3-ethoxy-1,1,1,2,3,4,4,5,5,6,6,6-dodecafluoro-2-(trifluoromethyl)-hexane

Endpoint summary

Additional information

The measured Henry’s Law constant (HLC) of CAS# 297730-93-9 is 4.7 x 10⁷ Pa m³/mol (464 atm m³/mol).  The water solubility is low (21.3 µg/L). Based on these values, the test substance will not remain in aqueous solution in open systems.  A distribution modeling study performed for a region in Japan provides further support for the conclusion that CAS# 297730-93-9 would not be present in surface waters.  Assuming release of 42 tons/year to that region’s airshed, the predicted CAS# 297730-93-9 concentration in water was <0.001 ppb.  In direct testing of volatilization rate from water, the volatilization process followed first order kinetics. Rate constants for volatilization were 0.0798/hour for open vials, 0.108/hour for closed but unshaken vials, and 0.279/hour for closed and shaken vials, through an interfacial area in the range of 2.4 cm² to 4.5 cm². In a feasibility study preliminary to a sediment bioconcentration study, it was determined that CAS# 297730-93-9 could not be stably maintained in open systems.  Soil:sand and soil:sand:water mixtures which were spiked with CAS# 297730-93-9 and left open to the air quickly lost recoverable analyte.  Recovery of analyte from soil:sand:water mixtures quickly fell below the method quantitation limit, and rough estimate of half-life by a first-order approximation of loss kinetics was 13.7 ± 64.8 minutes.  CAS# 297730-93-9 was detected in soils exposed to vapor-phase chemical in tightly sealed vials, but was well below the method quantitation limit in water exposed in the same fashion.  As noted, in open containers the flux of CAS# 297730-93-9 is out from soils, rather than in to soils. The logarithm of the organic carbon-normalized adsorption coefficient to soil and sediment (log Koc) of CAS# 297730-93-9 was determined to be 4.88 using an HPLC method. If any CAS# 297730-93-9 were to be present in water despite its volatility, it would likely partition to soils and sediments from the aqueous phase. However, based on its environmental fate, it is not anticipated that CAS# 297730-93-9 would ever be present in the water from its use.

 

PFBA, TFA, and HF are strong acids which are miscible in water and rapidly deprotonated in aqueous solution.  These acids are not expected to be volatile, and the main removal pathway from the atmosphere is expected to be wet and dry deposition. The Koc of PFBA was estimated to be ca. 1 at pH values >4, and PFBA is not expected to partition to soils or sediments from the aqueous phase. Literature values of K_d for TFA ranged from <2 to 20 in various soils^₍₁₎. Using a reported log K_ow value of -2.10⁽¹⁾, a log K_oc value of -1.006 was calculated using a linear free energy relationship⁽²⁾ for use in further assessment. HF is an inorganic chemical which dissociates to hydronium and fluoride ions in the environment. As a strong inorganic acid, it has a low potential for adsorption.

 

The Henry’s Law constant 4.7 x 10⁷ Pa m³/mol for CAS# 297730-93-9 is equivalent to a dimensionless log K_aw (air-water partition coefficient) of 4.28 at 23 °C.  Given its log (octanol-water partition coefficient) of 6.0, a log (octanol-air partition coefficient) or log K_oa of 1.72 may be calculated for CAS# 297730-93-9 (where log K_oa = log K_ow – log K_aw).

Additional distribution modeling was achieved using EUSES v2.1.1.

1. Boutonnet (Ed)., 1999. Environmental Risk Assessment of Trifluoroacetic Acid. Human and Ecological Risk Assessment: Vol. 5, No. 1, pp. 59-124.

 

2. U.S. EPA. 2009. KOCWIN v.2.00