Toluene, atmosphere

At one time benzene was widely used as a solvent This use virtually disappeared when statistical studies revealed an increased incidence of leukemia among workers exposed to atmospheric levels of benzene as low as 1 ppm Toluene has replaced benzene as an inexpensive organic solvent because it has similar solvent properties but has not been determined to be carcinogenic m the cell systems and at the dose levels that benzene is... 

Hydrochloric acid [7647-01-0], which is formed as by-product from unreacted chloroacetic acid, is fed into an absorption column. After the addition of acid and alcohol is complete, the mixture is heated at reflux for 6—8 h, whereby the intermediate malonic acid ester monoamide is hydroly2ed to a dialkyl malonate. The pure ester is obtained from the mixture of cmde esters by extraction with ben2ene [71-43-2], toluene [108-88-3], or xylene [1330-20-7]. The organic phase is washed with dilute sodium hydroxide [1310-73-2] to remove small amounts of the monoester. The diester is then separated from solvent by distillation at atmospheric pressure, and the malonic ester obtained by redistillation under vacuum as a colorless Hquid with a minimum assay of 99%. The aqueous phase contains considerable amounts of mineral acid and salts and must be treated before being fed to the waste treatment plant. The process is suitable for both the dimethyl and diethyl esters. The yield based on sodium chloroacetate is 75—85%. Various low molecular mass hydrocarbons, some of them partially chlorinated, are formed as by-products. Although a relatively simple plant is sufficient for the reaction itself, a si2eable investment is required for treatment of the wastewater and exhaust gas. 

The second processing step, in which benzoic acid is oxidized and hydrolyzed to phenol, is carried out in two reactors in series. In the first reactor, the benzoic acid is oxidized to phenyl benzoate in the presence of air and a catalyst mixture of copper and magnesium salts. The reactor is operated at 234°C and 147 kPa gauge (1.5 kg/cm g uge). The phenyl benzoate is then hydrolyzed with steam in the second reactor to yield phenol and carbon dioxide. This occurs at 200°C and atmospheric pressure. The overall yield of phenol from benzoic acid is around 88 mol %. Figure 2 shows a simplified diagram for the toluene—benzoic acid process. 

The Tatoray process, which was developed by Toray Industries, Inc., and is available for Hcense through UOP, can be appHed to the production of xylenes and benzene from feedstock that consists typically of toluene [108-88-3] either alone or blended with aromatics (particularly trimethylbenzenes and ethyl-toluenes). The main reactions are transalkylation (or disproportionation) of toluene to xylene and benzene or of toluene and trimethylbenzenes to xylenes in the vapor phase over a highly selective fixed-bed catalyst in a hydrogen atmosphere at 350—500°C and 1—5 MPa (10—50 atm). Ethyl groups are... 

Aminophenol. This is the most stable of the isomers under atmospheric conditions. It forms white prisms when crystallized from water or toluene. The orthorhombic crystals have a tetramolecular unit and a density of 1.195 g/cm (1.206 and 1.269 also quoted) (15,16) (see Tables 3—5). 

The equihbrium shown in equation 3 normally ties far to the left. Usually the water formed is removed by azeotropic distillation with excess alcohol or a suitable azeotroping solvent such as benzene, toluene, or various petroleum distillate fractions. The procedure used depends on the specific ester desired. Preparation of methyl borate and ethyl borate is compHcated by the formation of low boiling azeotropes (Table 1) which are the lowest boiling constituents in these systems. Consequently, the ester—alcohol azeotrope must be prepared and then separated in another step. Some of the methods that have been used to separate methyl borate from the azeotrope are extraction with sulfuric acid and distillation of the enriched phase (18), treatment with calcium chloride or lithium chloride (19,20), washing with a hydrocarbon and distillation (21), fractional distillation at 709 kPa (7 atmospheres) (22), and addition of a third component that will form a low boiling methanol azeotrope (23). 

The main advantages of the Cosorb process over the older copper ammonium salt process are low corrosion rate, abiHty to work in carbon dioxide atmospheres, and low energy consumption. The active CuAlCl C H CH complex is considerably more stable than the cuprous ammonium salt, and solvent toluene losses are much lower than the ammonia losses of the older process (94). 

Mixing cellulose esters in nonpolar hydrocarbons, such as toluene or xylene, may result in static electricity buildup that can cause a flash fire or explosion. When adding cellulose esters to any flammable Hquid, an inert gas atmosphere should be maintained within the vessel (132). This risk may be reduced by the use of conductive solvents in combination with the hydrocarbon or by use of an antistatic additive. Protective clothing and devices should be provided. 

