Fluorocarbon hydrocarbon comparison

Substitution of fluorine for hydrogen in an organic compound has a profound influence on the compound s chemical and physical properties. Several factors that are characteristic of fluorine and that underHe the observed effects are the large electronegativity of fluorine, its small size, the low degree of polarizabiHty of the carbon—fluorine bond and the weak intermolecular forces. These effects are illustrated by the comparisons of properties of fluorocarbons to chlorocarbons and hydrocarbons in Tables 1 and 2. 

Although to-date the emphasis has been on plasma polymerized films produced from hydrocarbon based systems, this trend in more recent times has swung towards fluorocarbons in an attempt to produce polymers of similar properties to conventionally prepared linear fluoropolymers. However, it will become clear from the account to follow that in many respects plasma polymerized fluorocarbons differ significantly from their linear counterparts. It is to the plasma polymerization of organic monomers containing solely carbon and fluorine therefore that we shall devote our attention in this section with only brief references to hydrocarbon and fluorohydrocarbon polymers for comparison purposes. 

There is nothing magical about fluorocarbons or, specifically, the -(CF2) F group [2]. The -(CF2)MF is similar to -(CH2) H in many ways. These include dipole moments and polarizabilities that are related to intermolecular forces and, hence, surface tension. Where they do differ is in size, specifically diameter, and a relative comparison for a typical hydrocarbon and similar fluorocarbon surfactant is shown in Figure 6.54. 

Part of the interest in fluorocarbon systems lies in a comparison of the chemistry, and particularly reaction mechanisms, of fluorocarbon derivatives with those of the corresponding hydrocarbon compounds. Indeed, such comparisons pose quite a strenuous test on our theories of organic chemistry. As will be seen, our understanding of the influence of carbon-fluorine bonds on reaction mechanisms has made considerable progress. Nevertheless, it must be emphasised that fluorocarbon derivatives present much more complicated systems than their corresponding hydrocarbon compounds because, in addition to effects arising from different electronegativities, the effect of the lone pairs of electrons of fluorine that are not involved in o-bonds must be taken into consideration. Furthermore, the relative importance of these effects seems to be very dependent on the centre to which the fluorine is attached. 

Initial experiments performed at the INL compared different catalysts, fluids, and operating conditions to determine the effect of SCF on solid acid catalyst alkylation (5). Three sets of studies were performed a catalyst comparison using six different catalysts (i.e., two zeolites, two sulfated metal oxides, and two Nafion catalysts) with methane as a cosolvent an exploration of the effect of varying methane addition on alkylation using a USY zeolite catalyst and a study of the effect of seven cosolvents (i.e., three hydrocarbons, two fluorocarbons, carbon dioxide, and sulfur hexafluoride) at L, ML, NC-L, and SCF conditions on the USY catalyst performance. 

In addition, highly perfluoroalkyl-substituted molecules are kinetically and thermodynamically stable due to sterical protection by the bulky perfluoroalkyl groups from any external attacks. Comparison of the half-lives of thermal isomerization of the perfluoroalkylated strained molecules (28 and 30) with those of the parent hydrocarbons (29 and 31) reveals an exceptionally high stability of these fluorocarbons (Scheme 1.38) [10]. Both the strengthening C—C bond and the steric protection of the inner carbon skeleton by perfluoroalkyl groups are responsible. 

Unsymmetrically 1,1 -disubstituted ferrocenes 43 ( = 11-16) were synthesized by combining the organic substituents used to prepare 41 (n) and 42 ( ). Introduction of dissymmetry had two effects on the thermal and mesomorphic properties. First, a depression in the melting points was observed. Second, the smectogenic character of the materials was enhanced. Indeed, with the exception of 43 ( = 11), which showed only a SmA phase, all the members of the series showed both SmC and SmA phases. In view of the mesomorphic properties obtained for 43 ( ) in comparison with those of 41 ( ) and 42 ( ), one can anticipate that the combination of very different substituents (e.g., chiral with non-chiral moieties, hydrocarbon with fluorocarbon motifs) should lead to ferrocenes showing rich mesomorphism. 

Although liquid crystals were discovered in 1888 [369], chemical concepts are only now being developed for converting the type of mesophase exhibited by a given chemical structure. Compounds which normally form only nematic mesophases can be forced to order into smectic layers by incorporating immiscible fluorocarbon units into their hydrocarbon chemical structure. Comparison of the data in Tables 7, 20 and 21 demonstrate that smectic layering is induced not only in low molar mass liquid crystals, but... 

