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Environmental fate & pathways

Phototransformation in air

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Description of key information

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The phototransformation of isooctyl acrylate was assessed through a series of 10 unique QSAR studies. The QSAR studies were conducted using the AOPWIN v1.92 submodel within EPI Suite v4.00. IOA has a nominal composition consisting of >1.25% branched C7 isoheptyl acrylate, >94.0% C8 branched isooctyl acrylate, and >4.0% C9 branched isononyl acrylate. There are a wide range of branched isomers of this complex mixture and a single representative example of each secondary branched homolog was run for C7, C8, and C9. Because of the UVCB nature of the IOA test material, a series of 10 structures were modeled in AOPWIN v1.92 and these consisted of the following types: C7 acrylate with a one, two, or three branching points; C8 acrylate with a one, two, or three branching points; and C9 acrylate with a one, two, three, or four branching points.

Hydroxyl radical reaction rate constants (k) were estimated for each of the 10 test substances to give a range of rates and these were used to calculate a range of atmospheric half lives using the ECHA accepted atmospheric hydroxyl radical concentration of 5E+05 radicals per cubic centimetre.

QSAR Determined Rate Constants (kin units of 10^-12 cubic centimetres per molecule per sec)

# Carbons

Branching Range

Rate Constant (k)

Half life (days)


singly branched to maximally branched

18.003 - 19.013



singly branched to maximally branched

19.416 - 19.969



singly branched to maximally branched

20.829 – 22.116



These estimated results for IOA components indicate the half life in the atmospheric compartment is expected to be between 1.45 and 1.78 days. Based on this range of half lives IOA is not expected to be persistent in the atmospheric compartment.