Litsea cubeba, ext.

Vapour pressure

Link to relevant study record(s)

Reference

Endpoint:

vapour pressure

Type of information:

(Q)SAR

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: 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

Reason / purpose for cross-reference:

reference to same study

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 substance 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

Key result

Temp.:

25 °C

Vapour pressure:

60.29 Pa

Remarks on result:

other: Initial vapour pressure

Substance	CAS	Estimated vapour pressure (Pa at 25ºC)
L-Limonene	5989-54-8	193
Neral	106-26-3	12.2
Geranial	141-27-5	12.2
(+)-Citronellal	2385-77-5	33.9
Geraniol	106-24-1	2.12
β-(+)-Citronellol	1117-61-9	2.26
Methyl heptenone	110-93-0	238
(-)-Linalol	126-91-0	11.1
beta-Caryophyllene	87-44-5	4.16
alpha-(-)-Pinene	80-56-8	536
1,8-Cineol	470-82-6	208
Sabinene	3387-41-5	981
beta-Myrcene	123-53-3	320
Verbenol	473-67-6	1.06
Isoneral	72203-97-5	19.9
Isogeranial	72203-98-6	19.9
Nerol	106-25-2	2.12

The sum of the vapour pressures multiplied by the fractions in the mixture is 58.63 Pa. To correct for the 3.4% 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 / 0.966.

The vapour pressure of the constituents ranges from 1.06 to 981 Pa.

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 vapour 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 vapour 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.

Conclusions:

The initial vapour pressure of Litsea cubeba oil is 60.29 Pa at 25ºC.

Executive summary:

The initial vapour pressure of Litsea cubeba 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 Litsea cubeba oil was found to be 60.29 Pa at 25ºC. The vapour pressure of the constituents ranges from 1.06 to 981 Pa.

Description of key information

The initial vapour pressure of Litsea cubeba oil was found to be 60.29 Pa at 25ºC. The vapour pressure of the constituents ranges from 1.06 to 981 Pa.

Key value for chemical safety assessment

Vapour pressure:

60.29 Pa

at the temperature of:

25 °C

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