Oxidation in Alkaline Solution

The action of the hypohalites is generally far more drastic in alkaline solution than in acid or neutral media. As the values of the oxidation potentials (Table I) do not predict this result, the effect may be attributed in part to the action of alkali on the sugars. The oxidation is not con- 

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Methylpyridinium quaternary salts, such as (12), undergo oxidation in alkaline solution in the presence of potassium ferricyanide to give 2-pyridones, eg, A/-methyl-2-pyridone [694-85-9] (16). Frequendy nucleophilic attack at position 2 by excess hydroxide leads to ring opening this and synthetically useful recycli2ations have been reviewed (17). 

Hydroxyphenylpyruvic acid is rapidly oxidized in alkaline solution. Commercially available compressed nitrogen may be used if the gas is further purified by passage through an alkaline solution of pyrogallol (45 g. of pyrogallol dissolved in 300 ml. of 50% sodium hydroxide solution). 

S. Neophytides, D. Tsiplakides, P. Stonehart, M.M. Jaksic, and C.G. Vayenas, Non-Faradaic Electrochemical enhancement of H2 oxidation in alkaline solutions, J. Phys. Chem. 100, 14803-14814 (1996). 

Evans, Nicoll, Strause and Waring46 oxidized D-glucose and D-fructose in aqueous solution with excess cupric acetate at 50° for the purpose of ascertaining whether the general principles underlying the mechanism of carbohydrate oxidation in alkaline solutions are sufficient to explain the course of such oxidations in acid solutions. D-Glucosone was claimed to be one of the first products of oxidation the osone was not isolated, and,... 

Oxidation of one molar proportion with sodium pieriodate produces two equivalents of formic acid, in accordance with the existence of hydroxyl groups attached to four contiguous carbon atoms. This oxidation (and also that carried out with lead tetraacetate) gives an aldehyde, whose semicar-bazone has an analysis corresponding to that of the semicarbazone of an ethyl formyl-methyl-furoate (XII). By oxidation of aldehyde XII with silver oxide in alkaline solution, 2-methyl-3,4-furandicarboxylic acid (XIV) was obtained this was identical with the compound described by Alder and Rickert.20 The identity was confirmed by preparation of the respective dianilides. The acid XIV has also been prepared by the reaction between the sodium salt of ethyl acetoacetate and ethyl bromopyruvate.9... 

Solyom [37] has carried out intercalibration studies on methods for the determination of total nitrogen in sludges. Nitrogen was determined by oxidation in alkaline solution with potassium peroxydisulphate, followed... 

Manganese is reactive when pure, it burns in 02 it dissolves in dilute acids. Roughly similar to iron in several physical and chemical properties, but harder, more brittle and less refractory. At elevated temperatures it reacts violently with several non-metals. The Mn11 is the most stable state, readily oxidized in alkaline solutions. The highest oxidation state is VII (corresponding to the total number of 3d and 45 electrons). 

Nickel(lll) oxide, prepared from a nickel(ii) salt and sodium hypochlorite, is used for the oxidation of alkanols in aqueous alkali [46]. Residual nickel(Ii) oxide can be re-activated by reaction with sodium hypochlorite. Nickel oxides have also long been used in the manufacture of the positive pole in the Edison nickel-iron rechargeable battery, now largely superseded by die lead-acid accumulator, and in the Jungner nickel-cadmium batteries used as button cells for calculators [47]. Here, prepared nickel oxide is pressed into a holding plate of perforated nickel. Such prepared plates of nickel(lli) oxide have been proposed as reagent for the oxidation, in alkaline solution, of secondary alcohols to ketones and primary alcohols to carboxylic acids [48]. Used plates can be regenerated by anodic oxidation. 

The ion-exchange mechanism of exfracfion does nof occur only for amino acids. We observed if also for cafecholamines [26]. These compounds are efficiently extracted into ILs in the cationic form, af pH 1-8. Af fhese pH, the primary (dopamine) or secondary (adrenaline and dobutamine) amino groups are protonated (catecholamines are oxidized in alkaline solutions at pH > 8). By analogy with amino acids, extraction may be described by the cation-exchange reaction ... 

