Isopropyl benzene alkylation

If the side chain is in an iso form, a more complex aromatic olefin forms. Isopropyl benzene leads to a methyl styrene and styrene [70], The long-chain alkylate aromatics decay to styrene, phenyl, benzyl, benzene, and alkyl fragments. The oxidation processes of the xylenes follow somewhat similar mechanisms [71, 72],... 

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)-... 

Alkylation, In petrochemicals, any reaction involving the thermal or catalytic addition of an olefin to a branch-chain hydrocarbon or aromatic hydrocarbon. The most notable example in petrochemicals is the addition of ethylene or propylene to benzene to produce ethylbenzene or isopropyl benzene (cumene). Other examples include the production of detergent alkylates. 

In another related study (using hexadecyltrimethyl ammonium bromide micelles), isopropyl benzene was solubilized, and the chemical shifts of aromatic and alkyl protons were observed. The results suggest that the isopropyl benzene molecules are oriented such that the isopropyl groups are buried more deeply in the core of the micelle, while the benzene ring is in the more hydrated palisade layer. This plus the conclusion of Item 3 is consistent with the description presented in Section 8.3, which located the benzene in a relatively polar portion of the micelle. 

Carbocations can rearrange during the Friedel-Crafts alkylation reaction, leading to the formation of unpredicted products. One example is the formation of isopropyl benzene by the reaction of propyl chloride with benzene. 

Beside isopropyl benzene (IPB) a substantial amount of polyalkylates is formed by consecutive reactions, mostly as C6H5-(C3H7)2 (DIPB) with some C6H5-(C3H7)3 (TPB). The main reaction has a large exothermal effect, of-113kJ/mol in standard conditions. The alkylation reaction is promoted by acid-type catalysts. The synthesis can be performed in gas or liquid phase. Before 1990 gas-phase alkylation processes dominated, but today liquid-phase processes with zeolite catalysts prevail. Recent developments make use of reactive distillation. 

Other more prominent process for production of resorcinol is through alkylation of benzene using propylene in such as a way that alkylation is done carefully to introduce isopropyl in 1 and 3 position, i.e., diisopropyl benzene which is then converted to resorcinol using a similar process of phenol from isopropyl benzene or cresols from iosopropyl toluene. 

Ammoxidation of alkylbenzenes with side-chains of different length leads to reaction at the position a to the benzene ring [38]. Reactivity increases with increasing length of the alkyl group (toluene < ethyl benzene < isopropyl benzene [58,59]), but in all cases only benzonitrile is formed. 

The major product is isopropyl benzene—approximately twice as much as -propyl benzene. The rearrangement in this mechanism occurs because primary cations do not exist in solution (Chapter 17) so that the alkyl halide-AlCl3 complex must either react directly or rearrange to the more stable secondary carbocation. 

Another important potential application is the class of benzene alkylation, as the manufacture of ethylbenzene or isopropyl-benzene (cumene). The synthesis is described by a set of parallel-consecutive equilibrium reactions, as for example ... 

One can see from Table VI that the dissociative ionization process which is of greatest importance in isopropyl benzene and of overwhelming importance in t-amylbenzene is displacement of the alkyl group from the aromatic nucleus to form the alkyl ion. The large alkyl ion intensity is accompanied by a diminution in the intensities of (M + H)" " and (M -I- CjHj), and it is postulated that the alkyl ions are formed by alkyl ion displacement reactions ... 

A more complex example is the manufacture of cumene (isopropyl benzene) by the alkylation of benzene with propylene, taken from the 1997 National Student Design Competition of the AIChE. Cumene is widely used to make acetone and phenol. The fresh feeds are as follows, where the benzene feed is nearly pure, but a refinery cut of a propylene-propane mixture is used rather than a more expensive feed of nearly pure propylene. 

Cumene (isopropylbenzene, isopropylben-zol, cumol) n. C6H5CH(CH3)2. A volatile liquid in the alkyl-aromatic family of hydrocarbons. It is used as a solvent and intermediate for the production of phenol, acetone, and a-methyl styrene and as a catalyst for acrylic and polyester resins. Properties bp, 153°C sp gr, 0.862/20°C refractive index, 1.506. Known also as isopropyl benzene (See image). 

In the first step, benzene is alkylated with propylene to give isopropyl benzene (cumene). The reaction may be carried out in either the vapour or liquid phase. In the vapour phase process (which is now more common), propylene and an excess of benzene are passed over a catalyst of phosphoric add supported on... 

