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 limited documentation / justification
Justification for type of information:
1. SOFTWARE
MPBPWIN v1.43 (US EPA)

2. MODEL (incl. version number)
Estimation using modified Grain method

3. SMILES OR OTHER IDENTIFIERS USED AS INPUT FOR THE MODEL
CC(C)(C)NC[C@H](O)CO

4. SCIENTIFIC VALIDITY OF THE (Q)SAR MODEL
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 estimat
e 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 as described in the Boiling Point section of
this help file. When a boiling point is entered on the data entry screen, MPBPWIN uses it.
Antoine Method: Chapter 14 of Lyman et al (1990) includes the description of the Antoine method
used by MPBPWIN. It was developed for gases and liquids. Modified Grain Method: Chapter 2 of Lyman (1985) describes the modified Grain method used by MPBPWIN. This method is a modification
and significant improvement of the modified Watson method. It is applicable to solids, liquids and ga
ses. The modified Grain method may be the best all-around VP estimation method currently available.
Mackay Method: Mackay derived the equation to estimate VP (Lyman, 1985) from two chemical
classes: hydrocarbons (aliphatic and aromatic) and halogenated compounds (again aliphatic and
aromatic).
MPBPWIN reports the VP estimate from all three methods. It then reports a "suggested" VP. For soli
ds, the modified Grain estimate is the 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 su
ggested VP because its application is currently limited to its derivation classes.

The accuracy of MPBPWIN's "suggested" VP estimate was tested on a dataset of 3037 compounds
with known, experimental VP values between 15 and 30 deg C (the vast majority at 25 or 20 deg C).
The experimental values were taken from the PHYSPROP Database that is part of the EPI Suite.
For this test, the CAS numbers were run through MPBPWIN as a standard batch-mode run (using the
default VP estimation temperature of 25 deg C) and the batch estimates were compared to PHYSP
ROP's experimental VP.
The estimation error increases as the vapor pressure (both experimental and estimated) decreases,
especially when the vapor pressure decreases below 1x10-6 mm Hg.
The estimation methodology uses the normal boil point to estimate the liquid-phase vapor pressure.
For solids, the melting point is required to convert the liquid-phase vapor pressure to the solid-phase
vapor pressure. VP estimation error can be introduced by:
(1) poor Boiling Point estimates or values
(2) poor Melting Point estimates or values (for solids)
The 3037 compound test set contains 1642 compounds with available experimental Boiling points and
Melting points .For this subset of compounds, the estimation accuracy statistics are (based on log VP):
number = 1642
r2 = 0.949
std deviation = 0.59
avg deviation = 0.32
These statistics clearly indicate that VP estimates are more accurate with experimental BP and MP
data.

5. 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 Mole
cular Weight range of the training set compounds, and/or that have more instances of a given fragme
nt 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 inte
rpreting model results.
The complete training sets for MPBPWIN's estimation methodology are not available. Therefore,
describing a precise estimation domain for this methodology is not possible.
The current applicability of the MPBPWIN methodology is best described by its accuracy in predicting
vapor pressure as described above in the Accuracy section.

6. ADEQUACY OF THE RESULT
The estimate value has been generated by a valid model. The model is applicable to the substance with the necessary level of reliability and is sufficiently relevant for the regulatory purpose.

Data source

Reference
Reference Type:
other: calculation
Title:
MPBVP 1.43
Author:
US EPA
Year:
2014
Bibliographic source:
EPI Suite v4.11

Materials and methods

Principles of method if other than guideline:
Prediction data.
GLP compliance:
no
Type of method:
other: Modified Grain method

Test material

Reference
Name:
Unnamed
Test material form:
solid: particulate/powder

Results and discussion

Vapour pressure
Key result
Temp.:
25 °C
Vapour pressure:
0.162 Pa

Applicant's summary and conclusion

Conclusions:
Predicted Vapour pressure (EPI v4.11): 0.00121 mmHg / 0.162 Pa at 25°C