Fluorine molecular

A simple equihbrium calculation reveals that, at 25°C and atmospheric pressure, fluorine is less than 1% dissociated, whereas at 325°C an estimated 4.6% dissociation of molecular fluorine is calculated. Obviously, less than 1% of the coUisions occurring at RT would result in reaction if step la were the only important initiation step. At 325°C the fluorine atom initiation step should become more important. From the viewpoint of energy control, as shown in Table 1, it would be advantageous to have step lb predominate over step 2a and promote attack by molecular rather than atomic fluorine. Ambient or lower temperatures keep the atomic fluorine concentration low. 

In other work Rozen added molecular fluorine to a steroidal ene-one dissolved in ethanol at low temperatures to produce a vicinal difluonde in a cleaner, better yield reaction than previously obtainable [55] Although the reaction was not general, the stereoselectivity was very high, and contrary to addition of other halogens, addition was r>ii, characteristic of an electrophilic addition pathway... 

Substituted aryl hydrazones can be converted to geminal difluondes in satis factory yields by molecular fluorine [H4, iodine fluoride [ 5], and N bromo-suc-cinimide-pyridinium polyhydrogen fluoride or A -bromosuccinimide-polyvi-nylpyridinium polyhvdrogen fluoride [5(5] (equation 21) (Table 6)... 

Iodine fluoride is a more versatile reagent than molecular fluorine in geminal fluorination of other hydrazones and related compounds under milder reaction conditions [55] Substrates fluorinated include hydrazones of simple cyclic or steroidal ketones (e g, 4 tert butylcyclohexanone, 70%, 3 cholestanone, 70%), W methyl and A/N dimethylhydrazones [R2C=NNH(CH3) 70%, R2C=NNC(CH3)2, 50%], semicarbazones (R2C=NNHCONH2, 25-50%), and 2,4-dinitrophenylhy-drazones [R2C==NNH-C6H3-2,4(N02)2, 25-50%]... 

High yields (65-94%) of geminal difluoro compounds can be obtained tram diazoketones and dilute molecular fluorine [90] (equation 25)... 

In contrast to molecular fluorine, trifluoromethyl hypofluonte has limited synthetic value for geminal fluorination of diazoketones owing to formation of complex mixtures [97]... 

Fluorination of O- and N-heterocycles with molecular fluorine in the synthesis of fluorine-containing bioactive compounds 98YGK107. 

The diatomic molecule of fluorine does not form higher compounds (such as F3, F4, - ) because each fluorine atom has only one partially filled valence orbital. Each nucleus in Fs is close to a number of electrons sufficient to fill the valence orbitals. Under these circumstances, the diatomic molecule behaves like an inert gas atom toward other such molecules. The forces that cause molecular fluorine to condense at 85°K are, then, the same as those that cause the inert gases to condense. These forces are named van der Waals forces, after the Dutch scientist who studied them. 

Eveiy bond has a characteristic length and strength. Example compares molecular hydrogen with molecular fluorine. 

The bond length of molecular fluorine is 142 pm, and the bond energy is 155 kJ/mol. Draw a figure similar to Figure 9 that includes both F2 and H2. Write a caption for the figure that summarizes the comparison of these two diatomic molecules. 

A similar situation arises when two fluorine atoms approach each other. The first valence orbitals to overlap are the 2 p orbitals pointing along the axis that joins the atoms. Figure 10-5 shows that bond formation in molecular fluorine results from the strong directional overlap of these two atomic 2 p orbitals. 

Some industrial uses of fluorine require molecular fluorine, F2, which is produced by electrolysis of HF. As Figure 21-16 shows, the cell uses liquid HF to which KF is added as an electrolyte. The redox chemistry is Anode 2 F" F2 + 2 e ... 

Schematic view of an electrolytic cell used for the production of molecular fluorine, showing the molecular species involved in the redox reactions.

Figure 7 Emission spectra obtained in the reaction of DMS with F2. (A) 155 mtorr CH3SCH3, 30 mtorr F2, 570 mtorr He (B) 30 mtorr CH3SCH3, 20 mtorr F2, 350 mtorr He (C) 30 mtorr CH3SCH3, 50 mtorr F2, 900 mtorr He. (Reprinted from RJ Glinski, EA Mishalanie, JW Birks, Molecular emission spectra in the visible and near IR produced in the chemiluminescent reactions of molecular fluorine with organosulfur compounds, Journal of Photochemistry 37 223, 1987, with permission from Elsevier Science.)...

Milligan and Jacox 44 have recently reported an elegant synthesis of CF2 in an argon matrix. Carbon atoms, produced from the photolysis of cyanogen azide, were allowed to react with molecular fluorine, and the presence of CF2 was demonstrated from infrared spectra. Use of radiation effective in photolyzing F2 produced CF3 from the reaction of the CF2 with atomic fluorine. 

The molecules participate in the chemical reactions as carriers of the atoms and radicals. According to such an interpretation one can consider molecular fluorine as the simplest chemical compound of atoms—FF (like C1F,... 

BrF, AgF, FOF, FKrF, FXeF) and its chemical properties as the result of oxidizing ability and reactivity of the fluorine atoms. The real conditions of the reaction system (temperature, pressure, agent content, reaction environment, the composition and properties of the initial agents and reaction products...) have a great influence on the chemical behavior of molecular fluorine, limiting or sharply increasing its chemical activity. 

In this respect XeF2 is similar to molecular fluorine. The relatively low oxidizing ability and reactivity ofXeF2 in the same type of chemical reactions is explained by its greater dissociation energy. The activation energy of the dissociation (XeF2-> XeF + F) is 190-210 kJ/mol. The XeF radicals are very weakly bound (EXcF = 58-80 kJ/mol) and can be an effective source ofF atoms.3... 

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