Alkylation with propene

Ethylation, which involves an unstable ethylcarbenium ion as intermediate, is much slower (1500 times over AICI3) than isopropylation. It is also the case in benzene alkylation with propene for the undesired formation of n-propylbenzene, which involves a primary n-propyl carbocation. Furthermore, as alkyl substituents activate the aromatic ring, consecutive alkylation of the primary product occurs with a greater rate than the first alkylation step ( 2 > i)-... 

Tphe rate-limiting processes in catalytic reaction over zeolites remain A largely undefined, mainly because of the lack of information on counterdiffusion rates at reaction conditions. Thomas and Barmby (7), Chen et al. (2, 3), and Nace (4) speculate on possible diffusional limitations in catalytic cracking over zeolites, and Katzer (5) has shown that intracrystalline diffusional limitations do not exist in liquid-phase benzene alkylation with propene. Tan and Fuller (6) propose internal mass transfer limitations and rapid fouling in benzene alkylation with cyclohexene over Y zeolite, based on the occurrence of a maximum in the reaction rate at about 100 min in flow reaction studies. Venuto et al (7, 8, 9) report similar rate maxima for vapor- and liquid-phase alkylation of benzene and dehydro-... 

Cumene is obtained from benzene by FfiedeNDrafts alkylation with propene. 

Acid-t T)e catalysts. Sulfuric acid of 96-98% concentration catalyzes the alkylation of isoparaffins with butenes and higher molecular weight olefins at 0-20°. Alkylation with propene requires acid of 98-100% concentration and a temperature of 30 . Alkylation with ethylene has not been very successful, presumably because stable ethyl hydrogen sulfate or diethyl sulfate forms too readily. 

Typical yields of alkylate obtained in plants operated during World War II were in the order of 1-2 gallons per pound of catalyst in the alkylation of isobutane with butylenes and only about 0.5 gallon per pound for alkylation with propene or amylenes (Anonymous, 39). The octane numbers of the alkylates (175° end point) obtained with butylenes, propene, and amylenes were about 92-94, 88-89, and 89-90, respectively. 

Naphthalene has been alkylated with propene over the polymeric catalyst In the gas phase. At 220°C, the yield of isopropylnaphthalene Is 37% with the 6-Isomer being 90% (52). 

The starting material for the Haarmann-Reimer process is m-cresol, which is alkylated with propene. Hydrogenation then produces the racemates of menthol, neomenthol, isomenthol and neoisomenthol. Although the boiling points lie... 

Studies by Kiersznicki and co-workers demonstrated that chlorosulfonic acid is an effective catalyst in the alkylation of arenes by reaction with alkenes. Benzene, toluene and ethylbenzene were alkylated by propene, elhene and 2-butene in the presence of chlorosulfonic acid which strongly catalysed the alkylations and inhibited polyalkylation. Increasing the concentration of the catalyst enhanced the proportion of /7-isomers in the products. Fluoro-, chloro-and bromobenzenes were similarly alkylated by reaction with C2-C4 alkenes using chlorosulfonic acid as catalyst. The optimum alkylation conditions were with a halobenzene alkene ratio of 1 0.25, a catalyst concentration of 0.33 mol mol" of fluorobenzene and 0.5 mol mol of the other halobenzenes, a temperature of 70 C and a reaction time of 2 hours. Alkylation with propene gave haloisopropylbenzenes the monoalkyl products were obtained as o-, m- and p- mixtures, the relative amounts depended on the quantity of catalyst used and the by-products were dialkyl derivatives, sulfonic acids and sulfones. In the reaction of benzene with propene, fluorosulfonic acid was a more potent alkylation catalyst than chlorosulfonic acid. ... 

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)... 

Phthalimidobutyl)-2,3,4,4u,5,6-hexahydro-l//-pyrazino[l,2-u]quino-line was obtained in the reaction of 2,3,4,4u,5,6-hexahydro-l//-pyrazino[l,2-u]quinoline and A-(4-bromobutyl)phthalimide in boiling MeCN in the presence of K2CO3 (97MIP12). 2,3,4,4u,6,7-He-xahydro-l//-pyrazino[l,2-ujquinolines were N-alkylated with 3-dimethylaminomethyl-l//-pyrrolo[2,3-6]pyridine and a mixture of l//-pyrrolo[2,3-6]pyridine and 37% aqueous H2CO in aqueous AcOH in the presence of NaOAc (96USP5576319). 3-[3-Substituted 2-propen-l-yl]-2,3,4,4u, 5,6-hexahydro-l//-pyrazino[l,2-u]qui-... 

