Benzene handling

The inflammable solvents most frequently used for reaction media, extraction or recrystallisation are diethyl ether, petroleum ether (b.p. 40-60° and higher ranges), carbon disulphide, acetone, methyl and ethyl alcohols, di-Mo-propyl ether, benzene, and toluene. Special precautions must be taken in handling these (and other equivalent) solvents if the danger of Are is to be more or less completely eliminated. It is advisable to have, if possible, a special bench in the laboratory devoted entirely to the recovery or distillation of these solvents no flames are permitted on this bench. 

Modern mass spectrometers are interfaced with computerized data handling sys terns capable of displaying the mass spectrum according to a number of different for mats Bar graphs on which relative intensity is plotted versus m z are the most common Figure 13 40 shows the mass spectrum of benzene m bar graph form... 

Hexane is classified as a flammable liquid by the ICC, and normal handling precautions for this type of material should be observed. According to the ACGIH, the maximum concentration of hexane vapor in air to which a worker may be exposed without danger of adverse health effects is 125 ppm benzene is rated at 10 ppm. 

Ethjlben ne Synthesis. The synthesis of ethylbenzene for styrene production is another process in which ZSM-5 catalysts are employed. Although some ethylbenzene is obtained direcdy from petroleum, about 90% is synthetic. In earlier processes, benzene was alkylated with high purity ethylene in liquid-phase slurry reactors with promoted AlCl catalysts or the vapor-phase reaction of benzene with a dilute ethylene-containing feedstock with a BF catalyst supported on alumina. Both of these catalysts are corrosive and their handling presents problems. 

For the process step involving handling of spent sulfuric acid, several patents have been issued in which improvements in this step were a main claim. The azeotropic nitration of benzene essentially eliminates the need to reconcentrate sulfuric acid (10,11). The nitration step is carried out at higher than usual temperatures (120—160°C). Because excess benzene is used, the higher temperature allows water to be removed as a water—benzene azeotrope. The water is separated and the benzene phase, containing approximately 8% nitrobenzene, is recycled back into the reactor. The dry sulfuric acid is then reused continuously. 

The solubiHty of phosphoms in water is about 3 ppm. However, process water used in phosphoms manufacture or handling often catties larger amounts of phosphoms as particulates or small droplets, depending on the water temperature. Phosphoms-contaminated water is commonly called phossy water. Phosphoms has low solubiHty in most common solvents, but is quite soluble in carbon disulfide and some other special solvents. The solubiHty in CS2 and benzene was formerly used in phosphoms analyses, but toxicity and increasing waste disposal costs have led to mote use of toluene and xylene, and mote tecentiy to the use of nonchemical turbidity measurements. 

The radioactive isotopes available for use as precursors for radioactive tracer manufacturing include barium [ C]-carbonate [1882-53-7], tritium gas, p2p] phosphoric acid or pP]-phosphoric acid [15364-02-0], p S]-sulfuric acid [13770-01 -9], and sodium [ I]-iodide [24359-64-6]. It is from these chemical forms that the corresponding radioactive tracer chemicals are synthesized. [ C]-Carbon dioxide, [ C]-benzene, and [ C]-methyl iodide require vacuum-line handling in weU-ventilated fume hoods. Tritium gas, pH]-methyl iodide, sodium borotritide, and [ I]-iodine, which are the most difficult forms of these isotopes to contain, must be handled in specialized closed systems. Sodium p S]-sulfate and sodium [ I]-iodide must be handled similarly in closed systems to avoid the Uberation of volatile p S]-sulfur oxides and [ I]-iodine. Adequate shielding must be provided when handling P P]-phosphoric acid to minimize exposure to external radiation. 

Manufacturers of benzene are requited by federal law to pubHsh Material Safety Data Sheets (MSDS) that describe in detail the procedures for its safe handling. Benzene is classified as a flammable Hquid and should be stored away from any potential source of ignition. Fine and explosion hazard data for benzene are shown (91). 

Because HCl is constandy present in most parts of the equipment, corrosion is always a potential problem. Chlorine and benzene, or any recycled material, must be free of water to trace amounts to prevent corrosion and deactivation of the catalyst. The reactor product contains HCl and iron. In some plants, the product is neutralized with aqueous NaOH before distillation. In others, it is handled in a suitably-designed distillation train, which includes a final residue from which FeCl can be removed with the high boiling tars. 

The copper complex 1s available from Strem Chemicals, Inc., under the name cuprous triflate (benzene complex). The checkers recommend handling the material In a dry box because of Its high moisture and air sensitivity. 

