Fluorine chemistry at the millennium

In this “perspective” paper, some of the landmark discoveries and accomplishments of the past within the field of fluorine chemistry will be reviewed. Within this review, the dramatic changes (and growth in size and diversity) that the field has undergone, particularly over the last 50 years, will also be discussed. Then finally, where fluorine chemistry is and where it appears to be going will be briefly discussed. The future of fluorine chemistry indeed appears bright, with fluorine chemistry set to play a role, and usually a significant role in most important areas of technology of the 21st century. New perspectives will be required, but then, fluorine chemists have been providing such “new perspectives” to this ever-changing field for the last 75 years.     

Quantum chemistry studies of unbranched fluoropolymers

The results of quantum chemistry calculations of energy and topology parameters, vibration and NMR spectra of model fluorocarbon and unbranched hydrocarbon molecules are presented in this work. The formation of radicals and branches in fluorocarbon molecules and mechanisms of hydrogen substitution by fluorine at fluorination of hydrocarbon paraffins and polymers are discussed based on obtained results.     

Can fluorine chemistry be green chemistry?

The roles of the element fluorine and its compounds in relationship to green chemistry and clean chemical manufacturing are considered.     

Fluorine chemistry at Central Glass

Central Glass produces a diverse range of fluorocompounds for pharmaceuticals, agrochemicals as well as for semiconductor industries. Some of its products and chemistry developed at Central Glass in the field of industrial fluorine compounds are described.     

Fluorine in medicinal chemistry

It has become evident that fluorinated compounds have a remarkable record in medicinal chemistry and will play a continuing role in providing lead compounds for therapeutic applications. This tutorial review provides a sampling of renowned fluorinated drugs and their mode of action with a discussion clarifying the role and impact of fluorine substitution on drug potency.     

Understanding organofluorine chemistry. An introduction to the C-F bond

Fluorine is the most electronegative element in the periodic table. When bound to carbon it forms the strongest bonds in organic chemistry and this makes fluorine substitution attractive for the development of pharmaceuticals and a wide range of speciality materials. Although highly polarised, the C-F bond gains stability from the resultant electrostatic attraction between the polarised C delta+ and F delta- atoms. This polarity suppresses lone pair donation from fluorine and in general fluorine is a weak coordinator. However, the C-F bond has interesting properties which can be understood either in terms of electrostatic/dipole interactions or by considering stereoelectronic interactions with neighbouring bonds or lone pairs. In this tutorial review these fundamental aspects of the C-F bond are explored to rationalise the geometry, conformation and reactivity of individual organofluorine compounds.     

Perspective on fluorocarbon chemistry

Fluorocarbons, organic molecules with carbon skeletons and fluorine "skins", differ fundamentally from their hydrocarbon counterparts in interesting and useful ways. A selection of the myriad applications fluorocarbons and their derivatives have found in modern life is described and related to molecular properties. Salient aspects of the nature and reactivity of fluorocarbon compounds are highlighted by comparison with their more familiar hydrocarbon analogues.     

Instrumental neutron activation analysis and inductively coupled plasma mass spectrometry on atmospheric biomonitors

Sensitivities for detecting fluorine, distributed uniformly in elements with atomic numbers 8, 13, 20, 28, 34, 42, 50, 60, 68 and 79, through the F(p,αγ)O reaction, have been calculated using experimentally measured excitation functions and the available energy-range data. Thick target yields of the prompt 6.13 MeV gammas, as well as of the three gamma-lines of 6.13, 6.92 and 7.12 MeV combined, have been plotted as a function of the incident energy of up to 4.16 MeV. From these yield curves the sensitivity of detecting fluorine in thick or thin samples, and even in a layer of known thickness at a particular depth within a thick target, can be directly read for known bombarding and detecting conditions. The curves should also be valid, to a certain approximation, for neighbouring elements and for mixtures or compounds with similar average atomic numbers. Furthermore, it is explained as to how these yield curves can also be used in non-destructive profile analysis of fluorine to much greater depths than can be achieved by the well-known resonance-shift method.     

