Big Chemical Encyclopedia

Chemical substances, components, reactions, process design ...

Articles Figures Tables About

Dimethyl sulphonic acids, Reactions

Goheen and Bennett9 showed that regular nitric acid could be used, in about two molar excess, for the oxidation of dimethyl sulphoxide to dimethyl sulphone in 86% yield. The reaction temperature was 120-150°C with a reaction time of about 4 hours. The mechanism for this reaction was postulated to involve initially a protonated sulphoxide species (which has been shown to be present in other strongly acidic systems101 ) followed by nucleophilic attack by nitrate, and the loss of nitrogen dioxide as shown in equations (4) and (5). [Pg.971]

The first report of the use of bromine for the oxidation of sulphoxides appeared in 1966116. Diphenyl sulphone was isolated in 0.5-1% yield when the sulphoxide was treated with bromine in aqueous acetic acid for several hours. The yield was increased to about 5% by quenching the reaction with sodium carbonate. A kinetic study117 of a similar reaction involving dimethyl sulphoxide showed no significant yield improvement but postulated that the mechanism proceeds via an equilibrium step forming a bromosulph-onium type intermediate which reacted slowly with water giving dimethyl sulphone as indicated in equation (35). [Pg.981]

Gollnick and Stracke176 investigated the very complex mechanism involved in the photolysis of dimethyl sulphoxide and concluded that disproportionation is probably the route for the major sulphone-producing reaction. Other oxidized species such as methanesulphonic acid are also produced and are also probably formed by a series of disproportionation reactions, for example equation (62). Thus photolysis of dimethyl sulphoxide is not a synthetically useful reaction due to the large number of compounds produced. [Pg.988]

Selenium has been determined with 5,5-dimethyl-1,3-cyclohexanedione [51], 6-amino-1-hydroxynaphthalenesulphonic acid [52,53], and l-aminonaphthalene-7-sulphonic acid [54], Determinations of Se involved also the following dyes Rhodamine B [55], Methylene Blue [56], Xylenol Orange [57], and Rhodamine 6G (by the amplification method, in iodide medium, after oxidation of iodide to iodine, and reaction of the I03 with the dye) [58]. [Pg.382]

In contrast to the usual reaction of aromatic aldehydes with cyclic ketones o-nitrobenzaldehyde condenses with 17-ketones to produce good yields of seco-acids, a reaction which has been applied to the preparation of 16-oxa-steroids. Thus, 3 -hydroxy-5a-androstan-17-one or its acetate affords the seco-steroid (153), which can be oxidised either as the free acid by ozone and alkaline hydrogen peroxide to the diacid (155) or, as its methyl ester (154), with chromium trioxide to the monomethyl ester (156). Diborane reduction of the diacid (155) or lithium aluminium hydride reduction of the dimethyl ester (157) gave the trans-diol (158), cyclised with toluene-p-sulphonic acid to 16-oxa-androstan-3)5-ol (159) or, by oxidation with Jones reagent to the lactone (152) (as 3-ketone) in quantitative yield. This lactone could also be obtained by lithium borohydride reduction of the monomethyl ester (156), whilst diborane reduction of (156) and cyclisation of the resulting (151) afforded the isomeric lactone (150). The diacid (155) reacted with acetic anhydride to afford exclusively the cis-anhydride (161) which was reduced directly with lithium aluminium hydride to the cis-lactone (160) or, as its derived dimethyl ester (162) to the cis-diol (163) which cyclised to 16-oxa-14)5-androstan-3) -ol (164). [Pg.428]

Sulphonic acids may normally be obtained in 65-75% yields upon oxidation of thiols, thiolates or disulphides with 30% hydrogen peroxide234-240. Higher yields are realized if a tertiary thiol is used. The same products may also be realized by reaction of either thiols or disulphides with aqueous dimethyl sulphoxide (equation 37), in the presence of a catalytic amount of bromine, iodine or a hydrogen halide241,242. In this latter oxidation, dimethyl sulphide is formed as a by-product, but is easily removed by aspiration. [Pg.360]

Sulphonyl halides may be hydrolysed in alkaline or acidic solution, and in boiling water, to give good yields of the parent acid296-303, as shown in equation 60. In addition, a reaction has been reported where a sulphonyl chloride is converted into the corresponding sulphonic acid when the former is dissolved in dimethyl sulphoxide304. The solvent takes part in the reaction as shown in equation 61. [Pg.365]

The phosphoryl group evidently, and not surprisingly, deactivates an attached benzene ring during electrophilic substitution reactions the sulphonation (with SO3) of phenylphosphonic acid leads initially to the 3-sulphonic acid, and subsequently at 180-240 °C to the 3,5-disulphonic acid. The nitrations of (4-chlorophenyl- or (4-bro-mophenyl)-phosphonic acids have given products described as the 3-nitro derivatives, but it has also been stated that the nitration of dimethyl phenylphosphonate gives dimethyl (4-nitrophenyl)phosphonate, a pattern of substitution certainly observed in the nitration of... [Pg.498]

The reaction of dialkyl acylphosphonates with sulphonic acids was reported lead to sulphonic esters and acylphosphonic acids ". Reinvestigation of this reaction using P NMR spectroscopy revealed that the reaction of equimolar amounts of dimethyl ben-zoylphosphonate and/ -toluenesulphonic acid at room temperature gives dimethyl hydro-genphosphonate (equation 71). It was proposed that the by-product of this reaction, benzoic / -toluenesulphonic anhydride, reacts with the excess / -toluenesulphonic acid to yield / -toluenesulphonic anhydride and benzoic acid. Heating these two compounds with... [Pg.688]