Pressure affects flash point. A decrease in pressure lowers the flash point. With toluene, for example, at two-thirds of an atmosphere the vapor pressure must be only 0.74 kPa (5.6 mm Hg) to equal the LFL of 1.1 percent. (No significant difference in LFL will exist at two-thirds of an atmosphere compared to the published LFL of 1.1 percent at one atmosphere.) This vapor pressure occurs at —3°C, corresponding to a decrease in flash point of about 7.4°C from one atmosphere. Conversely, an increase in pressure raises the flash point. 

To a 3QQ-mL, round-bottomed flask fitted with a water separator, (Note 1) which contains 15 g of Linde 4A molecular sieve l/16-1nch pellets and Is filled with toluene, are added 7.3 g (0.04 mol) of cyclododecanone, 11.4 g (0.16 mol) of pyrrolidine, 100 mL of toluene, and 0.57 g (0.004 mol) of boron trifluoride etherate. The solution is heated under reflux for 20 hr. The water separator is replaced by a distillation head, and about 90 mL of the toluene is removed by distillation at atmospheric pressure. The residue containing l-(N-pyrrolidino)-l-cyclododecene (1) is used in the next step without further purification (Note 2). 

Because phenols are weak acids, they can be freed from neutral impurities by dissolution in aqueous N sodium hydroxide and extraction with a solvent such as diethyl ether, or by steam distillation to remove the non-acidic material. The phenol is recovered by acidification of the aqueous phase with 2N sulfuric acid, and either extracted with ether or steam distilled. In the second case the phenol is extracted from the steam distillate after saturating it with sodium chloride (salting out). A solvent is necessary when large quantities of liquid phenols are purified. The phenol is fractionated by distillation under reduced pressure, preferably in an atmosphere of nitrogen to minimise oxidation. Solid phenols can be crystallised from toluene, petroleum ether or a mixture of these solvents, and can be sublimed under vacuum. Purification can also be effected by fractional crystallisation or zone refining. For further purification of phenols via their acetyl or benzoyl derivatives (vide supra). 

Has been purified by co-distillation with ethylene glycol (boils at 197.5°), from which it can be recovered by additn of water, followed by crysm from 95% EtOH, benzene, toluene, a mixture of benzene/xylene (4 1), or EtjO. It has also been chromatographed on alumina with pet ether in a dark room (to avoid photo-oxidation of adsorbed anthracene to anthraquinone). Other purification methods include sublimation in a N2 atmosphere (in some cases after refluxing with sodium), and recrystd from toluene [Gorman et al. J Am Chem Soc 107 4404 1985]. 

Cyanoanthracene (anthracene-9-carbonitrile) [1210-12-4] M 203.2, m 134-137°. Purified by crystn from EtOH or toluene, and vacuum sublimed in the dark and in an inert atmosphere [Ebied et al. 7 Chem Soc, Faraday Trans 7 76 2170 1980 Kikuchi et al. J Phys Chem 91 574 1987. ... 

Carbon soot from resistive heating of a carbon rod in a partial helium atmosphere (0.3bar) under specified conditions is extracted with boiling C H or toluene, filtered and the red-brown soln evapd to give crystalline material in 14% yield which is mainly a mixture of fullerenes C q and C70. Chromatographic filtration of the crude mixture with allows no separation of components, but some separation was observed on silica gel... 

Environmental Fate. A portion of releases of toluene to land and water will evaporate. Toluene may also be degraded by microorganisms. Once volatilized, toluene in the lower atmosphere will react with other atmospheric components contributing to the formation of ground-level ozone and other air pollutants. 

A man was asked to clean a 45-m tank that had contained toluene. It was 20 ft (6 m) tall and 10 ft (3 m) diameter. It had not been gas-freed, and the atmosphere had apparently not been tested. He entered the tank through the 16-in.-diameter top opening, using a rope for descent. Self-contained breathing apparatus was available on the job, but he did not wear it. He was overcome by tbe vapor and lack of air and collapsed on the floor of the tank. 

P4S3 is the most stable compound in the series and can be prepared by heating the required amounts of red P and sulfur above 180° in an inert atmosphere and then purifying the product by distillation at 420° or by recrystallization from toluene. The retention of a P3 ring in the structure is notable. Its reactions and commercial application in match manufacture are discussed on p. 509. 

A 250-ml round-bottom flask is charged with a mixture of cyclohexanone (14.7 g, 0.15 mole), morpholine (15.7 g, 0.18 mole), and / -toluenesulfonic acid monohydrate (0.15 g) in 50 ml of toluene. The flask is fitted with a water separator and a condenser and is brought to reflux (mantle). The separation of water begins immediately and the theoretical amount (2.7 ml) is obtained in about 1 hour. Without further treatment, the reaction mixture may then be distilled. After removal of the toluene at atmospheric pressure, the product is obtained by distillation at reduced pressure, bp II8-I207IO mm, 1.5122-1.5129, in about 75% yield. 

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