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Vapour pressure

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Reference
Endpoint:
vapour pressure
Type of information:
(Q)SAR
Adequacy of study:
key study
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
Estimation Programs Interface Suite™ for Microsoft® Windows v4.11. US EPA, United States Environmental Protection Agency, Washington, DC, USA.

2. MODEL (incl. version number)
MPBPWIN v1.43 (September 2010)

3. SMILES OR OTHER IDENTIFIERS USED AS INPUT FOR THE MODEL
O=C3C=CC(=O)N3Cc1cc(CN2C(=O)C=CC2(=O))ccc1
CAS: 13676-53-4
Melting point: 120°C

4. SCIENTIFIC VALIDITY OF THE (Q)SAR MODEL

- Defined endpoint:
vapour pressure

- Unambiguous algorithm:
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. The Antoine equation used to estimate vapor pressure from the normal boiling (Tb) is shown in the attached document. 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 as shown below.
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 modified Grain method equations are shown in the attached document.
Mackay Method: The equation derived by Mackay to estimate VP (Lyman, 1985) is shown in the attached document.
All three methods use the normal boiling point to estimate VP. Unless the user enters a boiling point on the data entry screen, MPBPWIN uses the estimated boiling point from the adapted Stein and Brown method (For more information see: Stein, S.E. and Brown, R.L. 1994. Estimation of normal boiling points from group contributions. J. Chem. Inf. Comput. Sci. 34: 581-7). MPBPWIN reports the VP estimate from all three methods. It then reports a "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.

- Defined domain of applicability:
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.
Training Set Molecular Weights:
Minimum MW: 16.04
Maximum MW: 943.17
Average MW: 194.22

- Appropriate measures of goodness-of-fit and robustness and predictivity:
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.

- Mechanistic interpretation:
MPBPWIN estimates vapor pressure (VP) by three separate methods: (1) the Antoine method, (2) the modified Grain method, and (3) the Mackay method. For more detailed information about the methodologies please refer also to 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. and Lyman, W.J., Reehl, W.F. and Rosenblatt, D.H. 1990. Handbook of Chemical Property Estimation Methods. Washington, DC: American Chemical Society, Chapter 14.

5. APPLICABILITY DOMAIN

- Descriptor domain:
Molecular weight

- Similarity with analogues in the training set:
The substance consists of several fragments which are all present in the training data sets. Moreover, based on molecular weight the substance also falls into the applicability domain of the model.


6. ADEQUACY OF THE RESULT
The estimation is based on i.a. boiling point and experimental data (Differential Scanning Calorimetry) revealed that m- Xylylenebismaleimide has no boiling point but decomposes instead. However, since the substance falls into the molecular weight range predictivity of the model used and a reliable melting point was obtained from experimental data, the prediction is considered to be sufficient to provide reliable results for classification and labelling and/or risk assessment. Furthermore, the vapour pressure obtained from the QSAR prediction is very low which substantiates the assumption that testing of vapour pressure is technically not feasible.

For further informations on the model used please refer to the attached justification.
Qualifier:
no guideline followed
Principles of method if other than guideline:
QSAR prediction performed with EPISuite software /MPBPWIN v 1.43 (Spetember 2010).
GLP compliance:
no
Type of method:
other: QSAR estimation method
Key result
Test no.:
#1
Temp.:
25 °C
Vapour pressure:
0 Pa
Remarks on result:
other: Result from QSAR estimation

SMILES : O=C3C=CC(=O)N3Cc1cc(CN2C(=O)C=CC2(=O))ccc1

CHEM   : m-Xylylenebismaleimide

MOL FOR: C16 H12 N2 O4

MOL WT : 296.28

------------------------ SUMMARY MPBPWIN v1.43 --------------------

Vapor Pressure Estimations (25 deg C):

(Using BP: 610.94 deg C (estimated))

(Using MP: 120.00 deg C (user entered))

VP       :  3.19E-016 mm Hg (Antoine Method)

            :  4.26E-014 Pa  (Antoine Method)

VP       :  4.36E-012 mm Hg (Modified Grain Method)

            :  5.81E-010 Pa  (Modified Grain Method)

VP       :  9.3E-012 mm Hg (Mackay Method)

            :  1.24E-009 Pa  (Mackay Method)

Selected VP       :  4.36E-012 mm Hg (Modified Grain Method)

                         :  5.81E-010 Pa (Modified Grain Method)

Subcooled liquid VP       :  3.82E-011 mm Hg (25 deg C, Mod-Grain method)

                                     :  5.09E-009 Pa  (25 deg C, Mod-Grain method)

Conclusions:
According to EPISuite/MPBPWIN v 1.43 the vapour pressure of m-Xylylenebismaleimide is 5.81E-010 Pa at 25°C.

Description of key information

- QSAR estimation of vapour pressure using EPISuite software and MPBPWIN model, 5.81E-10 Pa at 25°C.

Key value for chemical safety assessment

Vapour pressure:
0 Pa
at the temperature of:
25 °C

Additional information

According to EPISuite/MPBPWIN v 1.43 the vapour pressure of m-Xylylenebismaleimide is 5.81E-010 Pa at 25°C.

The estimation is based on i.a. boiling point and experimental data (Differential Scanning Calorimetry) which revealed that m- Xylylenebismaleimide has no boiling point but decomposes instead. However, since the substance falls into the molecular weight range of the model predictivity and a reliable melting point was obtained from experimental data, the prediction is considered to be sufficient to provide reliable results for classification and labelling and/or risk assessment. Furthermore, the vapour pressure obtained from the QSAR prediction is very low which substantiates the assumption that testing of vapour pressure is technically not feasible.