Thioglycollic acid, oxidation

Mercaptides are unchallenged as the ligand of choice for the other entities bonded to the tin, but carboxylates can also be used. Whereas a variety of mercaptans are used, the thioglycolic acid derivatives remain the largest single mercaptan. Dibutyltin bis(isooctyl thioglycolate) [25168-24-5] and butyltin tris(isooctyl thioglycolate) [25852-70A] are two common examples. These materials are produced by the reaction of the appropriate alkyl tin chloride or oxide, and the mercaptan. 

Other ions, eg, ferrate, chloride, and formate, are determined by first removing the cyanide ion at ca pH 3.5 (methyl orange end point). Iron is titrated, using thioglycolic acid, and the optical density of the resulting pink solution is measured at 538 nm. Formate is oxidized by titration with mercuric chloride. The mercurous chloride produced is determined gravimetricaHy. Chloride ion is determined by a titration with 0.1 Ai silver nitrate. The end point is determined electrometricaHy. 

Diaryl-thiazolidin-4-one 5,5-dioxides 162 were obtained by reacting thioglycolic acid with Schiff bases, followed by oxidation at the sulfur atom... 

The cyclized analog of meralluride is prepared by a similar synthesis. Thus, condensation of camphoric acid (42) (obtained by oxidation of camphor) with ammonia gives the bicyclic succinimide (44). Reaction with allyl isocyanate followed by ring opening and then reaction with mercuric acetate affords the mercury derivative (45) as the acetate rather than the hydroxide as above. Reaction with sodium chloride converts that acetate to the halide (46). Displacement on mercury with the disodium salt of thioglycollic acid affords the diuretic mercaptomerine (47). ... 

Procedure. Prepare the dithiol reagent by adding 0.1 -0.2 g of dithiol to 100 mL of 0.25M sodium hydroxide solution, followed by 0.5 mL of thioglycollic acid (to inhibit oxidation of the reagent) keep at 5 °C and prepare fresh daily. 

Acetate, (C6H5)4AsC1, citrate, 2,3-dimercaptopropanol, EDTA, I-, Na5P3O10, SO)-, S20)-, tartrate, tiron, tetraphenylarsonium chloride, triethanolamine, thioglycolic acid Acetylacetone, citrate, CN-, EDTA, I-, NH3, N02, SCN-, S20)-, tartrate, triethanol amine Citrate, CN-, EDTA, I-, NH3, N02, SCN-, S20 -, tartrate, urea Reduction to Pu(IV) with sulfamic acid C20)-, citrate, EDTA, F-, tartrate Oxidation to perrhenate Citrate, tartrate, thiourea CN-, thiourea... 

This gap in our knowledge is now closed, as the first paper on the uncatalyzed outer-sphere oxidation of an aliphatic thiol was recently published (12).This work selected thioglycolic acid (TGA, mercaptoacetic acid, HSCH2CO2H) as a representative thiol because of its high water solubility, low vapor pressure, and simple structure. The oxidant was [IrCle]2-, a well-characterized one-electron oxidant that frequently reacts through an outer-sphere mechanism. As is typical of such... 

In view of its importance, reductive dissolution of Fe oxides has been widely studied. Reductants investigated include dithionite, thioglycolic acid, thiocyanate, hydrazine, ascorbic acid, hydroquinone, H2S, H2, Fe ", tris (picolinato) V", fulvic acid, fructose, sucrose and biomass/bacteria (Tab. 12.3). Under the appropriate conditions, reductive dissolution may also be effected photochemically. As with protonation, the extent of reduction may be strongly influenced by ligand and proton adsorption on the oxide surface. 

In a similar way, 1,4-oxathian-2-one and l,4-dioxan-2-one were obtained from the condensation of thioglycolic acid and glycolic acid, respectively <1979J(P1)1893, 1998T11445>, and from palladium-catalyzed <1999JOC6750> or oxoammonium salt <2004JOC5116> oxidations of 2,2 -thiodiethanol or diethylene glycol. Asymmetric syntheses... 

Experimental observations indicate that the oxidation of cobalt (II) to cobalt (III) and the formation of ethylenediamine from N-hydroxyethylethylene-diamine occur simultaneously. This is quite the opposite to what is usually assumed in other instances of transition metal catalysis of organic reactions—for example, the catalytic effect of manganese in the oxidation of oxalic acid (7, 8), of iron in the oxidation of cysteine to cystine (22) and of thioglycolic acid to dithioglycolic acid (5, 23), of copper in the oxidation of pyrocatechol to quinone and in the oxidation of ascorbic acid (29, 30), and of cobalt in the oxidation of aldehydes and unsaturated hydrocarbons (4). In all these reactions the oxidation of the organic molecule occurs by the abstraction of an electron by the oxidized form of the metal ion. 

Ferric ions and complexes in aqueous media react readily with cysteine (13, 21) or thioglycollic acid (14, 22) to form purple complexes which rapidly change to the ferrous form with accompanying formation of disulfides. It was not unreasonable, therefore, to assume that such a reaction provided rapid production of RS radicals in the initial stages of co-oxidation and that this rate should decrease as reduction to ferrous occurred. Eventually reoxidation of ferrous to ferric by peroxide would assert itself, and the rate could rise again. 

Metal chelates of 8-hydroxyquinoline such as (111) with photoconductive properties are reported to be useful in electrophotographic systems.233 The incorporation of a tin complex into a photo-conductive zinc oxide layer is stated to reduce dark decay . In other words, the electrostatic charge applied to the photoconductor has a longer lifetime. Two of the complexes disclosed for this application are (112) and (113). These compounds are prepared from dibutyltin oxide by reaction with 2-mercaptopropionic add and thioglycolic acid, respectively 234... 

In another route (Scheme 2), mixing benzhydrol 12 with thioglycolic acid 13 in trifluoroacetic acid afforded benzhydrylsulfanylacetic acid 14 in 99% yield. The treatment of acid 14 with thionyl chloride, followed by concentrated ammonium hydroxide gave acetamide 11 in 87% yield. The oxidation of the thioether moiety with 30% H202 in acetic acid produced racemic modafmil 1 in 67% yield.27 The overall yield of the three-step route is approximately 57%. 

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