Preparation of Ethylbenzene

Introduction. The principle of the method used for the preparation of ethylbenzene is discussed in the introduction to Experiment 10. A mixture of aryl and alkyl halides, when treated with sodium under anhydrous conditions, forms alkyl-substituted aromatic hydrocarbons  

The use of two different halides increases the possibility of side reactions. In the preparation of ethylbenzene, two molecules of ethyl bromide, or two molecules of bromobenzene may react  

The macro method gives fairly good yields (40-55 per cent of theory), but involves the disadvantage of having the reaction mixture stand in the laboratory, as it cannot be finished in a single laboratory period. The yield when the semimicro method is employed is somewhat less. 

The mixture is filtered into a distilling tube through a very small funnel provided with a plug of glass wool or of cotton. The reaction tube is rinsed with 2 ml of ether and the washings are filtered 

Note -Propylbenzene and n-butylbenzene may be prepared by the same method and with the same quantities of bromobenzene and alkyl branide. The fraction which is collected in the preparation of n-propyl-benzene boils at 156-162°. For n-butylbenzene the fraction collected is 180-186°. The yield of n-butylbenzene is about 50 per cent of theory. 

---

The Fittig Reaction is employed in the following preparation of ethylbenzene. 

The reaction is illustrated by the preparation of ethylbenzene from acetophenone the resulting hydrocarbon is quite pure and free from unsaturated compounds ... 

Recently, the results of the isomerization and transalkylation of isomeric diethylbenzenes with benzene in the presence of triflic acid have been reported. The aim is to find the best condition for the preparation of ethylbenzene.283 285ort/ta-Diethylbenzene and benzene reacting in 1 1 molar ratio at 35°C gave ethylbenzene in 49% yield in 6h 285 An even higher yield was obtained with /mra-diethylbenzene (51% at 22°C), whereas meta-diethylbenzene produced ethylbenzene only in 29% yield.283 Both decreasing temperature and decreasing diethylbenzene/benzene ratio resulted in decreasing yields. 

An alternative milder procedure is the reduction of the corresponding toluene-p-sulphonylhydrazones with catecholborane, followed by decomposition of the intermediate with sodium acetate in the presence of dimethyl sulphoxide, or with tetrabutylammonium acetate.1 These methods, which do not have the disadvantages of the Clemmensen reduction, are illustrated by the preparation of ethylbenzene from acetophenone (Expt 6.4, Methods A and B). Outline mechanisms for these reactions are given below. 

Smith LA Jr, Arganbright RP, Hearn D. Preparation of ethylbenzene in a catalytic distillation column reactor. U.S. Patent 5,476,978, Chemical Research and Licensing Company, 1995. 

Zhang J, Li D, Fu J, Cao G. Process and apparatus for preparation of ethylbenzene by alkylation of benzene with dilute ethylene contained in dry gas by catalytic distillation. U.S. Patent Appl. 2001018545, 2001. 

R.F. Preparation of Ethylbenzene and Substituted Derivatives by Alkylation Using Unpurified Reac- 27. tion Products of Ethylene Prepared by Dehydrogenation of Ethane World Patent WO 96/34843,... 

Alkylation plays an important role in the production of synthetic rubber of the GR-S type, this unit process being employed for the preparation of ethylbenzene from which styrene is derived. Much lauryl mercaptan has been manufactured for use as a modifier in making synthetic rubber. 

Ethylbenzene. Prepare a suspension of phenyl-sodium from 23 g. of sodium wire, 200 ml. of light petroleum (b.p. 40-60°) and 56 3 g. (50 9 ml.) of chlorobenzene as described above for p-Toluic acid. Add 43 -5 g. (30 ml.) of ethyl bromide during 30-45 minutes at 30° and stir the mixture for a further hour. Add water slowly to decompose the excess of sodium and work up the product as detailed for n-Butylbenzene. The yield of ethylbenzene, b.p. 135-136°, is 23 g. 

Styrene (or vuiylbenzene) is prepared technicall by the cracking dehydre enation of ethylbenzene ... 

Alkenyl halides such as vinyl chloride (H2C=CHC1) do not form carbocations on treatment with aluminum chloride and so cannot be used m Friedel-Crafts reactions Thus the industrial preparation of styrene from benzene and ethylene does not involve vinyl chloride but proceeds by way of ethylbenzene... 

Dehydrogenation (Section 5 1) Elimination in which H2 is lost from adjacent atoms The term is most commonly en countered in the mdustnal preparation of ethylene from ethane propene from propane 1 3 butadiene from butane and styrene from ethylbenzene... 

The generation of caibocations from these sources is well documented (see Section 5.4). The reaction of aromatics with alkenes in the presence of Lewis acid catalysts is the basis for the industrial production of many alkylated aromatic compounds. Styrene, for example, is prepared by dehydrogenation of ethylbenzene made from benzene and ethylene. 

