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The test substance ‘Benzenepropanoic acid, 3,5-bis(1,1-dimethylethyl)-4-hydroxy-,2-ethylhexylester’ (CAS# 144429-84-5) is one C8 component of the UVCB substance ‘Reaction mass of isomers of: C7-9-alkyl 3-(3,5-di-trans-butyl-4-hydroxyphenyl)propionate' (EC# 406-040-9), which typically consists of branched isomers of C7 to C9 alkyl esters. The composition and the intrinsic properties of the UVCB substance depend on the alcohol feedstock; however, there will not be an important difference in the physico-chemical properties between the C8 isomer and the C7-C9 mixture that typically consists of branched C8 isomers and small quantities of branched C7 and C9 isomers. This conclusion is supported by experimental data of the structural analogue (C4 isomer) ‘Butyl 3,5-bis(1,1-dimethylethyl)-4-hydroxybenzenepropanoate’ (CAS# 52449-44-2): Even in this case there are no significant differences between the intrinsic properties of a C4 and a C8 alkyl ester despite the shorter chain length. Hence, it is safe to say that the values of the C8 isomer ‘Benzenepropanoic acid, 3,5-bis(1,1-dimethylethyl)-4-hydroxy-,2-ethylhexylester’ are likely to be similar to those of a C7-C9 mixture and as a result, read across is justified. Depending on the quantity of C7 and C9 components respectively, the values for the UVCB substance are expected to be either smaller, greater or equal to the values reported for the C8 isomer (for further information please refer to the “read-across justification“ attached to IUCLID section 13). Finally, with the aid of the EPIWIN software some physical-chemical properties were calculated as supporting information. Calculations with this program are only possible for mono constituent substances and not for UVCB substances as Z72 (reaction mass of isomers). Therefore, C9 alkyl ester was chosen to be reference for Z72. C9-structure was also found to be suitable due to the reason that this molecular structure is not covered by the read-across substances while C8-structure belong to Z77 and C7-structure can be assessed using the values of C4-structure from Z44.

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