Perfluorohexane
Perfluorohexane (C₆F₁₄) is a perfluorinated alkane, a fully fluorinated analog of n-hexane, characterized by its high chemical and thermal stability due to the strong carbon-fluorine bonds.[1] It exists as a clear, colorless, odorless liquid with a boiling point of 56.7 °C, a density of 1.684 g/mL at 20 °C, and limited solubility in water but good solubility in organic solvents.[2] These properties stem from its nonpolar nature and inertness, making it resistant to hydrolysis, oxidation, and biological degradation under normal conditions.[1] Perfluorohexane has been utilized in medical applications, particularly as a component in ultrasound contrast agents like perflexane microspheres for echocardiographic imaging, leveraging its ability to carry gases such as oxygen and undergo acoustic droplet vaporization for enhanced visualization.[1] [3] In engineering contexts, it serves as a heat transfer fluid and coolant in systems requiring high thermal stability, including space applications and flow boiling experiments.[4] [5] It has also been evaluated as a clean fire extinguishing agent, offering effective suppression without residue due to its rapid vaporization and non-conductive properties.[6] Safety data indicate low acute toxicity, with no significant hazards under standard handling, though inhalation of vapors may cause temporary central nervous system effects at high concentrations.[1] Notable research explores perfluorohexane in nanotechnology, such as lipid-shelled nanoemulsions for targeted drug delivery and high-intensity focused ultrasound therapy, capitalizing on its phase-change behavior for controlled release.[7] Environmentally, as a volatile perfluorocarbon, it contributes minimally to bioaccumulation compared to functionalized PFAS but possesses a high global warming potential owing to its long atmospheric lifetime, prompting scrutiny in applications phased out under regulations like the Montreal Protocol for ozone-depleting alternatives.[8]
Chemical Identity and Properties
Molecular Structure and Nomenclature
Perfluorohexane has the molecular formula C₆F₁₄, consisting of a linear chain of six carbon atoms fully saturated with fluorine atoms and devoid of hydrogen.[1] The structure features two terminal –CF₃ groups connected by four –CF₂– units, forming an unbranched perfluorocarbon analogous to n-hexane but with all C–H bonds replaced by C–F bonds, which imparts high chemical stability due to the strong carbon-fluorine bonds.[9] This configuration results in a molecule with no dipole moment and is non-polar, consistent with its classification as a perfluoroalkane.[1] The nomenclature of perfluorohexane follows conventions for fluorinated hydrocarbons. The preferred IUPAC name is tetradecafluorohexane, indicating fourteen fluorine substituents on a hexane parent chain.[1] The systematic substitutive name is 1,1,1,2,2,3,3,4,4,5,5,6,6,6-tetradecafluorohexane, specifying the positions of the fluorine atoms along the carbon chain.[9] In technical and commercial contexts, it is commonly designated as perfluorohexane or perfluoro-n-hexane to emphasize its complete fluorination and straight-chain structure, distinguishing it from branched perfluorohexane isomers.[1] The CAS registry number is 355-42-0.[9]Physical Properties
Perfluorohexane (C₆F₁₄) is a colorless, odorless liquid at standard ambient temperature and pressure.[10] Its molecular weight is 338.04 g/mol.[10] The compound exhibits low intermolecular forces typical of perfluorocarbons, resulting in a low boiling point relative to its molecular size.[11] Key thermodynamic properties include a solidification point of -90 °C and an initial boiling point ranging from 58 °C to 60 °C.[10] The density is 1.669 g/cm³ at 25 °C.[10] Vapor pressure measures 309 hPa at 20 °C, with a vapor density of 11.7 (air = 1) under the same conditions.[10] Optical and surface properties feature a refractive index of 1.252 and surface tension of 11.3 mN/m.[11] Due to its fully fluorinated structure, perfluorohexane displays high hydrophobicity, with water solubility limited to 0.01 g/L at 25 °C and a calculated n-octanol/water partition coefficient (log Pₒₓ) of 6.02.[10] It is miscible with non-polar solvents but immiscible with polar ones.[12]| Property | Value | Conditions |
|---|---|---|
| Melting point | -82 °C | - |
| Boiling point | 57–60 °C | 1 atm |
| Density | 1.67 g/cm³ | 25 °C |
| Refractive index | 1.2515–1.252 | 20–22 °C, D-line |
| Vapor pressure | 309 hPa | 20 °C |
| Surface tension | 11.3 mN/m | - |