Sulfide anions

The anion, bisulfide SH further dissociates into anionic sulfide S and cationic hydrogen ion H ... 

An alternate viewpoint (27) suggests that the incompletely sulfided catalyst consists of a surface layer containing both oxide and sulfide anions, sulfiding occurring preferentially on the more weakly bound oxide... 

The deprotonation reaction of Cp2Ti(SH)2 with NaH in THF proceeds unexpectedly with the elimination of GpH to give the anionic sulfide-bridged titanium(iv) dimer, Na2[CpTi(/x-S)(S)]2. The molecular structure of this compound has been determined by X-ray diffraction and shows a terminal sulfido ligand with a short Ti-S bond distance of ca. 2.2 A, indicating nearly double bond character (Scheme 417). It adopts a yy/z-Ti=S configuration and is stabilized by interactions with THF-solvated sodium cations.1009... 

The basis of the CBD method is the slow release of anions (sulfide or selenides) with free metal ions (Cd +, Ztf+, or Pb +) into a solution such that their concentration just exceeds the solubility product of semiconductor. In the bath, a low concentration of the cations is maintained by their complexation with ligands such as TEOA and/or ammonia. The anions are formed by hydrolysis of thiourea, in the case of sulfide, or hydrolysis of selenosulfate or selenourea, in the case of selenides. The material is precipitated due to a super-saturation condition when the concentration of sulfide/selenide anions exceeds the solubility product of CdS/Se. 

The stability of the various cumulenic anions depends to a large extent upon the nature of the groups linked to the cumulenic system. Whereas solutions of lithiated allenic ethers and sulfides in diethyl ether or THF can be kept for a limited period at about O C, the lithiated hydrocarbons LiCH=C=CH-R are transformed into the isomeric lithium acetylides at temperatures above about -20 C, probably via HC C-C(Li )R R Lithiated 1,2,4-trienes, LiCH=C=C-C=C-, are... 

The anions derived from allenic sulfides, RCH=C=C-SR , which are stable in liquid... 

The higher reactivity of 2-halogenothiazoles with respect to halogenopyridines can be related to the different aromaticity of the two systems, less for thiazole than for pyridine, for example, the relatively stronger fixation of the tt bond in the thiazole than in the case of pyridine. As the data reported in Table V-1 (footnote a) indicates, the free thiophenol is more reactive than the thiolate anion toward the 2-halogenothiazoles. This fact should be considered when one prepares the thiazolyl sulfides. 

MSH (a metal hydrogen sulfide a source of the nucleophilic anion HS )... 

Hydrogen sulfide ion HS and anions of the type RS are substantially less basic than hydroxide ion and react with both primary and secondary alkyl halides to give mainly substitution products... 

Inorganic Analysis The most important precipitants for inorganic cations are chromate, the halides, hydroxide, oxalate, sulfate, sulfide, and phosphate. A summary of selected methods, grouped by precipitant, is shown in Table 8.1. Many inorganic anions can be determined using the same reactions by reversing the analyte... 

The basic flow sheet for the flotation-concentration of nonsulfide minerals is essentially the same as that for treating sulfides but the family of reagents used is different. The reagents utilized for nonsulfide mineral concentrations by flotation are usually fatty acids or their salts (RCOOH, RCOOM), sulfonates (RSO M), sulfates (RSO M), where M is usually Na or K, and R represents a linear, branched, or cycHc hydrocarbon chain and amines [R2N(R)3]A where R and R are hydrocarbon chains and A is an anion such as Cl or Br . Collectors for most nonsulfides can be selected on the basis of their isoelectric points. Thus at pH > pH p cationic surfactants are suitable collectors whereas at lower pH values anion-type collectors are selected as illustrated in Figure 10 (28). Figure 13 shows an iron ore flotation flow sheet as a representative of high volume oxide flotation practice. 

Several iron sulfide nitrosyl compounds are known. These have stmctures that in some cases are formally related to the FeS clusters by replacement of thiolate by NO. The compounds include the anions [Fe2S2(NO)4] and [Fe4S2(NO)2] (Roussin s red and black salts, respectively) and the neutral compounds [Fe2S2(NO)4] and [Fe4S4(NO)4]. Roussin s black salt has found use as a NO releasing vasodilator. 

Ma.nufa.cture. The preferred method for making nickel sulfate is adding nickel powder to hot dilute sulfuric acid. Adding sulfuric acid to nickel powder in hot water enhances the formation of H2S. Hydrogen sulfide always forms as a by-product upon reaction of metallic nickel and sulfuric acid. The hberated hydrogen is absorbed by the metal and then reduces the sulfate anion to H2S. 

Solvent extraction—purification of wet-process phosphoric acid is based on preferential extraction of H PO by an organic solvent vs the cationic impurities present in the acid. Because selectivity of acid over anionic impurities is usually not sufficient, precipitation or evaporation steps are included in the purification process for removal. Cmde wet-process acid is typically concentrated and clarified prior to extraction to remove post-precipitated sludge and improve partition of the acid into the solvent. Concentration also partially eliminates fluoride by evaporation of HF and/or SiF. Chemical precipitation of sulfate (as Ba or Ca salts), fluorosiUcates (as Na salt), and arsenic (as sulfides) may also be used as a prepurification step preceding solvent extraction. 

