Partially fluorinated alkanes

Polyfluoroalkyl- andperfluoroalkyl-substituted CO and CN multiple bonds as dipolarophiles. Dmzo alkanes are well known to react with carbonyl compounds, usually under very mild conditions, to give oxiranes and ketones The reaction has been interpreted as a nucleophilic attack of the diazo alkane on the carbonyl group to yield diazonium betaines or 1,2,3 oxadiazol 2 ines as reaction intermediates, which generally are too unstable to be isolated Aromatic diazo compounds react readily with partially fluorinated and perfluorinated ketones to give l,3,4-oxadiazol-3-ines m high yield At 25 °C and above, the aryloxa-diazolines lose nitrogen to give epoxides [111]... 

At the end of this development phase, partially fluorinated compounds of the RFRH type [27], with different ratios of alkane and perfluoroalkane chains linked together, were introduced into the market [26]. 

The different PFCLs used as interoperative tools can be categorised as a group of compounds with more or less uniform behaviour. On the contrary, the partially fluorinated species have to be regarded as individuals each. This is due to the hybrid character of these compounds, which combine the behaviours of alkanes and perfluoroalkanes. Especially, the toxicological behaviour cannot be optimised by simple modifications of the degree of fluorination. If the two molecule parts are combined in the right balance, the cytotoxic behaviour of the alkyl chain can be overcompensated by the inert perfluorinated part of the compound. But each compound should be tested individually to ensure its suitability as a candidate for ophthalmic use. 

A further important issue is the balance between the perfluoroalkane and the alkane part in the RFRH molecules and the branching ratio in both these compartments. This is of special importance if penetration processes into tissues must be taken into consideration. Especially low molecular weight species or partial fluorinated liquids with their distinctly higher lipophilic potential as PFCLs can easily penetrate tissues. 

F. Malchiodi-Albedi, A. Matteucci, G. Formisano, S. Paradisi, G. Carnovale-Scaizo, G. Scorcia, H. Hoerauf, Induction of apoptosis in rat retinal cell cultures by partially fluorinated alkanes. Am. J. Ophthalmol. 139 (2005) 737-739. 

H. Hoerauf, K. Kobuch, J. Dresp, D.H. Menz, Combined use of partially fluorinated alkanes, perfluorocarbon liquids and silicone oil—an experimental study, Graefes Arch. Clin. Exp. Ophthalmol. 239 (2001) 373-381. 

Similarly,both Meinert and Gambaretto, with their respective co-workers [80, 172, 175], have invoked this mechanism to explain the formation of partially fluorinated products in ECF reactions of the amines, tripropylamine, AT-methyl-morpholine, and a series of a,co-dimorpholino- and dipiperidino-alkanes. The selective order in which the hydrogens were substituted in these molecules was said to be consistent with that expected for the mechanism in that carbon atoms nearest to oxygen (in the morpholine rings), where the electron density is greatest, were the first to react, and those nearest to the quaternised nitrogen the last, not in a random order as might be expected in a radical mechanism. 

As early as the 1940s Emeleus and Haszeldine [17] discovered that perfluoroalkyl iodides are not only cleaved into perfluoroalkyl radicals by light but also that they add readily to a variety of olefins to yield telomers and 1 1 adducts [18]. This kind of radical chain reaction can also be initiated by high temperatures (Scheme 2.100). The addition of perfluoroalkyl iodides to olefins is a very important method for synthesis of partially fluorinated alkanes, polymers, oligomers, and their derivatives [19]. The synthesis of some perfluoroalkyl aromatic compounds can also be achieved [20]. 

If equimolar quantities of tetramethylammonium fluoride and a threefold excess of Me3SiCF3 or its homologues are used the perfluoroalkyltrimethyl silane acts as an effective source of nucleophilic perfluoroalkyl equivalents for nucleophilic substitution of aliphatic triflates [90] (Scheme 2.136). This method enables the simple synthesis of partially fluorinated alkane structures which are of interest in the chemistry of liquid crystals and other functional materials. 

