100-41-4 Ethylbenzene

Ethylbenzene (boiling point 136°C, density 0.8672, flash point 21°C) is a colorless liquid that is manufactured from benzene and ethylene by several modifications of the older mixed liquid-gas reaction system using aluminum chloride as a catalyst (Friedel-Crafts reaction). The reaction takes place in the gas phase over a fixed-bed unit at 370 C under a pressure of 1450 to 2850 kPa. Unchanged andpolyethylated materials are recirculated, making a yield of 98 percent possible. The catalyst operates several days before requiring regeneration. 

Excess benzene is used if the formation of di- and trimethylbenzenes is to be avoided or minimized. The benzene is recycled. 

In the more modern process (Fig. 1) the reaction takes place in the liquid phase, using a zeolite catalyst and cycle lengths in excess of 3 years are expected for the catalyst. 

A vapor-phase method with boron trifluoride, phosphoric acid, or alumina-silica as catalyst has given away to a liquid-phase reaction with aluminum chloride at 90°C and atmospheric pressure. A zeolite catalyst at 420°C and 175 to 300 psi in the gas phase is also available. 

Despite the elaborate separations required, including washing with caustic and water and three distillation columns, the overall yield of ethylbenzene is 98 percent. Ethylbenzene is used predominantly (C6H5CH=CH2) manufacture a minor amount is used as a solvent. 

Ethylbenzene boils at 135°, and has the specific gravity 0.883 at 0°. The yield in the preparation should be 25 to 28 grams. 

—(a) In the preparation of hydrocarbons by the Fittig synthesis the halides used are often diluted with ether in order to moderate the reaction the volume of ether used ordinarily is twice that of the halogen compounds. Benzene and petroleum ether are also used as diluents, especially in the ease of very active substances, when it is desired to have the reaction take place very slowly. When reaction takes place sluggishly, the mixture without diluents can be heated on a water-bath or in an oil-bath. The reaction between halides and sodium is catalyzed by a few drops of ethyl acetate or methyl cyanide. 

If all the substances used have not been carefully dried, the hydrogen formed as the result of the reaction between sodium and water reduces a part of the halides to hydrocarbons. 

In the preparation of hydrocarbons containing two different radicals, the product obtained is usually a mixture in addition to ethylbenzene, some diphenyl and butane are formed in the preparation described above. 

Ethylbenzene (eth-il-BEN-zeen) is a colorless flammable liquid with a pleasant aromatic odor. It is an aromatic hydrocarbon, that is, a compound consisting of carbon and hydrogen only with a molecular structure similar to that of benzene (C6H6). In 3004 it ranked fifteenth among chemicals produced in the United States. Its primary use is in the manufacture of another aromatic hydrocarbon, styrene (C6HSCH=CH2), widely used to make a number of polymers, such as polystyrene, styrene-butadiene latex, SBR rubber, and ABS rubber. 

Ethylbenzene occurs to some extent as a component of petroleum. It can be extracted from petroleum by fractional distillation, the process by which individual components of petroleum are separated from each other by heating in a distilling tower. Ethylbenzene can also be made synthetically 

Ethylbenzene. Black atoms are carbon white atoms are hydrogen. Bonds in the benzene ring are represented by the double striped sticks. White sticks show single bonds. 

More than 99 percent of the ethylbenzene made is used for a single purpose—the production of styrene. Styrene is a very important industrial chemical, ranking seventeenth among all chemicals produced in the United States in 2004. It is used to make a number of important and popular polymers, the best known of which may he polystyrene. Much smaller amounts of ethylbenzene are used in solvents or as additives to a variety of products. Some products that contain ethylbenzene include synthetic rubber, gasoline and other fuels, paints and varnishes, inks, carpet glues, tobacco products, and insecticides. 

CATALYST A material that increases the rate of a chemical reaction without undergoing any change in its own chemical structure. MISCIBLE Able to be mixed especially applies to the mixing of one liquid with another. 

