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Physical & Chemical properties

Vapour pressure

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Administrative data

Endpoint:
vapour pressure
Type of information:
(Q)SAR
Adequacy of study:
key study
Study period:
2018-03-08
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)
MPBPWIN v1.43

3. SMILES OR OTHER IDENTIFIERS USED AS INPUT FOR THE MODEL
c1(C)c(N=C(=O))c(CC)c(N=C(=O))c(CC)c1

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 3,5-Diethyltoluene-2,4-diisocyanate seems reasonable. The model allows entering both experimental melting and boiling point to increase accuracy. So, the experimentally determined melting point of 17.9°C was entered, but disregarded by the model as it is not used for liquids. Only the experimentally determined boiling point is relevant. DETDI has a boiling range from at 272 - 289 °C at atmospheric pressure as determined by differential scanning calorimetry. Consequently, vapour pressure was estimated using both the upper and lower value to cover both extremes, which results in a range of the vapour pressure itself. As the boiling point is rather high, it is clearly indicated that the estimated vapour pressure does not underestimate a potential hazard via inhalation, so estimation of the vapour pressure is considered adequate.
The estimated vapour pressure using the lower boiling point of 272°C is 1.1 Pa, using a boiling point of 289°C, the resulting vapour pressure is 0.466 Pa at 25°C. Taking into account the magnitude of the vapour pressure result it is considered that both boiling points would reveal a result clearly indicating that DETDI is not volatile.

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
GLP compliance:
no
Remarks:
(not applicable)
Type of method:
other: QSAR calculation

Test material

Constituent 1
Chemical structure
Reference substance name:
1,3-diethyl-2,4-diisocyanato-5-methylbenzene
Cas Number:
2162-70-1
Molecular formula:
C13H14N2O2
IUPAC Name:
1,3-diethyl-2,4-diisocyanato-5-methylbenzene
Test material form:
liquid
Details on test material:
SMILES Code: c1(C)c(N=C(=O))c(CC)c(N=C(=O))c(CC)c1

Results and discussion

Vapour pressureopen allclose all
Key result
Temp.:
25 °C
Vapour pressure:
>= 0.466 - <= 1.1 Pa
Remarks on result:
other: Mean of Antoine & Grain methods
Remarks:
boundary values estimated using both extremes of the experimentally determined boiling point range of 272-289°C
Temp.:
25 °C
Vapour pressure:
>= 0.394 - <= 1.07 Pa
Remarks on result:
other: Antoine Method
Remarks:
boundary values estimated using both extremes of the experimentally determined boiling point range of 272-289°C
Temp.:
25 °C
Vapour pressure:
>= 0.466 - <= 1.14 Pa
Remarks on result:
other: Modified Grain Method
Remarks:
boundary values estimated using both extremes of the experimentally determined boiling point range of 272-289°C
Temp.:
25 °C
Vapour pressure:
>= 0.868 - <= 2.07 Pa
Remarks on result:
other: Mackay Method
Remarks:
boundary values estimated using both extremes of the experimentally determined boiling point range of 272-289°C

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.
The calculation resulted in a value of 0.466-1.1 Pa at 25 °C.
Executive summary:

The vapour pressure of DETDI 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]. The experimentally determined boiling point range of 272 - 289 °C is used, and an ambient temperature of 25 °C is assumed. The Antoine Method gives a result of 0.394-1.07 Pa, the Mackay Method results in a value of 0.868-2.07 Pa and according to the Modified Grain Method the substance has a vapour pressure of 0,466-1.14 Pa, which results in a mean of Mean of Antoine & Grain methods of 0.466-1.1 Pa at 25°C.