2-Mercapto ethanol

The more reactive bromacetone gives not only 2-mercapto-4-methylthiazole but also its substitution products. The higher homologs, as far as C15. are obtained in reasonably good yield in absolute ethanol (150, 156. 234. 316, 530). The best result (85%) was obtained by working in aqueous solution with the 3-bromobutan-2-one (597). 

Other solvents can be divided into several classes. In hydrogen bond-breaking solvents (dipolar aprotics), the simple amino, hydroxy and mercapto heterocycles all dissolve. In the hydrophobic solvents, hydrogen bonding substituents greatly decrease the solubility. Ethanol and other alcohols take up a position intermediate between water and the hydro-phobic solvents (63PMH 1)177). 

The use of an acidic solution of p-anisaldehyde in ethanol to detect aldehyde functionalities on polystyrene polymer supports has been reported (beads are treated with a freshly made solution of p-anisaldehyde (2.55 mL), ethanol (88 mL), sulfuric acid (9 mL), acetic acid (1 mL) and heated at 110°C for 4 min). The colour of the beads depends on the percentage of CHO content such that at 0% of CHO groups, the beads are colourless, -50% CHO content, the beads appear red and at 98% CHO the beads appear burgundy [Vdzquez and Albericio Tetrahedron Lett 42 6691 200]]. A different approach utilises 4-amino-3-hydrazino-5-mercapto-1,2,4-triazole (Purpald) as the visualizing agent for CHO groups. Resins containing aldehyde functionalities turn dark brown to purple after a 5 min reaction followed by a 10 minute air oxidation [Coumoyer et al. J Comb Chem 4 120 2002]. 

For the detection of the ergot alkaloids 0.2 g o-phthalaldehyde in 100 ml cone, sulfuric acid ( ) [15] or buffer solution is employed as spray solution. Cysteine [11, 12, 15, 19] or sulfurous acid [17] is occasionally substituted for mercapto-ethanol. 

After the addition of 750 parts water, a crystalline product is precipitated. The mixture is further stirred overnight. The solid is then filtered off and recrystallized from a mixture of ethanol and water (1 1 by volume) to yield dl-1 -(1 -phenylethyl)-2-mercapto-5-(ethoxycar-bony Dimidazole its melting point is 129.8°C to 130.8°C. 

N 24.12% brick red solid mp, decomps when heated over 300°. Insol in w and the usual organic solvents as well as weak acids and alkalies. Comm prepn (Ref 3) is from thiocyanic acid and/or thiocyanates either by anodic oxidation or by interaction with hydrogen peroxide or halogens. The yield is impure because it contains both H and O. The S content varies between 45 and 55%. Lab prepn of the pure polymer is by reacting the Na salt of 5-chlor-3-mercapto 1,2,4-thiodiazols with either acet, ethanol or w (Refs 1 2)... 

Absorption spectra of formazans have been studied in detail. Almost all formazans exhibit UV/visible spectra between 300 and 600 nm.1,2,12,13,40,62,325 326 The absorption maxima are very sensitive to substituent effects. For example, the 1,5-diphenyl formazan 185 when X is hydrogen, methyl, phenyl, cyano, and mercapto shows a band at 420, 410, 470, 504, and 590nm in ethanol, respectively. The 3-chloro derivative 186 when X is hydrogen, iodine, bromine, chlorine, and fluorine has a band at 433,433,430,421, and 417 nm, respectively. Table 13 shows the influence of substituents on the absorption maxima in the trisubstituted formazans 3. Table 14 shows the influence of substituents on the absorption maxima of... 

When bis-hydrazonoyl chloride is treated with 3-mercapto-l,2,4-triazole 431 (R = H) in ethanol in the presence of triethylamine at reflux, compound 34 is isolated in 52% yield (Equation 99) <2004JCR(S)264>. 

Transformations of 5-substituted 3-mercapto-4-amino[l,2,4]triazoles 143 with bromomalonitrile are shown in Scheme 27. These reactions were carried out in ethanolic potassium hydroxide to yield A -phthalazinemethylene 144a, <2003PS1987> substituted 1-naphthyl-1-ethyl 144b, <2002HAC199> and 2-naphthyloxymethyl derivatives 144c, 2001PS223>. 

