With sulfur dioxide

Sulfur dioxide inserts into alkyltin bonds to give stannylsulfinates, R3Sn0-S(0)R,46 but the reactivity falls off in the sequence R = allyl allenyl propargyl phenyl benzyl methyl. Insertion into a vinyl-tin bond occurs with retention of configuration. The reaction with aryl and benzyl compounds is cleanly first order in each of the two reactants, and is rather insensitive to the nature of any substituents in the benzyl ring. 

The mechanism is probably best represented as a closed SE2(C)/SN2(Sn) process, with the development of some charge in the transition state. 

The SN2(Sn)(coord) mechanism, however, is familiar in the synthetically important Sn/Li transmetallation reaction that occurs between tetraalkyltin compounds and alkyl lithiums. This process is discussed in Section 19.1.1, and its applications in synthesis in Section 22.1. 

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Similar halogenations have been done on 2-lithio-l-phenylsulfonylindole[2], 2-Lithio-l-phenylsulfonylindole is readily converted to the 2-(trimethylsilyl) derivative[2,3]. 2-Trialkylstannylindoles can also be prepared via 2-lithio-indoles[4,5], 2-Sulfonamido groups can be introduced by reaction of a 2-lithioindole with sulfur dioxide, followed by conversion of the sulfinic acid group to the sulfonyl chloride with A-chlorosuccinimide[6]. 

Sodium suifite, acid (saturated) dissolve 600 g of NaHS03 in water and dilute to 1 liter for the preparation of addition compounds with aldehydes and ketones prepare a saturated solution of sodium carbonate in water and saturate with sulfur dioxide. 

Sulfurous acid, H2SO3 saturate water with sulfur dioxide. 

Formation of emissions from fluidised-bed combustion is considerably different from that associated with grate-fired systems. Flyash generation is a design parameter, and typically >90% of all soHds are removed from the system as flyash. SO2 and HCl are controlled by reactions with calcium in the bed, where the lime-stone fed to the bed first calcines to CaO and CO2, and then the lime reacts with sulfur dioxide and oxygen, or with hydrogen chloride, to form calcium sulfate and calcium chloride, respectively. SO2 and HCl capture rates of 70—90% are readily achieved with fluidi2ed beds. The limestone in the bed plus the very low combustion temperatures inhibit conversion of fuel N to NO. ... 

Modem chrome-tanning methods are weU controUed and employ an extensive knowledge of the chemistry of the system. The most common chromium-tanning material used is basic chromium sulfate [12336-95-7] Cr(0H)S04, made by the reduction of sodium bichromate with sulfur dioxide or by sulfuric acid and a sugar. 

Benzene SuIfona.tion. In the benzene sulfonation process, benzene reacts with concentrated sulfuric acid to form benzenesulfonic acid at about 150°C. The benzenesulfonic acid is neutralized with sodium sulfate to produce sodium benzenesulfonate, which is then fused with caustic soda to yield sodium phenate. The sodium phenate is acidified with sulfur dioxide and a small amount of sulfuric acid to release the phenol from the sodium salt. The phenol yield by this process can be as high as 88 mol % to that of the theoretical value based on benzene. Plants employing this technology have been shut down for environmental and economic reasons. 

Selenium and precious metals can be removed selectively from the chlorination Hquor by reduction with sulfur dioxide. However, conditions of acidity, temperature, and a rate of reduction must be carefliUy controlled to avoid the formation of selenium monochloride, which reacts with elemental selenium already generated to form a tar-like substance. This tar gradually hardens to form an intractable mass which must be chipped from the reactor. Under proper conditions of precipitation, a selenium/precious metals product substantially free of other impurities can be obtained. Selenium can be recovered in a pure state by vacuum distillation, leaving behind a precious metals residue. 

Simultaneous treatment of an alkane with sulfur dioxide and chlorine affords a sulfonyl chloride, eg, hexylsulfonyl chloride [14532-24-2] and is referred to as chlorosulfonation or the Reed reaction (247,248). 

Uses. The dominant use of sulfur dioxide is as a captive intermediate for production of sulfuric acid. There is also substantial captive production in the pulp and paper industry for sulfite pulping, and it is used as an intermediate for on-site production of bleaches, eg, chlorine dioxide or sodium hydrosulfite (see Bleaching agents). There is a substantial merchant market for sulfur dioxide in the paper and pulp industry. Sulfur dioxide is used for the production of chlorine dioxide at the paper (qv) mill site by reduction of sodium chlorate in sulfuric acid solution and also for production of sodium dithionite by the reaction of sodium borohydride with sulfur dioxide (315). This last appHcation was growing rapidly in North America as of the late 1990s. 

Manufacture. Aqueous sodium hydroxide, sodium bicarbonate, sodium carbonate, or sodium sulfite solution are treated with sulfur dioxide to produce sodium metabisulfite solution. In one operation, the mother Hquor from the previous batch is reinforced with additional sodium carbonate, which need not be totally in solution, and then is treated with sulfur dioxide (341,342). In some plants, the reaction is conducted in a series of two or more stainless steel vessels or columns in which the sulfur dioxide is passed countercurrent to the alkaH. The solution is cooled and the sodium metabisulfite is removed by centrifuging or filtration. Rapid drying, eg, in a stream-heated shelf dryer or a flash dryer, avoids excessive decomposition or oxidation to which moist sodium metabisulfite is susceptible. 