Fluorinated and partially fluorinated alkanes, chloroalkanes, and carboxylic acids Alkanes, chloroalkalies, alkanoic acid fluorides Phillips Petroleum... 

Fig. 5.7. Entropies of transition for partially fluorinated n-alkanes of the type F(CF2-)i2(CH2-) H for values of n frcan 0 to 20. Drawrn after Ref.

Entropies of Transition of Partially Fluorinated n-Alkanes 150r... 

The partially fluorinated alkane or alkene is surface active in hydrocarbon media (see Section 1.8) and can be visualized to function as a cosurfactant in the emulsion. 

Meinert et al. [104-106] found that already small quantities [1 or 2% (w/v)] of partially fluorinated alkanes, C, F2 ,+ iC H2h+i, stabilize perfluorodecalin-Pluronic F68 emulsions. Riess et al. [130] deseribed a binary emulsifier system, consisting of a nonfluorinated surfactant in conjunction with a partially fluorinated alkene. Riess et al. [130] named the fluorinated amphiphile a dowel," suggesting that its fluorophilic end adsorbs in the fluorocarbon surface and its lipophilic end penetrates the lipophilic part of the egg-yolk phospholipid. The dowel, C8Fi7CH=CHCsHi7, increased the stability of a perfluorooctyl bromide (PFOB)-egg-yolk lipid emulsion stability considerably. The droplet size (0.25, m) remained constant over 9 months, even at 40 C. In the absence of the dowel, the droplet size more than doubled at 25 C to 0.49 jum. 

We have seen (Rec. 8-6) that the partial double-bond character of the carbon-chlorine bond in the chloroethylenes and chlorobenzenes provides an explanation of the great stability of these substances relative to the cliloroparaffins. The same explanation8 applies to the fact7 that although the substitution of one fluorine atom in an alkane moie-... 

Table 4.14 Structure (top) and physical properties [41] table below) of semi-fluorinated n-alkanes (60-63) and the homologous dialkyl bicyclohexyl liquid c stals 64 and 65 from which they are structurally derived. The spacefill model of 63 shows the helical conformation of the central perfluoroalkylene segment in contrast with the pentyl side-chains with their typical hydrocarbon zigzag conformation. The differences in charge distribution (red and blue denote negative and positive partial charges, respectively) are visualized by mapping of the electrostatic potential on to the electron density of 63 (B3LYP/6-31C //PM3 level of theory) [44, 50].

Sulfides and l,l,l-tris(methylthio)alkanes behave slightly differently. Fluoro-Pummerer rearrangement of sulfides leads to a-fluoro sulfides, whereas partial replacement of the SMe groups with fluorine atoms and concomitant a-bromination seems to be the option for the orthothioesters. ... 

The word oil is used for an organic phase that is essentially immiscible with water and is thus relatively apolar. It can refer to a hydrocarbon, a partially or totally chlorinated or fluorinated hydrocarbon, single-chain alkane, cyclic or aromatic hydrocarbon, polar monoester such as ethyl oleate, long-chain alcohol such as dodecanol, triglyceride natural oil, or polycyclic cholesterol. The most typical oil phase is, of course, n-alkane, which would be characterized by its length or alkane carbon number (ACN). 

At 188 MHz four additional defect resonances (1, 5, 6, and 7) appear in the F NMR spectrum of PVFj [sec (b) in Figure 2.13]. Ferguson and Brame [57] also observed these additional defect peaks and tentatively assigned them to defect structures drawn in Figure 2.13(b) based on a-, fi-, and y-substituent effects derived from the CFj resonances observed in various saturated, partially fluor-inated linear alkanes. In addition to dp p, and 5 F chemical shifts were also calculated for the ddect fluorines 1,5,6, and 7. F y-effects(yp,cHp Vf.cf ... 

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