Registration Dossier

Administrative data

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
Remarks:
Values for individual constituents of this natural complex substance (NCS) were calculated using a validated QSAR. All constituents fall within the applicability domain of the QSAR.
Justification for type of information:
1. The software used: see attached QMRF
2. The model(s) used: see attached QPRF

1. SOFTWARE
MPBPVPWIN v1.43 QSAR for vapour pressure in Pa at 25°C Dr. Robert
Boethling, U.S. Environmental Protection Agency, 1200 Pennsylvania Ave.,
N.W. (Mail Code 7406M) Washington, DC 20460, USA, Phone: # (202) 564-
8 5 3 3 , e - m a i l : b o e t h l i n g . b o b @ e p a . g o v
h t t p : / / w w w . e p a . g o v / o p p t i n t r / e x p o s u r e / p u b s / e p i s u i t e . h t m

2. MODEL (incl. version number)
Model or submodel name: MPBPVPWIN
Model version: Version 1.43
Reference to QMRF: QSAR for vapour pressure in Pa at 25ºC
Cross-reference
Reason / purpose:
reference to same study

Data source

Reference
Reference Type:
other: QSAR model
Title:
MPBPWIN v1.43
Author:
U.S. Environmental Protection Agency
Year:
2008
Bibliographic source:
US EPA. [2008]. Estimation Programs Interface Suite™ for Microsoft® Windows, v 4.00. United States Environmental Protection Agency, Washington, DC, USA

Materials and methods

Test guideline
Qualifier:
according to
Guideline:
other: REACH Guidance on QSARs R.6
Version / remarks:
replaces OECD Guideline 104 (Vapour Pressure Curve)
Deviations:
not applicable
Principles of method if other than guideline:
This parameter varies as the composition of the mixture changes during evaporation. For Type 1 NCSs with known constituents the “initial” vapour pressure can be calculated as the sum of the partial pressure of the known constituents. Also a range of the vapour pressure can be given. Therefore, the first approach will be a calculation of the vapour pressure based on constituents. Extreme non-volatile constituents (<1 Pa) are not relevant for the volatility of the NCS. For the initial vapour pressure, the estimated values are used in the calculation. The “initial” vapour pressure is calculated as the sum of the partial pressure of the constituents (based on molecular fraction).
GLP compliance:
no
Type of method:
other: Calculation by estimation / QSAR

Test material

Reference
Name:
Unnamed
Type:
Constituent
Test material form:
other: not applicable for in silico study
Details on test material:
- Name of test material (as cited in study report): Ceadrwood Texas oil distilled - Cedrol
- Commercially available test material - not applicable for in silico study

Results and discussion

Vapour pressure
Key result
Temp.:
25 °C
Vapour pressure:
0.67 Pa
Remarks on result:
other: Initial vapour pressure

Any other information on results incl. tables

 Constituent  CAS  VP (Pa @ 25ºC)
 Widdrol  6892 -80 -4  0.00951
 Cedrol  77 -53 -2  0.0165
 Bergamotene alpha  17699 -05 -7  3.69
 Himachalene beta 1461 -03 -6 1.47
 Chamigrene alpha  19912 -83 -5  2.28
 Himachalene gamma  53111 -25 -4  2.13
 Himachalene alpha  3853 -83 -6  2.80
 Cuparene  16982 -00 -6  0.773
 Thujopsene  470 -40 -6  9.37
 Cedrene alpha  469 -61 -4  0.0184
 Cedrene beta  546 -28 -1  6.08
 Diepi-alpha-cedrene  50894 -66 -1  0.0184

Weight percentages of constituents are converted to molar percentages using the molecular weight (MW).

To correct for the 13,6 % unknown constituents (assuming the average vapour pressure for the unknown constituents is similar to the average vapour pressure of the known constituents), this number is multiplied by [1 / x].

MPBPWIN v1.43 model details

Reference to the type of model used

This program (MPBPWIN) estimates the boiling point (at 760 mm Hg), melting point and vapor pressure of organic compounds. MPBPWIN requires only a chemical structure to make these predictions. MPBPWIN estimates vapour pressure (VP) using the estimated boiling point.

 

Description of the applicability 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.

 

Training Set Molecular Weights:

Minimum MW: 16.04

Maximum MW: 943.17

Average MW: 194.22

Description and results of any possible structural analogues of the substance to assess reliability of the prediction

Internal validation with a dataset containing 3037 substances resulted in a correlation coefficient (r2) of 0.914, a standard deviation of 1.057 and an average deviation of 0.644.

Predictivity assessment of the internal validation set:

Validation Set Estimation Error:

within <= 0.10 - 34.1%

within <= 0.20 - 45.6%

within <= 0.40 - 60.0%

within <= 0.50 - 64.9%

within <= 0.60 - 69.0%

within <= 0.80 - 75.0%

within <= 1.00 - 80.0%

Uncertainty of the prediction

All constituents for which estimations were made fall within the applicability domain of the model.

Mechanistic domain

This program (MPBPWIN) estimates the boiling point (at 760 mm Hg), melting point and vapour pressure of organic compounds. MPBPWIN requires only a chemical structure to make these predictions. 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. 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.

Applicant's summary and conclusion

Conclusions:
The initial vapour pressure of Cedarwood Texas oil distilled - Cedrol is 0.67 Pa at 25 °C.
Executive summary:

The initial vapour pressure of Cedarwood Texas oil distilled - Cedrol was estimated by calculation. Vapour pressures for the known constituents were estimated using the QSAR MPBPWIN v 1.43. The sum of the vapour pressures multiplied by the fraction of the substance in the NCS was taken as an initial estimate for the vapour pressure of the mixture. The number obtained was then corrected for the unknown constituents (assuming the average vapour pressure for the unknown constituents is similar to the average vapour pressure of the known constituents).

The initial vapour pressure of Cedarwood Texas oil distilled - Cedrol was found to be 0.67 Pa at 25°C. The vapour pressure of the constituents ranges from 0.00951 - 9.37 Pa.