Sulfites, reactions with acids

Sulfur dioxide is an economically important gas that is used as a refrigerant, disinfectant, and reducing atmosphere for preserving food. Although it is also used in the manufacture of many other sulfur compounds, the most important use of S02 is as a precursor in producing sulfuric acid. It can be obtained by burning sulfur, but it is also produced in numerous other reactions. Sulfites react with acids by liberating so2. 

MONOCROTOPHOS (6923-22-4) Alkaline pesticides. Attacks black iron, drum steel, stainless steel, brass. MONOSODIUM SALT of SULFUROUS ACID (7631-90-5) HOjS Na Slowly oxidized to the sulfate on contact with air. Sulfites may react explosively with strong oxidizers. Reaction with acid produces toxic sulfur dioxide gas. Attacks many metals. MONOTfflOETHYLENEGL YCOL (60-24-2) CjHjOS Combustible liquid [explosion limits in air (vol %) 2.3 to 18 flash point 165°F/74°C Fire Rating 2]. Violent reaction with strong oxidizers. Incompatible with strong acids (may release flammable hydrogen gas), aldehydes, azo/diazo compounds caustics, aliphatic... 

SODIUM BISULFITE or SODIUM BISULFITE, SOLID or SODIUM BISULFITE, SOLUTION (7631-90-5) HOjS Na Slowly oxidized to the sulfate on contact with air. Sulfites may react explosively with strong oxidizers. Reaction with acid produces toxic sulfur dioxide gas. Attacks many metals. 

Reaction with acidic gases. Limestones react readily with gaseous hydrogen chloride and hydrogen fluoride, forming calcium chloride and fluoride respectively. Dry sulfur dioxide reacts with limestone at 95 °C and above to produce calcium sulfite. Sulfur trioxide also reacts with limestone to produce the sulfate. 

Polythiodipropionic acids and their esters are prepared from acryUc acid or an acrylate with sulfur, hydrogen sulfide, and ammonium polysulfide (32). These polythio compounds are converted to the dithio analogs by reaction with an inorganic sulfite or cyanide. 

By the Bucherer reaction (with sulfite) of the appropriate arninonaphthalenesulfonic acid. 

Because of the time and expense involved, biological assays are used primarily for research purposes. The first chemical method for assaying L-ascorbic acid was the titration with 2,6-dichlorophenolindophenol solution (76). This method is not appHcable in the presence of a variety of interfering substances, eg, reduced metal ions, sulfites, tannins, or colored dyes. This 2,6-dichlorophenolindophenol method and other chemical and physiochemical methods are based on the reducing character of L-ascorbic acid (77). Colorimetric reactions with metal ions as weU as other redox systems, eg, potassium hexacyanoferrate(III), methylene blue, chloramine, etc, have been used for the assay, but they are unspecific because of interferences from a large number of reducing substances contained in foods and natural products (78). These methods have been used extensively in fish research (79). A specific photometric method for the assay of vitamin C in biological samples is based on the oxidation of ascorbic acid to dehydroascorbic acid with 2,4-dinitrophenylhydrazine (80). In the microfluorometric method, ascorbic acid is oxidized to dehydroascorbic acid in the presence of charcoal. The oxidized form is reacted with o-phenylenediamine to produce a fluorescent compound that is detected with an excitation maximum of ca 350 nm and an emission maximum of ca 430 nm (81). 

The rate of reaction with sulfite is ca 100 times faster than the rate of reaction with hydroxide, and decreasing the Brooker basicity of the acidic nucleus in the merocarbocyanine increases the rate of reaction. 

It is often advantageous to proceed to a desired product through two nucleophilic displacements rather than directly when one can exploit a difference in the reactivity of two leaving groups. An example is the conversion of 4-chloro-2,6-dimethoxypyrimidine (109) (not satisfactorily reactive with sulfanilamide anion) by means of trimethylamine into the more reactive trimethylammonio derivative 110. Conversion of chloro-quinohnes and -pyrimi-dines into nitriles is best accomplished by conversion (with sulfite) into the sulfonic acids before reaction with cyanide. 

