Propene, alkylation

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. 

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%. 

The activation energy for the rate decay time constant with benzene ethylation over SK-500 at C6. C2 = 8 is 13.6 1 kcal/mole. That for HY in the ethene system at Ce C2 = 2 is 11 kcal/mole. For propene alkylation over HY the activation energy for rate decay is 4 kcal/mole and is independent of C6 0 8 mole ratio. 

The composition of a large number of alkylates, both those prepared in the laboratory using pure hydrocarbons and those obtained on a commercial scale using olefin mixtures, has been investigated. The principal products are for the most part similar to those obtained in the presence of the metal halide catalyst, the chief difference being in the relative amounts of the various isomers. Alkylation of isobutane ivith propene at 30° in the presence of 98% sulfuric acid yielded an alkylate that was 62-66% by weight 2,3-dimethylpentane and 8-12%, 2,4-dimethylpentane propane and trimethylpentanes (11-19%) were also obtained (McAllister et al., 12). A commercial isobutane-propene alkylate obtained at 21° was shown to contain about 36% by volume of 2,3- and 26% of 2,4-dimethylpentane as well as 15% of trimethylpentanes (Glasgow et al., 40). 

The cyclopropane ring represents an interesting intermediate between alkanes and alkenes. Theoreticians have had great fun with this molecule, for which no simple (i.e. non-wave mechanical) picture is satisfactory. There is certainly some electron density in the middle of the ring, and it can be hydrogenated to propane quite easily, although less easily than propene. Alkyl- and alkenylcyclopropanes react in interesting ways (Chapters 7 and 11). 

In a widely used industnal process the mixture of ethylene and propene that is obtained by dehydrogenation of natural gas is passed into concentrated sulfunc acid Water is added and the solution IS heated to hydrolyze the alkyl hydrogen sulfate The product is almost exclusively a sin gle alcohol Is this alcohol ethanol 1 propanol or 2 propanoH Why is this particular one formed almost exclusively" ... 

The degree to which allylic radicals are stabilized by delocalization of the unpaired electron causes reactions that generate them to proceed more readily than those that give simple alkyl radicals Compare for example the bond dissociation energies of the pri mary C—H bonds of propane and propene... 

Methylisoxazole (297 R = Me) and its homologs can be synthesized by reaction of hydroxylamine hydrochloride with 1-alkyl-3-dimethylamino-2-propen-l-one (296) (54IZV47), the anilino derivatives of acetoacetaldehyde (47G556), 3-dimethyl-aminomethylene-l-propyne (equation 7) (69ZOR1179) and the /3-ketoaldehyde (293) (66JOC3193). 

Polymerization - Polymerization is occasionally used to convert propene and butene to high octane gasoline blending components. The process is similar to alkylation in its feed and products, but is often used as a less expensive... 

Toxicity and Environmental Fate Information for Propylene CAS 115-07-1 Sourtes. Propylene (propene) is one of the light ends formed during catalytic and thermal cracking and coking operations, it is usually collected and used as a feedstock to the alkylation unit. Propylene is volatile and soluble in water making releases to both air and water significant. 

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)... 

Similarly alkylation (55) of l-N-pyrrolidino-2-methyl-l-propene (22) with propargyl bromide gave initial N alkylation to (23) with subsequent rearrangement to the allene (24). 

Coordination of the ethene or propene to Ti polarizes the C-C bond and allows ready migration of the alkyl group with its bonding electron-pair. This occurs as a concerted... 

The rates of hydration of alkenes increase dramatically with increasing alkyl substitution (see table at left). This is usually attributed to the relative stabilities of carbocations formed as intermediates in the initial (and rate-hmiting) step of the reaction, e.g., for hydration of propene. 

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-... 

Either concentrated sulfuric acid or anhydrous hydrofluoric acid is used as a catalyst for the alkylation reaction. These acid catalysts are capable of providing a proton, which reacts with the olefin to form a carbocation. For example, when propene is used with isohutane, a mixture of C5 isomers is produced. The following represents the reaction steps ... 

The second point to explore involves carbocation stability. 2-Methyl-propene might react with H+ to form a carbocation having three alkyl substituents (a tertiary ion, 3°), or it might react to form a carbocation having one alkyl substituent (a primary ion, 1°). Since the tertiary alkyl chloride, 2-chloro-2-methylpropane, is the only product observed, formation of the tertiary cation is evidently favored over formation of the primary cation. Thermodynamic measurements show that, indeed, the stability of carbocations increases with increasing substitution so that the stability order is tertiary > secondary > primary > methyl. 

Diastereoselective preparation of a-alkyl-a-amino acids is also possible using chiral Schiff base nickel(II) complexes of a-amino acids as Michael donors. The synthetic route to glutamic acid derivatives consists of the addition of the nickel(II) complex of the imine derived from (.S )-,V-[2-(phenylcarbonyl)phenyl]-l-benzyl-2-pyrrolidinecarboxamide and glycine to various activated olefins, i.e., 2-propenal, 3-phenyl-2-propenal and a,(f-unsaturated esters93- A... 

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. 

Low substrate selectivity accompanying high positional selectivity was also found in isopropylation of a range of alkyl and halogenobenzenes by /-propyl bromide or propene in nitromethane, tetramethylene sulphone, sulphur dioxide, or carbon disulphide, as indicated by the relative rates in Table 86. The toluene benzene reactivity ratio was measured under a wide range of conditions, and varied with /-propyl bromide (at 25 °C) from 1.41 (aluminium chloride-sulphur... 

In 1950 the Fischer-Tropsch synthesis was banned in Germany by the allied forces. Sinarol, a high paraffinic kerosene fraction sold by Shell, was used as a substitute. This ban coincided with the rapid development of the European petrochemical industry, and in due time Fischer-Tropsch synthesis applied to the production of paraffins became uneconomic anyway. After the war there was a steady worldwide increase in the demand for surfactants. In order to continually meet the demand for synthetic detergents, the industry was compelled to find a substitute for /z-paraffin. This was achieved by the oligomerization of the propene part of raffinate gases with phosphoric acid catalyst at 200°C and about 20 bars pressure to produce tetrapropene. Tetrapropene was inexpensive, comprising a defined C cut and an olefinic double bond. Instead of the Lewis acid, aluminum chloride, hydrofluoric acid could now be used as a considerably milder, more economical, and easier-to-handle alkylation catalyst [4],... 

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