Problem 16.21 Styrene, the simplest alkenylbenzene, is prepared commercially for use in plastics manufacture by catalytic dehydrogenation of ethylbenzene. How might you prepare styrene from benzene using reactions you ve studied ... 

Styrene (or viuylbenzene) is prepared technically by the cracking dehydrogenation of ethylbenzene ... 

Ethylbenzene, Thallium triacetate Ucmura, S. et al., Bull. Chem. Soc., Japan., 1971, 44, 2571 Application of a published method of thallation to ethylbenzene caused a violent explosion. A reaction mixture of thallium triacetate, acetic acid, perchloric acid and ethylbenzene was stirred at 65°C for 5 h, then filtered from thallous salts. Vacuum evaporation of the filtrate at 60°C gave a pasty residue which exploded. This preparation of ethylphenylthallic acetate perchlorate monohydrate had been done twice previously and uneventfully, as had been analogous preparations involving thallation of benzene, toluene, three isomeric xylenes and anisole in a total of 150 runs, where excessive evaporation had been avoided. 

An efficient oxidation catalyst, OMS-1 (octahedral mol. sieve), was prepared by microwave heating of a family of layered and tunnel-structured manganese oxide materials. These materials are known to interact strongly with microwave radiation, and thus pronounced effects on the microstructure were expected. Their catalytic activity was tested in the oxidative dehydrogenation of ethylbenzene to styrene [25]. 

In the preparation of microporous manganese oxide materials different chemical properties were observed for the microwave and thermal preparations. In the conversion of ethylbenzene to styrene the activity and selectivity of the materials was different [26]. 

The reaction of olefin epoxidation by peracids was discovered by Prilezhaev [235]. The first observation concerning catalytic olefin epoxidation was made in 1950 by Hawkins [236]. He discovered oxide formation from cyclohexene and 1-octane during the decomposition of cumyl hydroperoxide in the medium of these hydrocarbons in the presence of vanadium pentaoxide. From 1963 to 1965, the Halcon Co. developed and patented the process of preparation of propylene oxide and styrene from propylene and ethylbenzene in which the key stage is the catalytic epoxidation of propylene by ethylbenzene hydroperoxide [237,238]. In 1965, Indictor and Brill [239] published studies on the epoxidation of several olefins by 1,1-dimethylethyl hydroperoxide catalyzed by acetylacetonates of several metals. They observed the high yield of oxide (close to 100% with respect to hydroperoxide) for catalysis by molybdenum, vanadium, and chromium acetylacetonates. The low yield of oxide (15-28%) was observed in the case of catalysis by manganese, cobalt, iron, and copper acetylacetonates. The further studies showed that molybdenum, vanadium, and... 

Preparation of 4-fl -nhenvlethvloxvlbenzaldehvde. This benzylic ether was prepared from p-hydroxybenzaldehyde (8.05 or 0.066 mole), and 1-bromo-ethylbenzene (12.lg or 0.065 mole) under phase transfer conditions as described above for 4-(2-cyclohexenyloxy)-benzalde-hyde. After purification by preparative HPLC 13.9g (93%) of pure product was obtained. 

Prepare a series of standard solutions of toluene in cyclohexane that are 0.5,1, 2, and 3% toluene by volume. Use 25-mL volumetric flasks. Add exactly 0.50 mL of ethylbenzene to each flask before diluting to the mark with the cyclohexane. Shake well. The ethylbenzene is the internal standard. 

Peng F, Fu X, Yu H, Wang H (2007). Preparation of carbon nanotube-supported Fe203 catalysts and their catalytic activities for ethylbenzene dehydrogenation. New Carbon Mater. 22 213-217. 

The synthetic importance of non-nucleophilic strong bases such as lithium diisopro-pylamide (LDA) is well known but its synthesis involves the use of a transient butyl lithium species. In order to shorten the preparation and make it economically valuable for larger scale experiments an alternate method of synthesis has been developed which also involves a reaction cascade (Scheme 3.14) [92]. The direct reaction of lithium with diisopropylamine does not occur, even with sonication. An electron transfer agent is necessary, and one of the best in this case is isoprene. Styrene is used in the commercial preparation of LDA, but it is inconvenient in that it is transformed to ethylbenzene which is not easily removed. It can also lead to undesired reactions in the presence of some substrates. The advantages of isoprene are essentially that it is a lighter compound (R.M.M. = 68 instead of 104 for styrene) and it is transformed to the less reactive 2-methylbutene, an easily eliminated volatile compound. In the absence of ultrasound, attempts to use this electron carrier proved to be unsatisfactory. In this preparation lithium containing 2 % sodium is necessary, as pure lithium reacts much more slowly. 

---