Xanthic acid

Table 1. Nomenclature of Some Xanthic Acids and Related Compounds...

Reactions. The chemistry of the xanthates is essentially that of the dithio acids. The free xanthic acids readily decompose in polar solvents, the rate being 10 times greater in methanol than in hexane. The acids decompose at room temperature to carbon disulfide and the corresponding alcohol the resulting alcohol autocatalyticaHy faciUtates the decomposition. 

Esters derived from the primary alcohols are the most stable and those derived from the tertiary alcohols are the least stable. The decomposition temperature is lower in polar solvents, eg, dimethyl sulfoxide (DMSO), with decomposition occurring at 20°C for esters derived from the tertiary alcohols (38). Esters of benzyl xanthic acid yield stilbenes on heating, and those from neopentyl alcohols thermally rearrange to the corresponding dithiol esters (39,40). The dialkyl xanthate esters catalytically rearrange to the dithiol esters with conventional Lewis acids or trifluoroacetic acid (41,42). The esters are also catalytically rearranged to the dithiolesters by pyridine Ai-oxide catalysts (43) ... 

The acid chlorides of the xanthic acids can be prepared by the reaction of chlorine with a dixanthogen (55) ... 

Esters of dithioacids often give 1,2,3,4-thiatriazoles in good yield on treatment with sodium azide [Eq. (2)] however, this method is not as general as method 1. Dithiocarbamic and xanthic acids and... 

Xantho-gensaure, /, xanthogenic acid, xanthic acid. -kobaltchlorid, n, xanthocobaltic chloride, nitropentamminecobalt(III) chloride. -proteinsaure, /. xanthoproteic acid. 

Many alkali-metal xanthates are formed by direct xanthation of alcohols (23), but their chemistry is still vague. Acidification of the alkali-metal salts produces the unstable xanthic acids (24). 

Salts of the series of xanthic acids of the general formula ROCSSH. Certain xanthates such as ZIX are ultra accelerators for mbber. Cellulose xanthate is the intermediate product in the manufacture of viscose. See Viscose Rayon. Xanthogen Sulphide... 

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],... 

The different behavior of technetium and rhenium may arise because Re (VII) is not reduced by xanthic acid to the same oxidation state as Tc (VII). Other suitable extracting solvents are chloroform, 1.1.1-trichloroethane and isopropyl ether. 

Uses and Physiological Properties of Carbon Disulphide.—Besides its employment as a solvent (see p. 260), carbon disulphide is used extensively in the manufacture of viscose silk. Viscose is a solution of the sodium salt of the cellulose ester of thiolthioncarbonic acid (p. 268) in water or dilute aqueous sodium hydroxide, or it may be described as an aqueous solution of the sodium salt of cellulose xanthic acid. For its production cellulose is steeped in concentrated sodium hydroxide solution and then pressed, the product being called alkali-cellulose and the formula CeH10O5.NaOH assigned to it. This is converted into viscose by treatment with carbon disulphide, when the colour changes to golden yellow ... 

Xanthic Acid or Xanthogenic Acid is ethylthiolthionearbonic acid. Its potassium salt, which is yellow and has a disagreeable smell, is prepared by the action of alcoholic potash on carbon disulphide ... 

Xanthic acid is obtained as a colourless oil by the action of dilute sulphuric acid on the potassium salt in the cold. It decomposes at 24° C. into ethyl alcohol and carbon disulphide. The ethyl ester, when heated with water, yields carbon dioxide, hydrogen sulphide, ethyl alcohol and ethyl mercaptan, whilst with ammonia, ethyl mereaptan and ccanthogenamide or thiourethaiie, CgH5O.CS.NHa, are produced. These reactions indicate that the constitution of the acid is... 

Free xanthic acids (83), also referred to as O-alkyl- and O-aryl-dithiocarbonic acids, are not well-characterized compounds. They are strong acids and stable only in an extremely pure state. The isomeric acids (84) are unknown. 

Xanthic acid metal complexes, 588 X-Ray diffraction aqueous solution, 307 cone angles estimation, 1022 hydrates... 

Carbon disulfide is the dithio derivative of C02. It is only a weak electrophile. Actually, it is so unreactive that in many reactions it can be used as a solvent. Consequently, only good nucleophiles can add to the C—S double bond of carbon disulfide. For example, alkali metal alkoxides add to carbon disulfide forming alkali metal xan-thates A (Figure 7.4). If one were to protonate this compound this would provide compound B, which is a derivative of free dithiocarbonic acid. It is unstable in the condensed phase in pure form, just as free carbonic acid and the unsubstituted carbamic acid (Formula B in Figure 7.3) are unstable. Compound B would therefore decompose spontaneously into ROH and CS2. Stable derivatives of alkali metal xanthates A are their esters C. They are referred to as xanthic add esters or xanthates. They are obtained by an alkylation (almost always by a methylation) of the alkali metal xanthates A. You have already learned about synthesis applications of xanthic acid esters in Figures 1.32, 4.13, and 4.14. 

Colorimetric Method.—Molybdenum may be detected quantitatively by means of the xanthic acid test already described (p. 178). The red product is extracted with a mixture of ether and light petroleum (65 35) and the extract diluted with another mixture of ether and light petroleum (30 70) for comparison with the standard solution. If pure ether is used, decomposition takes place. 

Xanthx Acid.—Another solvent of cellulose is xanthlc acid, also called xanthonic or xanthogenic acid. Xanthic acid is the ethyl ether of -di-thio-carbonic acid. Its formula is HS-CS-OC2H5. When heated with water to 500° under pressure cellulose is dissolved and undergoes decomposition. 

Viscose Silk.—III. From Cellulose Xanthate. We have referred to the solvent action of xanthic acid, which is the ethyl ether of di-thio-carbonic acid, viz., HS-CS-OC2H5. When sodium cellulose is dissolved in xanthic acid the cellulose is in the form of sodium cellulose xanthate. A solution properly prepared by treating cellulose with sodimn hydroxide and carbon di-sulphide in the presence of benzene or carbon tetra-chloride, in which polymerization of the cellulose compound is effected, is decomposed by forcing capillary streams of the solution into a solution of ammonium sulphate. The cellulose is thus obtained as in the other processes in the form of fine filaments of a hydrated cellulose possessing silk-like properties. Artificial silk of this type is known as viscose silk and is made in large quantities. In 1914 about 20,000,000 pounds of artificial silk were made, of which about 3,000,000 pounds were made in the United States. Most of this product was viscose silk. 

The free xanthic acids are unstable, colodess, or yellow oils, and may decompose with explosive violence. They are soluble in the common organic solvents and are slightly soluble in water methyl xanthic acid at 0 0, 0.05 mol/L ethji xanthic acid at 0 0, 0.02 mol/L and -butyl xanthic acid at 0 0,0.0008 mol/L. Values for the dissociation constant for ethyl xanthic acid are (2.0—3.0) xl0 (5). Potentiometric determinations for Cg xanthic acids show a decreasing acid strength with increasing molecular weight (6,7). The values for the ethji derivative are (1.82—3.4) x 10 . Similar values determined by the same method are reported in Reference 8 for a series in dimethylformamide. Some piC values for alkyl xanthic acids are given in Table 2. 

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