Menthol

Vapour pressure

Link to relevant study record(s)

Reference

Reference 1

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 for cross-reference:

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.

Reference 2

Endpoint:

vapour pressure

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

weight of evidence

Justification for type of information:

Data from structural related substance (see attached justification)

Reason / purpose for cross-reference:

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.

Reference 3

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:

1. SOFTWARE
Individual model MPBPWIN included in the Estimation Programs Interface (EPI) Suite.

2. MODEL (incl. version number)
MPBPWIN v1.43 included in EPISuite v 4.11, 2000 - 2012
The Antoine method/ modified Grain method/ Mackay method (VERWENDETE METHODE AUSWÄHLEN)

3. SMILES OR OTHER IDENTIFIERS USED AS INPUT FOR THE MODEL
a. Input for prediction: A SMILES notation was entered in the initial data entry screen. In the structure window, the molecular weight, structural formula and the structure of the input SMILES notation is shown. If available, experimental determined values of melting point and boiling point are taken for input.
b. Descriptor values: As the substance is a solid, the model uses the melting point and the boiling point for estimation:
The following parameters were applied:
- Melting point: 43 °C (experimentally determined, Merck Index 2006)
- Boiling point: 212 °C at 1013 hPa (experimentally determined, Merck Index 2006)

4. SCIENTIFIC VALIDITY OF THE (Q)SAR MODEL
a. Defined endpoint: Vapour pressure
b. Unambigous algorithm: The modified Grain method equation was used for calculation.
c. Applicability domain: With a molecular weight of 156.27 g/mol the substance is within the applicable range of 16 - 943 g/mol. Regarding the structure, the fragment descriptors used by the program for the estimation of the boiling point are complete and listed in Appendix F of the MPBPWIN help file.
d. Statistical characteristics : Correlation coefficient of the total test set is r2= 0.949.
e. Mechanistic interpretation : The vapour pressure is related to fugacity models describing the distribution of the substance in the environment.
f. The uncertainty of the prediction (OECD principle 4):
DL-Menthol is not highly complex and the rules applied for the substance appear appropriate. An individual uncertainty for the investigated substance is not available.

5. APPLICABILITY DOMAIN
a.Domains:
i. Molecular weight: With a molecular weight of 156.27 g/mol DL-Menthol is within the range of the training set (16 - 943 g/mol).
ii. Structural fragment domain: Regarding the structure, the fragment descriptors used by the program for the estimation of the boiling point are complete and listed in Appendix F of the MPBPWIN help file.
iii. Mechanism domain: No information available
iv. Metabolic domain, if relevant: not relevant
b. Structural analogues: No information available
c. Considerations on structural analogues: No information available

6. ADEQUACY OF THE RESULT
a. Regulatory purpose: The data may be used under any regulatory purpose.
b. Approach for regulatory interpretation of the model result: If no experimental data are available the estimated value may be used to fill data gaps needed for hazard and risk assessment. Further the value is used for other calculations.
c. Outcome: The prediction of vapour pressure yields a useful result for further evaluation.
d. 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.
e. Conclusion: The result is considered as useful for regulatory purposes.

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