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Vapour pressure

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Description of key information

Vapour pressure data were read across from the butene substances (2-methylpropene, but-1-ene and 2-butene) to members of the C4, high 1,3 -butadiene (≥ 0.1%) category. The vapour pressures ranged from 484 to 1160 kPa at 25°C.

Key value for chemical safety assessment

Vapour pressure:
837.25 kPa
at the temperature of:
25 °C

Additional information

Vapour pressure data were read across from the butene substances (2-methylpropene: 1160 kPa at 25°C, but-1-ene: 1100 kPa at 25°C and 2-butene: 484 to 605 kPa at 25°C) for members of the category. The data were taken from the CRC handbook (Lide 2008), which is peer reviewed and considered a reliable source. The substances are C4 hydrocarbons and have a similar structure to the members of the category C4, high 1,3 -butadiene (0.1%). Due to their similar structures, they can be predicted to have similar physico-chemical properties and so read across from the butene substances is considered acceptable. The vapour pressure ranged from 484 to 1160 kPa at 25°C, and this range is considered to be representative of category C4, high 1,3 -butadiene (0.1%).

The mean of the vapour pressure values for the category is 837.25 kPa at 25°C and this has been used to complete the 'key value for chemical safety assessment'.

In the ECETOC TRA, any substance with a vapour pressure higher than 10 kPa is assigned a transfer to air factor of 1 (i.e. 100%) and the substance is considered to be completely released to air instantly. This is exactly what would happen to butadiene if it was to leak or be released into the environment. Therefore the model's basic underlying assumption is applicable to our substance.