Reaction alkylation of benzene

Alkylation of benzene with linear monoolefms is industrially preferred. The Detal process (Figure 10-9) combines the dehydrogenation of n-paraffins and the alkylation of benzene. Monoolefms from the dehydrogenation section are introduced to a fixed-bed alkylation reactor over a heterogeneous solid catalyst. Older processes use HF catalysts in a liquid phase process at a temperature range of 40-70°C. The general alkylation reaction of benzene using alpha olefins could be represented as ... 

Mechanism of the Friedel-Crafts alkylation reaction of benzene with 2-chloropropane to yield isopropylbenzene (cumene). 

Superacids were shown to have the ability to effect the protolytic ionization of a bonds to form carbocations even in the presence of benzene.190 The formed car-bocations then alkylate benzene to form alkylbenzenes. The alkylation reaction of benzene with Ci—C5 alkanes (methane, ethane, propane, butane, isobutane, isopentane) are accompanied by the usual acid-catalyzed side reactions (isomerization, disproportionation). Oxidative removal of hydrogen by SbF5 is the driving force of the reaction ... 

The synthetic detergents industry originated in the 1940s, when it was found that a new anionic surfactant type—alkylbenzene sulfonate—had detergent characteristics superior to those of natural soaps. The first surfactant of this kind was sodium dodecylbenzene sulfonate (SDBS). This material was produced by the Friedel-Crafts alkylation reaction of benzene with propylene tetramer (a mixture of Co olefin isomers), followed by sulfonation with oleum or sulfur trioxide and then neutralization, usually with sodium hydroxide. The alkylation was typically performed using homogenous acid catalysts, such as HF or sulfuric acid. 

These types of supported chloroaluminate-based, Lewis-acidic ILs were tested for the alkylation reaction of benzene with dodecene. In these investigations the supported catalysts showed improved activity and selectivity as compared to the... 

Alkylation of Aromatics with Liquid Catalysts. Forty years ago, ethylbenzene, cumene, and dodecyl benzenes were produced by alkylation reactions of benzene with liquid catalysts. Although some production processes still involve these catalysts, solid catalysts such as zeolites are now often the preferred catalysts. Olefins are generally employed for commercial alkylation reactions. The chemistry discussed next will involve liquid catalysts that are protonic acids or Friedel-Crafts catalysts. 

Mechanism of the Friedel-Crafts alkylation reaction of benzene with 2-chloropropane to yield isopropylbenzene (cumene). The electrophile is a carbocation, generated by AlCl3-assisted dissociation of an alkyl halide. 

Because of isomerization, alkylation of benzene with tertiary alkyl haUdes can also yield secondary alkylbenzenes rather than only tertiary alkylbenzenes (20). For example, the / fAhexylbenzene, which is first formed by the reaction of benzene with 2-chloro-2,3-dimethylbutane and AlCl isomerizes largely to 2,2-dimethyl-3-phenylbutane by a 1,2-CH2 shift. With ferric chloride as the catalyst, / fAhexylbenzene does not undergo isomerization and is isolated as such. 

Ethjlben ne Synthesis. The synthesis of ethylbenzene for styrene production is another process in which ZSM-5 catalysts are employed. Although some ethylbenzene is obtained direcdy from petroleum, about 90% is synthetic. In earlier processes, benzene was alkylated with high purity ethylene in liquid-phase slurry reactors with promoted AlCl catalysts or the vapor-phase reaction of benzene with a dilute ethylene-containing feedstock with a BF catalyst supported on alumina. Both of these catalysts are corrosive and their handling presents problems. 

Fluorobenzene is readily alkylated with alkenes in the presence of protic acids, however, the isomenc purity of the product is poor, and polysubstitution can result Thus, propene and sulfuric acid alkylate fluorobenzene at 20 C to yield a 45 55 ortho/para ratio of the inonoalkyl product m addition to di- and triiso propylfluorobenzene [i5] The reaction of benzene and trifluoropropene at 25 °C in HF-BF3 gives a mixture of mono-, bis-, and tns(3,3,3-trifluoropropyl)ben zene [72, 75] (equation 12)... 