The Claus process converts hydrogen sulfide to elemental sulfur via a two-step reaction. The first step involves controUed combustion of the feed gas to convert approximately one-third of the hydrogen sulfide to sulfur dioxide (eq. 9) and noncatalytic reaction of unbumed hydrogen sulfide with sulfur dioxide (eq. 10). In the second step, the Claus reaction, the hydrogen sulfide and sulfur dioxide react over a catalyst to produce sulfur and water (eq. 10). The principal reactions are as foUow ... 

To produce commercial (99.5%) tellurium, tellurium dioxide is dissolved in hydrochloric acid. The tellurium solution is saturated with sulfur dioxide gas to yield commercial tellurium powder, which is washed, dried, and melted. 

Sulfides react with sulfur dioxide, sulfite, or bisulfite ... 

Other commercial processes ate based on the reaction of sodium sulfide or hydrogen sulfide with sulfur dioxide, and caustic or soda ash ... 

Another procedure utilizes a slurry of sodium sulfite, produced by the reaction of soda ash with sulfur dioxide, which is digested with excess sulfur until all of the sulfite is used up ... 

This reaction seties continues until the last polysulfide is ammonium sulfide and the process is completed by reaction with sulfur dioxide ... 

Other method thiosulfates have been prepared by reaction of suspensions of the metal sulfide with sulfur dioxide. However, these thiosulfates are... 

The ancient process of stoving is stiU occasionally used to bleach wool and silk with sulfur dioxide. In this process, wet fabrics are hung in chambers of burning sulfur or sulfur dioxide gas for at least 8 h. The fabrics are then washed with sodium sulfite to remove excess sulfur dioxide. Fabric so treated may have unpleasant odors, and the original color eventually returns, but the process is simple and inexpensive. 

Allied-Signal Process. Cyclohexanone [108-94-1] is produced in 98% yield at 95% conversion by liquid-phase catal57tic hydrogenation of phenol. Hydroxylamine sulfate is produced in aqueous solution by the conventional Raschig process, wherein NO from the catalytic air oxidation of ammonia is absorbed in ammonium carbonate solution as ammonium nitrite (eq. 1). The latter is reduced with sulfur dioxide to hydroxylamine disulfonate (eq. 2), which is hydrolyzed to acidic hydroxylamine sulfate solution (eq. 3). 

The fumes from the roaster are passed through a train of water-spray scmbbers and an electrostatic precipitator. In the scmbber, selenium dioxide [7446-08-4] reacts with sulfur dioxide (eq. 37) to produce elemental selenium, which is purified to provide a commercial product. 

For operations producing 30,000 tons or less of copper annuaHy, hydrometaHurgy offers an alternative to smelting that avoids problems associated with sulfur dioxide recovery and environmental controls. Techniques include the Anaconda oxygen—ammonia leaching process, the Lake Shore roast-leach-electrowin process, and ferric chloride leaching processes for the treatment of copper sulfides. AH the facHities that use these techniques encountered serious technical problems and were shut down within a few years of start-up. 

Carbon-sulfur bonds can be formed by the reaction of elemental sulfur with a lithio derivative, as illustrated by the preparation of thiophene-2-thiol (201) (700S(50)104). If dialkyl or diaryl disulfides are used as reagents to introduce sulfur, then alkyl or aryl sulfides are formed sulfinic acids are available by reaction of lithium derivatives with sulfur dioxide. 

Fluid bed boilers have also been applied as a cure to sulfur dioxide air pollution from power plants. Various schemes have been developed in which combustion of a sulfur containing fuel takes place in a fluidized bed of particles which absorb or react with sulfur dioxide. The particles are usually regenerated to recover sulfur, which often has enough by-product value to make a significant contribution to process economics. 

A iD-Corticoids have been important intermediates since it was shown ° that substitution at C-9 enhances anti-inflammatory activity. These olefins are usually obtained from 11a- or 11)5-alcohols, and consequently several refined methods have been devised for effecting this dehydration. It is desirable that such methods be compatible with the presence of A" -3-ketone and 17-hydroxy functions. The first direct procedure for which high yields were claimed was described in a patent issued to Upjohn. According to this method, the alcohol (11a or )5) is treated first with A-bromoacetamide in pyridine, then with sulfur dioxide. Recently it has been claimed " that the A-haloamide/sulfur dioxide method gives results superior to other methods, although the methanesulfonyl chloride/sulfur dioxide procedure (see below) apparently was not compared (see also ref. 94). 

Tnfluoromethanesulfinate can be prepared from the reaction of trifluoromethyl bromide with sulfur dioxide and zinc [50] (equation 41) Similar insertion occurs when perfluoroalkyl iodides are used as precursors (equations 41 and 42)... 

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