Benzyl 4-[(1-butyl-5-cyano-1,6-dihydro-2-hydroxy-4-methyl-6-oxopyridin-3-yl)azo]benzoate

Vapour pressure

Link to relevant study record(s)

Reference

Endpoint:

vapour pressure

Type of information:

(Q)SAR

Adequacy of study:

key study

Study period:

2019

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

Justification for type of information:

SOFTWARE : EPI Suite (v 4.11)

MODEL: modified Grain method as implemented by MPBPWIN v. 1.43

SMILES OR OTHER IDENTIFIERS USED AS INPUT FOR THE MODEL : O=C(OCc1ccccc1)c2ccc(cc2)/N=N/C3=C(C)C(C#N)=C(O)N(CCCC)C3=O

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 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.
The Modified Grain Method was used. 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 gases.
The KF structural factors are available in chapter 14 of Lyman et al (1990); the variation of this parameter is related to chemical class and is small (roughly 0.99 to 1.2), so large errors in its selection are unlikely (Lyman, 1985).  The modified Grain method may be the best all-around VP estimation method currently available.

ADEQUACY OF THE RESULT
MPBPWIN reports the VP estimate from all three methods. It then reports a "suggested" VP. For solids, 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 suggested VP because its application is currently limited to its derivation classes.
The estimation error increases as the vapor pressure (both experimental and estimated) decreases, especially when the vapor pressure decreases below 0.000001 mmHg (0.0001333 Pascals).
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.
For maximum VP accuracy, good experimental Boiling Points and/or Melting Points should be entered on the data entry screen.

Estimation 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.
The complete training sets for MPBPWIN's estimation methodology are not available. Therefore, describing a precise estimation domain for this methodology is not possible.

Estimation accuracy
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 °C (the vast majority at 25 or 20 °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 °C) and the batch estimates were compared to PHYSPROP's experimental VP.  

Principles of method if other than guideline:

Calculation of vapour pressure was performed using EPI Suite (US-EPA, 2004) according to the Modified Grain Method.

GLP compliance:

no

Type of method:

other: data derived from assessment

Remarks on result:

other: negligible (calculated value)

Vapour pressure: 2.36 × 10^-14 Pa at 25 °C, using the modified Grain method

Conclusions:

Negligible.

Executive summary:

The vapour pressure of the substance was estimated by the MPBPWIN v 1.43 tool as implemented by EPI Suite; the calculated value was 2.36 × 10^-14 Pa at 25 °C.

Description of key information

negligible.

Additional information

The vapour pressure of the substance is calculated by EPI Suite using the MPBPWIN v 1.43 tool, based on the modified Grain method.

A calculated data on a structural analogue, Similar Substance 01, using the same method, confirmed such result.

Details on Similar Substance 01 are available in section 13.