Tnfluoroacetic anhydnde in a mixture with sulfuric acid is an efficient reagent for the sulfonylation of aromatic compounds [44] The reaction of benzene with this system in nitromethane at room temperature gives diphenyl sulfone in 61% yield Alkyl and alkoxy benzenes under similar conditions form the corresponding diaryl sulfones in almost quantitative yield, whereas yields of sulfones from deactivated arenes such as chlorobenzene are substantially lower [44] The same reagent (tnfluoroacetic anhydride-sulfunc acid) reacts with adamantane and its derivatives with formation of isomeric adamantanols, adamantanones, and cyclic sultones [45]... 

Keim and co-workers have carried out various alkylation reactions of aromatic compounds in ionic liquids substantially free of Lewis acidity [84]. An example is the reaction between benzene and decene in [BMIM][HS04], which was used together with sulfuric acid as the catalyst (Scheme 5.1-54). These authors have also claimed that these acid-ionic liquids systems can be used for esterification reactions. 

Aromatic compounds such as benzene react with alkyl chlorides in Ihe presence of AlCl i catalyst to yield alkylbenzenes. The reaction occurs through a carbocation intermediate, formed by reaction of the alkyl chloride with AICI3 (R—Cl + A1CI 1 - U+ + AICl4 ). How can you explain the observaiion that reaction of benzene with 1-chloropropane yields isopropylbenzene as the major product ... 

Just as an aromatic ring is alkylated by reaction with an alkyl chloride, it is acylated by reaction with a carboxylic acid chloride, RCOC1, in the presence of AICI3. That is, an acyl group (-COR pronounced a-sil) is substituted onto the aromatic ring. For example, reaction of benzene with acetyl chloride yields the ketone, acetophenone. 

The carbocation electrophile in a Friedel-Crafts reaction can be generated in ways other than by reaction of an alkyl chloride with AICI3. For example, reaction of benzene with 2-methylpropene in the presence of H3PO4 yields tert-butylbenzene. Propose a mechanism for this reaction. 

The results obtained from the alkylation reaction of (oj,m-dichloroalkyl)silanes with excess benzene are summarized in Table X. 

Many important reactions involve catalysis by Lewis acids or bases. One of the most important of these is the type of reaction carried out by Charles Friedel and James Crafts. These reactions, known as the Friedel-Crafts reactions, actually involve several types of important processes. One of these is alkylation, which is illustrated by the reaction of benzene with an alkyl halide in the presence of A1C13, a strong Lewis acid. 

If a higher ratio of alkylating agent to PX3 is used, the dialkyl and trialkyl compounds can also be obtained. At high temperature, the reaction of benzene and PC13 produces phenyldichlorophosphine, CsH5PC12, an intermediate in the preparation of parathion. 

Two other myo-inositol derivatives have been selectively alkylated. Reaction of DL-l,2 4,5-di-0-cyclohexylidene-myo-inositol with benzyl chloride-potassium hydroxide in benzene, followed by removal of the acetal groups, gave DL-1-O- and DL-4-O-benzyl-myu-inositol in the ratio of 5 2, whereas, under similar conditions, DL-1,2 5,6-O-cyclohexylidene-myo-inositol gave311 the same ethers in the ratio of 57 10. These results are not readily explicable in the absence of knowledge of the conformations adopted by the cyclic acetals. 

The most fundamental reaction is the alkylation of benzene with ethene.38,38a-38c Arylation of inactivated alkenes with inactivated arenes proceeds with the aid of a binuclear Ir(m) catalyst, [Ir(/x-acac-0,0,C3)(acac-0,0)(acac-C3)]2, to afford anti-Markovnikov hydroarylation products (Equation (33)). The iridium-catalyzed reaction of benzene with ethene at 180 °G for 3 h gives ethylbenzene (TN = 455, TOF = 0.0421 s 1). The reaction of benzene with propene leads to the formation of /z-propylbenzene and isopropylbenzene in 61% and 39% selectivities (TN = 13, TOF = 0.0110s-1). The catalytic reaction of the dinuclear Ir complex is shown to proceed via the formation of a mononuclear bis-acac-0,0 phenyl-Ir(m) species.388 The interesting aspect is the lack of /3-hydride elimination from the aryliridium intermediates giving the olefinic products. The reaction of substituted arenes with olefins provides a mixture of regioisomers. For example, the reaction of toluene with ethene affords m- and />-isomers in 63% and 37% selectivity, respectively. 