Despite the use of new catalys.s for manufacturing some industrial organic chemicals, many well-known classical reactions still abound. The Friedel-Crafts alkylation is one of the first reactions studied in electrophilic aromatic substitution. It is used on a large scale for making ethylbenzene. 

Excess benzene must be used. A common benzene ethylene ratio is 1.0 0.6. This avoids the formation of di- and triethylbenzenes. The first ethyl group, being electron donating inductively as compared to hydrogen, will activate the benzene ring toward electrophilic attack by stabilizing the intermediate carbocation. The benzene when in excess prevents this since it 

Almost all ethylbenzene (99%) is used to manufacture styrene. Only 1% is used as a solvent. 

2 Structural and molecular formulae and relative molecular mass 

Because ethylbenzene is used almost exclusively to produce styrene, the product specification on ethylbenzene is set to provide a satisfactory feedstock for styrene production. Levels of cumene, -propylbenzene, ethyltoluenes and xylenes in ethylbenzene are controlled to meet the required styrene purity specification. A typical sales specification is as follows purity, 99.5 wt% min. benzene, 0.1-0.3 wt% toluene, 0.1-0.3wt% ort/io-xylene + cumene, 0.02 wt% max. meto-xylene + para-xylene, 0.2 wt% max. allylbenzene + a-propylbenzene + ethyltoluene, 0.2 wt% max. diethylbenzene, 20 mg/kg max. total chlorides (as chlorine), 1-3 mg/kg max. and total organic sulfur, 4 mg/kg max. (Coty et al., 1987). 

Selected methods for the analysis of ethylbenzene in various matrices are given in Table 1. Ethylbenzene can be determined in biological material (blood, subcutaneous fat, plant foliage, fish samples) using head-space gas chromatography (GC), GC with mass spectrometry, and GC with flame ionization detection (WHO, 1996a). 

Determination of mandelic acid in urine has been recommended as a biomaiker of exposure to ethylbenzene. Several methods can be used to determine mandelic acid in urine samples. These include derivatization of the acid and GC analysis (detection limit, 1.0 mg/L) isotachophoresis (detection limit, 0.04 mmol/L) and high-performance liquid chromatography (detection limit, 0.01 mmol/L) (WHO, 1996a). 

Ethylbenzene was first produced on a commercial scale in the 1930s in Germany and the United States. The ethylbenzene-styrene industry remained relatively insignificant until the Second World War, when the demand for synthetic styrene-butadiene mbber prompted accelerated teehnology improvements and tremendous capacity expansion (Coty etal., 1987). 

Unsaturated hydrocarbons are present in nearly all products of the Clemmensen reduction of aromatic ketones and must be removed, if the hydrocarbon is requiral pure, by the above process. Secondary alcohols, often produced m small amount are not appreciably steam-volatile. 

Toluene. Use 200 g. of amalgamated zinc and 100 g. of freshly-distilled benzaldehyde. The yield of toluene, b.p. 109-110°, is 40 g. 

Method B (Huang - Minion modification of Wolff - Kishner reduction) 

Place 36 -0 g. of redistilled acetophenone, b.p. 201° (Section IV,136), 300 ml. of diethylene glycol, 30 ml. of 90 per cent, hydrazine hydrate and 40 g. of potassium hydroxide pellets in a 500 ml. Claisen flask provided with a reflux condenser and a thermometer dipping into the liquid (compare Fig. Ill, 31, 1). Warm the mixture on a boiling water bath until most of the potassium hydroxide has dissolved and then reflux (free flame) for one hour. Arrange the apparatus for distillation and distil until the temperature in the liquid rises to 175° (1) keep the distillate (ca. 50 ml.). Replace the reflux condenser in the flask and continue the refluxing for 3 hours. 