Olivier and Berger335, who measured the first-order rate coefficients for the aluminium chloride-catalysed reaction of 4-nitroben2yl chloride with excess aromatic (solvent) at 30 °C and obtained the rate coefficients (lO5/ ) PhCI, 1.40 PhH, 7.50 PhMe, 17.5. These results demonstrated the electrophilic nature of the reaction and also the unselective nature of the electrophile which has been confirmed many times since. That the electrophile in these reactions is not the simple and intuitively expected free carbonium ion was indicated by the observation by Calloway that the reactivity of alkyl halides was in the order RF > RC1 > RBr > RI, which is the reverse of that for acylation by acyl halides336. The low selectivity (and high steric hindrance) of the reaction was further demonstrated by Condon337 who measured the relative rates at 40 °C, by the competition method, of isopropylation of toluene and isopropylbenzene with propene catalyzed by boron trifluoride etherate (or aluminium chloride) these were as follows PhMe, 2.09 (1.10) PhEt, 1.73 (1.81) Ph-iPr, (1.69) Ph-tBu, 1.23 (1.40). The isomer distribution in the reactions337,338 yielded partial rate factors of 2.37 /mMe, 1.80 /pMe, 4.72 /, 0.35 / , 2.2 / Pr, 2.55337 339. 

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. 

Theoretically, even the direct alkylation of carbenium ions with isobutane is feasible. The reaction of isobutane with a r-butyl cation would lead to 2,2,3,3-tetramethylbutane as the primary product. With liquid superacids under controlled conditions, this has been observed (52), but under typical alkylation conditions 2,2,3,3-TMB is not produced. Kazansky et al. (26,27) proposed the direct alkylation of isopentane with propene in a two-step alkylation process. In this process, the alkene first forms the ester, which in the second step reacts with the isoalkane. Isopentane was found to add directly to the isopropyl ester via intermediate formation of (non-classical) carbonium ions. In this way, the carbenium ions are freed as the corresponding alkanes without hydride transfer (see Section II.D). This conclusion was inferred from the virtual absence of propane in the product mixture. Whether this reaction path is of significance in conventional alkylation processes is unclear at present. HF produces substantial amounts of propane in isobutane/propene alkylation. The lack of 2,2,4-TMP in the product, which is formed in almost all alkylates regardless of the feed (55), implies that the mechanism in the two-step alkylation process is different from that of conventional alkylation. 

With propene, n-butene, and n-pentene, the alkanes formed are propane, n-butane, and n-pentane (plus isopentane), respectively. The production of considerable amounts of light -alkanes is a disadvantage of this reaction route. Furthermore, the yield of the desired alkylate is reduced relative to isobutane and alkene consumption (8). For example, propene alkylation with HF can give more than 15 vol% yield of propane (21). Aluminum chloride-ether complexes also catalyze self-alkylation. However, when acidity is moderated with metal chlorides, the self-alkylation activity is drastically reduced. Intuitively, the formation of isobutylene via proton transfer from an isobutyl cation should be more pronounced at a weaker acidity, but the opposite has been found (92). Other properties besides acidity may contribute to the self-alkylation activity. Earlier publications concerned with zeolites claimed this mechanism to be a source of hydrogen for saturating cracking products or dimerization products (69,93). However, as shown in reaction (10), only the feed alkene will be saturated, and dehydrogenation does not take place. 

Table III provides a comparison of alkylate compositions for both the liquid acid-catalyzed reactions with various feed alkenes. The data show that H2SO4 produces a better alkylate with 1-butene, whereas HF gives better results with propene or isobutylene. The products from 2-butene and also from pentenes (not shown in Table III) are nearly the same with either acid.

Special interest attaches to the cyclic aliphatic hydrocarbons. Cyclopropane can be converted to oligomers by cationic catalysis [75, 76], and these appear to be essentially linear but whether they are really different from the polypropenes formed under the same conditions from propene is not yet settled. The initiation most probably involves formation of a non-classical cyclopropyl ion [77], as in alkylations with cyclopropane [78],... 

In MeOH the hydride reacts with higher a-olefins, propene, 1-hexene and 1-hexadecene with formation of only the linear insertion product, probably for steric reasons. In all the insertion products, the alkyl ligand presents the /f-agoslic interaction. At room temperature, the insertion of ethene is quantitative whereas with propene an appreciable amount of the hydride is present, with 1-hexene the hydride prevails, with 1-hexadecene only the hydride is present. The fact that the position of the insertion equilibrium strongly depends on the chain length of the alkyl substituent is probably connected with the high steric hindrance of the ligand [115]. 

Cyclopentadienyl ligands have become extremely important in catalysis for metal such as Ti, Zr, and Hf (Chapter 10) and in academic studies of related elements such as Ta. Ethylene polymerisation with the use of CpiTiCE (alkylated with aluminium alkyl compounds) has been known for many decades, but the intensive interest in derivatives of these compounds started in the early 1980 s following the discovery of MAO (methaluminoxane - see chapter 10) which boosted metallocene catalyst activities by several orders of magnitude. Commercial interest focussed on ethylene copolymers (LLDPE where more homogeneous comonomer incorporation resulted in greatly improved copolymer properties) and in enantiospecific polymerisations for propene, styrene, etc. 

Rigoreau, J., Laforge, S., Gnep, N.S., and Guisnet, M. (2005) Alkylation of toluene with propene over H-MCM-22 zeolite, location of the main and secondary reactions. /. Catal., 236, 45-54. 