Esters of sulfurous acid (sulfites) or sulfuric acid (sulfates) can be synthesized by reaction of alcohols with A -sulfinyldiimidazole (ImSOIm) and A A -sulfonyldiimidazole (ImS02Im), respectively. 

Reaction of the spirocyclic imidazoline 316 with glyoxal and sodium hydrogen sulfite results in hydrolysis of the aminal and subsequent double condensation to give the tetrazolopyridopyrazine 317 (Equation 109) <1999JHC117>. The pyridopyridazinylhydrazine 318 can be cyclized to the fused triazole 319 by reaction with formic acid (Equation 110) <1998SC2871>. 

The three rate constants for Eq. (98) correspond to the acid-catalyzed, the acid-independent and the hydrolytic paths of the dimer-monomer equilibrium, respectively, and were evaluated independently (107). The results clearly demonstrate that the complexity of the kinetic processes is due to the interplay of the hydrolytic and the complex-formation steps and is not a consequence of electron transfer reactions. In fact, the first-order decomposition of the FeS03 complex is the only redox step which contributes to the overall kinetic profiles, because subsequent reactions with the sulfite ion radical and other intermediates are considerably faster. The presence of dioxygen did not affect the kinetic traces when a large excess of the metal ion is present, confirming that either the formation of the SO5 radical (Eq. (91)) is suppressed by reaction (101), or the reactions of Fe(II) with SO and HSO5 are preferred over those of HSO3 as was predicted by Warneck and Ziajka (86). Recently, first-order formation of iron(II) was confirmed in this system (108), which supports the first possibility cited, though the other alternative can also be feasible under certain circumstances. 

Addition of magnesia to the scrubbing liquor increases the concentration of two dissolved sulfite species, SO3 and MgS0 , with CaS0 remaining constant. This increase in dissolved sulfite concentration makes the SOp absorption rate more dependent on the very fast liquid phase reactions of the basic sulfite species with the strong dibasic acid SOp(aq) ... 

Elemental sulfur is present in most soils and sediments (especially anaerobic), and is sufficiently soluble in most common organic solvents that the extract should be treated to remove it prior to analysis by ECD-GC or GC-MS. The most effective methods available are (1) reaction with mercury or a mercury amalgam [466] to form mercury sulfide (2) reaction with copper to form copper sulfide or (3) reaction with sodium sulfite in tetrabutyl ammonium hydroxide (Jensen s reagent) [490]. Removal of sulfur with mercury or copper requires the metal surface to be clean and reactive. For small amounts of sulfur, it is possible to include the metal in a clean-up column. However, if the metal surface becomes covered with sulfide, the reaction will cease and it needs to be cleaned with dilute nitric acid. For larger amounts of sulfur, it is more effective to shake the extract with Jensen s reagent [478]. 

The (8O3) radical is essentially the sulfur trioxide anion-radical. It is named the sulfite anion-radical because it is obtained from sodimn sulfite on reaction with titanimn trichloride in water. This reaction usually proceeds in the presence of ethylene diamine tetraacetic acid as a complexing agent and hydrogen peroxide as an oxidant (Bradic and Wilkins 1984). Under these conditions, the... 

Fogelman, K. D D. M. Walker, and D. W. Margerum, Non-Metal Redox Kinetics Hypochlorite and Hypochlorous Acid Reactions with Sulfite, Inorg. Chem., 28, 986-993 (1989). 

The sodium and potassium salts of S02 are simpler and more pleasant to use as they do not have the odor of the pure liquid or the 5% water solution. They are rapidly soluble in must where they react with a small portion of the natural acid present to liberate S02. There are two sodium salts of S02 available, Na2S03 (neutral sodium sulfite) and NaHS03 (sodium acid sulfite). The latter compound introduces less sodium into the wine and removes less acid from the wine for an equivalent amount of S02 liberated. Potassium acid sulfite and potassium pyrosulfite (potassium metabisulfite) are the two salts of potassium with S02 that are readily available, soluble in grape juice, and capable of yielding S02 upon reaction with the acid of the juice. Potassium salt is recommended when it is desired to keep the wine low in sodium ion content for diet reasons. The salts should be edible or food product grade, that is, free of heavy metals and other toxic impurities. They must be stored in tightly closed containers or they will react with the water vapor and... 

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