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Vapour pressure

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Reference
Endpoint:
vapour pressure
Type of information:
(Q)SAR
Adequacy of study:
key study
Study period:
November 17, 2016
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
accepted calculation method
Justification for type of information:
1. SOFTWARE: EPISUITE 4.1
2. MODEL : MPBPVP 1.43
3. SMILES USED AS INPUT FOR THE MODEL: [Br-].C[N+](C)(C)CCCCCCCCCCCCCCCCCC
Principles of method if other than guideline:
QSAR method
Smile notation: [Br-].C[N+](C)(C)CCCCCCCCCCCCCCCCCC
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 used by MPBPWIN is a modification and significant improvement of the modified Watson method.  It is applicable to solids, liquids and gases.
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 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 PHYSPROP's experimental VP.
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.
Type of method:
other: Estimation
Test no.:
#1
Temp.:
ca. 25 °C
Vapour pressure:
ca. 0 Pa
Remarks on result:
other: estimated value
Conclusions:
The estimated Vapour pressure of the test substance is 1.67*10^-9 Pa.
Executive summary:

Column 2 of the REACH Regulation (EC 1907/2006) Annex VII provides the following specific rules for adaptation of the standard information requirement for vapour pressure. The study does not need to be conducted if the melting point is above 300 °C. If the melting point is between 200 °C and 300 °C, a limit value based on measurement or a recognised calculation method is sufficient.’

The vapour pressure resulted: 1.67 *10 ^-9 Pa at 25° C.

Description of key information

The estimated Vapour pressure of the test substance is 1.67 × 10^-9 Pa at 25 °C.

Key value for chemical safety assessment

Vapour pressure:
0 Pa
at the temperature of:
25 °C

Additional information

Column 2 of the REACH Regulation Annex VII provides the following specific rules for adaptation of the standard information requirement for vapour pressure.

The study does not need to be conducted if the melting point is above 300 °C. If the melting point is between 200 °C and 300 °C, a limit value based on measurement or a recognised calculation method is sufficient.’

Based on the OECD Guideline 104, the calculated values of the vapour pressure can be used:

- for deciding which of the experimental methods is appropriate,

- for providing an estimate or limit value in cases where the experimental method cannot be applied due to technical reasons (including where the vapour pressure is very low, e.g., less than 10-3 Pa).

The estimation method proposed by the OECD 104 is the modified Watson correlation, for which the only experimental data required is the normal boiling point.

The substance during the DSC analysis showed a melting point of 267.82 °C. The boiling point is > 400° and an estimated value was calulated by EPISuite 4.1.

Therefore, the modified Watson correlation cannot be used. Nevertheless a prediction made by Epiwin 4.1 of the US EPA by a Modified Grain method has been conducted and the vapour pressure resulted: 1.67 × 10 ^-9 Pa at 25 °C.

The smile notation used for estimation is:[Br-].C[N+](C)(C)CCCCCCCCCCCCCCCCCC.

The calculated value has been reported as key value for the Chemical Safety Assessment.

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