Organofluorine chemistry

Organofluorine compounds find diverse applications ranging from oil and water repellents to pharmaceuticals, refrigerants, and reagents in catalysis.

In addition to these applications, some organofluorine compounds are pollutants because of their contributions to ozone depletion, global warming, bioaccumulation, and toxicity.

[citation needed] On the other hand, aryl fluorides, e.g. fluoroanilines and fluorophenols, often undergo nucleophilic substitution efficiently.

Because of the reduced intermolecular van der Waals interactions, fluorocarbon-based compounds are sometimes used as lubricants or are highly volatile.

Their atmospheric concentrations and contribution to anthropogenic greenhouse gas emissions are rapidly increasing, causing international concern about their radiative forcing.

[8] On 15 October 2016, due to these chemicals contribution to climate change, negotiators from 197 nations meeting at the summit of the United Nations Environment Programme in Kigali, Rwanda reached a legally-binding accord to phase out hydrofluorocarbons (HFCs) in an amendment to the Montreal Protocol.

Organofluorine compounds are prepared by numerous routes, depending on the degree and regiochemistry of fluorination sought and the nature of the precursors.

[13] Illustrative of this approach is the preparation of a precursor to anti-inflammatory agents:[14] A specialized but important method of electrophilic fluorination involves electrosynthesis.

[21] Many of these display improved properties such as better safety profile, higher thermodynamic stability, ease of handling, high enantioselectivity, and selectivity over elimination side-reactions.

A special but significant application of the fluorinated building block approach is the synthesis of tetrafluoroethylene, which is produced on a large-scale industrially via the intermediacy of difluorocarbene.

The process begins with the thermal (600-800 °C) dehydrochlorination of chlorodifluoromethane:[6] Sodium fluorodichloroacetate (CAS# 2837-90-3) is used to generate chlorofluorocarbene, for cyclopropanations.

[25] Illustrative of the methods is the preparation of fluoride-modified glucose by displacement of a triflate by a labeled fluoride nucleophile: Biologically synthesized organofluorines have been found in microorganisms and plants, but not animals.

[27] Other biologically synthesized organofluorines include ω-fluoro fatty acids, fluoroacetone, and 2-fluorocitrate which are all believed to be biosynthesized in biochemical pathways from the intermediate fluoroacetaldehyde.

The C-F bond is found in pharmaceuticals, agrichemicals, fluoropolymers, refrigerants, surfactants, anesthetics, oil-repellents, catalysis, and water-repellents, among others.

[29][30] Examples include 5-fluorouracil, flunitrazepam (Rohypnol), fluoxetine (Prozac), paroxetine (Paxil), ciprofloxacin (Cipro), mefloquine, and fluconazole.

CFC inhalers were banned as of 2008[update] as part of the Montreal Protocol[32] because of environmental concerns with the ozone layer.

Fluorosurfactants, which have a polyfluorinated "tail" and a hydrophilic "head", serve as surfactants because they concentrate at the liquid-air interface due to their lipophobicity.

Triphenylphosphine has been modified by attachment of perfluoroalkyl substituents that confer solubility in perfluorohexane as well as supercritical carbon dioxide.

CFCs have potent ozone depletion potential due to the homolytic cleavage of the carbon-chlorine bonds; their use is largely prohibited by the Montreal Protocol.

Fluorine-substituted ethers are volatile anesthetics, including the commercial products methoxyflurane, enflurane, isoflurane, sevoflurane and desflurane.

A premier example is "Eufod," a coordination complex of europium(III) that features a perfluoroheptyl modified acetylacetonate ligand.

Highly fluorinated substituents, e.g. perfluorohexyl (C6F13) confer distinctive solubility properties to molecules, which facilitates purification of products in organic synthesis.

In contrast to the many naturally-occurring organic compounds containing the heavier halides, chloride, bromide, and iodide, only a handful of biologically synthesized carbon-fluorine bonds are known.

[18][39] The first organofluorine compound was discovered in 1835, when Dumas and Péligot distilled dimethyl sulfate with potassium fluoride and got fluoromethane.

[39][41] Besides salts, organofluorine compounds were often prepared using HF as the F− source because elemental fluorine, as its discoverer Henri Moissan and his followers found out, was prone to explosions when mixed with organics.

[39] On April 6, 1938, Roy J. Plunkett a young research chemist who worked at DuPont's Jackson Laboratory in Deepwater, New Jersey, accidentally discovered polytetrafluoroethylene (PTFE).

Electrochemical fluorination ("electrofluorination") was announced, which Joseph H. Simons had developed in the 1930s to generate highly stable perfluorinated materials compatible with uranium hexafluoride.

[15] These new methodologies allowed the synthesis of C-F bonds without using elemental fluorine and without relying on metathetical methods.

[citation needed] Because of the compound's effect on climate, the G-20 major economies agreed in 2013 to support initiatives to phase out use of HCFCs.

They affirmed the roles of the Montreal Protocol and the United Nations Framework Convention on Climate Change in global HCFC accounting and reduction.