Two types of complex are formed on reaction of benzene with Cu montmorillonite. In the Type 1 species the benzene retains Its aromaticity and is considered to be edge bonded to the Cu(II), whereas in the Type 2 complex there is an absence of aromaticity (85,86). ESR spectra of the Type 2 complex consist of a narrow peak close to the free spin g-value and this result can be explained in terras of electron donation from the organic molecule to the Cu(II), to produce a complex of Cu(I) and an organic radical cation. Similar types of reaction occur with other aromatic molecules. However with phenol and alkyl-substituted benzenes only Type 1 complexes were observed (87), although both types of complex were seen on the adsorption of arene molecules on to Cu(II) montmorillonites (88) and anisole and some related aromatic ethers on to Cu(II) hectorite... 

Pines, H., W. D. Huntsman and V. N. Ipatieff Isomerization Accompanying Alkylation. VII. Reaction of Benzene with Methylcyclopropane, Ethylcyclopropane and with Dimethylcyclopropanes. J. Amer. chem. Soc. 73, 4343 (1951). 

In the polyalkylation reaction of benzene with allylchlorosilanes, trialkylated compounds are the most substituted products obtained in appreciable amount due to increased steric interactions with additional allyltrichlorosilane. This is the case even when more than a four-fold excess of allyltrichlorosilane is used. In addition, multi-step alkylation reactions give the trialkylated products in higher yields than the one-step reaction. 

Acid-catalyzed reactions of aromatics with monoolefins result in nuclear alkylation. But the base-catalyzed reactions of aromatics with olefins do not result in nuclear alkylation as long as benzylic hydrogens are available. This is true even with aromatics, such as cumene, which have deactivated benzylic hydrogens resulting in facile metalation of the ring. Apparently phenyl carbanions do not readily add to olefins. Pines and Mark (20) found that in the presence of sodium and promoters only small yields of alkylate were produced at 300° in reactions of benzene with ethylene and isobutylene and of t-butylbenzene with ethylene. With potassium, larger yields may be obtained at 190° (24)-... 

The alkylation product of benzene (W) and ferf-butylbenzene (S4) with ethylene yields predominantly sec-butyl alkylates. This is the case because the ethylbenzene alkylate formed reacts very rapidly in the normal side-chain alkylation reaction. The sec-butyl aromatic alkylates much less readily. The much greater ease of side-chain alkylation over nuclear alkylation also accounts for the exclusive formation of side-chain alkylates from compounds, such as cumene, that are predominantly metalated on the ring by alkylalkali metal compounds. 

More recently, Kim and coworkers have developed a novel radical alkylation reaction of organic nitro derivatives 16a-d via bis(silyloxy)enamines 17a-d (Scheme 16). This method enables not only P -alkylation to the nitro gronp, bnt also the conversion of the nitro group (16a-d) into an oxime ether fnnctionahty (18a-d). The irradiation of a solntion of 16a-d with iodomethyl phenyl snlfone (or ethyl iodoacetate) and hexamethylditin in benzene at 300 nm give the oxime ethers 18a-d in good yields. 

In a similar manner to that described for bicyclic lactams (Section 1.1.1.3.3.4.1.5.I.). alkylation reactions of tricyclic lactams, which contain a fused benzene ring adjacent to the carbon undergoing alkylation, have been exploited14. The first alkylation of the benzo-annulated bicyclic lactam 1 gives a mixture of diastereomers, which is then further alkylated. In the second alkylation step, the counterion on the alkoxide, which is formed prior to enolate formation, proved to be crucial for the diastereoselectivity of the subsequent alkylation reaction. The best diastcrcoselectivity was obtained when either dichlorobis(ij5-cyclopentadienyl)zirconium or triisopropoxytitanium chloride was added to the preformed alkoxide, followed by enolization and alkylation. Using this method the second alkylation step gives a satisfactory diastereoselectivity. Hydride reduction of the purified major diastereomer 2, followed by acid treatment of the product, furnishes chiral naphthalenones 414. 

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