Sulfur trioxide,

Sulfur dioxide is formed by reacting sulfur with sulfur trioxide  

5 10 t of sulfur dioxide was produced in the Federal Republic of Germany in 1994. 

Applications. In 1994 ca. 305 10 t of liquid sulfur dioxide was consumed just in the USA, of which 40% was utilized in the manufacture of sulfur-containing chemicals such as sulfites, hydrogen sulfites, thiosulfites, dithionites and salts of hydroxyalkane sulfinic acid and alkane sulfonates. It is also utilized in cellulose manufacture, in the chemical dressing of manganese ores, in the removal of sulfur-containing impurities from mineral oils, for disinfection and preservation in the food industry and for the treatment of water. 

Manufacture Pure sulfur trioxide is industrially produced from oleum by distillation in stainless steel falling film evaporators or forced circulation evaporators and liquefaction of the vapor, in which a minimum temperature of 27 °C must be respected to prevent solidification of sulfur trioxide. The formation of solid sulfur trioxide modifications during longer transport times is hindered by the removal of water and the addition of stabilizers such as thionyl chloride or oxalyl chloride. 

Applications 100% sulfur trioxide is utilized for the manufacture of chlorosulfonic acid, thionyl chloride, aminosulfonic acid, dimethyl sulfate and for the sulfonation of organic substances, in particular for the detergent industry. It is superseding chlorosulfonic acid as a sulfonation agent to an ever greater extent, because no corrosive hydrogen chloride is produced. 

Less than an equivalent quantity of sulfur trioxide is distilled from 60 per cent oleum into a solution of 88 g. of redistilled dioxane in 300 ml. of ethylene chloride, which is chilled and stirred mechanically. The white crystalline addition compound precipitates where the sulfur trioxide strikes the surface of the solution. The compound is filtered and dried as in the previous cases. It usually contains considerable sulfate, J since dioxane-sulfur trioxide is very sensitive to moisture. 

Pyridine-sulfur trioxide is a white crystalline compound that is only slightly soluble in cold water, ether, chloroform, or carbon tetrachloride. It is hydrolyzed quantitatively to pyridine and sulfuric acid by hot water. Pyridine-sulfur trioxide reacts with aniline to form the pyridinium salt of fV-phenylsulfamic acid. - Both aqueous and liquid ammonia ammonolyze pyridine-sulfur trioxide, yielding ammonium sulfamate. 

Dimethylaniline-sulfur trioxide is very similar to pyridine-sulfur trioxide in appearance. However, it is much more easily hydrolyzed even by atmospheric moisture. This is in accordance with the general rule that compounds of the type formula RsN-SOs, become less stable when one of the alkyl groups is replaced by an aryl radical. Dimethylaniline-sulfur trioxide reacts with absolute ethyl alcohol, phenol, aniline, and aqueous or liquid ammonia.  

Dioxane-sulfur trioxide is stable at room temperature under anhydrous conditions but is decomposed on heating to 75° in carbon tetrachloride. It is much more reactive than is pyridine-sulfur trioxide and is hydrolyzed instantly by water to form sulfuric acid and dioxane. Its use as a sulfonating agent for a wide variety of organic compounds has been the subject of an extensive investigation by Suter, Evans, and Kiefer.  

Ilek private communication, GrasseUi Experimental Laboratory, Cleve- 

In the gas phase, monomeric SO3 has a planar (D3/,) structure with S-O 142 pm. This species is in equilibrium with the cyclic triraer S3O9 in both the gaseous and liquid phases Kp I atm-2 at 25°, AW° 125kJ (mole 8309) . Bulk properties therefore often refer to this equilibrium mixture, e.g. bp 44.6°C, d(25°) 

Handling, Storage, and Precautions an aqueous acetone solution of the reagent is quite stable at rt and loss of active oxygen amounts to 1-2% per week. Since the reagent is a peroxide and potentially explosive, care is required in canying out reactions with it. During workup, check for peroxides before solvent removal. 