Scheme 44 also shows two further synthetic routes to [l,3,4]thiadiazolo[2,3-c][l,2,4]triazinones. Reaction of the 3-mercapto- or 3-methylsulfanyltriazinone 221 (R1 = H or R1 = Me) with a set of isothiocyanates was reported to give the 2-amino-substituted fused ring system 222 in medium to good yield (36-84%) <1997JHC1351>. Derivative 223 was described to undergo cyclization to a fused thiadiazole 224 by treatment with carbon disulfide in the presence of potassium hydroxide in ethanol <2001PHA376>. 

A third, not too widely used, approach is transformation of an iV-aminotriazine compound, as shown in Scheme 56. The 3-mercapto-4-amino[l,2,4]triazine derivative 361 was treated with an active methylene ketone and NBS in ethanol to yield the cyclized product 362 in moderate to excellent yield <2001JHC711>. A similar synthetic strategy was also applied in another case <2003KGS1844>. 

Several crown ethers that possess side chains with terminal mercapto groups enhance the rate of transesterification of amino-acid p-nitrophenyl esters. Matsui and Koga (1978) reported the reactions of a number of amino-acid p-nitrophenyl ester hydrobromides dissolved in mixtures of ethanol and dichloromethane (1 4) and buffered with acetic acid and pyridine (pH 4.60 in... 

Thompson, E. O. P., and I. J. O Donnell Quantitative reduction of disulfide bonds in proteins using high concentrations of mercapto-ethanol. Biochim. Biophys. Acta 53, 447 —449 (1961). 

When the 3-thiourea derivative (59) was heated in boiling ethanol for 3 h, and then the evaporated reaction mixture was treated with 10% NaOH solution at 100°C for 20 min, anhydro 2-methyl-3-mercapto-4-hydroxy-5,6,7,8-tetrahydro[l,2-6]pyridazinium hydroxide (61) was obtained (71CPB159). The mercapto group was alkylated with benzyl bromide and was treated with HgCla in boiling ethanol to yield the 3-chloromercurithio derivative. Anhydro 3,4-dihydroxy-2-methyl-5,6,7,8-tetrahydropyrido[l,2-f ]pyridazinium hydroxide (62) was O-acylated with acetic anhydride, but the structure of the product was not elucidated (71CPB159). 

Coumarinyl-substituted thiazolo[3,2-h][l,2,4]triazoles have also been reported. They are available in one step by reaction of 5-aryl-3-mercapto[l,2, 4]triazoles with 3-bromoacetylcoumarin (ethanol, reflux, 8 h yield 44-65%) (81AP435) or in a two-step reaction from the corresponding S-alkylated intermediates with PPA [93MI2 94IJC(B)579]. 2-Aminothiazolo[3,2-h][l,2,4]triazoles are also available from 3-mercaptotriazoles. Treatment of 5-amino-3-mercaptotriazole with chloroacetone (DMF, K2CO3) and subsequent acid-catalyzed cyclization yields 146 [90JAP(K)02/142797]. 

Some components of sample buffers, e.g., Tris or 2-mercapto-ethanol, disturb most of the (chemical) protein determinations. If the lanes of an electrophoresis should be compared quantitatively, if a UV measurement of the sample is impossible, and if the sample contains enough material, the protein content in electrophoresis sample buffer can be measured using the following protocol. 

C RPMI medium, 5% ECS (v/v), 0.35ml/100ml 2-mercapto-ethanol, lOU/lOOml streptomycin, lOU/lOOml penicillin, 29 mg/100 ml L-glutamine... 

SDS-PAGE loading buffer (4x). 200 mM Tris-HCl, pH 6.8, 8% SDS, 32% glycerol, 0.008% bromophenol blue, 8% 2-mercapto ethanol Store at room temperature. 

Hydroxy- bzw. 2-Mercapto-imidazolc allgemeine Arbeitsvorschrift122 0,05 mol l,2-Bis-[trimethylsilyl-oxy]-l-alken werden mit 0,2 mol Harnstoff oder Thioharnstoff und 0,5 ml 2,5 M Salzsaure in 25 ml Cy-clohexanol 3h bei 160° gcriihrt. Dann wird filtriert, das Losungsmittel abdestilliert und der Riickstand aus Ethanol/Wasser umkristallisiert. 

CH2-CH(CHj)2 4-Hydroxy-2-mercapto-5-(2-methyl-propyl)-... 60 176 (Wasser/Ethanol)... 

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