Fluorine and its derivatives

Recently, the use of fluorine as an oxidant has been considered feasible. E.g. the reaction of fluorine with hydrazine gives a particularly large theoretical specific impulse (7S) amounting to 298 sec. 

Fluorine with hydrogen gives 7S = 352 sec, whereas oxygen with hydrogen has a somewhat lower value (342 sec). 

Nevertheless it should be borne in mind that the use of liquid fluorine has considerable disadvantages. Its boiling point is — 187°C. To prevent corrosion special vessels of nickel alloys surrounded by a jacket filled with liquid nitrogen (boiling point — 199.5°C) are required. 

Operating with liquid hydrogen as a combustible also creates exceptional difficulties, due to its exceedingly low boiling point (—253°C). 

In addition to fluorine itself, fluorine compounds have also been recommended. Chlorine trifluoride (C1F3) with a boiling point of 12°C and a density of 1.77 g/cm3 is the most promising for use in rocket propulsion. Its specific gravity is 1.85, heat of formation —AH =41.0 kcal/mole. It is obtainable by the action of fluorine on chlorine in an atmosphere of nitrogen at 280°C, in a reactor of copper or nickel. 

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Although modern chemistry allows development of even more effective rocket propellants, energy efficiency is not the only consideration factor. For example, fluorine and its derivatives arc better oxidizers than oxygen, but their extreme toxicity make them environmentally dangerous. The same concerns prevent the use of beryllium hydride—an excellent fuel that combines high density with the energy efficiency comparable to liquid hydrogen. 

Partial fluorination [50] and perfluorination [5/] of aromatic systems can be accomplished electrochemically. A number of other reagents add fluorine to benzene and its derivatives, as elaborated in equation 5 [52, 53, 54, 551... 

Fluorinatton of graphite with fluorine gives graphite fluorides that have interesting properties, as recently reviewed [63]. Pyridine and its derivatives add elemental fluorine to form unstable N-fluoro adducts [14, 26, 64, 65]. These may decompose to 2-fluoropyndines [65] or be stabilized by treatment with inflate salts to form useful electrophilic fluonnating agents [64]... 

Kirk and Cohen (1969, 1971, 1973 Kirk et al., 1973) successfully applied the photo-fluoro-de-diazoniation method for the introduction of fluorine into imidazole and its derivatives with various substituents (e.g., histidine) 2- and 4-fluoroimi-dazole had not previously been synthesized by other methods. 2-Fluoroimidazole, in contrast to the 4-isomer, is easily hydrolyzed in water (Kirk et al., 1973). 

Synthesis and Properties of Fluorine-Containing Aromatic Condensation Polymers Obtained from Bisphenol AF and Its Derivatives... 

Research on fluorine-containing condensation polymers is rather limited compared to that on fluorine-containing addition polymers. This fact is attributed to the difficulty in synthesis and the high cost of fluorine-containing condensation monomers. Recently, 2,2-bis(4-hydroxyhpenyl)-1,1,1,3,3,3-hexafluoropropane (Bisphenol AF) with a hexafluoroisopropylidene unit, HOC6H4C(CF3)2-C6H4OH, was produced commercially from hexafluoroacetone and phenol, and now Bisphenol AF and its derivatives are available as condensation monomers. 

This chapter deals with the synthesis and properties of fluorine-containing condensation polymers from Bishpenol AF and its derivatives. Much of the work reported has been conducted in our laboratory. An extensive review has already been published by Cassidy and co-workers1 on the synthesis of fluorine-... 

Several classes of polymers including epoxies have been developed from 2-phenyl-l,l,l,3,3,3-hexafluoropropan-2-ol and its derivatives.1 Fluorinated epoxy resins are the key intermediates for the new types ofpractical organic coatings and plastics, which have fluorocarbon properties and convenient characteristics such as hydrophobicity, oleophobicity, light stability, low friction, and, in some cases, possibly high thermal stability. 