When an alkene is reacted with the peroxy acid (1) In aqueous acetone, the anti hydroxylation product is obtained direcdy. Cyclohexene (8) is converted to the trans-dioX (9) (eq 3). Reagent (1) has been used for the synthesis of ( ) y-rhodomycinone (11) via frans hydroxylation of the alkene (10) (eq 4).  

It Is of interest to note that the electron-deficient alkene maleic add has been hydroxylated to furnish tartaric acid in 80% yield. Phenylglyceric acid has been similarly prepared from cinnamic add. 

Epoxidation of Alkenes. Epoxides have been isolated by reacting alkenes with the peroxy acid (1) in the presence of a solid buffer such as sodium carbonate. Epoxides have been prepared from 0 terpineol and cholesterol in 82% and 89% yields, 

Baeyer-Villiger Reaction. Baeyer-Villiger reaction of cyclohexanone takes place readily at 0 °C with (1) (4-6 h) to furnish hexanollde In 80% yield. Peracid (1) did not react with the ketone (12) and 4,4 dimethylcholestan 3 one. Reaction of (12) with peracetic add boron trifluoride etherate furnished the lactone (13) in 36% 3deld.  

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Product removal during reaction. Sometimes the equilibrium conversion can be increased by removing the product (or one of the products) continuously from the reactor as the reaction progresses, e.g., by allowing it to vaporize from a liquid-phase reactor. Another way is to carry out the reaction in stages with intermediate separation of the products. As an example of intermediate separation, consider the production of sulfuric acid as illustrated in Fig. 2.4. Sulfur dioxide is oxidized to sulfur trioxide ... 

Tantalum is a gray, heavy, and very hard metal. When pure, it is ductile and can be drawn into fine wire, which is used as a filament for evaporating metals such as aluminum. Tantalum is almost completely immune to chemical attack at temperatures below ISOoC, and is attacked only by hydrofluoric acid, acidic solutions containing the fluoride ion, and free sulfur trioxide. Alkalis attack it only slowly. At high temperatures, tantalum becomes much more reactive. The element has a melting point exceeded only by tungsten and rhenium. Tantalum is used to make a variety... 

In many cases, the a-haloketone does not appear to be an intermediate in this reaction, since reagents such as sulfur trioxide, sulfuric, or 60% nitric add lead to 2-aminothiazole but with lower yields (11 to 43%). Formamidine disulfide [-S-C(=NH)NH2]2, a product of the oxidation of thiourea, seems to be the intermediate in this reaction, since upon treatment with ketones, it gives 2-aminothiazole (604). However, the true mechanism of this reaction has not yet been completely elucidated. 

IS reversible but can be driven to completion by several techniques Removing the water formed m the reaction for example allows benzene sulfonic acid to be obtained m vir tually quantitative yield When a solution of sulfur trioxide m sulfuric acid is used as the sulfonatmg agent the rate of sulfonation is much faster and the equilibrium is dis placed entirely to the side of products according to the equation... 

On being heated with sulfur trioxide in sulfuric acid 124 5 tetramethylbenzene was converted to a product of molecular formula C10H14O3S m 94% yield Suggest a reasonable structure for this product... 

Sulfonation (Section 12 4) Sulfonic acids are formed when aromatic compounds are treated with sources of sulfur trioxide These sources can be concentrated sulfuric acid (for very reactive arenes) or solutions of sulfur trioxide in sulfuric acid (for ben zene and arenes less reactive than ben zene)... 

Dimethylsulfoxide Acyl and aryl halides, boron compounds, bromomethane, nitrogen dioxide, magnesium perchlorate, periodic acid, silver difluoride, sodium hydride, sulfur trioxide... 

Iodine Acetaldehyde, acetylene, aluminum, ammonia (aqueous or anhydrous), antimony, bromine pentafluoride, carbides, cesium oxide, chlorine, ethanol, fluorine, formamide, lithium, magnesium, phosphorus, pyridine, silver azide, sulfur trioxide... 

Nitryl chloride Ammonia, sulfur trioxide, tin(IV) bromide and iodide... 

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