Friedel-Crafts Catalysts aluminum chloride

Aldehyde Synthesis. Formylation would be expected to take place when formyl chloride or formic anhydride reacts with an aromatic compound ia the presence of aluminum chloride or other Friedel-Crafts catalysts. However, the acid chloride and anhydride of formic acid are both too unstable to be of preparative iaterest. 

Acid Halides (Lewis Acids). AH metal haUde-type Lewis catalysts, generally known as Friedel-Crafts catalysts, have an electron-deficient central metal atom capable of electron acceptance from the basic reagents. The most frequendy used are aluminum chloride and bromide, followed by... 

Solid Superacids. Most large-scale petrochemical and chemical industrial processes ate preferably done, whenever possible, over soHd catalysts. SoHd acid systems have been developed with considerably higher acidity than those of acidic oxides. Graphite-intercalated AlCl is an effective sohd Friedel-Crafts catalyst but loses catalytic activity because of partial hydrolysis and leaching of the Lewis acid halide from the graphite. Aluminum chloride can also be complexed to sulfonate polystyrene resins but again the stabiUty of the catalyst is limited. 

Weak Base Anion Exchangers. Both styreoic and acryHc copolymers can be converted to weak base anion-exchange resias, but differeat syathetic routes are aecessary. Styreae—DVB copolymers are chloromethylated and aminated ia a two-step process. Chloromethyl groups are attached to the aromatic rings (5) by reactioa of chloromethyl methyl ether [107-30-2] CH2OCH2CI, with the copolymer ia the preseace of a Friedel-Crafts catalyst such as aluminum chloride [7446-70-0], AlCl, iroa(III) chloride [7705-08-0], FeCl, or ziac chloride [7646-85-7], ZaCl. ... 

Ai lepiesents an aiyl group. Diaiyl products are obtained after long reaction times. Other Friedel-Crafts catalysts, eg, ZnCl2, FeCl2, FIF, and BF, can also be used. In most cases, stoichiometric amounts of the catalyst ate requited. Flowever, strong complexation of the phosphine by the catalyst necessitates separation by vacuum distillation, hydrolysis, or addition of reagents such as POCl to form more stable aluminum chloride complexes. Whereas yields up to 70—80% are possible for some aryl derivatives, yields of aliphatic derivatives are generally much less (19). 

Quaternary Salts. Herbicides paraquat (20) and diquat (59) are the quaternary salts of 4,4 -bipyridine (19) and 2,2 -bipyridine with methyl chloride and 1,2-dibromoethane, respectively. Higher alkylpyridinium salts are used in the textile industry as dye ancillaries and spin bath additives. The higher alkylpyridinium salt, hexadecylpytidinium chloride [123-03-5] (67) (cetylpyridinium chloride) is a topical antiseptic. Amprolium (62), a quaternary salt of a-picohne (2), is a coccidiostat. Bisaryl salts of butylpyridinium bromide (or its lower 1-alkyl homologues) with aluminum chloride have been used as battery electrolytes (84), in aluminum electroplating baths (85), as Friedel-Crafts catalysts (86), and for the formylation of toluene by carbon monoxide (87) (see QuaternaryAA ONiUM compounds). 

Friedel-Crafts Acylation. The Friedel-Crafts acylation procedure is the most important method for preparing aromatic ketones and thein derivatives. Acetyl chloride (acetic anhydride) reacts with benzene ia the presence of aluminum chloride or acid catalysts to produce acetophenone [98-86-2], CgHgO (1-phenylethanone). Benzene can also be condensed with dicarboxyHc acid anhydrides to yield benzoyl derivatives of carboxyHc acids. These benzoyl derivatives are often used for constmcting polycycHc molecules (Haworth reaction). For example, benzene reacts with succinic anhydride ia the presence of aluminum chloride to produce P-benzoylpropionic acid [2051-95-8] which is converted iato a-tetralone [529-34-0] (30). 

