Alkyl fluorides conductivity

The transitory existence of alkylcarbonium ions in alkyl halide-Lewis acid halide systems has been inferred from a variety of observations, sueh as vapour-pressure depressions of OHsCl and C2H5CI in the presence of gallium chloride (Brown et al., 1950), the electric conductivities of aluminium chloride in ethyl chloride (Wertyporoch and Firla, 1933) and of alkyl fluorides in boron trifluoride (Olah et al., 1957), as well as the... 

Alkyl fluoride boron trifluoride systems were first investigated by Olah et al. (1957). 1 1 Addition complexes were observed at low temperatures, and their specific conductivity was measured. The specific conductivity of the propyl and butyl fluoride boron trifluoride systems was found three orders of magnitude larger than those of the methyl- and ethyl-fluoride systems. The latter systems on heating dissociated into their starting materials, whereas the former gave polymer mixtures (Olah, unpublished). 

CAUTION Alkyl fluorides are said to be highly toxic. Great care should be taken not to inhale the vapours conduct the entire operation in an efficient fume cupboard. 

Aikyl fluorides by exchange from alkyl halides or methanesulfonates. The resin used for the reaction is the F form of Amberlyst-A26 (Rohm and Haas), a macroreticular anion-exchange resin containing ammonium groups. When this material and primary alkyl halides or sulfonates are refluxed in a solvent (pentane, hexane, ether), alkyl fluorides are formed, usually in satisfactory yields. Alkenes accompany fluorides in the reaction of secondary substrates. This reaction has been conducted previously under phase-transfer catalysis (5, 322). ... 

In most processes recirculation of the stable feed hydrocarbon is maintained and the reactive olefin is fed into the recycling stream sometimes at several points. Thus, the concentration of olefin is always low and polymerization reactions are minimized. The alkylation reaction is favored by high pressures and low temperatures. However, in order to accomplish the reaction without catalysts, temperatures of 900 to 975 F are required.Polymerization also occurs rapidly at such temperatures, and hence the olefin concentration must be kept low. Thermal alkylation is conducted at 3,000 to 8,000 psig, whereas by means of catalysts such as sulfuric acid, boron fluoride, - aluminum chloride, double halides of alkali metals with aluminum, and hydrogen fluoride, pressures less than 500 psi and temperatures ranging from 450°F down to below zero may be employed. Sulfuric acid was widely used early in World War II as a catalyst in commercial installations, and a revival of interest has occurred since 1951. The process operates at 30 to 60 F for butenes and at substantially atmospheric pressure. The hydrofluoric acid process also proved during World War II to be a highly successful process, but only... 

In order to achieve high yields, the reaction usually is conducted by application of high pressure. For laboratory use, the need for high-pressure equipment, together with the toxicity of carbon monoxide, makes that reaction less practicable. The scope of that reaction is limited to benzene, alkyl substituted and certain other electron-rich aromatic compounds. With mono-substituted benzenes, thepara-for-mylated product is formed preferentially. Super-acidic catalysts have been developed, for example generated from trifluoromethanesulfonic acid, hydrogen fluoride and boron trifluoride the application of elevated pressure is then not necessary. 

The base-catalysed addition of thiols to Jt-electron-deficient alkenes is an important aspect of synthetic organic chemistry. Particular use of Triton-B, in place of inorganic bases, has been made in the reaction of both aryl and alkyl thiols with 1-acyloxy-l-cyanoethene, which behaves as a formyl anion equivalent in the reaction [1], Tetra-n-butylammonium and benzyltriethylammonium fluoride also catalyse the Michael-type addition of thiols to a,P-unsaturated carbonyl compounds [2], The reaction is usually conducted under homogeneous conditions in telrahydrofuran, 1,2-dimethoxyethane, acetone, or acetonitrile, to produce the thioethers in almost quantitative yields (Table 4.22). Use has also been made of polymer-supported qua-... 

Boron trifluoride and boron trifluoride-diethyl ether complex can be used as a source of fluoride ions in the presence of hypobromites and hypochlorites, e.g. methyl hypobromitc, tert-butyl hypobromite, methyl hypochlorite in carbon tetrachloride at 25 C. The addition of bromine monofluoride" and chlorine monofluoride" to various alkenes is accompanied by the formation of the corresponding alkoxybromides and alkoxychlorides which hinder the isolation of the halofluorinated products.57 jV-Bromo- and A -chloro-substiluted alkyl- and arylamines. -amides, and -imides, A -chloro-A,-methylamine, A -bromo-A -methylamine, A -chloro-A, /V-dimethylamine, A-bromo-A.A-dimethylamine, ACV-dichloro-A -methylamine, V,fV-dibromo-,V-mcthylaminc, A -bromosuccinimide, -V-chlorosuccinimide, Af-bromoacct-amide, A.A -dichlorourethane, can be used in the reaction instead of the hypohalites. The reactions with various alkenes conducted in dichloromethane at room temperature in the presence of boron trifluoride-diethyl ether complex produce bromofluoro and chlorofluoro addition products in 40-80 % yield. However, the reactions are complicated by the addition of A -halo-succinimides and Af.A-dichlorourcthane to the C = C bonds.58... 

Alkyl aryl ethers. This fluoride can serve as base for the alkylation of phenols with alkyl halides (DMF, 20°). Yields are in the range 65-85%. In the case of 2,6-disubstituted phenols the reaction is conducted at 100°. The method is even satisfactory for alkylation of 2- and 4-nitrophenols. The success of this method probably is a result of the ability of to serve as a hydrogen-bond electron donor. 

Ito and coworkers developed a mild and efficient procedure for generating o-quinodimethanes" as reactive intermediates in [4 -I- 2] cycloadditions. The key step in the sequence, illustrated here by the synthesis of Estrone methyl ether (146 Scheme 53) involves a fluoride-induced fragmentation of the o-[a-(trimethylsilyl)alkyl]benzyltrimethylammonium iodide (144) to give the o-quinodimethane (145), which underwent stereoselective intramolecular [4 + 2] cycloaddition to give the desired tetracyclic framework in (146). The entire process was conducted at room temperature. The annulation reaction is not limited to intramolecular cycloadditions intermolecular versions of the reaction proceed equally well. 

Cosolvents and Tri-n-butyltin Fluoride. Dunn and Oldfield (15) first reported the ability of tri-n-butyltin fluoride to dramatically increase the viscosity of a relatively light alkane, namely hexane. Tri-n-butyltin fluoride exists in the form of a penta co-ordinate species, and is thereby able to form linear polymer chains by weak dipole-dipole interactions between the fluorine and tin of adjacent molecules. The fluid in which the tri-alkyltin fluoride is dissolved must have no dipole moment in order not to disrupt the transient associations which form the long chain polymer. As stated earlier, this compound was only very slightly soluble in CO2 (less than two weight percent) and no viscosity increase was observed. Heller et at. (2, 7) have conducted extensive research on these tri-alkyltin fluorides varying the alkyl groups in an attempt to enhance their solubility in 002 ... 

Amino-3-cyano-thiophenes or 2-amino-thiophene-3-esters result from this route, generally conducted as a one-pot process, involving a ketone that has an a-methylene, ethyl cyanoacetate or malononitrile, sulfur, and morpholine. Various improvements to the original procedure include using microwave irradiation on solid snpport, or with potassium fluoride on alumina as the base, or solvent-free,and using morpho-lininm acetate in excess morpholine for aryl alkyl ketones. 

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