ANG Angelis, M.G.de, Merkel, T.C., Bondar, V.I., Freeman, B.D., Doghieri, F., and Sartim G.C., Hydrocarbon and fluorocarbon solubility and dilation in poly(dimethylsiloxane) comparison of experimental data with predictions of the Sanchez-Lacombe equation of state,/. Polym. Sci. PartB Polym. Phys., 37, 3011, 1999. 

A comparison of the data in Table 1 with those in Table 4 shows that the values of the three principal excess functions G , and F for aromatic fluorocarbon + aromatic hydrocarbon mixtures are everywhere much less positive than those for mixtures containing a non-aromatic fluorocarbon. The experimental excess functions for aromatic fluorocarbons + alicyclic hydrocarbon are seen to occupy an intermediate position. Another notable trend that is obvious from the data in Table 4 is that there is a negative contribution to the excess functions associated with an increase in the degree of substitution of the hydrocarbon. This trend applies to mixtures of aromatic fluorocarbons with both aromatic and alicyclic hydrocarbons. 

When a comparison is made between fluorocarbons and hydrocarbons containing equal numbers of carbon atoms, it is found that, under the same... 

Ohsaka et al. [393] reported on the preparation by electrochemical oxidation and properties of thin films of 1-naphthylamine in acetonitrile solutions. These films had conductivities of 10 to 10" S cm". Aminocoronene, which consists of seven fused aromatic rings and an amino group, has also been polymerized [394]. Eaves et al. [395] polymerized perfluorocyclopentene in dimethyl formamide in the presence of tetrabutlyammonium perchlorate. The fluorocarbon polymers could exhibit enhanced environmental stability in comparison with hydrocarbon polymers. 

Molecular Structure.—A review has appeared that compares the relationship between polymer structure and surface-active properties of the poly(dimethyl siloxane)s (PDMS) with that of hydrocarbon and fluorocarbon polymer systems." A mathematical study of the spreading of (PDMS) oil drops has been presented and experimental data shown to be in good agreement with predictions. Quantitative comparison of previously published n.m.r. spin-relaxation data for poly(diethyl iloxane)s with theoretical predictions for a variety of motional processes, have allowed both the nature and time scale of molecular motions to be identified."... 

Wolf C, Bressel K, Drechsler M, Gradzielski M. Comparison of vesicle formation in zwitanionic and catanionic mixtures of hydrocarbon and fluorocarbon surfactants phase behavior and structural progression. Langmuir 2009 25 11358. 

Reactions of hydrocarbon acid chlorides with silicon hydrides in the presence of palladium have been reported (Citron, J. D., J. Org. Chem. 1969, 34, 1977). Significant reactivity differences are usually found in comparisons of hydrocarbon- and fluorocarbon-substituted carbonyl substrates, and the fluorinated aldehydes discussed in this chapter further exemplify this trend. 

As a result of the efforts of many chemists during the last two or three years fluorocarbon derivatives of metals have been described in ever increasing numbers, so that it can now be reasonably said that their study forms an important subarea both of fluorine chemistry and of organometallic chemistry. As anticipated by the early work 1-4), the new compounds display novel properties and reactions in comparison with those of their hydrocarbon... 

Frequently, fluorocarbon-metal compounds are known where the comparable alkyl or aryl derivatives are not. To some extent this may be because no serious attempts have been made to prepare the particular alkyl or aryl metal compounds, thus making them unavailable for comparison piuq>oses. However, in many instances either unsuccessful attempts at synthesis have been made, or the hydrocarbon derivative is known but is thermally much less stable than the fluorocarbon analog. At the time of writing much less common are situations where a o--bonded alkyl transition metal group is thermally as robust as the analogous o-bonded fluorocarbon-transition metal group. 

Based on the available data, it can be stated that a fluorosurfactant film at a water-C02 microemulsion interface appears to be less densely packed than the equivalent hydrocarbon surfactant in water-in-oil phases. The value of 110 A represents approximately twice (xl.87) the physical cross section of two fluorocarbon chains (56 A [52]). For n-alkyl sulfosuccinates the equivalent factor is around 1.55X a close-packed chain cross section [44]. The origin of this may be the finite, although small, solubility of water in CO2, which is not the case in water-oil systems. This comparison of molecular areas is valid only for strongly adsorbed surfactants, i.e., a negligible amount of free monomer in the bulk phases. For the CO2 systems, if there were to be a significant loss of surfactant from the interface, then the effective w value would increase because it would become [D20]/([surfactant],oBi - [surfactant]free) [58]. The upshot would be to reduce the gradient of the... 

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