Allylmagnesium bromide, 41, 49 reaction with acrolein, 41, 49 5-Allyl-l,2,3,4,5-pentachlorocyclopen-tadiene, 43, 92 Allyltriphenyltin, 41, 31 reaction with phenyllithium, 41, 30 Aluminum chloride, as catalyst, for isomerization, 42, 9 for nuclear bromination and chlorination of aromatic aldehydes and ketones, 40, 9 as Friedel-Crafts catalyst, 41, 1 Amidation, of aniline with maleic anhydride, 41, 93... 

The first compounds of this class46 have been obtained via Route A. The initial condensation of phthalic anhydride with dimethylaniline requires a Friedel-Crafts catalyst, while condensation of the resulting benzophenone with the indole requires acetic anhydride. For Route B preparation of the intermediate l,2-dimethyl-3-(2-carboxybenzoyl)indole has also been described47 by condensation of the two components in the presence of aluminum chloride. However, in our experience, aluminum chloride is, in this case, unnecessary, thus rendering this route the method of choice. 

Friedel became internationally known for the synthetic method called the Friedel-Crafts Reaction using aluminum chloride as a catalyst in the the introduction of an alkyl or acyl group into benzene. James Mason Crafts was an American professor from MIT working with Friedel in 1877 at the Sorbonne. Crafts later became president of MIT. 

The metal halide catalysts include aluminum chloride, aluminum bromide, ferric chloride, zinc chloride, stannic chloride, titanium tetrachloride and other halides of the group known as the Friedel-Crafts catalysts. Boron fluoride, a nonmetal halide, has an activity similar to that of aluminum chloride. 

Aluminum chloride, boron fluoride and certain other Friedel-Crafts catalysts catalyze the polymerization of isobutylene, at temperatures below about —70° recent work has indicated that the presence of a promoter such as water is usually necessary (see Section V). A rubberlike polymer is obtained. 

The low temperature polymerization of isobutylene (that is, polymerization at temperatures below about —70°) in the presence of Friedel-Crafts catalysts (particularly boron fluoride, aluminum chloride, and titanium tetrachloride, has been studied quite intensely. The reaction is commercially important because it yields a high molecular weight... 

The catalytic activity of certain of the Friedel-Crafts catalysts was shown to decrease over a very wide range in the series boron fluoride, aluminum bromide, titanium tetrachloride, titanium tetrabromide, boron chloride, boron bromide and stannic chloride (Fairbrother and Seymour, mentioned in Plesch al., 83). When boron fluoride is added to isobutylene at dry ice temperatures, the olefin is converted to a solid polymer within a very few seconds. The time required for complete polymerization with aluminum bromide hardly extends to a few minutes while reaction times of hours are required with titanium chloride and periods of days with stannic chloride. 

In carrying out the alkylation of benzene the propylene tetramer is reacted with an excess of benzene in the presence of a Friedel-Crafts catalyst such as aluminum chloride, boron trifluoride, or hydrofluoric acid. With careful control of this reaction, yields of alkylate boiling from 500° to 650° F. are of the order of 80% of theory with the losses due to slight olefin degradation and dialkylation. Inspection of commercial aromatic products, believed to be typical of this process, indicates the composition to be that shown in... 

Besides aluminum chloride, the most often used and studied Friedel-Crafts catalyst, many other acid catalysts are effective in alkylation. Although Friedel-Crafts alkylation was discovered and explored mainly with alkyl halides, from a practical point of view, alkenes are the most important alkylating agents. Others include alcohols, ethers, and esters. 

Inflates of aluminum, gallium and boron, which are readily available by the reaction of the corresponding chlorides with triflic acid, are effective Friedel-Crafts catalysts for alkylation and acylation of aromatic compounds [119, 120] Thus alkylation of toluene with various alkyl halides in the presence of these catalysts proceeds rapidly at room temperature 111 methylene chloride or ni-tromethane Favorable properties of the Inflates in comparison with the correspond 1 ng fluorides or chlorides are considerably decreased volatility and higher catalytic activity [120]... 

