Butanamine, N,N-dibutyl-, branched and linear, fluorinated

Endpoint summary

Additional information

Henry’s Law constant (HLC) is used to describe the tendency for a substance to partition from water to air, the higher the value the greater the tendency for partitioning from water to air. An experimentally measured dimensionless HLC of ≥166000 (≥4.07E+08 Pa∙m³/mol or ≥4020 atm∙m³/mol) was determined at 22 °C for PTBA. Based on this HLC value, PTBA is likely to volatilize from the aquatic compartment into the atmosphere.

The logarithm of the normalized organic carbon adsorption coefficient (log Koc) of PTBA was calculated⁽¹⁾ to be 5.0 based on an experimental average log Kow of 6.1 for FC-43. The experimental water solubility of PTBA is very low (≤ 0.0561 ug/L). The experimental vapor pressure (0.02 mm Hg) and high experimental Henry’s Law constant (≥166000 dimensionless or ≥4020atm∙m³/mol) indicate that PTBA is expected to partition from any terrestrial compartment into the atmosphere. Soil volatilization half-lives are estimated to be 28.1 hours from agriculture soil and 1.76 hours from grassland and industrial soils. A related substance (PMM, the categorical member perfluoro-N-methylmorpholine) has an experimental soil-atmosphere partitioning half life of 66.1 ± 16.0 minutes (substantially shortly than that predicted by EUSES), which indicates that it will be removed from soil and sediments quickly. This half life may underestimate the atmospheric partitioning from natural soils due to the layer of water on soil particulates (volatilization driven by water-atmosphere partitioning rather than soil-atmosphere partitioning). Once in the atmospheric compartment, this compound will not partition to terrestrial or aquatic compartments based on the same properties. Therefore, this compound will remain in the atmosphere when released from industrial applications. Owing to this, further testing of sorption of PTBA in the terrestrial compartment would provide no useful information.

The logarithm of the octanol air partition (log Koa) coefficient is used to describe the tendency of a substance to partition from air into the lipid rich tissues of air breathing organisms. The logarithm of the octanol air partition coefficient (log Koa) of PTBA was calculated to be ≤ 0.88 based on the experimentally measured dimensionless Henry’s Law constant for FC-43 (≥166000 dimensionless) at 22 °C and the experimentally determined average log Kow for FC-43 of 6.1 (1260000 dimensionless) at 23 °C. This log Koa value indicates PTBA has low potential to partition from air to the lipid rich tissues of air-breathing organisms.

All of the members of this category stem from the same manufacturing process, have similar physicochemical properties including high vapor pressure and low water solubility relative to the hydrocarbon analogs (e. g., hexanes v. perfluorohexanes), and also lack any chemically reactive groups, which forms the technical basis for the category. Members of this category are fully fluorinated, meaning that fluorine, rather than hydrogen, is bonded to all carbon atoms in the molecule. Fluorine is the most electronegative of the elements (fluorine has an electronegativity of 3.98 on the Pauling scale, as compared to 2.55 for carbon or 2.20 for hydrogen). This electronegativity is expected to dominate over all other aspects of substance chemistry and is the underlying basis for similarity of substances in this category. Because these substances exhibit similarity in their physicochemical properties and toxicological properties in mammals, and because available data indicates that parent molecules are not reactive toward biological molecules and cannot undergo bioactivation or indeed any reaction by normal enzymatic processes, they are considered to constitute a chemical category. Data gaps for transport and distribution can therefore be addressed by read-across between category members. Please see Appendix A for the category justification and a matrix of physicochemical and distribution data for members of the Perfluorinated Organic Chemicals C5-C18 category.

(1) European Chemicals Bureau: Technical Guidance Document of Risk Assessment, Chapter 4