Phospha-organic chemistry: panorama and perspectives

Since the beginning of the seventies, organophosphorus chemistry has been completely rejuvenated by the discovery of stable derivatives in which phosphorus has the coordination numbers one or two. The chemistry of these compounds mimics the chemistry of their all-carbon analogues. In this Review article this analogy is discussed for the phosphorus counterparts of alkenes, alkynes, and carbenes. In each case, the synthesis, reactivity, and coordination modes are briefly examined. Some special electronic configurations are also discussed, which include one-electron Pbond;P bonds, strained bonds, and aromatic systems. To conclude, some potential applications of this chemistry in the areas of molecular materials and homogeneous catalysis are presented.     

Current and future developments of synthetic methods in organofluorine chemistry

Although fluorine chemistry is rapidly approaching its 100th anniversary, organofluorine chemistry, as most of us know it, is only 40–50 years old. Interest and enthusiasm in this area of chemistry essentially traces its origins to the discovery and industrial applications of the Freons and polytetrafluoroethylene (Teflon). The unique properties of these materials attracted attention to this neglected area of organic chemistry—particularly industrially—and stimulated work on methods for the introduction of fluorine into organic molecules.     

Extreme modulation properties of aromatic fluorine

Thorough examination of the current literature as well as publicly available databases allowed us to qualify aromatic fluorine as a unique modulator of biological properties of organic compounds. In some rare cases, introduction of fluorine increased biological activity 100,000 times and even higher. We have also identified several examples where aromatic fluorine substantially reduced biological activity. Selected individual cases of extreme modulation are presented and discussed in the paper.     

有机氟改性环氧树脂的研究进展

利用有机氟改性环氧树脂是提高环氧树脂综合性能的有效途径。目前含氟环氧树脂已经成为学者研究的重点。文章扼要综述了有机氟对改善环氧树脂的表面性能、耐热性能、介电性能、耐摩擦性能及阻燃性能的最新研究进展。展望了有机氟改性环氧树脂的发展趋势。     

UF6 plasma chemistry reconstitution experiments using high-temperature fluorine

Prior results indicate techniques have been developed for fluid mechanical confinement of high-temperature uranium hexafluoride (UF₆) plasma for long test times while simultaneously minimizing uranium compound deposition on the walls. Follow-on investigations were conducted to demonstrate a UF₆/argon injection, separation, and reconstitution system for use with rf-heated uranium plasma confinement experiments applicable to UF₆ plasma core reactors. A static fluorine batch-type regeneration test reactor and a flowing preheated fluorine/UF₆ regeneration system were developed for converting all the nonvolatile uranium compound exhaust products back to pure UF₆ using a single reactant. Pure fluorine preheat temperatures up to 1000 K resulted in on-line regeneration efficiencies up to about 90%; static batch-type experiments resulted in 100% regeneration efficiencies but required significantly longer residence times. A custom-built, ruggedized time-of-flight (T.O.F.) mass spectrometer, sampling, and data acquisition system permitted on-line quantitative measurements of the UF₆ concentrations down to 30 ppm at various sections of the exhaust system; this system proved operational after long-time exposure to corrosive UF₆ and other uranium halides.     

The chemistry of fluorine containing phosphaalkenes, arsaalkenes and selenocarbonyls

This review covers our extensive research activities in the area of fluorine containing phospha- and arsaalkenes as well as selenocarbonyls, which differ considerably in their properties and reactivities from their alkyl and aryl counterparts and thus contribute in a gratifying manner to the still growing field of unsaturated element-carbon compounds of 3rd and 4th row main group elements E. Of particular interest is the influence of the fluorine substituents and other small groups (OR, NR₂) with either inductive and/or mesomeric effects on the polarity and reactivity of the EC bond. Addition reactions of proton acidic and hydridic polar HX reactants as well as [2+2], [3+2] and [4+2] cycloadditions have been thoroughly studied. The results obtained allow a classification of the EC systems within five different types, A to E, and prove a change from “normal” to “inverse” heteroalkenes in this sequence. The ligand properties of some derivatives have also been investigated in some detail.     

