Bisulfide ions

Zinc compounds such as zinc oxide and basic zinc carbonate are used in some drilling fluids. Their function is to react out swiftly sulfide and bisulfide ions... 

Chemical/Physical. Although no products were identified, the estimated hydrolysis half-life in water at 25 °C and pH 7 is 44 yr (Mabey and Mill, 1978). Bromochloromethane reacts with bisulfide ion (HS ), produced by microbial reduction of sulfate, forming 1,3,5-trithiane and dithiomethane. Estimated reaction rate constants at 25 and 35 °C were 7.29 x 10 and 2.42 x 10 VM-sec, respectively (Roberts et al, 1992). 

The bisulfide ion present in the kraft process is even a better nucleophile than hydroxide, so when it is present it attacks the quinonemethide intermediate. An episulfide is formed that then hydrolyzes to a thiol-alcohol. 

Roberts, A. L., Sanborn, P. N. Gschwend, P.M. (1992). Nucleophilic substitution reactions of dihalomethanes with the bisulfide ion HS . Environmental Science Technology, 26, 2263-74. 

Bisulfide and Polvsulfide as Nucleophiles. Hydrogen sulfide (H2S) and bisulfide ion (HS ) are probably the primary sulfur nucleophiles (i.e. species with a lone pair of electrons on sulfur) in reducing sediments. However, several environmental factors such as diffusion of oxygen, the presence of Fe(III) may cause incomplete oxidation of sulfide to form polysulfide ions (S,2-, where n>l) (21)-... 

Kinetic data show that in seawater medium S42 reacts about 20-30 times faster than HS with acrylic acid, whereas the reaction of S42 with acrylonitrile is only about 4-6 times higher than with HS. However, in any environment, the importance of polysulfide versus bisulfide reactions is also dependent on their relative concentrations. In a situation where polysulfide and bisulfide ions are present in similar concentrations, our results imply that polysulfide ions, rather than bisulfide, are the important sulfur nucleophiles for reactions with activated unsaturated molecules having a terminal carboxyl group (e.g. acrylic acid, cinnamic acid). However, for neutral molecules such as fucoxanthin, in addition to polysulfide ions, reactions with bisulfide ions will also be of importance. 

Sulfide is here represented by the bisulfide ion, the major free species at the oceanographic pH of 8.2. Relative to sulfate (0.01 M), equilibrium sulfide concentrations are on the order of 10 140 M in this system (261. It can be calculated that an imaginaty search through IO100 terrestrial oceans would be needed to yield even a single molecule of the bisulfide if it were under equilibrium control. A number of kinetic studies have shown that the sulfides are also short lived in oxic seawater. Oxidation experiments are complicated by catalytic and wall effects so that lifetimes have varied from minutes to days, but the latest values fall towards the upper end of the range (12.131. 

Table L Average Surface Carbonyl Sulfide Concentrations for Various Productivity Zones (6), and Bisulfide Ion Levels Corresponding to them in the Hydrolysis-Oxidation Steady State (Equations 1,2, and 3). Units are Picomolar...

Table III. The Ratio of Concentrations for Selected Complexes to those of the Aquo Ion M24, (17.31.321. and Free Bisulfide Ion Concentrations (Molar) Required to Sustain Like Stability, all as Base 10 Logarithms.

Figure 3. Rough ratios of equilibrium concentrations for inorganic (31.321 and organic (20-221 copper species to those of the aquo ion Cu2+, with sulfide complexes plotted as functions of free bisulfide ion level and set at the lower limit in Table II.

If copper interactions were minimized in real seawater, abundant metals of lesser sulfide affinity would take up some of the slack. ITiis is partially evident from analyses of the type in Table III. For example, nickel has mixed layer concentrations on the order of nanomolar (22), and its sulfide equilibria and inorganic seawater speciations may resemble those of zinc (lv-19.31.32). Titration, however, should only lower free sulfide to a Table m SH equivalence point, or, to roughly picomolar. In a follow up to 1Z, Dyrssen and coworkers treat Cu(II) as a variable parameter, and find that in its absence, nickel, zinc and lead can all become sulfides while the bisulfide ion still hovers well above pM (18). Again, it must be emphasized that error margins in the various equilibria remain to be investigated. 

The rate constants kt and k2 were found to be 0.5 M 1 min-1 and 29.0 M-1 min-1 respectively at pH 5.05 and 25 C. The rate law and other data suggest a nucleophilic displacement by the bisulfide ion (HS ) on H202 as the rate-determining step with subsequent formation of polysulfide as intermediates. The rate of the reaction was found to decrease as HS ion in solution decreases and hence the optimal pH for oxidation was determined to be 7. They postulated the following mechanism for the second term in the rate expression ... 

