Cedrus atlantica, ext.

Vapour pressure

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:

SEE ATTACHED QMRF and QPRF report

1. SOFTWARE

2. MODEL (incl. version number)

3. SMILES OR OTHER IDENTIFIERS USED AS INPUT FOR THE MODEL

4. SCIENTIFIC VALIDITY OF THE (Q)SAR MODEL
[Explain how the model fulfils the OECD principles for (Q)SAR model validation. Consider attaching the QMRF or providing a link]
- Defined endpoint:
- Unambiguous algorithm:
- Defined domain of applicability:
- Appropriate measures of goodness-of-fit and robustness and predictivity:
- Mechanistic interpretation:

5. APPLICABILITY DOMAIN
[Explain how the substance falls within the applicability domain of the model]
- Descriptor domain:
- Structural and mechanistic domains:
- Similarity with analogues in the training set:
- Other considerations (as appropriate):

6. ADEQUACY OF THE RESULT
[Explain how the prediction fits the purpose of classification and labelling and/or risk assessment]

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

Guideline:

other: REACH Guidance on QSARs R.6

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 individual 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. As for many constituents no measured information is available, QSARs have been used to estimate the vapour pressure for the individual constituents. The relevance and reliability of the used QSAR for these constituents is shown in the attached QMRF and QPRF. It should also be noted that extreme non-volatile constituents (<1 Pa) are not relevant for the volatility of the NCS. 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

Test material

Test material information

Constituent 1

Reference substance name:

Cedrus atlantica, ext.

EC Number:

295-985-9

EC Name:

Cedrus atlantica, ext.

Cas Number:

92201-55-3

Molecular formula:

Not applicable due to UVCB nature of the substance

IUPAC Name:

Essential oil of Cedarwood Atlas obtained from the wood of Cedrus atlantica by steam distillation

Test material form:

liquid

Results and discussion

Vapour pressure

Key result

Temp.:

25 °C

Vapour pressure:

1.89 Pa

Remarks on result:

other: Initial vapour pressure

Any other information on results incl. tables

Constituent	CAS	Estimated vapour pressure (Pa at 25ºC)
(+)-Aromadendrene	489-39-4	5.27
Longifolene	475-20-7	2.5
β-Cedrene	546-28-1	6.08
α-(+)-Longipinene	5989-08-2	4.52
α-Cedrene	469-61-4	0.0184
Thujopsene	470-40-6	9.37
cis-Calamenene	72937-55-4	0.909
Calacorene (group of isomers)	21391-99-1; 168398-95-6; 50277-34-4; 24048-45-1	0.721 (1)
γ-Dehydro-Ar-himachalene	51766-65-5	0.316
α-Himachalene	3853-83-6	2.8
γ-Himachalene	53111-25-4	2.13
Δ-Cadinene	483-76-1	2.51
β-Himachalene	1461-03-6	1.47
Atlantones (α,β,γ)	26294-59-7	0.433
Cedrol	77-53-2	0.0165
Deodarone 1 & 2	41943-81-1	0.0463

The sum of the vapour pressures multiplied by the fractions in the mixture is 1.82 Pa. To correct for the 3.5% 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 / 0.965.

The vapour pressure of the constituents ranges from 0.0165 to 9.37 Pa.

(1) Worst-case value for beta-Calacorene was used.

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 vapor 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 vapor 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 atlas oil is 1.89 Pa at 25ºC.

Executive summary:

The initial vapour pressure of Cedarwood atlas oil 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 atlas oil was found to be 1.89 Pa at 25ºC. The vapour pressure of the constituents ranges from 0.0165 to 9.37 Pa.