Xanthate salt

Table 8 summarizes domestic consumption by use for amyl alcohols. About 55% of the total 1-pentanol and 2-methyl-1-butanol production is used for zinc diamyldithiophosphate lubrication oil additives (150) as important corrosion inhibitors and antiwear additives. Amyl xanthate salts are useful as frothers in the flotation of metal ores because of their low water solubiUty and miscibility with phenoHcs and natural oils. Potassium amyl xanthate, a collector in flotation of copper, lead, and zinc ores, is no longer produced in the United States, but imports from Germany and Yugoslavia were 910 —1100 t in 1989 (150). 

The heavy metal salts, ia contrast to the alkah metal salts, have lower melting points and are more soluble ia organic solvents, eg, methylene chloride, chloroform, tetrahydrofiiran, and benzene. They are slightly soluble ia water, alcohol, ahphatic hydrocarbons, and ethyl ether (18). Their thermal decompositions have been extensively studied by dta and tga (thermal gravimetric analysis) methods. They decompose to the metal sulfides and gaseous products, which are primarily carbonyl sulfide and carbon disulfide ia varying ratios. In some cases, the dialkyl xanthate forms. Solvent extraction studies of a large number of elements as their xanthate salts have been reported (19). 

Because of hydrate formation, the sodium salts tend to be difficult to dry. Excess water over that of hydration is beheved to accelerate the decomposition of the xanthate salts. The effect of heat on the dryiag of sodium ethyl xanthate at 50°C has been studied (84) ... 

Salts of O-alkyldithiocarbonatcs ( xanthates ) are hazardous as dusts, forming explosive suspensions in air. The lower-alkyl salts are claimed to be explosive in the solid state when dry [1]. Explosions reported when drying hydrated xanthate salts are probably the consequence of release of carbon disulphide to form an inflammable atmosphere of very low autoignition temperature in the oven [2], Xanthate esters are thermally unstable by a variety of eliminations and rearrangements, all distinctly exothermic and many evolving extremely flammable gases and vapours. Free xanthic acids, which may be isolated on acidification, decompose autocatalytically and perhaps explosively [3],... 

Figure 4.41 presents the FTIR reflection spectra of ethyl xanthate adsorption on marmatite at different pH. The characteristic absorption peaks 1210, 1108, 1025 cm occurred. It has been reported that the characteristic absorption bands of dixanthogen are 1260, 1240, 1020 and 1105 cm and those bands of zinc xanthate are 1030, 1125 and 1212 cm (Mielezarski, 1986 Leppinen, 1990). It is derived from Fig.4.41 that there may exist the mixture of dixanthogen and zinc xanthate because both distinct peaks of dixanthogen and xanthate salt appeares in Fig. 4.41, which further confirms the results from the UV analysis in Fig. 4.36 and Fig. 4.37. It can also be seen from Fig. 4.41 that the intensity of the IR peaks is strong indicating the stronger adsorption of xanthate on marmatite accounting for its good floatability in weak pH media. When pH increased above 7, only a very weak peak appeared in the spectra indicating very weak or no adsorption of xanthate on marmatite accounting for its very poor floatability in alkaline pH media.

Because of the strong hydrolysis property of antimony salt, it is very difficult to prepare antimony xanthate salt to obtain its IR spectrums. Therefore, the formation of antimony xanthate is difficult to be identified by the UV and FTIR analysis, which has been determined by using XPS. Finally, it can be concluded that the interaction mechanism between ethyl xanthate and jamesonite are attributed to the formation of lead and antimony xanthate on the surface in the light of flotation results, voltammogram measurement, UV and FTIR as well as XPS analyses. 

Abstract In this chapter, the depression mechanism of five kinds of depressants is introduced respectively. The principle of depression by hydroxyl ion and hydrosulphide is explained which regulates the pH to make the given mineral float or not. And so the critical pH for certain minerals is determined. Thereafter, the depression by cyanide and hydrogen peroxide is narrated respectively which are that for cyanide the formation of metal cyanide complex results in depression of minerals while for hydrogen peroxide the decomposition of xanthate salts gives rise to the inhibitation of flotation. Lastly, the depression by the thio-organic such as polyhydroxyl and poly carboxylic xanthate is accounted for in detail including die flotation behavior, effect of pulp potential, adsorption mechanism and structure-property relation. 