Alkylation. Ethylbenzene [100-41-4], the precursor of styrene, is produced from benzene and ethylene. The ethylation of benzene is conducted either in the liquid phase in the presence of a Friedel-Crafts catalyst (A1C13, BF3, FeCl3) or in the vapor phase with a suitable catalyst. The Monsanto/Lummus process uses an aluminum chloride catalyst that yields more than 99% ethylbenzene (13). More recently, Lummus and Union Oil commercialized a zeolite catalyst process for liquid-phase alkylation (14). Badger and Mobil also have a vapor-phase alkylation process using zeolite catalysts (15). Almost all ethylbenzene produced is used for the manufacture of styrene [100-42-3], which is obtained by dehydrogenation in the presence of a suitable catalyst at 550—640°C and relatively low pressure, <0.1 MPa (<1 atm). 

In Chapter 1, we arbitrarily defined Lewis superacids as those that are stronger than anhydrous aluminum chloride in their reactivity, the most commonly used Friedel-Crafts catalyst. Of course, Lewis acidity is only a relative term concerning specific bases and involved counterions (association, steric hindrance, etc.). The physical properties of some of the Lewis superacids are given in Table 2.3. 

Sulfonation of aromatic compounds is generally carried out with sulfuric acid, halosulfuric acids, or sulfur trioxide as reagent with or without solvent.458,459 Friedel-Crafts catalysts such as aluminum chloride and boron trifluoride are effective catalysts in certain sulfonations with sulfuric acid and chlorosulfuric acid. 

The halogenation of a wide variety of aromatic compounds proceeds readily in the presence of ferric chloride, aluminum chloride, and related Friedel-Crafts catalysts. Halogenating agents generally used are elemental chlorine, bromine, or iodine and interhalogen compounds (such as iodine monochloride, bromine monochloride, etc.). These reactions were reviewed554 and are outside the scope of the present discussion. 

The importance of acyl cations in acetylation is indicated in several studies (Gore, 1955). Friedel-Crafts catalysts alter the rate of acylation but do not modify the selectivity of the reaction. For example, the antimony pentachloride-catalyzed benzoylation of toluene proceeds 1.3 x 103 more rapidly than the aluminum chloride-catalyzed reaction. 

Ethylbenzene (boiling point 136°C, density 0.8672, flash point 21°C) is a colorless liquid that is manufactured from benzene and ethylene by several modifications of the older mixed liquid-gas reaction system using aluminum chloride as a catalyst (Friedel-Crafts reaction). The reaction takes place in the gas phase over a fixed-bed unit at 370 C under a pressure of 1450 to 2850 kPa. Unchanged andpolyethylated materials are recirculated, making a yield of 98 percent possible. The catalyst operates several days before requiring regeneration. 

A typical cationic polymerization is conducted with highly purified monomer free of moisture and residual alcohol, both of which act as inhibitors, in a suitably dry unreactive solvent such as toluene with a Friedel-Crafts catalyst, eg, boron trifluoride, aluminum trichloride, and stannic chloride. Usually low temperatures (—40 to — 70° C) are favored in order to prevent chain-transfer or sidereactions. 

Within the last few years, it has conclusively been demonstrated that the Diels-Alder reaction is susceptible to catalysis with Lewis acids or Friedel-Crafts catalysts such as aluminum chloride (15, 18, 36, 37, 38, 39, 40, 57, 67, 68, 69, 70, 71, 82, 86). As a result of catalysis, it was possible to change the following ... 

Friedel-Crafts alkylation of benzene was first commercialized for ethylbenzene and cumene in the 1940s. Aluminum chloride is the Friedel-Crafts catalyst, and the process is operated in the liquid phase. Several alternatives to aluminum chloride technology were developed later, but zeolitic catalysts are a rather recent introduction. UOP began using zeolitic catalysts in the 1990s. 

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