Terephthalic acid

Vapour pressure

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

vapour pressure

Type of information:

(Q)SAR

Adequacy of study:

key study

Study period:

11-Aug-2020

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:

1. SOFTWARE
Estimation Programme Interface (EPI) Suite programme for Microsoft Windows v4.11.


2. MODEL (incl. version number)
MPBPVP v1.43


3. SMILES OR OTHER IDENTIFIERS USED AS INPUT FOR THE MODEL
SMILES: O=C(O)c(ccc(c1)C(=O)O)c1


4. SCIENTIFIC VALIDITY OF THE (Q)SAR MODEL
Please refer to attached justification.


5. APPLICABILITY DOMAIN
Please refer to attached justification.


6. ADEQUACY OF THE RESULT
Please refer to attached justification.

Guideline:

other: ECHA's Guidance on information requirements and chemical safety assessment Chapter R.6: QSARs and grouping of chemicals

Version / remarks:

May 2008

Principles of method if other than guideline:

The estimation of the vapour pressure of terephthalic acid was performed using the model MPBPVP v.1.43 (September 2008). Three estimation methods: Antoine, Modified Grain and Mackay, which – for solids - all rely on input of measured or estimated boiling and melting points, were used to predict vapour pressure. The model database contained no measured values of either parameter for terephthalic acid and the vapour pressure calculation therefore relied on estimated inputs. When applied to solids, the Modified Grain procedure is preferred over the Antoine method and the Mackay procedure has a relatively narrow range of applicability and is therefore ranked lowest in order of preference.

- Software tool(s) used including version:
Estimation Programme Interface (EPI) Suite programme for Microsoft Windows v4.11.

- Model(s) used:
KOCWIN v1.43

GLP compliance:

no

Remarks:

Not relevant (calculated endpoint).

Type of method:

other: (Q)SAR calculated endpoint

Specific details on test material used for the study:

SMILES: O=C(O)c(ccc(c1)C(=O)O)c1

Key result

Temp.:

25 °C

Vapour pressure:

0.002 Pa

Remarks on result:

other: QSAR estimate (Modified Grain method), based on estimated boiling and melting point values.

Temp.:

25 °C

Vapour pressure:

0.001 Pa

Remarks on result:

other: experimental data from model database

Table 1: Vapour pressure estimates for terephthalic acid provided by the MPBPVP model

 

Vapour pressure (Pa) at 25°C
Value	Estimation method
0.000725	Antoine
0.00158	Modified Grain
0.0032	Mackay

 

Table 2: Vapour pressure estimates for terephthalic acid provided by the MPBPVP model using experimental melting point as input from Park and Sheehan 1996 (using closed bottle method)

Vapour pressure (Pa) at 25°C
Value	Estimation method
0.000000138	Antoine
0.000000302	Modified Grain
0.00000339	Mackay

 

As the substance undergoes sublimation under normal conditions it does not melt, nor truly boil. Thus any experimental values do not truly represent the properties of the substance nor its fragments. As such the predictions for melting point and boiling point act as a good surrogate for the experimental data, acting as pseudo-endpoints (based on the sum of the fragments but that will not occur in normal conditions).

 

The test substance has a high sublimation point as outlined above, therefore, it is expected that vapour pressure at ambient temperature would also be low. Which is indicated during all model runs.

 

All three vapour pressure estimates for terephthalic acid are very low, compared to standard atmospheric pressure and TPA is not likely to volatilise to the atmosphere under standard conditions. 

 

Taking all the above into account the definitive value selected by the model is the estimate of 0.00158 Pa provided by the Modified Grain method, which is the most appropriate method for solids.

Conclusions:

MPBPVP predicts a vapour pressure value (Modified Grain method) for terephthalic acid of 0.00158 Pa at 25 ºC.

Executive summary:

Due to substance properties, a solid that sublimes, the estimation via MPBPVP v1.43 is considered the most relevant endpoint.

 

The vapour pressure of terephthalic acid was estimated using the MPBPVP v1.43 (Q)SAR model available from the US EPA. The estimated vapour pressure of terephthalic acid is 0.00158 Pa at 25 ºC (Modified Grain method).

Reference 2

Endpoint:

vapour pressure

Type of information:

other: Mathematical relationship between temperature and vapour pressure for TPA, derived from published VP measurements at various temperatures.

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: see 'Remark'

Remarks:

Information contained in a compilation of physico-chemical characteristics of terephthalic and isophthalic acids, drawn from company data/information relevant to the commercial production of TPA and IPA at the Amoco Chemical Company and from other sources.

Reason / purpose for cross-reference:

reference to same study

Qualifier:

no guideline followed

Principles of method if other than guideline:

Mathematical relationship between temperature and vapour pressure for TPA, derived from published VP measurements at various temperatures.

GLP compliance:

no

Type of method:

other: Mathematical relationship between temperature and vapour pressure for TPA, derived from published VP measurements at various temperatures.

Temp.:

25 °C

Vapour pressure:

0 mm Hg

Remarks on result:

other: The vapour pressure at 25 degrees C is extrapolated beyond the range of the data used to construct the equation relating VP to temperature. Nevertheless, the estimate is very low compared to standard atmospheric pressure.

The original vapour pressure measurements used to construct the mathematical relationship were as follows:

0.0000012, 0.00024, 0.016 and 0.73 mm Hg at 100, 150, 200 and 250 degrees C, respectively.

Conclusions:

Based on a mathematical relationship between temperature and vapour pressure for TPA, derived from published VP measurements at various temperatures, the VP of TPA at 25 degrees C is estimated to be 0.0000000000259 mm Hg. The vapour pressure of TPA at 25 degrees C is extremely low compared to standard atmospheric pressure.

Description of key information

Vapour Pressure: 0.00158 Pa; MPBPVP v1.43; H.-H. Maguire (2020)

Key value for chemical safety assessment

Vapour pressure:

0.002 Pa

at the temperature of:

25 °C

Additional information

The vapour pressure of terephthalic acid was estimated using the QSAR model MPBPVP v.1.43 of the US EPA (Maguire, 2020).  The definitive value selected by the model is the estimate of 0.00158 Pa calculated according to the Modified Grain method.  The validation set, and analogues of the substance included in it, with a low error and high R2 value, proved the validity of the model (see QPRF for details).  The value derived from this method was used as the key value and was seen as more accurate than the extrapolation used by Sheehan (1986).

 

Further, this QSAR result was supported by a study conducted by Sheehan (1986) which based vapour pressure on a mathematical relationship between temperature and vapour pressure for TPA, derived from published VP measurements at temperatures in the range 100 to 250 degrees C, the vapour pressure of TPA at 25 degrees C is estimated to be 0.0000000000259 mm Hg.  However, for the Sheehan (1986) study due to extrapolation to 25 degrees C, there is uncertainty regarding the result.

 

The vapour pressure estimate for terephthalic acid is very low, compared to standard atmospheric pressure and TPA is therefore not likely to volatilise to the atmosphere.