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Partition coefficient

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Description of key information

Key value for chemical safety assessment

Additional information

Partition coefficient values (n-octanol/water) are difficult to measure for substances that exhibit surface-active properties under environmental conditions, such as the members of the DMA category (N,N-dimethyl-alkyl-1-amines, carbon chain lengths: C10 to C18). Instead, several studies were performed to derive the solubilities in water and in n-octanol for unprotonated and protonated (hydrochlorides) DMAs with diffierent chain length. The values derived in these studies were used to calculate the log Kow values.

log Kow values of DMAs and DMA hydrochlorides

 

C10-DMA

C12-DMA

C14-DMA

C16-DMA

C18-DMA

log Kow – Amine

4.3

4.3

4.5

4.6

5.1

Log Kow - Hydrochlorides

1.3

1.5

1.8

2.0

1.9

Dissociation of DMA category members

The percentage of neutral (i.e. amine) and protonated forms of DMA category members can be calculated from thepKaof9.78 (25 °C; identical for all category members)for a given pH using the Henderson-Hasselbach equation. For example, 99.8 % are protonated at a pH of 7. Full details are provided in IUCLID Chapter 4.21)

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