A, propylbenzene

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). 

What product(s) would result from nitration of each of the following compounds a. propylbenzene d. benzenesulfonic acid... 

Draw the displayed formula of a propylbenzene b l-ethyl-4-methylbenzene c 1,3,5-triethylbenzene,... 

The yield of iso-propylbenzene is influenced considerably by the quality of the anhydrous aluminium chloride employed. It Is recommended that a good grade of technical material be purchase in small bottles containing not more than 100 g. each undue exposure to the atmosphere, which results in some hydrolysis, is thus avoided. Sealed bottles containing the reagent sometimes have a high internal pressure they should be wrapped in a dry cloth and opened with care. 

This contains only a small proportion of unsaturated compounds.- these are easily removed by three washings with one tenth of the volume of concentrated sulphuric acid (compare Section III,7, Note 2). The resulting pure n-propylbenzene boils at 158-159°. 

Prepare a solution of benzyl magnesium chloride in a 2-litre three-necked flask from 24-3 g. of magnesium turnings, 600 ml. of sodium-dried ether and 126-5 g. (115 ml.) of redistilled benzyl chloride follow the experimental details given under n-Propylbenzene (Section IV,7). Cool the flask in running water or in ice water. Place a solution of 456 g. of n-butyl-p-toluenesulphonate (Section IV,198) in about twice its volume of anhydrous ether in the dropping funnel, and add it slowly with stirring, at such a rate that the ether just boils a white solid soon forms. The addition is complete after about 2 hours. Pour the reaction product... 

In an attempt to prepare propylbenzene a chemist alkylated benzene with 1 chloropropane and aluminum chloride However two isomeric hydrocarbons were obtained m a ratio of 2 1 the desired propylbenzene being the minor component What do you think was the major product How did it anse ... 

The identification of a specific nitrating species can be approached by comparing selectivity with that of nitration under conditions known to involve the nitronium ion. Examination of part B of Table 10.7 shows that the position selectivity exhibited by acetyl nitrate toward toluene and ethylbenzene is not dramatically different from that observed with nitronium ion. The data for i-propylbenzene suggest a lower ortho para ratio for acetyl nitrate nitrations. This could indicate a larger steric factor for nitration by acetyl nitrate. 

FIGURE l.l Hydrophobic interaction and reversed-phase chromatography (HIC-RPC). Two-dimensional separation of proteins and alkylbenzenes in consecutive HIC and RPC modes. Column 100 X 8 mm i.d. HIC mobile phase, gradient decreasing from 1.7 to 0 mol/liter ammonium sulfate in 0.02 mol/liter phosphate buffer solution (pH 7) in 15 min. RPC mobile phase, 0.02 mol/liter phosphate buffer solution (pH 7) acetonitrile (65 35 vol/vol) flow rate, I ml/min UV detection 254 nm. Peaks (I) cytochrome c, (2) ribonuclease A, (3) conalbumin, (4) lysozyme, (5) soybean trypsin inhibitor, (6) benzene, (7) toluene, (8) ethylbenzene, (9) propylbenzene, (10) butylbenzene, and (II) amylbenzene. [Reprinted from J. M. J. Frechet (1996). Pore-size specific modification as an approach to a separation media for single-column, two-dimensional HPLC, Am. Lab. 28, 18, p. 31. Copyright 1996 by International Scientific Communications, Inc.. Shelton, CT.]... 

Repeat your analysis for n-propylbenzene. (Compare geometries of 1-propylbenzene radical cation and 1-propylbenzene.) Where would you expect a strong peak in the mass spectrum Identify the ion responsible. 

Side-chain bromination at the benzylic position occurs when an alkylbenzene is treated with /V-bromosuccinimide (NBS). For example, propylbenzene gives (l-bromopropyl)benzene in 97% yield on reaction tvith NBS in the presence of benzoyl peroxide, (PhC02)2f as a radical initiator. Bromination occurs exclusively in the benzylic position and does not give a mixture of products. 

Solution "What is an immediate precursor of the target " The final step will involve introduction of one of three groups—chlorine, propyl, or sulfonic acid—so we have to consider three possibilities. Of the three, the chlorination of o-propylbenzene-sulfonic acid can t be used because the reaction would occur at the wrong position. Similarly, a Friedel-Crafts reaction can t be used as the final step because this reaction doesn t work on sulfonic acid-substituted (strongly deactivated) benzenes. Thus, the immediate precursor of the desired product is probably m-chloropropyl-benzene, which can be sulfonated to give a mixture of product isomers that must then be separated. 

Second-order rate coefficients at 20 °C were as follows benzene (0.0133), toluene (1.26), p-xylene (62) o-xylene (70.2), and i-propylbenzene (0.395). It is difficult to evaluable the quantitative significance of this data, however, since there must be a solvent correction factor to each rate, arising from the differing polarities of the media. That this can be significant can be seen from the data in Table 67,... 

The above mechanism for chloromethylation seems to be general for halo-methylation since bromomethylation gives the same ortho para ratio for toluene, ethylbenzene, and i-propylbenzene, which is entirely in accord with the halogen being substituted in a non rate-determining step of the reaction386. 

The greater steric hindrance to acetylation was also shown by a comparison of the rate of (103At2) of acetylation of toluene (0.763), ethylbenzene (0.660), i-propylbenzene (0.606) and f-butylbenzene (0.462) with those (determined by the competition method) for benzoylation both sets of data (Table 112) were obtained with dichloroethane as solvent at 25 °C, all reagent concentrations being 0.1 A/421. Relative rates of acylation other aromatics under the same conditions have also been obtained and are given in Table 113422. The different steric requirements for acetylation and benzoylation are further shown by the following respective relative rates for acylation of naphthalene derivatives in chloroform at 0 °C naphthalene (1 position) 1.00,1.00, (2 position) 0.31,0.04 2,3-dimethylnaphthalene (1 position) 1.59, 172, (5 position) 7.14, 38.2, (6 position) 3.68, 7.7422a. 

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