Abstract
In polar aprotic organic solvents, fluorine might be an element of choice for life that uses selected fluorinated building blocks as monomers of choice for self-assembling of its catalytic polymers. Organofluorine compounds are extremely rare in the chemistry of life as we know it. Biomolecules, when fluorinated such as peptides or proteins, exhibit a “fluorous effect”, i.e., they are fluorophilic (neither hydrophilic nor lipophilic). Such polymers, capable of creating self-sorting assemblies, resist denaturation by organic solvents by exclusion of fluorocarbon side chains from the organic phase. Fluorous cores consist of a compact interior, which is shielded from the surrounding solvent. Thus, we can anticipate that fluorine-containing “teflon”-like or “non-sticking” building blocks might be monomers of choice for the synthesis of organized polymeric structures in fluorine-rich planetary environments. Although no fluorine-rich planetary environment is known, theoretical considerations might help us to define chemistries that might support life in such environments. For example, one scenario is that all molecular oxygen may be used up by oxidation reactions on a planetary surface and fluorine gas could be released from F-rich magma later in the history of a planetary body to result in a fluorine-rich planetary environment.
Highlights
Fluorine is the 24th most abundant element in the universe (4 × 10−5%), and relatively rare.in Earth’s crust it is enriched and is the 13th most abundant element by weight percent (0.054%), just ahead of carbon (0.02%)
Solvation of hydrofluoric acid (HF) in water extends it to a medium strong acid, which makes it more suitable to be used by life as a solvent
Polymeric materials modified by multiple fluorinated carbons possess elevated hydrophobicity and stability. These considerations might be of particular importance in assessing whether life might be able to exist in hydrophobic solvents [9,32] under “reverse phase” conditions
Summary
Fluorine is the 24th most abundant element in the universe (4 × 10−5%), and relatively rare. The elements to which fluorine has a high affinity, Si, Al, Ca, and Mg are common, both in Earth’s crust and the universe (28.2/0.07%, 8.1/0.005%, 4.1/0.007%, and 2.3/0.06%, respectively). Fluorine abundance in Earth’s crust is quite high, it is rare in the oceans, probably due to the low water solubility of its salts (fluorides). This is why, for instance, chlorides are much more common in sea water than fluorides (19,000 vs 1.3 ppm) despite the latter being more abundant in. Life appears not to have used fluoroorganic motifs due to the low availability of fluorides in solution and its relative low availability compared to direct competitors of fluorine such as oxygen, chlorine, and hydrogen
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