Acetyl fluoride

Acetyl Fluoride, (a)2 In a pressure bottle stoppered with rubber is placed 150 g. of acetyl chloride It is cooled to —15°, and 10 g. of anhydrous zinc fluoride is introduced the bottle is stoppered and allowed to warm to room temperature with shaking.. It is then cooled, a second 10-g. portion of the salt is added, and the bottle is stoppered and shaken as before. When 100 g. of zinc fluoride has been added in this way the temperature is allowed to rise gradually to 50°. The reaction mixture is cooled, and the product is distilled. Acetyl fluoride boils at 20° the yield is quantitative. 

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Alkoxy fluorides are prepared using acetyl fluoride. Alternatively, antimony trifluoride can be used to replace one alkoxyl by fluorine (58) ... 

During electrochemical fluorination retention of important functional groups or atoms in molecules is essential. Acyl fluorides and chlorides, but not carboxylic acids and anhydrides (which decarboxylate), survive perfluorination to the perfluorinated acid fluorides, albeit with some cyclization in longer chain (>C4) species [73]. Electrochemical fluorination of acetyl fluoride produces perfluoro-acetyl fluoride in 36-45% yields [85]. Electrochemical fluorination of octanoyl chloride results in perfluorinated cyclic ethers as well as perfluorinated octanoyl fluonde. Cyclization decreases as initial substrate concentration increases and has been linked to hydrogen-bonded onium polycations [73]. Cyclization is a common phenomenon involving longer (>C4) and branched chains. a-Alkyl-substituted carboxylic acid chlorides, fluorides, and methyl esters produce both the perfluorinated cyclic five- and six-membered ring ethers as well as the perfluorinated acid... 

Sulfur tnoxide adds to 2,2 difluoroethylenesulfonyl fluoride to afford the P sultone and its rearrangement product, bis(fluorosulfonyl)acetyl fluoride Potassium fluoride acts as a base and reacts with the acetyl fluoride to eliminate the elements of hydrogen fluoride and produce bis(fluorosulfonyl)ketene [IS] (equation 6)... 

Microwave studies of equilibrium orientations of methyl groups show that the forces act like repulsions, i.e., the hydrogens are staggered with respect to the atoms at the other end, at least in ethyl chloride, methyl silane, methyl fluorosilane, and methyl germane. Where there are only two attached atoms at one end, one connected by a single, the other by a double bond, as in acetaldehyde, propylene, acetyl fluoride and chloride, one of the methyl hydrogens is opposite the double bond, i.e., eclipsed. 

Fig. 26. Dominant stabilizing pi type orbital interactions in the S and E conformers of acetyl fluoride...

Partial experimental support for this idea is found in the methyl rotational barrier of acetyl fluoride and acetic acid. Specifically, the methyl rotational barrier increases by 561 cal/mol when -OH is replaced by F131 132) 1371. 

It is interesting to compare the toxicity of fluoroacetyl chloride with the isomeric chloroacetyl fluoride. The former possessed a toxicity comparable to that of methyl fluoroacetate, whereas the latter was relatively non-toxic. This is readily understandable in that fluoroacetyl chloride gives the toxic fluoroacetic acid, whereas chloroacetyl fluoride hydrolyses to chloroacetic acid and the relatively non-toxic (at the concentrations employed) hydrogen fluoride. Fluoroacetyl fluoride also possessed a toxicity comparable with that of fluoroacetyl chloride or of methyl fluoroacetate, again showing that the COF group contributed practically nothing. Acetyl fluoride was also non-toxic. 

The described procedure, first applied by Colson and Freden-hagen, is useful for the preparation of a wide variety of acyl fluorides. The yields are normally 80-90%. Some examples of acyl fluorides prepared are listed in Table I. Benzoyl fluoride can also be employed as a convenient source of acetyl fluoride by reaction with acetic acid. ... 

In this procedure, the ketone is first converted to its enol acetate by reaction with acetic anhydride in the presence of a proton acid. Since this enol acetylation is performed under equilibrating conditions, the more stable enol acetate (usually the more highly substituted isomer) is produced. Acetylation of this enol acetate, catalyzed by the Lewis acid boron trifluoride, usually leads to the formation of the enol acetate of a /3-diketone which is cleaved by boron trifluoride to form acetyl fluoride and the borofluoride complex of the /3-diketone. Thus, this procedure offers a convenient and general synthetic route... 

Examples of these include 1,2-dichloroethane (80% retention of the 1,2-dich-loro structure) acetyl fluoride (85% yield of fluorinated acetyl fluorides) tetrafluorocyclobutane (90% retention of cyclic structure) isopropyl trifluoro-acetate (to the perfluoroester and subsequently hexafluoroacetone). 

Novak and Boa [176], using ring-disc electrode techniques, studied intermediates and transients in the fluorination of acetyl fluoride and methanesulphonyl fluoride and concluded that the initial step was the discharge of the organic substrate in the adsorbed state, according to the following scheme ... 

Furthermore, the cleavage of organic sulfites and sulfates by hydrogen fluoride gives the corresponding alkyl or acyl fluorides in fair to good yield,287 e.g. formation of acetyl fluoride from the mixed anhydride287 or sulfonyl fluorides from sulfonic acid anhydrides.287... 

The products of the selective electrochemical fluorination of butadiene with platinum electrodes in amine/ HF mixtures, particularly Et,N 3HF, were 3,4-difluorobut-1-cnc and 1,4-difluorobut-2-ene in a ratio of 1 2, 2.3-dimethyIbut-2-enc gave 2.3-difluoro-2,3-dimelhylbutane (yield 22%), while 2-mcthylbut-2-ene gave 2,3-difluoro-2-methyIbutanc (yield 23%) and 2,2-difluoro-3-methylbutane (yield 11 %). Oct-1-ene could not be fluorinated instead, the solvent degraded. Volatile degradation products were acetaldehyde, acetyl fluoride and fluorocthane. 

The liquid state of arsenic(III) fluoride and miscibility with many solvents and other liquids is an advantage permitting variation of the reaction conditions over a wide range. The first reported application of arsenic(III) fluoride as a fluorinating agent was the conversion of acetyl chloride into acetyl fluoride.3... 

Reaction of 2,2-difluoro-2-(methoxycarbonyl)acetyl chloride (3) with potassium fluoride affords 2,2-difluoro-2-(methoxycarbonyl)acetyl fluoride (4) in 90 % yield, which is one of the precursors for the preparation of perfluorovinyl ethers containing a carboxylic group.30... 

Difluoro(diethoxyphosphinyl)acetyl chloride (7) is characterized by its conversion to the unstable difluoro(diethoxyphosphinyl)acetyl fluoride (8) by treating with potassium fluoride.31 Both compounds have been analyzed by 19FNMR spectroscopy. 

Another interesting substitution reaction is the conversion of l-methoxybicyclo[2.2.2]octane (3a) and l-methoxy-4-methylbicyclo[2.2.2]octane (3b) with acetyl fluoride and boron trifluoride,9 but this has not yet been extended to other substrates. 

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