Monofluorides, structures

Monodentate oligopyridines, 30 72-73 Monodentate uiazenide structures, 30 5, 6, 8 bond lengths and angles, 30 8 Mono-2-ethyl hexyl phosphoric acid, in liquid-liquid extraction, 9 44—47 Monofluorides, structures, 27 84-85 Mono(fluoroxyperfluoroalkyl) peroxides, 16 153-156... 

As with graphite oxide, there are currently two views as to the structure of carbon monofluoride. Although detailed X-ray diffraction work suggested a chair arrangement of the sp -hybridized, carbon sheets (Ml), second-moment calculations of the adsorption mode of the fluorine nuclear magnetic resonance suggested that a boat arrangement is more plausible iE2). The structures are illustrated in Fig. 3. 

An ideal kinetic study would be made under conditions where the product is only graphite fluoride or polycarbon monofluoride with no byproducts formed. In terms of reaction kinetics, one method to follow the reaction is to measure the weight change as a function of the reaction time. Using this method the reaction rate of fluorine with carbon can be evaluated. Various carbon structures have been employed with sufficient fluorination contact time provided at a particular temperature for the carbon to reach fluorine saturation. The weight increase vs the temperature can be monitored at atmospheric pressure. Figure 515 shows the carbon structure and the temperature dependency of the fluorination reaction of various graphites. 

The only example of a monofluoride is that of silver, although such compounds might be expected for copper and gold, in the same triad. Silver fluoride has the simple rock-salt structure, and the most recent... 

It is convenient here to consider the compound disilver monofluoride (or silver subfluoride). This was reported to have an anti-cadmium iodide structure in early work (5), and this has been confirmed more recently (6). From X-ray single-crystal results the unit cell is hexagonal, a = 2.996, c = 5.691 A, space-group C3m, and the Ag—F separation 2.451 A, almost identical with that in silver monofluoride (2.468 A). The structure consists of layers, with a plane of fluorine atoms sandwiched between two planes of silver atoms, giving the fluorine atom a coordination of six silver atoms, the same as in silver monofluoride. The silver atoms have separations of 2.996 and 2.814 A, compared with 2.889 A in the metal itself, and in line with the metallic conductivity of the compound. 

We believe the use of a direct gaseous phase fluorination process for modifying the surface and structure of zeolites to be a new process (18). The literature does contain references to the use of hydrogen fluoride (20, 22, 23), boron trifluoride (21, 24), aluminum monofluoride (sic) (19) and silica difluoride (sic) (19) to treat the surface of a zeolite to obtain higher catalytic activity. However, the use of fluorine gas to modify both surface and structure has not been reported before. The purpose of this paper is to report results of fluorination of zeolites and to describe the process involved in such a treatment. Detailed results on fluorine-treated zeolites and their unusual properties, both adsorptive and catalytic, will be discussed in forthcoming papers. 

Solvent extraction, potentiometry, and calorimetry have been used to determine the thermodynamic parameters of the formation of the monofluoride complex of the trivalent lanthanide ions at 25°C. and an ionic strength of IM (NaClOj ). The enthalpies were all endothermic, ranging from 4.0 to 9.5 Kcal./mole consequently, the large, positive entropies, ranging from 25 to 48 cal./°C./mole, explain the high stability constants. This large entropy results from the decrease in overall water structure when the fluoride ion is complexed. The difference in the enthalpies of formation of LnF and LnAc " can possibly be explained by a difference in covalence for Ln-F and Ln-O bonds. 

The structure of tetracarbon monofluoride (C4F) has been discussed by Riidorff Riidorff (1947 6) and Riidorff (1959). While it cannot be unequivocally demonstrated from their X-ray powder diffraction data, they proposed that in C4F the carbon atom sheets were flat and that the fluorine atoms made close ca. 1.4 Af) contacts to the carbons. Their finding ofhigh electrical conductivity for C4Fj, j(HF)4 also supported their notion that the carbon atom sheets were planar. Recent work in these laboratories (Mallouk Bartlett 1983 Mallouk 1983) has established that chemical fluorination of graphite, to compositions C4.Fj, 5(HF),5, x > 2.3, may... 

Fig. 3. The chair (top) and boat (bottom) models for the structure of poly(carbon monofluoride). ( , C O, F.)...

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