In the later work (110) they reported the relative rates of additions of both bisulfide (HS") and polysulfide (S42 ) to acrylic acid and to acrylonitrile (CH2=CH-CN) for a range in pH and ionic strength. Results showed that at equal nucleophile concentrations, the addition of the polysulfide ion was much faster than that of the bisulfide ion. The difference in rate for the two nucleophiles was greater for acrylic acid, which is largely the anion under the pH conditions, than for acrylonitrile which is neutral. Effects of ionic strength... 

The presence of specific chemical species in the corrosive environment poisons or retards the rate of the Hads atom combination reaction, thereby permitting a higher fraction of the H atoms generated by corrosion to become absorbed by (enter into) the steel. Bisulfide ions (HS ), formed when H2S molecules are dissolved in water, are very effective H atom combination poisons. Other effective H atom combination poisons are cyanide ions (CN ) and arsenic ions (As3+). 

It is the H+ ion that makes the solution acidic. Hydrogen sulfide is diprotic because it has two reactions that both form the hydrogen ion. Furthermore, when hydrogen sulfide is dissolved in water it exists as three species - the molecular form (H2S) and the two ionic forms the bisulfide ion (HS ) and the sulfide ion (S2 ). 

The liberation of H2S is controlled not only by the rate of its production by SO -reducing bacteria, but also by its pH-dependent speciation, its tendency to rapidly precipitate as metal sulfides, and its rapid chemical and biological oxidation. Only the protonated species (H2S) is volatile, and at neutral pH, most inorganic sulfide is present as bisulfide ion (HS ), whereas sulfide (S ) dominates under alkaline conditions. These three species are known collectively as SH2S. Hence, the escape of sulfide should be enhanced at low pH. Sulfate reduction is most dominant in marine sediments and this is where the highest emissions of gaseous H2S occur (Hines, 1996). However, DeLaune et al. (2002) reported higher emissions of H2S from brackish... 

Figure 12 Arrhenius plot for the second-order rate constant (fens-) for the nucleophilic displacement of bromide from 1,2-dihromoethane (EDB) by bisulfide ion (HS ) (after Barbash, 1993).

Because of the poorly known value for, Fl2(H2S), it has become traditional to write solubility product expressions for the Fe(II) sulfides in terms of bisulfide ion and elemental sulfur instead of S . Assuming for simplicity that the amorphous sulfide and mackinawite are 1 1 solids, their dissolution expressions are ... 

Figure 3. Current versus concentration plots from SDC polarographlc data for bisulfide ion and glutathione in pH 10 buffer solution.

The formation of thiols appears related to the oxidaton of sulfide or sulfide minerals in Great Marsh, Delaware because of high sulfate excesses whenever thiols are present. Conversely, reaction of bisulfide ion with labile organic compounds such as... 

Polysulfides can be generated via two major pathways. First, polysulfides can be formed by the oxidation of dissolved sulfide and sulfide minerals(l, 2). Second, they can be formed by the reaction of elemental sulfur with bisulfide ion(35). Polysulfide levels can be predicted for the second process as described in previous studies(, 36-38). Equilibrium calculations as described in a previous study(22) were performed for the polysulfide levels in these samples. The ratio of S(0) experimental to S(0) calculated for all samples from Great Sippewissett were 0.145 (4-8 cm), 0.137 (8-13 cm) and 0.128 (23-28 cm). Because these ratios are less than 1.0, these results indicate that polysulfides should form primarily from the reaction of bisulfide ion with elemental sulfur(5) rather than sulfide oxidation. This data set is... 

The carbonyl sulfide formed in reaction ii may be converted to monothiocarbonate by carbonic anhydrase (reaction viii). Monothiocarbonate may further spontaneously degrade in reaction ix, regenerating carbonyl sulfide or forming carbon dioxide and sulfide bisulfide ion (HS) (reaction vii). 

By comparison the free energy change for dissociation of the bisulfide ion,... 

A number of dialkyl sulfides were identified in an aquifer polluted from a waste-water tank of a chemical plant that manufactured a range of alkyl halides. This observation indicated that nucleophiles other than water and OH could be active in the environment. Sulfur is widely distributed and under reducing conditions hydrogen sulfide can be produced. This acid has a pAia of 7.0 and the bisulfide ion (HS ) would predominate at basic pH values. Laboratory studies with bromohexane demonstrated that the bisulfide ion could compete with water in substitution reactions. A reaction sequence for the production of dialkyl sulfides is as follows ... 

General overviews of STM studies of metal electrodes have been provided [10, 23-25] in addition, an extensive review that focused on ordered anion monolayers on metal electrode surfaces has been published [26]. Charge-induced surface phase transitions on ordered Au(lll) caused by increasing iodide adsorption from an aqueous electrolyte solutions have been observed [27]. The formation of copper sulflde nanostripe patterns on a Au(lll) electrode surface formed by exposure of a single copper monolayer on this electrode and exposed to bisulfide ions in the electrolyte solution has been studied with in situ STM [28]. Correlations between... 

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