Thioglycolic acid Thiol

Persulfate (41) reacts with transition metal ions (e.g. Ag, Fe21, Ti31) according to Scheme 3.42. Various other reduetants have been described. These include halide ions, thiols (e.g. 2-mercaptoethanol, thioglycolic acid, cysteine, thiourea), bisulfite, thiosulfate, amines (triethanolamine, tetramethylethylenediamine, hydrazine hydrate), ascorbic acid, and solvated electrons (e.g. in radiolysis). The mechanisms and the initiating species produced have not been fully elucidated for... 

A range of functional thiols e.g. thioglycolic acid (2) and mercaptoethanol (3)] has been used to produce monofunctional polymers10"54 50 (Section 7.5.2) and thcncc as precursors for diblock copolymers.47... 

However, more recent work has shown that the reaction of thioglycollic acid (HSCH2COOH) with methylcobalamin to give the methyl thioether requires oxygen and shows an induction period [which can be reduced by increasing the pH, the thiol concentration, or the partial pressure of O2, and eliminated by the addition of the Co(II) complex], followed by a steady-state reaction [ whose rate increases with pH, the concentration of the CH3C0 and Co(II) complexes and the partial pressure of O2, but is independent of thiol concentration]. Neither the induction period nor the steady-state... 

Linen esterified with thioglycolic acid to incorporate thiol groups, these being more strongly nucleophilic than hydroxy groups. 

A development reported recently [519] involves reduction of the cystine disulphide bonds in wool with either thioglycolic acid or tetrakis(hydroxymethyl)phosphonium chloride to form thiol groups, followed by crosslinking with bifunctional reactive dyes. This gave improved insect resistance but had adverse effects on physical properties such as strength, shrinkage and stiffness, thus limiting the potential of the process for commercial use. 

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... 

A very early example of this reaction was provided by Meriwether et al., who reacted molybdate with various thiols, including 1,2-ethanedithiol and thioglycolic acid, to produce EPR active complexes (66). These reactions have now been shown, through spectral comparisons with authentic materials, to yield complexes such as [Mo 0(SCH2 CH2S)2] (158) and [Mo 0(L-SO)2]" (Section IV.B.2.b) (133). The reactions with molybdate may be written as Eq. (22). 

The oxidation of thiols in the form of L-cysteine, penicillamine, and thioglycollic acid by [Mo(CN)g] in aqueous acidic solution also formed disulfides as final products 111). The reactions show a second-order substrate dependence, and the rates are found to decrease with increasing hydrogen ion concentration. This is attributed to the deprotonation of the —SH and —COOH groups in these thiols prior to electron transfer. The reactions are interpreted in terms of outer-sphere activation. An explanation for the second-order dependence on thiol concentration involves ion association between the cyano complex and a protonated form of the thiol, followed by reaction of this complex with a second thiol molecule. 

Thioamide synthesis from dithiocarboxylates and amines under basic conditions gives thiols as rather unpleasant parallel products. This problem is avoided by using S-thioacylated thioglycolic acids (17), as... 

Mercuric chloride, other mercury-containing antibacterials and silver will inhibit enzymes in the membrane, and for that matter in the cytoplasm, which contain thiol, -SH, groups. A similar action is shown by 2-bromo-2-nitropropan-l,3-diol (bronopol) and /so-thiazolones. Under appropriate conditions the toxic action on cell thiol groups may be reversed by addition of an extrinsic thiol compound, e.g. cysteine or thioglycollic acid (see also Chapter 20). Particularly susceptible enzymes are the dehydrogenases involved in membrane-associated redox processes. 

Improved syntheses for [Mo(CN)8]3 salts based on the use of NaN02 in mineral acid as oxidant have appeared nitrosonium ion, NO+, is believed to be the active agent in this proton-assisted reaction.650 Thiols such as L-cysteine, penicillamine, and thioglycolic acid are oxidized to disulfides by [Mo(CN)g]3, with concomitant formation of [Mo(CN)8]4 kinetics studies of these reactions have been reported.651 The structural and chemical properties of [Mo(CN)8]3 and related species have been reviewed.652... 

---