The neat resin preparation for PPS is quite compHcated, despite the fact that the overall polymerization reaction appears to be simple. Several commercial PPS polymerization processes that feature some steps in common have been described (1,2). At least three different mechanisms have been pubUshed in an attempt to describe the basic reaction of a sodium sulfide equivalent and -dichlorobenzene these are S Ar (13,16,19), radical cation (20,21), and Buimett s (22) Sj l radical anion (23—25) mechanisms. The benzyne mechanism was ruled out (16) based on the observation that the para-substitution pattern of the monomer, -dichlorobenzene, is retained in the repeating unit of the polymer. Demonstration that the step-growth polymerization of sodium sulfide and /)-dichlorohenzene proceeds via the S Ar mechanism is fairly recent (1991) (26). Eurther complexity in the polymerization is the incorporation of comonomers that alter the polymer stmcture, thereby modifying the properties of the polymer. Additionally, post-polymerization treatments can be utilized, which modify the properties of the polymer. Preparation of the neat resin is an area of significant latitude and extreme importance for the end user. 

In the presence of sulfide or sulfhydryl anions, the quinonemethide is attacked and a benzyl thiol formed. The P-aryl ether linkage to the next phenylpropane unit is broken down as a result of neighboring-group attack by the sulfur, eliminating the aryloxy group which becomes reactive phenolate ion (eq. 2). If sulfide is not present, a principal reaction is the formation of the stable aryl enol ether, ArCH=CHOAr. A smaller amount of this product also forms in the presence of sulfhydryl anion. 

Silver compounds having anions that are inherently toxic, eg, silver arsenate and silver cyanide, can cause adverse health effects. The reported rat oral LD values for silver nitrate, silver arsenate [13510-44-6] and silver cyanide are 500—800 (29), 200—400 (29), and 123 mg/kg (30), respectively. Silver compounds or complexes ia which the silver ion is not biologically available, eg, silver sulfide and silver thiosulfate complexes, are considered to be without adverse health effects and essentially nontoxic. 

Certain base adducts of borane, such as triethylamine borane [1722-26-5] (C2H )2N BH, dimethyl sulfide borane [13292-87-OJ, (CH2)2S BH, and tetrahydrofuran borane [14044-65-6] C HgO BH, are more easily and safely handled than B2H and are commercially available. These compounds find wide use as reducing agents and in hydroboration reactions (57). A wide variety of borane reducing agents and hydroborating agents is available from Aldrich Chemical Co., Milwaukee, Wisconsin. Base displacement reactions can be used to convert one adduct to another. The relative stabiUties of BH adducts as a function of Group 15 and 16 donor atoms are P > N and S > O. This order has sparked controversy because the trend opposes the normal order estabUshed by BF. In the case of anionic nucleophiles, base displacement leads to ionic hydroborate adducts (eqs. 20,21). 

Use of Surfa.cta.nts, Although the use of steam to improve dewatering is consistently beneficial, the effects of surfactants on residual moisture are highly inconsistent. Additions of anionic, nonionic, or sometimes cationic surfactants of a few hundredths weight percent of the slurry, 0.02—0.5 kg/1 of soHds (50), are as effective as viscosity reduction in removing water from a number of filter cakes, including froth-floated coal, metal sulfide concentrates, and fine iron ores (Table 2). A few studies have used both steam and a surfactant on coal and iron ore and found that the effects are additive, giving twice the moisture reduction of either treatment alone (44—46,49). 

Ion-selective electrodes are available for the electro analysis of most small anions, eg, haUdes, sulfide, carbonate, nitrate, etc, and cations, eg, lithium, sodium, potassium, hydrogen, magnesium, calcium, etc, but having varying degrees of selectivity. The most successful uses of these electrodes involve process monitoring, eg, for pH, where precision beyond the unstable reference electrode s abiUty to deUver is not generally required, and for clinical apphcations, eg, sodium, potassium, chloride, and carbonate in blood, urine, and semm. 

Thiirane 1-oxide undergoes acid-catalyzed ring opening by ethanethiol to give ethyl 2-ethylthioethyl disulfide. Treatment of thiirane 1,1-dioxide with thiolate anions, sodium sulfide or thiourea gives /3-mercaptosulfinic acid derivatives (75S55). Thiiranium ions are attacked at carbon by most sulfur nucleophiles (79ACR282), but see Section 5.06.3.4.3 for exceptions. 

Hydrogen Sulfide HjS Cause of rotten egg odor corrosion Aeration, chlorination, highly basic anion exchange... 

Ion exchange, in which cation and/or anion resins are used to replace undesirable anionic species in liquid solutions with nonhazardous ions. For example, cation-exchange resins may contain nonhazardous, mobile, positive ions (e g., sodium, hydrogen) which are attached to immobile acid groups (e.g., sulfonic or carboxylic). Similarly, anion-exchange resins may include nonhazardous, mobile, negative ions (e.g., hydroxyl or chloride) attached to immobile basic ions (e.g., amine). These resins can be used to eliminate various species from wastewater, such as dissolved metals, sulfides, cyanides, amines, phenols, and halides. 

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