Traps fluorocarbon

A popular, related technique is to inject some sort of a volatile material into the polymer while it s still molten, causing it to foam immediately. Fluorocarbons are used this way in making polyurethane foams suitable for insulation. The trapped fluorocarbon is even better than air as an insulator. Fluorocarbon or air is used to expand PS foams also. The gas is injected as the molten polymer is forced through a die. The foamed PS is then immediately injected into a mold to make items like egg cartons and trays for meats, produce, or fast-food. 

These composites were prepared by mixing a fluorocarbon solution of the perfluorinated PPl dendrimers with an aqueous ethanolic solution of Pd, thereby forming an emulsion. After phase separation, the fluorous phase, which contains the dendrimer-encapsulated Pd +, was treated with a reducing agent yielding zero-valent Pd nanoclusters trapped within the dendrimer (Fig. 24). 

All connections between the pieces of equipment are made with a in. copper tubing. Whenever the fluorocarbon obtained in the reaction is volatile at room temperature, a cold finger-type trap is placed between 8 and 9 to catch the product. The temperature of the trap must be high enough for passage of... 

A mixture of 1//-decafluoroheptane (24.7g, 67mmol), NOz (6.6g), and Cl2 (5.2g) (molar ratio 1 2 1) was passed through the reactor (sloping 52 x 2.5 cm empty Ni pipe in a 33-cm electric tube furnace) at a wall temperature of 600 C in 15 min with a contact time of 11 s. The product in the ice trap (17.8 g) was hydrolyzed in cold H20 (100 mL), and coned H2S04 (25 mL) was added which caused the separation of a lower phase containing theperfluoro acid. The aqueous phase was extracted with perfluoro inert c-C6F 20 (a cyclic ether), in which fluorocarbon acids are soluble. The lower layer was separated and the product was recovered from the perfluorinated solvent by distillation yield 11.1 g(46%) bp 170-175 C/740Torr. 

This trapped carbene (which actually exists as a dimer with tetra-coordinated Li atoms) smokes on exposure to air and also on grinding with fluorocarbon solvent, from which it seems able to remove fluoride. 

An essential feature of this process is the reaction of a nucleophile with a fluorocarbon radical. It is important to emphasise that radicals, being electron-deficient, are electrophilic and therefore that fluorocarbon radicals are even more electrophilic. These processes are, of course, aided by ultraviolet irradiation and inhibited by radical traps, or the radicals may be intercepted, e.g. by norbomene as in the example shown in Figure 5.7a [15], Further examples are given in Table 5.2. 

Fluoride-ion-induced reactions A similar polymer to that in Figure 7.87 is obtained upon anionic polymerisation of hexafluoro-2-butyne initiated by fluoride ion in a solvent [311-313] (Figure 7.89). This is a clear example of an anionic polymerisation of an unsaturated fluorocarbon, although the growing anion can be trapped by a sufficiently reactive system [291, 314], such as pentafluoropyridine [315] (Figure 7.90). There is little difference between the ultraviolet spectra of 7.90A and 7.90B, confirming that conjugation in the polyene system is inhibited by steric effects. 

Into a stainless steel reactor (i.d. 25 mm, length 400 mm) filled with K2C03 powder (82.3 g) at 200 C, was passed helium at a rate of 100 mL - min-1 and perfluoro(2-azepan-l-ylpropanoy fluoride) at a rate of4 g over 31 min after evaporation. The outlet gas was trapped at — 78 C to give 2.88 gofa fluorocarbon mixture. The mixture was almost pure product yield 2.88 g (84%, 100% conversion) bp 102-103 C. 

A 500-niL stainless steel reaction vessel charged w ith perfluorobutanoyl chloride (46 g, 0.2 mol), Ni(C0)4 (34 g, 0.2 mol) and benzene (176g, 2.2 mol) was closed and heated at 150 C with agitation for 6 h. The mixture was cooled, vented through a trap cooled in a dry ice/acetone slush to condense the volatile fluorocarbons, filtered to remove the solid products, and the filtrate was fractionally distilled yield 18-20 g (35-40%) bp 128 C 115- 1.3765. 

Carbanions, generated by reaction of fluoride ion with unsaturated fluorocarbons, may be trapped by reaction with activated polyfluoroaromatic compounds, resulting in the introduction of polyfluoroalkyl groups.303 307 These are, of course, reminiscent of familiar cationic processes and may be thought of as nucleophilic Friedel-Crafts reactions (Eqs. 80 and 81).307... 

Gases are transferred in a standard Pyrex glass vacuum line equipped with high-vacuum stopcocks (lubricated with a fluorocarbon grease [Halocarbon]) to which is attached a four-trap system used for low-temperature trap-to-trap distillation (Fig. 1). Because of the reactivity of the compounds, a Heise-Bourdon tube gauge [Dresser Ind.], is used for PVT measurements. 

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