Separate the upper hydrocarbon layer from the distillate and extract the aqueous layer twice with 20 ml. portions of ether dry the combined upper layer and ethereal extracts with anhydrous magnesium sulphate, remove the ether on a water bath, and distil the residue from a 50 ml. Claisen flask. Collect the ethylbenzene at 135-136° the yield is 20 g. By extracting the s3Tupy liquid in the reaction flask with three 30 ml. portions of ether, a further 2 g. of ethylbenzene, b.p. 136°, may be obtained. Note, 

PROPERTIES RESEARCH GRADE PURE GRADE TECHNICAL GRADE 

Ethylbenzene is sometimes stablized with 2,6 diteniarybutyl 4-methylphenol which can be removed by distillation. 

Physical Characteristics - Colourless liquid, mp -95 C, bp 136°C. - Soluble in most organic solvents. 

Spectrometer Injetsystem Source Temperature Electron Energy Scan Range 

Physical Characteristics - Slightly yellow powder, mp 144 - 14d°C. - Not soluble. 

Current uses - Antistatic agent, lubricant, release agent. 

Phvaical Characteristics - Slightly yellow ciystalline powder, mp 169 - Soluble in acetone, methanol, chlorofonn. 

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If the byproduct reaction is reversible and inerts are present, then changing the concentration of inerts if there is a change in the number of moles should be considered, as discussed above. Whether or not there is a change in the number of moles, recycling byproducts can suppress their formation if the bj iroduct-forming reaction is reversible. An example is in the production of ethylbenzene from benzene and ethylene ... 

Polyethylbenzenes (diethylbenzene, triethylbenzene, etc.) are also formed as unwanted byproducts through reversible reactions in series with respect to ethylbenzene but parallel with respect to ethylene. For example,... 

Benzene was first isolated by Faraday in 1825 from the liquid condensed by compressing oil gas. It is the lightest fraction obtained from the distillation of the coal-tar hydrocarbons, but most benzene is now manufactured from suitable petroleum fractions by dehydrogenation (54%) and dealkylation processes. Its principal industrial use is as a starting point for other chemicals, particularly ethylbenzene, cumene, cyclohexane, styrene (45%), phenol (20%), and Nylon (17%) precursors. U.S. production 1979 2-6 B gals. 

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 ... 

The ethylbenzene contains some unsaturated compounds. These can be removed by repeated shaking with 5 per cent, of the volume of concentrated... 

Oxidation of a side chain by alkaline permanganate. Aromatic hydrocarbons containing side chains may be oxidised to the corresponding acids the results are generally satisfactory for compounds with one side chain e.g., toluene or ethylbenzene -> benzoic acid nitrotoluene -> nitrobenzoic acid) or with two side chains e.g., o-xylene -> phthalic acid). 

Alkylbenzenes are also obtained (but in somewhat lower yield) from phenyl-sodium and alkyl bromides. Thus ethylbenzene is produced from phenyl-sodium and ethyl bromide ... 

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 ... 

Quantitative analysis. Spectroscopic analysis is widely used in the analysis of vitamin preparations, mixtures of hydrocarbons (e.y., benzene, toluene, ethylbenzene, xylenes) and other systems exhibiting characteristic electronic spectra. The extinction coefficient at 326 mp, after suitable treatment to remove other materials absorbing in this region, provides the best method for the estimation of the vitamin A content of fish oils. 

The rates of nitration of benzene, toluene, and ethylbenzene in solutions of nitric acid c. 3-7 mol 1 ) in nitromethane were independent... 

MejSiCI - Nal - CH3CN as an Efficient and Practical Reducing Agent for Benzoic Alcohols. A typical procedure for the present reduction is as follows To a mixture of MejSiCI (1.54 ml, 12 mmol), Nal (1.8 g, 12 mmol), and acetonitrile (0.6 ml, 12 mmol) was added a solution of 1-phenylethanol (244 mg, 2 mmol) in hexane (2 ml). The mixture was stirred for 24 h at room temperature. Dilution with water, extraction with ether and subsequent isolation process gave ethylbenzene (158 mg) with sufficient purity in 75% yield. ... 

Note 2. Heating for longer periods at higher temperatures leads to the formation of more ethylbenzene. 

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