Organofluorine chemistry: synthesis and conformation of vicinal fluoromethylene motifs

The C-F bond is the most polar bond in organic chemistry, and thus the bond has a relatively large dipole moment with a significant -ve charge density on the fluorine atom and correspondingly a +ve charge density on carbon. The electrostatic nature of the bond renders it the strongest one in organic chemistry. However, the fluorine atom itself is nonpolarizable, and thus, despite the charge localization on fluorine, it is a poor hydrogen-bonding acceptor. These properties of the C-F bond make it attractive in the design of nonviscous but polar organic compounds, with a polarity limited to influencing the intramolecular nature of the molecule and less so intermolecular interactions with the immediate environment. In this Perspective, the synthesis of aliphatic chains carrying multivicinal fluoromethylene motifs is described. It emerges that the dipoles of adjacent C-F bonds orientate relative to each other, and thus, individual diastereoisomers display different backbone carbon chain conformations. These conformational preferences recognize the influence of the well-known gauche effect associated with 1,2-difluoroethane but extend to considering 1,3-fluorine-fluorine dipolar repulsions. The synthesis of carbon chains carrying two, three, four, five, and six vicinal fluoromethylene motifs is described, with an emphasis on our own research contributions. These motifs obey almost predictable conformational behavior, and they emerge as candidates for inclusion in the design of performance organic molecules.     

New trends in the chemistry of α-fluorinated ethers, thioethers, amines and phosphines

Fluorine, the most electronegative element plays nowadays a key role in pharmaceutical, agrochemical and material sciences. About 20% of all pharmaceuticals and about 30% of agrochemicals under development or recently introduced on the market contain fluorine. However, when one examines the relevant structures more closely, one quickly recognizes a structural monotony. The same fluorine bearing aromatic or heterocyclic “cores” appear over and over again. The search for novel molecules having “emergent” fluorinated groups and the development of an efficient access toward them is a challenging task for industrial as well as academic laboratories. For example, the trifluoromethoxy group finds increased utility as a substituent in bioactives, but it is still perhaps the least well understood fluorine substituent in currency. The present review will give an updated overview on the synthesis of α-fluorinated ethers, thioethers, amines and phosphines.     

Sources and availability of raw materials for fluorine chemistry

The two most important sources of fluorine are the minerals fluorite, commercially known as fluorspar, and fluorapatite, commercially known as phosphate rock.The major consumers of fluorspar are the aluminum, chemical, and steel industries. Acid-grade fluorspar, one of three commercial grades, is used primarily to make hydrogen fluoride, which is then used to produce synthetic cryolite, aluminum fluoride, fluorocarbons, and other fluorochemicals. Elemental fluorine is prepared from anhydrous hydrogen fluoride by electrolysis. Fluosilicic acid is used primarily for water fluoridation but also to make aluminum fluoride and cryolite. Reported U.S. consumption of fluorspar was 753,000 tons in 1984. U.S. demand for fluorspar was projected to increase at an average annual rate of 2.7% between 1983 and 2000.U.S. production of finished fluorspar in 1984 was 72,000 tons. Fluosilicic acid production was 61,000 tons or 107,000 tons as equivalent fluorspar. More than 85% of domestic demand was imported, primarily from Mexico and the Republic of South Africa.A U.S. Bureau of Mines investigation of major fluorspar reserves and resources in market economy countries and China found approximately 900,000 tons of demonstrated and 1,200,000 tons of identified reserves in the United States. Total world demonstrated and identified reserves were 135 million tons and 262 million tons, respectively. The potential resources of fluosilicic acid were estimated at 12 million tons of equivalent fluorspar in the United States and 360 million tons for the total world. Fluorine reserves appear adequate through the year 2000 given current projections.     

Organometallic chemistry of fluorinated propadienes and butadienes

1,1-Difluoroallene (1,1-difluoropropadiene) and tetrafluoroallene are not only strong π acidic ligands but versatile starting materials for the generation of more complex fluoroorganic ligands by metal induced dimerization reactions, CF bond activation and fluorine migration. Palladium catalyzed CC coupling reactions of organometallic fluorovinyl compounds allow the systematic synthesis and study of the ligand properties of fluorinated buta-1,3-dienes. Furthermore, they are the key compounds for the synthesis of butatrienes like tetrafluorobutatriene which now can be studied in detail.