Bisulfite ion

Sulfite is oxidized rapidly (/t = 1 X 10 ) to sulfate by ozone (39). Bisulfite ion and sulfurous acid also are oxidized rapidly (to bisulfate and sulfuric acid) with k values of 3.2 X 10 and 2 X 10 , lespectively. 

In reactions at the sulfur atom of a sulfinate ion to form a sulfone, of a sulfoxide to form R3S+—0, or of bisulfite ion to form a sulfonic acid, the fractionally positive sulfur becomes more positively charged in the poly-ionic transition states. Definitive experimental evidence... 

A nucleophilic attack of the hydroxide (or the alkoxide) ions on the sulfur atom of the thiirane dioxide ring to give sulfonic acids or similar intermediates, which then decompose to alkenes and bisulfite ion, has been suggested for these reactions16-17>". 

Reaction between naphthols, bisulfite ion, and ammonia or amines... 

Although acidic pulping methods have largely been displaced over the past 50 years by neutral and alkaline processes, there is still a significant amount carried out. Acid sulfite pulping uses combinations of sulfur dioxide and water at high temperatures and pressures. An appropriate base is used to control the pH and, although usually acidic, it is possible to perform these reactions at neutral or even alkaline pH. The most active nucleophile present is the bisulfite ion,... 

The concentration of sulfur dioxide, bisulfite ion and sulfite ion will be a function of pH, and the mole percent of the bisulfite ion is a maximum at around pH 4 (Figure 3.11). 

At lower pH, sulfur dioxide is mostly present and, as the pH increases from 4 to 9, the proportion of sulfite ion increases and that of the bisulfite ion decreases. Usually either calcium or magnesium bases are used to control the pH within the acidic range. The pH is dependent upon the relative solubility of the calcium or magnesium sulfite, and upon the excess of sulfur dioxide which is used. Because of the greater solubility of magnesium sulfite, the magnesium-based... 

The enhancement effect of magnesia on S02 removal is caused by increased concentrations of basic sulfite species, SO3 and MgS0 , that react with the strong acid S02(aq) to form bisulfite ion, HSO3. 

The catalytic cycle of HRP can be represented by the sequence of reactions shown in Eqs. (4)-(7). This applies to most, but not all, reactions catalyzed by the enzyme, irrespective of the specific isoenzyme involved. Exceptions include the oxidations of iodide (138) and bisulfite ions (139, 140), both of which can involve a single two-electron reduction step. 

The initiators used in emulsion polymerization are water-soluble initiators such as potassium or ammonium persulfate, hydrogen peroxide, and 2,2 -azobis(2-amidinopropane) dihydrochloride. Partially water-soluble peroxides such a succinic acid peroxide and f-butyl hydroperoxide and azo compounds such as 4,4 -azobis(4-cyanopentanoic acid) have also been used. Redox systems such as persulfate with ferrous ion (Eq. 3-38a) are commonly used. Redox systems are advantageous in yielding desirable initiation rates at temperatures below 50°C. Other useful redox systems include cumyl hydroperoxide or hydrogen peroxide with ferrous, sulfite, or bisulfite ion. 

As a result, dissolved S02 really includes three chemical species hydrated S02 (S02 H20), the bisulfite ion (HSOj), and the sulfite ion (SO2-). While HSOJ is commonly referred to as bisulfite, it should be noted that it can exist in two possible structures HOS02- or... 

The predominant form dissolved in solution depends on the acidity of the solution in which S02 dissolves. Figure 8.7 shows the concentrations of the three species as a function of pH over the pH range typical of atmospheric droplets, 2-6, most of the dissolved S02 is in the form of bisulfite ion (HSOj). 

In the sulfite pulp process, the digestion fluid is typically made by dissolving sulfur dioxide in water in the presence of limestone until the solution contains 7.0% by weight S02, three-quarters of which is in the form of bisulfite ion. Why is this done In support of your answer to this question, calculate the pH of (a) the digestion solution prepared as above, (b) a hypothetical 7% solution of S02 alone, and (c) an actual saturated solution of S02 alone (2.9% S02), if the first acid dissociation constant of sulfurous acid is 1.7 x 10-2, at ambient temperature and pressure. 

Hydroxy Sulfonic Acids 0-41 Reaction between epoxides and bisulfite ion... 

A number of protic nucleophiles including water, 2-mercaptoethanoI, bisulfite ion, and hydroxylamine have been shown to form anionic a-adducts by reaction with l,3-dimethyl-5-nitrouracil in aqueous solution.57 These adducts have the general structure 119, which is characterized by strong absorption maxima in the range 320-326 nm (e 1-2 x 104 M 1 cm"1), involving a small bathochromic shift with respect to the substrate (Amax = 308 nm). Also, H-NMR data show a strong upheld shift of the ring proton of the order of 3.3 ppm. 

Adducts 119 are of relevance as reaction intermediates in the chemistry of several uracil and cytosine derivatives, which show a strong tendency to undergo covalent nucleophilic addition across the 5,6 double bond with such reagents as water, alcohols, hydroxylamine, and bisulfite ion. 

Indirect evidence for the formation of anionic adducts has been obtained for some dehalogenation reactions of 5-haIouracils or 5-halo-5,6-dihydro-uracils with bisulfite ion in water.163"165 However, no adducts were detected in the course of these reactions. Similarly, the formation of adduct 120 was assumed in the reaction of 6-bromomethyl-l,3-dimethyl-5-nitrouracil with KCN to yield 6-cyano-l,3-dimethyl-5-nitrocyclothymine.166 Clearly, in all these reactions involving the uracil system, the ring charge delocalization is quite limited, and the resulting stability of the adducts is markedly reduced. 

Bisulfite ions, HS03", condense with anthocyanins. This reversible reaction decreases the color by forming a colorless compound (12) (16). This effect is less evident in strongly acid media because the bisulfite ions are not as numerous since they are being converted to the undissociated acid. This property explains the decolorization of red wines following sulfite treatment but, since it is reversible, the color gradually reappears as the free S02 (bisulfite ions) disappears. The major role of tannins in the color of old wines explains their insensitivity to color change with SOo. 

The second method utilizes the fact that anthocyanins form colorless compounds with bisulfite ion (12). Again, the other wine constituents do not interfere, and the variation in color, after a large excess of bisulfite is added, is proportional to the concentration of anthocyanins. 

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