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Vapour pressure

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Endpoint:
vapour pressure
Type of information:
experimental study
Adequacy of study:
weight of evidence
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
data from handbook or collection of data
Reason / purpose:
read-across: supporting information
Principles of method if other than guideline:
no data
GLP compliance:
not specified
Type of method:
other: no data
Temp.:
25 °C
Vapour pressure:
0.147 hPa
Remarks on result:
other: Value has been calculated from the vapour pressures detailed in the handbook.

Vapour pressure from L-Menthol for different temperatures:

 Temperature °C  Vapour pressure in hPa
 56 1.33 
 83.2  6.66
 96.0  13.33
 110.3  26.66
 126.1  53.33
 136.1  79.99
 149.4 133.32
 168.3 266.64
 190.2  533.29
 212.0  1013.25

L-Menthol exists as a solid in four different modifications. The melting point of the isomers varies from 31 - 43 ° C.

Executive summary:

The vapour pressure of L-Menthol is 0.147 hPa at 25°C and 1013 hPa.

Endpoint:
vapour pressure
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Justification for type of information:
Data from structural related substance (see attached justification)
Reason / purpose:
read-across source
Temp.:
25 °C
Vapour pressure:
0.147 hPa
Remarks on result:
other: Value has been calculated from the vapour pressures detailed in the handbook.

Vapour pressure from L-Menthol for different temperatures:

 Temperature °C  Vapour pressure in hPa
 56 1.33 
 83.2  6.66
 96.0  13.33
 110.3  26.66
 126.1  53.33
 136.1  79.99
 149.4 133.32
 168.3 266.64
 190.2  533.29
 212.0  1013.25

Menthol is a solids in four different modifications. The melting point of the isomere is 31 - 43 ° C.

Hypothesis for the read-across approach:

REACH regulation (Corrigendum) EC 1907/2006 on page L 136/120: “Substances whose physicochemical, toxicological and ecotoxicological properties are likely to be similar or follow a regular pattern as a result of structural similarity may be considered as a group, or ‘category’ of substances. Application of the group concept requires that physicochemical properties, human health effects and environmental effects or environmental fate may be predicted from data for reference substance(s) within the group by interpolation to other substances in the group (read-across approach).”

Further, ECHA guidance document “Guidance on information requirements and chemical safety assessment – Chapter R.6: QSARs and grouping of chemicals (May, 2008)” provides information on the use of read-across (page 78) as follows: “In the read-across technique, endpoint information for one chemical is used to predict the same endpoint for another chemical, which is considered to be similar in some way (usually on the basis of structural similarity). In principle, read-across can be applied to characterise physico-chemical properties, environmental fate, human health effects and ecotoxicity.”

It can be stated that menthols act as a prime example of substances that are suitable for read-across since menthols are (stereo)isomeres and, thus ideally fulfill the recommended criteria of structural similarity. Further, the OECD SIDS report on menthols (2003) assessed data of the isomers L-menthol (CAS no. 2216-51-5), D-menthol (CAS no. 15356-60-2), the racemate and menthol (unspecified isomers; CAS no. 1490-04-6). The report concludes on page 4 that “the menthols can be considered as a category because of their similarity in physico-chemical, toxicological, ecotoxicological and environmental fate properties” which is another requirement to justify the application of the read-across approach.

In the OECD SIDS report (2003) the physical properties of the enantiomeric menthols are given to be identically (apart from their specific rotation). Racemats are described to differ from the optically active forms in, for example, their melting points. However, the report gives that the slight differences in the cited data are within the range of uncertainty of laboratory tests.

Thus, read-across is possible and data from Jordan (1954) on L-menthol (CAS no. 2216-51-5) was used vapour pressure of 1.33 hPa at 56°C and 1013 hPa at 212°C.

Executive summary:

The vapour pressure of L-Menthol is 0.147 hPa at 25°C and 1013 hPa.

In the OECD SIDS report (2003) the physical properties of the enantiomeric Menthols are given to be identically (apart from their specific rotation). Racemats are described to differ from the optically active forms in, for example, their melting points. However, the report gives that the slight differences in the cited data are within the range of uncertainty of laboratory tests.

Thus, read-across is possible and data from Jordan (1954) on vapour pressure of L-Menthol (CAS no. 2216-51-5) were used for DL-Menthol.

Endpoint:
vapour pressure
Type of information:
(Q)SAR
Adequacy of study:
weight of evidence
Study period:
2017
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
accepted calculation method
Justification for type of information:
QSAR prediction
Guideline:
other: REACH guidance on QSARs R.6, May 2008
Principles of method if other than guideline:
The Estimation Program Interface (EPI) Suite v4.11 includes the model MPBPWIN for estimating the vapour pressure of organic compounds. The Estimation Programs Interface was developed by the US Environmental Agency's Office of Pollution Prevention and Toxics and Syracuse Research Corporation (SRC). © 2000 - 2012 U.S. Environmental Protection Agency for EPI SuiteTM. Published online in November 2012.
GLP compliance:
no
Type of method:
other: QSAR
Temp.:
25 °C
Vapour pressure:
2.95 Pa
Remarks on result:
other: modified Grain method

Validity of the model:

1. Defined Endpoint: Vapour pressure

2. Unambigous algorithm: The modified Grain method equation was used for calculation.

3. Applicability domain: Because an experimental boiling and melting point is available for the substance the applicablity domain is just described by the molecular weight range. With a molecular weight of 156.27 g/mol the substance is within the applicable range of 16 - 943 g/mol.

4. Statistical characteristics: Correlation coefficient of the total test set is r2= 0.949.

5. Mechanistic interpretation: The vapour pressure is related to fugacity models describing the distribution of the substance in the environment.

Adequacy of prediction: The result for DL-Menthol falls within the applicability domain described above and the estimation rules applied for the substance appears appropriate. Therefore the predicted value can be considered reliable yielding a useful result for further assessment.

Conclusions:
The QSAR determination of the vapour pressure of DL-Menthol using the model MPBPWIN included in the Estimation Program Interface (EPI) Suite v4.11 revealed a value of 2.95 Pa at 25 °C. The predicted value can be considered reliable yielding a useful result for further assessment.
Executive summary:

The vapour pressure of DL-Menthol was predicted using the QSAR calculation of the Estimation Programm Interface EPI-Suite v4.11. The experimental melting point of 43 °C and boiling point of 212 °C (at 1013 hPa) were taken into account for estimation. Using the modified Grain method, the vapour pressure was estimated to be 2.95 Pa at 25 °C. The predicted value can be considered reliable yielding a useful result for further assessment.

Description of key information

The vapour pressure 0.147 hPa at 25 °C for L-Menthol has been calculated from the vapour pressures detailed in the handbook (Jordan, 1954). This value is adopted for DL-Menthol.

The vapour pressure has also been predicted by EPI-Suite as 2.95 Pa at 25 °C (Currenta, 2017). Thus both values are in the same range.

Key value for chemical safety assessment

Vapour pressure:
0.147 hPa
at the temperature of:
25 °C

Additional information