In contrast, there are relatively few publications on the conversion of polynuclear aromatics in zeolite catalysts. Lee et al. [16] found unusually high selectivities for 4,4 -diisopropylbiphenyl when dealuminated mordenite was used as catalyst for the alkylation of biphenyl with propene. The reactions of 1- and 2-methylnaphthalene on acid forms of zeolite X, Y, Omega, mordenite and ZSM-5 were studied byDimitrov etal. [17], S o 1 i n a s et... 

Table 1. Catalytic Alkylation of Biphenyl with Propene...

Shape selectivity was strongly Influenced by the bulkiness of alkylating agents. The alkylation with ethene was nonselectlve. However, the alkylation with higher olefins occurred para-selectively as in the case of propene. These differences in para-selectivlty reflect the sterlc circumstances of transition... 

Alkylation of m-cresol with propene in the presence of an aluminium catalyst results in the formation of thymol, which upon hydrogenation gives a rnkture of all eight isomers of menthol, D-menthol, L-menthol, neomenthol, isomenthol and neoisomenthol (Scheme 13.3). The preferred isomer is L-menthol, because of its ability to induce physiologically the sense of cold which is desired in many products such as chewing gum and toothpaste L-menthol is about... 

Formation of C8 alkanes in the alkylation of isobutane even when it reacts with propene or pentenes is explained by the ready formation of isobutylene in the systems (by olefin oligomerization-cleavage reaction) (Scheme 5.2). Hydrogen transfer converting an alkane to an alkene is also a side reaction of acid-catalyzed alkylations. Isobutylene thus formed may participate in alkylation Cg alkanes, therefore, are formed via the isobutylene-isobutane alkylation. 

Benzene alkylation with ethene was studied over HY, LaY, and SK-500 between 488° and 599°K and for C6 C2 from 0.7 to 10. Ethylbenzene ethylation was also studied. For propene alkylation, conditions were similar except that the temperature range was 350° to 493°K, and the study was less complete than for the ethene system. The experimental rate data typically exhibited a maximum with respect to time and underwent extended decay (Figure 1). The location of the peak is a function of reaction conditions, particularly temperature. The propene system deactivated more rapidly than the ethene system. Data for the ethene system were reproducible to 10%. 

Similarly, benzo[6]thiophene also yields mixtures of 2- and 3-alkyl derivatives on alkylation with alkenes or alkanols in the presence of acids <70AHC(11)177). Thus with isopropyl chloride, isopropanol or propene, mixtures of 2- and 3-isopropyl derivatives are formed. Alkylation by 2-methylpropene in the presence of PPA gives 2-7-butyl- (22%) and 3-7-butyl-(71%) benzo[6]thiophenes with 7-butanol and cone. H2S04, the yields are 2-7-butyl (6%) and 3-7-butyl (89%) (72JCS(Pl)414). 

Friedel-Crafts alkylation of benzo[6]thiophene has received little attention. The published results, which deserve reexamination, indicate that exclusive 3-substitution occurs in some cases, whereas in others, 2-substitution predominates. Benzo[6]thiophene is alkylated with isopropyl chloride, isopropanol, or propene in the presence of various acid catalysts under a variety of reaction conditions to give a mixture of 2- and 3-isopropylbenzo[6]thiophene in which the 2-isomer predominates (78-92%).358 410 In contrast, alkylation with isobutene in the presence of either 80% sulfuric acid415 or 100% phosphoric acid416 is said to afford exclusively 3-/er<-butylbenzo[6]thiophene in yields of 100 and 75%, respectively. In neither case was the structure of the product rigorously confirmed. Likewise, 3-Jeri-amylbenzo [63-thiophene is the exclusive product of alkylation with tert-amyl alcohol in the presence of stannic chloride414 alkylation with pent-l-ene, hex-l-ene, and a Ci8 propylene polymer is also claimed to give... 

Superacid-catalyzed alkylation of adamantane with lower alkenes (ethene, propene, isomeric butenes) has been investigated by Olah et al.151 in triflic acid and triflic acid-B(0S02CF3)3. Only trace amounts of 1 -ferf-butyladamantane (37) were detected in alkylation with 1- and 2-butenes, whereas isobutylene gave consistently relatively good yield of 37. Since isomerization of isomeric 1-butyladamantane under identical conditions did not give even traces of 37, its formation can be accounted for by (r-alkylation, that is, through the insertion of the ferf-butyl cation into the C—H bond (Scheme 5.22). This reaction is similar to that between ferf-butyl cation and isobutane to form 2,2,3,3-tetramethylbutane discussed above (Scheme 5.21). In either case, the pentacoordinate carbocation intermedate, which may also lead to hydride transfer, does not attain a linear geometry, despite the unfavorable steric interactions. 

Friedel Crafts alkylation has been studied by Poliakoff in a continuous-flow reactor (Hitzler et al., 1998a). The reaction of mesitylene and anisole with propene or 2-propanol over a solid acid catalyst (based on a Deloxan support) in sc C02 provided exclusive formation of the monoalkylated products at 50% conversion. Use of the continuous-flow reactor prevents catalyst deactivation, and permits use of comparatively small reactors. The... 

Isopropylbenzene may also be prepared by alkylation of benzene with propene in the presence of sulfuric acid. 

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