Caution BenaCaJanthraaene and benzene ane knoiM carainogene. Alt appvopniate pneaautione ehould be taken in handling these substances. 

Cupric trifluoromethylsulfonate (copper II triflate) [34946-82-2] M 361.7, pK <-3.0 (for triflic acid). Dissolve in MeCN, add dry Et20 until cloudy and cool at -20° in a freezer. The light blue ppte is collected and dried in a vacuum oven at 130°/20mm for 8h. It has Xmax 737nm (e 22.4M cm ) in AcOH. [J Am Chem Soc 95 330 1973], It has also been dried in a vessel at O.lTorr by heating with a Fischer burner [J Org Chem 43 3422 1978], It has been dried at 110-120°/5mm for Ih before use and forms a benzene complex which should be handled in a dry box because it is air sensitive [Chem Pharm Bull Jpn 28 262 I980-, J Am Chem Soc 95 330 1973]. 

An electrostatic precipitator is used to remove more tar from coke oven gas. The tar is then sent to storage. Ammonia liquor is also separated from the tar decanter and sent to wastewater treatment after ammonia recovery. Coke oven gas is further cooled in a final cooler. Naphthalene is removed in a separator on the final cooler. Light oil is then removed from the coke oven gas and is fractionated to recover benzene, toluene, and xylene. Some facilities may include an onsite tar distillation unit. The Claus process is normally used to recover sulfur from coke oven gas. During the coke quenching, handling, and screening operation, coke breeze is produced. The breeze is either reused on site (e.g., in the sinter plant) or sold offsite as a by-product. 

Solubility — the amount of a given substance (the solute) that dissolves in a unit volume of a liquid (the solvent). This property is of importance in the handling and recovery of spilled hazardous materials. Water-insoluble ehemicals are much easier to reeover from water than spills of water-soluble chemicals. Acetone, which is miscible/soluble in water in all proportions, is not readily reeoverable from water. In contrast, benzene, which is lighter than water and insoluble as well, can be readily trapped with a skimmer. For organie eompounds, solubility tends to deerease with inereasing moleeular weight and ehlorine content. 

Many valuable compounds are aromatic in part, including steroids such as estrone and well-known pharmaceuticals such as the cholesterol-lowering drug alorvastatin, marketed as Lipitor. Benzene itself has been found to cause bone marrow depression and a consequent lowered white blood ceil count on prolonged exposure. Benzene should therefore be handled cautiously if used as a laboratory solvent. 

Safety procedures must be observed in the laboratory at all times. Many chemicals encountered in analysis are poisonous and must be carefully handled. Whereas the dangerous properties of concentrated acids and of widely recognised poisons such as potassium cyanide are well known, the dangers associated with organo-chlorine solvents, benzene and many other chemicals are less apparent. 

Examples of the intermolecular C-P bond formation by means of radical phosphonation and phosphination have been achieved by reaction of aryl halides with trialkyl phosphites and chlorodiphenylphosphine, respectively, in the presence of (TMSlsSiH under standard radical conditions. The phosphonation reaction (Reaction 71) worked well either under UV irradiation at room temperature or in refluxing toluene. The radical phosphina-tion (Reaction 72) required pyridine in boiling benzene for 20 h. Phosphinated products were handled as phosphine sulfides. Scheme 15 shows the reaction mechanism for the phosphination procedure that involves in situ formation of tetraphenylbiphosphine. This approach has also been extended to the phosphination of alkyl halides and sequential radical cyclization/phosphination reaction. ... 

Avramoff et al. have already reported that the reaction of hydrocarbons such as toluene with tetramethylammonium tribromide (TMA Br3) in benzene, in the presence of benzoyl peroxide at room temperature gave benzylic bromination products (ref. 21). However, TMA Br3 is not easy to handle in comparison with the stable BTMA Br3 because of its hydroscopic character. Furthermore, as shown in their literature, a large excess of TMA Br3 is necessary to brominate arenes. 

The chemical reactivity of the organoruthenium and -osmium porphyrin complexes varies considerably, with some complexes (M(Por)R2, M(Por)R and Os(OEP)(NO)R) at least moderately air stable, while most are light sensitive and Stability is improved by handling them in the dark. Chemical transformations directly involving the methyl group have been observed for Ru(TTP) NO)Me, which inserts SO2 to form Ru(TTP)(N0) 0S(0)Me and Ru(OEP)Me which undergoes H- atom abstraction reactions with the radical trap TEMPO in benzene solution to yield Ru(OEP)(CO)(TEMPO). Isotope labeling studies indicate that the carbonyl carbon atom is derived from the methyl carbon atom. "" Reaction of... 

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