Starting from Trifluoroacetic Acid Derivatives Trifluoroacetic acid and its derivatives (e.g., esters, anhydride, fluoral, trifluoroethanol) are the major channel of the organic fluorine industry. They are relatively inexpensive and, compared to halons, they do not exhibit major environmental problems. They are the main source for the synthesis of trifluoromethylated compounds. 

Fluorouracil and its derivatives are still important dmgs in the chemotherapy of numerous cancers (doxifluridine, tegafur, carmofur) (cf. Chapter 8). Studies on the mechanism of action of 5-FU had great influence on the development of other antitumor drugs that are derived from pyrimidine and purine. 5-FU is industrially prepared by fluorination of uracil with elemental fluorine (cf. Figure 2.6, Chapter 2). 

To overcome problems associated with the removal of iodobenzene and its derivatives formed upon fluorination of arylalkenes and arylalkynes with (difluoroiodo)arenes, polymer-supported (difluoroiodo)arenes were proposed.139 With these agents, the separation procedures are reduced to filtration of the iodinated polymer. For this purpose popcorn polystyrene is io-dinated and then transformed into the difluoroiodide by treatment with xenon difluoride in the presence of hydrogen fluoride in dichloromelhane at 25 C. The amount of active fluorine bonded to iodine atoms on the polymer support is estimated by iodometric titration. The reactions with phenyl-substituted alkenes result in rearranged gew-difluorides. The procedure provides the same fluorination products as with (difluoroiodo)benzenc (see Section 4.13.) but in much higher yields, e.g. PhCF2CH2Ph (96%), PhCF2CH(Me)Ph (95%). PhCH2CF2H (86%), and l,l-difluoro-2-phenylcyclopentanc (91 %). 

The tetrafluoroammonium cation (NF/) has high electronegativity (the oxidation number of nitrogen is + 5) and high kinetic stability (NF4+ is isoelectronic with CF4).15 -17 It has been shown that in anhydrous hydrogen fluoride, benzene and its derivatives are fluorinated by tetrafluoroammonium tetrafluoroborate with substitution of hydrogen by fluorine.15-17... 

Trichloromethyl)benzene and its derivatives are easily fluorinated with antimony(III) fluoride however, with a trifluorosilyl group in the 2-position, the use of antimony(V) chloride catalyst is required. Trifluoro[2-(trifiuoromethyl)phenyl]silane (6) can be prepared by this procedure in 87% yield.80... 

Blowing agents - [FOAMED PLASTICS] (Vol 11) - [PLASTICPROCESSING] (Vol 19) -from chloroformates [CARBONIC AND CARBONOCHLOFJDIC ESTERS] (Vol 5) -fluorine compounds [FLUORINE COMPOUNDS, ORGANIC - INPRODUCTION] (Vol 11) -HF mprdnof [FLUORINE COMPOUNDS, INORGANIC - HYDROGEN] (Vol 11) -hydrazines as [HYDRAZINE AND ITS DERIVATIVES] (Vol 13)... 

The SNAr reaction between thiolates and monofluorobenzene and its derivatives requires high temperatures and polar aprotic solvents [19, 20, 21]. Polyfluoroaro-matics show very little selectivity for fluorine replacement [22, 23] (equation 13 J. 

Prior to 1975, discussions of fluonnatcd pharmaceuticals focused mainly on anti-inflammatory steroids, antipsychotic phenothiazines, and 5-fluorouracil and its derivatives as anticancer agents [/ 2] During the past 25 years, and especially in the last decade, fluonnated dmgs have been marketed for the treatment of a wide variety of diseases This section wdl focus on those presently marketed drugs where the presence of fluorine has produced significant therapeutic advantages... 

In addition to the synthesis of enantiomerically pure (camphorylsulfonyl)oxaziridine7 and its derivatives,8 the (camphorsulfonyl)imine has been used in the preparation of (-)-2,10-camphorsultam (Oppolzers auxiliary),6-9 (+)-(3-oxocamphorysulfonyl)oxaziridine10 and the N-fluoro-2,10-camphorsultam, an enantioselective fluorinating reagent.11... 

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