Thio Michler’s ketone

Thio-Michler s Ketone [1226-46-6] M 284.6, A,nax 457 nm ( 2.92 x 10 in 30% aq n-propanol). Purified by recrystn from hot EtOH or by triturating with a small volume of CHCI3, followed by filtration and washing with hot EtOH [Terbell and Wystrade JPC 68 2110 1964]. 

A sensitive method for determining chlorine in tap water has been based on the reaction of chlorine with thio-Michler s ketone (formula 46.2) (e = 7.7T0 at 640 nm). The method has been applied in the FIA technique [65]. The reaction of chlorine with 4-nitroaniline has been applied in the continuous method of determining chlorine in air [66]. 

Many methods developed are based on organic reagents having sulphur as the ligand atom, such as the dithizone and dithiocarbamates, thio-Michler s ketone (in 30% DMF, e =... 

A sensitive and selective method utilizing Rhodamine B, and a simple bromide method are discussed later. Among other methods, those with other basic dyes (in addition to Rhodamine B), and with thio-Michler s ketone merit attention. 

Thio-Michler s ketone (formula 46.2) reduces Au(III) and forms various complexes with Au(I) (pH 1- ), generally with participation of halide ions or solvent molecules. These complexes allow the sensitive determination of Au in water-ethanol, water-DMF, CHCI3, or CHCl3-butanol media. Molar absorptivity values vary, according to the medium, from 1-10 to 2-10 at 525-560 nm [58,59]. 

Two methods are presented in detail an extractive dithizone method and the thio-Michler s ketone method. Both of them have good selectivity but the latter is more sensitive. Methods based on ion-associates formed by anionic mercury complexes with basic dyes are also noteworthy. 

In the reaction of mercury(II) ions with thio-Michler s ketone (TMK, formula 46.2) the ions are reduced to Hg(I) and then complexed. This colour reaction, in various forms, has been recommended for selective and sensitive determination of Hg [40-42]. 

Thio-Michler s ketone (TMK), O.OOIM solution in dimethylformamide (DMF) (28.5 mg of TMK in 100 ml). The solution should be kept in darkness. 

A number of organic sulphur compounds are recommended as reagents for mercury. The thio-Michler s ketone and the dithizone methods have been described above. Other, less sensitive reagents include, thiodibenzoylmethane [59], thiobenzoylacetone (e = 1.7-10 ) [60], l-salicylidene-5-(2-pyridylmethylidene)-isothiocarbonehydrazide (40% DMF, e = 1.7-10 at 400 nm) [61], and 1-(2-thienyl)benzothiazoline [62]. 

A dithizone method, a very sensitive thio-Michler s ketone method, and a less sensitive iodide method are discussed below. A simple modification of the iodide method gives a very sensitive method involving the formation of the blue starch-iodine complex. 

Palladium and thio-Michler s ketone (TMK) (formula 46.2) form red mixed ligand complexes Pd(TMK)2X2 (X = CF, Br, T, or SCN ) on extraction with CHCI3, in the presence of suitable halide ions in weakly acidic aqueous solution. The complexes [Pd(TMK)4(Sol)2] are formed when the extraction is done with mixtures of CHCI3 with a polar solvent (Sol) such as ethanol or DMF, or with only a polar solvent, e.g., amyl alcohol. Similar complexes (Pd TMK = 1 4) form in mixed organic-aqueous solutions containing 30-40% of DMF or 40-50% of ethanol. 

The thio-Michler s ketone has been proposed for a very sensitive spectrophotometric determination of palladium [30.31]. Depending on the conditions, the value of e for the method is 110 -310 . 

Many organic spectrophotometric reagents for Pd incorporate sulphur as a ligand atom. Apart from dithizone and thio-Michler s ketone, which have been discussed above, examples include the thiourea derivatives [33-36] p-dimethylaminobenzylidene-rhodanine (rhodanine) (e = 4.9 10 ) [37] and its derivatives [38], thiodibenzoylmethane [39,40], and thiosemicarbazone derivatives [41—47]. 

The methods described in detail in Section 36.2, or only mentioned, have been used as follows for spectrophotometric determination of palladium the thio-Michler s ketone — in silver, copper, and anodic slime [32], in catalysts [31] with thiosemicarbazide derivatives — in water [44] and alloys [46] with palladium-carbon powder — with a-benzilmonoxime [48] with PAR — in catalysts and ores [58] with thiazolylazo derivatives — in Ni-Al catalysts [63] with 5-Br-PADAP — in titanium alloys with pyridylazo derivatives - in nickel alloys [68] with sulphonitrophenol - in silver alloys [70] with Arsenazo III — in iron and meteorites and with Palladiazo — in catalysts, minerals, silica gel, and calcium carbonate [78]. 

Among the many spectrophotometric methods for determining silver, the dithizone method is particularly important. Some newer methods, such as that using thio-Michler s ketone, and methods based on ion-associates with dyes, can be recommended. 

The thio-Michler s ketone was applied for the determination of silver in mineral waters [59,60], sewage [61], and lead [59,60. ... 

Example 7.1. Palladium reacts with Thio-Michler s ketone, forming a colored 1 4 complex. A 0.20 ppm Pd sample gave an absorbance of 0.390 at 520 nm using a 1.00-cm cell. Calculate the molar absorptivity (e) for the palladium Thio-Michler s ketone complex. 

Figure 7.11. Job curves of thio-Michler s ketone TMK) complexes of mercury (O) and of palladium ( ). From K. L. Cheng, Absorptiometry, in J. D. Winefordner, ed., Spectrochemical Methods of Analysis, New York Wiley-Interscience, 1971, chap. 6, by permission of the editor and John Wiley and Sons.

When dilute aqueous solutions of chlorine, bromine or iodine are shaken with the yellow benzene solution of 4,4 -bis-dimethylamino-thiobenzophe-none (thio-Michler s ketone) a deep blue results. The same color reaction occurs when dissolved or gaseous halogens come into contact with filter paper impregnated with the thioketone. 

The resulting chlorine can be detected in the gas phase with thio-Michler s ketone, that is, by contact with reagent papers which contain 4,4 -bis-dimethylamino-thiobenzophenone, or fluorescein with alkali bromide. The yellow reagent papers turn blue or red, respectively. Concerning the chemistry of these two color reactions and the preparation of the reagent papers, see pages 143 and 144. 

The above procedure can not be used directly if halogenates or nitrates are present. The former likewise yield free chlorine when fused with CdClj. The latter yield Cd(N08)i initially, which then loses Na04 on dry heating, and thus also oxidizes thio-Michler s ketone to a blue compound. These inter-... 

Thio-Michler s ketone paper For preparation see page 144. 

Thiomalic acid, see M-00026 Thiomandelic acid, see M-00019 Thio-Michler s ketone, see B-00326 Thionalide, see M-00038 3-Thionaphthoyltrifluoroacetone, see B-00109... 

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