Methyl, ethyl, benzyl, benzhydryl, p-nitrobenzyl, p-methoxy-benzyl, 4-picolyl, j3j -trichloroethyl, j3-methylthioethyl, /J-p-toluenesulphonylethyl, and -p-nitrophenylthioethyl esters may be prepared directly from the acid and alcohol. TTie most usual method [4, 5] consists of heating the acid and an excess of the alcohol with an acid catalyst (e.g., Fischer-Speier, hydrochloric or sulphuric acid). The extent of reaction is improved if the water formed is removed by azeotropic distillation with an inert solvent (benzene, carbon tetrachloride, or chloroform). Considerable variation is possible in the natvire of the acid catalyst thus phosphoric acid [6], aryl sulphonic acids [7, 8, 9], alkyl sulphates [10], and acidic ion-exchange resins [11] may be employed. Removal of the water by azeotropic distillation during the formation of methyl esters is difficult and Brown and Lovette [12] introduced the novel reagent acetone dimethyl acetal (7) for the direct formation of methyl esters. In the presence of a trace of methanol and an acid catalyst the reagent acts as a scavenger of water formed by esterification and liberates further methanol for reaction. [Pg.185]

Nickel(IV) complexes react with dimethyl sulphoxide in acidic solution to give the sulphone and nickel(II) ions. The kinetics of this reaction have been studied and found to be very complex in nature. The reaction probably proceeds by initial complexation of the dimethyl sulphoxide to the nickel(IV) species followed by electron transfer and oxygen atom transfer producing the observed products149. [Pg.985]

The base catalysed autoxidation of dimethyl sulphoxide and methyl phenyl sulphoxide at 80 °C produces low quantities of methanesulphonic acid in both cases and benzenesul-phonic acid in the latter case189 (equation 71 and 72). There is no evidence of sulphone formation in either reaction. Dimethyl sulphoxide oxidation to methanesulphonic acid also occurs in the presence of trace quantities of acid and oxygen. Again the reaction would not be synthetically useful190. [Pg.990]

Douglas investigated heats of formation of dimethyl sulphoxide (and also of the sulphone) and proposed in a footnote that it could be determined by 5-min reaction with potassium permanganate/sulphuric acid, then adding excess iron(II) sulphate and finally titrating with permanganate. The same principle was used by Krishnan and Patel to determine dimethyl sulphoxide in various complexes (with perchlorates of titanyl, zirconyl and thorium), and by Krull and Friedmann to determine the same compound but using only dilute sulphuric acid and 5-min reaction. [Pg.114]

Sodium tungstate has also been used as a catalyst in the oxidation of dimethyl sulphoxide to the sulphone. The kinetics of this reaction have been studied in great detail and it has been shown that oxygen transfer to the sulphoxide takes place via two peroxytungstic acid species (HWOj and HWOg ). [Pg.973]

Peroxomonophosphoric acid (PMPA) oxidizes dimethyl sulphoxide in high yield in water and aqueous ethanol . In neutral solution the reaction mechanism was thought to be very complex but actually occurs by two different mechanisms that are very similar to those for sulphoxide oxidation by peracids in acidic and basic media. In an alkaline medium the mechanism involves nucleophilic attack by a phosphorus-containing species (probably POs ) on the sulphur atom of the sulphoxide, followed by O—O bond scission yielding the sulphone (equation 24). In acidic solution, on the other hand, the sulphoxide is the nucleophilic species as detailed in equation (25). It should be noted however that there is some evidence that these mechanisms are oversimplified since there are other nucleophilic species (such as H2P05 and HPO ") present in aqueous solutions of PMPA over a wide pH range . [Pg.978]

The sodium salt of sulphonated polysulphone Na-SPS was obtained by reaction of polysulphone resin (P-1700 or P-3500) with chlorosulphonic acid in 1,2-dichloroethane ( ). This was followed by dissolution in dimethyl formamide, precipitation in 10% NaCl, and rinsing with large voliunes of water until the washings were free of NaCl. [Pg.352]

PREPARATIVE TECHNIQUES Synthesized by condensation/step-growth polymerization between ethylene glycol and terephthalic acid. Low-viscosity and easily spinnable PET are synthesized by ester interchange. Dimethyl terephthalate is reacted with ethylene glycol in a 1 1.7 ratio at 0.020 atm and 160-230°C. Final reaction occur at 260-300°C under vacuum at 0.001 atm. Synthesis of PET is done by using aromatic sulphonates as catalysts ... [Pg.558]


See other pages where Dimethyl sulphonic acids, Reactions is mentioned: [Pg.429]    [Pg.317]    [Pg.983]    [Pg.971]    [Pg.983]    [Pg.338]    [Pg.174]    [Pg.13]    [Pg.371]    [Pg.371]    [Pg.816]    [Pg.147]    [Pg.320]    [Pg.76]    [Pg.274]    [Pg.241]    [Pg.114]    [Pg.971]    [Pg.978]    [Pg.193]    [Pg.232]    [Pg.21]    [Pg.841]    [Pg.84]    [Pg.896]    [Pg.256]    [Pg.174]   
See also in sourсe #XX -- [ Pg.522 ]




SEARCH



Dimethyl reactions

Dimethyl sulphone

Sulphonic acids acidity

Sulphonic acids, reactions

Sulphonic acids—

© 2024 chempedia.info