dimethyl 1,2-benzenedicarboxylate;reaction mass of: 1,2-dimethylpropylidene dihydroperoxide

Vapour pressure

Link to relevant study record(s)

Reference

Endpoint:

vapour pressure

Type of information:

experimental study

Adequacy of study:

key study

Study period:

20 March 2002 - 21 March 2002

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 104 (Vapour Pressure Curve)

Qualifier:

according to guideline

Guideline:

EU Method A.4 (Vapour Pressure)

GLP compliance:

yes

Type of method:

static method

Temp.:

9.31 °C

Vapour pressure:

495 Pa

Temp.:

15.48 °C

Vapour pressure:

632 Pa

Temp.:

20.86 °C

Vapour pressure:

790 Pa

Transition / decomposition:

no

Based on the structural formula, a lower vapour pressure was expected. Probably the relative high vapour pressure was caused by the presence of water and 3-methyl2 -butanone.

Fitting these data using the least squares method gives a value of 761 Pa for the vapour pressure of the test substance at 20°C with 23 Pa for 2σ_n-1 (i.e. 3.0%). The maximum deviation between the fit and the data points is always less than about 0.6%. Errors made in estimating the mean value per temperature series are up to 1.2%. So a value of 30 Pa (i.e. 3.9%) is a reasonable value for the uncertainty in the final result.

The vapour pressure was determined to be: p (20°C) = 761 ± 30 Pa = 5.71 ± 0.23 mm Hg

Conclusions:

The vapour pressure at 20°C was determined to be: p (20°C) = 761 ± 30 Pa = 5.71 ± 0.23 mm Hg

Executive summary:

The determination of the vapour pressure of was based on the following guidelines:

European Economic Community (EEC), EEC directive 92/69 EEC, Part A, Methods for the determination of physico-chemical properties, A.4 "Vapour pressure", EEC Publication No. L383, December 1992.

Organisation for Economic Co-operation and Development (OECD), OECD guidelines for testing chemicals, Guideline NO.104: "Vapour pressure curve", July 27, 1995.

Using the Static Technique, the vapour pressure at 20°C was determined to be: P (20°C) = 761 ± 30 Pa = 5.71 ± 0.23 mm Hg

Based on the structural formula of Trigonox R-938, a lower vapour pressure was expected. Probably the relative high vapour pressure was caused by the presence of water and 3-methyl-2-butanone.

Description of key information

The vapour pressure at 20°C was determined to be: p (20°C) = 761 ± 30 Pa = 5.71 ± 0.23 mm Hg. The Notox VP report states: “Based on the structural formula of Trigonox R-938, a lower vapour pressure was expected. Probably the relative high vapour pressure was caused by the presence of water and 3-methyl2-butanone.” This VP is too high, since it is partly based on exposure to non-hazardous impurities. Therefore, exposure to the peroxide is overestimated when using this VP.

The test method for determination of vapour pressure described in the test guideline A.4 of 2008/440/EC was replaced by a theory based evaluation as a reliable determination is not possible. The registered substance exists as solution in a stabiliser due to its reactivity.

It is shown by critical component assessment based on ECHA methodology that 1,2-Dimethylpropylidene dihydroperoxide is the critical component for inhalation exposure based on the VP, concentration in the mixture and DNEL. With Epiwin the following VPs are calculated for the substances as such: T3 and T4: 42.9  Pa, 25°C and 0.0892  Pa, 25°C (Modified Grain method). The VP for pure H2O is 2338 Pa at 20°C, MIKP 5500 Pa at 20°C, H2O2 299 Pa at 25°C and DMP 0.13 Pa at 20 °C.

Applying Raoult’s law (using mol fractions and individual saturated vapor pressures). The contribution of each component is then calculated. T3, T4, H2O2, H2O, DMP, MIPK, as components (total 100.2 wt%, Notox report). The following results are found (total pressure = 7.61 mbara (5.41 Mm Hg)) 20°C:

Type 3, Type 4: 2.325 mbara

H2O2: 0.149 mbara

H2O: 4.518 mbara

DMP: 0.003 mbara

MIPK: 0.615 mbara

The VP at 20°C for 2.325 mbara, or 232.5 Pa. In a similar way it was calculated that at 40°C the VP is 7.1 mbara, or 710 Pa, this value will be used in the Chesar risk assessment

Key value for chemical safety assessment

Vapour pressure:

710 Pa

at the temperature of:

40 °C