Like ethylene, propylene is produced by the cracking of hydrocarbons. The major use of propylene is to make polypropylene but it is also a feedstock to manufacture other industrial chemicals, including propylene glycol, acrylic acid, propylene oxide, cumene, and isopropyl alcohol. Propylene oxide is made by the oxidation of propylene, and hydrolysis of propylene oxide gives propylene glycol. The alkylation of benzene with propylene gives isopropyl benzene, more commonly called cumene. Note that the product is not n-propyl benzene. This is because the intermediate is the more stable secondary carbocation which results in isopropyl benzene. 

Most rapid advancement took place during World War II. Commercial processes for the manufacture or separation Of isopentane, isobutane, butene, 2-2-4-trimethylpentene (Codimer), isopropyl benzene (cumene), butadiene, styrene, toluene, 2-2-4-trimethylpentane (alkylate), alcohol, etc., were in operation. 

Other Alkylation (and Dealkylation). Phosphoric acid acts as a catalyst in uniting propylene with benzene to form isopropyl benzene or... 

Now let s draw the forward scheme. Benzene is converted into isopropyl benzene upon treatment with 2-chloropropane and a Lewis acid (via a Friedel-Crafts alkylation). Benzylic bromination replaces the benzylic hydrogen atom with a bromine atom. Conversion to a Grignard reagent, followed by reaction with carbon dioxide and subsequent acidification, gives the desired carboxylic acid. 

Alkyl-aralkyl peroxide Bis(tert-butylperoxy isopropyl) benzene 160 180... 

Isopropylbenzene is prepared by the Friedel-Crafts alkylation of benzene y using isopropyl chloride and aluminum chloride (Section 12 6) j... 

Mechanism. The mechanism of alkylation and of other related Friedel-Crafts reactions is best explained by the carbocation concept. The alkylation of benzene with isopropyl chloride may be used as a general example ... 

Diisopropjibenzenes (DIPB) are readily obtained via Eriedel-Crafts alkylation of benzene or cumene by propylene. This reaction inhquid phase has not evolved drastically since 1980 with the exception of the large variety of heterogeneous acid catalysts that are now being used, mainly zeoHtes, type HZSM-12, giving a para/meta ratio = 0.7 (4). In fact, propylene can also be replaced by isopropyl alcohol coming from the hydrogenation of acetone that... 

PMMA is not affected by most inorganic solutions, mineral oils, animal oils, low concentrations of alcohols paraffins, olefins, amines, alkyl monohahdes and ahphatic hydrocarbons and higher esters, ie, >10 carbon atoms. However, PMMA is attacked by lower esters, eg, ethyl acetate, isopropyl acetate aromatic hydrocarbons, eg, benzene, toluene, xylene phenols, eg, cresol, carboHc acid aryl hahdes, eg, chlorobenzene, bromobenzene ahphatic acids, eg, butyric acid, acetic acid alkyl polyhaHdes, eg, ethylene dichloride, methylene chloride high concentrations of alcohols, eg, methanol, ethanol 2-propanol and high concentrations of alkahes and oxidizing agents. 

C-Alkylations may be discussed under the headings of alkene reactions and A/-alkyl rearrangements. The isopropylation of benzene and naphthalene are two important examples of alkylation with alkenes (see Alkylation). Manufacture of j butylaniline, by heating /V-butylaniline with 2inc chloride, typifies the rearrangement reaction appropriate to and higher alkyl derivatives. 

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... 

Toluene alkylation with isopropyl alcohol was chosen as the test reaction as we can follow in a detail the effect of zeolite structural parameters on the toluene conversion, selectivity to cymenes, selectivity to para-cymene, and isopropyl/n-propyl ratio. It should be stressed that toluene/isopropyl alcohol molar ratio used in the feed was 9.6, which indicates the theoretical toluene conversion around 10.4 %. As you can see from Fig. 2 conversion of toluene over SSZ-33 after 15 min of T-O-S is 21 %, which is almost two times higher than the theoretical toluene conversion for alkylation reaction. The value of toluene conversion over SSZ-33 is influenced by a high rate of toluene disproportionation. About 50 % of toluene converted is transformed into benzene and xylenes. Toluene conversion over zeolites Beta and SSZ-35 is around 12 %, which is due to a much smaller contribution of toluene disproportionation to the overall toluene conversion. A slight increase in toluene conversion over ZSM-5 zeolite is connected with the fact that desorption and transport of products in toluene alkylation with isopropyl alcohol is the rate controlling step of this reaction [9]... 

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