Alkylation of this xanthate salt with an alkyl halide in absolute ethanol leads to an 0,S-dialkyl dithiocarbonate. 

Isolation of the intermediate xanthate salts in the preparation of the xanthate esters is not essential. The formation of the latter may be achieved, in one step, by converting the alcohol into the corresponding alkoxide by reaction with a potassium derivative of a tertiary alcohol (e.g. potassium t-pentoxide), followed by reaction successively with carbon disulphide and the alkyl halide. Both preparative procedures are illustrated in the following section. 

Another cellulose product is rayon. This is really cellulose itself, temporarily modified so that it can be dissolved and processed to give films or fibres. The starting materia) (from wood, cloth, or paper) is impregnated with concentrated NaOH solution. Addition of CS2 allows some of the OH groups to react to give a xanthate salt that is soluble in water. 

The potassium xanthate salts of some tertiary alcohols on pyrolysis yield alkenes. The overall yield in this case is often markedly better than those obtained from the corresponding 5-methyl xanthates (the classical Chugaev procedure). 

Xanthate salts add reversibly to electrophihc olefins, but this conjugate addition is reversible [17]. By operating under acidic conditions, the reverse reaction can be prevented and a high yield of the desired xanthates can be secured. In this way, a number of otherwise inaccessible xanthates can be prepared and used in radical addition reactions [18]. Of particular interest are tertiary xanthates, such as compound 14 shown in Scheme 7, since the inter-molecular addition leads to the formation of a quaternary centre. Further-... 

Other motifs can be eliminated besides sulfonyls in order to introduce an unsaturation. Nitrogen dioxide is a good leaving group in a radical sense and, since nitroolefins are excellent Michael acceptors, it is easy to prepare /3-nitro xanthates by conjugate addition of a xanthate salt. Exposure of these compounds to an equivalent amount of lauroyl peroxide furnishes the corres-... 

Not only acyl, but also alkoxycarbonyl radicals can be generated from the corresponding xanthates, and their capture by addition to olefins produces esters or lactones, depending on whether the addition reaction is inter-or intra-molecular [53]. Grainger and Innocenti found that xanthates derived from carbamoyl chlorides were difficult to make and handle but, by replacing the xanthate salt by a dithiocarbamate, better precursors for the desired aminocarbonyl radicals were obtained [54]. Irradiation with a tungsten lamp proved more efficient than chemical initiation with lauroyl peroxide and lactams of various sizes could be readily obtained, as illustrated by the... 

However, more complex sulfur nucleophiles, such as thiourea, thiocyanate ion, and xanthate salts appeared to accomplish deoxygenation of the oxaziridines by ring-opening attack at carbon followed by the usual reactions leading to thia-ziridines, which lost elemental sulfur." ... 

Reactions of diaryliodonium salts with various organochalcogen anions led to the arylchalcogen derivatives. (Table 5.7) The anions of sulfur compounds afford generally the 5-aryl derivatives. Sometimes the intermediate iodanes can be isolated. Examples are the reaction of dithiocarbamate and xanthate salts with diaryliodonium. Upon heating, the dithiocarbamate derived iodane afforded the aryldithiocarbamates.133 Thermal decomposition of the xanthate derived iodanes gave mixtures of arylxanthates and diaryldisulfides. ... 

A significant development in this regard was the correlation of the solubility products of a series of heavy metal-ethyl xanthate salts with the floatability of corresponding sulfide minerals by (Kakovsky, 1980). He found the decrease in the order of the solubility product of sulfide minerals to be in line with the increase in the order of their floatability. From exchange reactions of lead-diethyl xanthate, the well-known Barsky equation can be derived ... 

Using Eq. (4.42), the pMe -pH diagrams given in Fig. 4.40 can be generated. In this diagram, the horizontal line at the bottom represents the minimum concentration of metallic ions which is necessary for the formation of ethyl xanthate salt the intersection point of horizontal and vertical lines gives the upper pH limit for the mineral flotation. 

A similar rearrangement which involves migration of the thionoalkoxy group is assumed to occur during the reaction of xanthate salts with epoxides, which leads to trithiocarbonates . The proposed mechanism is presented in equation (4). 

Xanthate salts, R-O-CS-S" 1100-1000 9.10-10.00 s Have three strong bands in region 1250-1030 cm (see... 

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