² = 0.914
- std dev = 1.057
- avg dev = 0.644
The estimation error increases as the vapor pressure (both experimental and estimated) decreases, especially when the vapor pressure decreases below 1x10-6 mm Hg (0.0001333 Pascals).The estimation methodology uses the normal boil point to estimate the liquid-phase vapor pressure. For solids, the melting point is required to convert the liquid-phase vapor pressure to the solid-phase vapor pressure. VP estimation error can be introduced by poor boiling point estimates or values and 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.
For maximum VP accuracy, good experimental boiling points and/or melting points should be entered on the data entry screen (or available from the experimental databases included with the EPI Suite).

Estimation 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 vapor pressure as described above in the accuracy section.

Data source

Reference Type:
other: Software
EPI Suite, Estimation Programs Interface Suite™ for Microsoft® Windows, v 4.11
Bibliographic source:
United States Environmental Protection Agency, Washington, DC, USA.

Materials and methods

Test guideline
other: REACH Guidance on QSARs R.6
GLP compliance:
not specified
Type of method:
other: calculated by the Modified Grain Method

Test material

Constituent 1
Chemical structure
Reference substance name:
EC Number:
EC Name:
Cas Number:
Molecular formula:
Test material form:
Details on test material:
QSAR calculation
Specific details on test material used for the study:

Results and discussion

Vapour pressure
25 °C
Vapour pressure:
0 other: 9.12E-012 Pa
Remarks on result:
other: QSAR predicted value

Any other information on results incl. tables

MPBPWIN v1.43 estimated that N-[2-(4-oxo-4H-3,1-benzoxazin-2-yl)phenyl]naphthalene-2-sulphonamide has a vapour pressure of 6.84E-014 mm Hg; 9.12E-012 Pa at 25 °C.

Experimental Database Structure Match:  no data

SMILES: O=C(OC(=Nc1cccc2)c(c(NS(=O)(=O)c(ccc(c3ccc4)c4)c3)ccc5)c5)c12

CHEM: 2-Naphthalenesulfonamide, N- 2-(4-oxo-4H-3,1-benzoxazin-2-yl)phenyl -

MOL FOR: C24 H16 N2 O4 S1

MOL WT : 428.47

Vapor Pressure Estimations (25 °C): boiling point (estimated): 647.67 °C and melting point: 194.4 °C (user entered)

- Antoine Method: 4.04E-019 mm Hg; 5.38E-017 Pa

- Modified Grain Method: 6.84E-014 mm Hg; 9.12E-012 Pa

- Mackay Method: 1.82E-013 mm Hg; 2.43E-011 Pa

 Selected VP: Modified Grain Method: 6.84E-014 mm Hg; 9.12E-012 Pa

Applicant's summary and conclusion

MPBPWIN v1.43 estimated that N-[2-(4-oxo-4H-3,1-benzoxazin-2-yl)phenyl]naphthalene-2-sulphonamide has a vapour pressure of 6.84E-014 mm Hg; 9.12E-012 Pa at 25 °C.

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