Reactions. w-Hydroxybenzoic acid affords a variety of products, depending on the catalyst and conditions employed. Catalytic reduction over platinum black or platinum oxide in alkaline solution gives 3-hydroxycyclohexanecarboxylic acid [22267-35-2]. Reduction of a warm aqueous solution over platinum oxide or over colloidal platinum yields cyclohexanecarboxylic acid. w-Hydroxybenzaldehyde can be prepared by reducing ///-hydroxybenzoic acid with sodium amalgam. Finally, reduction over Raney nickel gives cydohexanol. 

The properties of 5-hydroxylamino-3-phenyl-l,2,4-thiadiazole (272) have been studied in some detail.170 The compound dissolves in alkalis, giving intensely green solutions (273), from which the red azo-1,2,4-thiadiazole 274 is precipitated upon acidification. Hydrogen sulfide reduces 274 to the colorless hydrazothiadiazole 275, which is reconverted, by air oxidation in alkaline solution, into 273 (i.e. 274 as base-adduct). 

The characteristic transient yellow-green fluorescence exhibited by adrenaline solutions that were undergoing oxidation in the presence of alkali was first reported in 1918.182 This phenomenon was later shown to be general, and similar (but usually weaker) fluorescences were observed when other catecholamines were oxidized in alkaline solution.133 Many years were to elapse before the correct explanation of this phenomenon was forthcoming, i.e. that the fluorescent product derived from adrenaline was a rearrangement product of adrenochrome (the red oxidation product of adrenaline). 

The most important half-cell reactions are shown in equations (28) and (29).476 Oxovanadium(IV) can be oxidized by 02, more easily as pH increases in acidic solutions, the blue V02+ solutions are stable to air. Air oxidation in alkaline solutions (0.006-3.8 M NaOH) is rapid at 15 °C.477 The initial rate is proportional to [OH-]. Fein catalyzes the reaction while Cr inhibits it. With [V]> 0.002 M, the rate is controlled by diffusion of oxygen. When V02+ is chelated, oxidation may be considerably retarded and—as a rule—the more stable the complexes, the more pronounced this retardation effect. However, in 1 1 solutions of oxovanadium(IV) and tartrate at pH 8, the oxidation is rapid.478 The dissolved oxygen was depleted within a few seconds. 

Boyd and Marie22 have conducted a thorough study of the ease of addition of various substituted phenols to ethylene oxide in alkaline solution (Eq- 690). Using no loss than 25 different phenols, these authors... 

The buff-coloured bis chelate formed by 2-aminobenzenethiol (334) can be oxidized in alkaline solution to a blue-coloured complex of nickel(II) which contains the ligand in an oxidized form (Scheme 34).2422,2462 Complex (334) reacts with Mel in acetone affording the six-coordinate complex NiL containing the S-methylated ligand.2452... 

Oxidation of Alkali Lignin Studies on Oxidation in Alkaline Solution... 

In order to gain some information on the degradation mechanisms, experiments with substances assumed to represent essential intermediates were undertaken. 2-Hydroxy-3-methoxy-5-methylbenzal acetone (XVII) is considered to play a dominant role in the proposed degradation mechanism when 6,6 -bicreosol is oxidized in alkaline solution although it could not be detected among the degradation products. The benzal acetone (XVII) was oxidized and underwent alkaline hydrolysis under our standard conditions. Alkaline hydrolysis in nitrogen atmosphere yielded rather small amounts of acetone (about 10% of theoretical amount). Oxidation yielded... 

A cyclic diacetal of this type was employed by Ohle and Berend34ta) and by Link and his coworkers34(b)(o) in the synthesis of D-galacturonic acid. These investigators found that l,2 3,4-diisopropylidene-D-galac-tose was converted by permanganate oxidation in alkaline solution to the... 

Reaction of the a-nitrosulfones (2) with aqueous TiCl3 results unexpectedly in nitriles, RC=N, in about 75% yield, a-Nitrosulfones are oxidized in alkaline solution by excess KMn04 to carboxylic acids, RCOOH, in 80-90% yield, probably via the acyl sulfone. 

The mechanism may change from acids to alkalis in some cases [365], This may be related to the higher sensivity of the Fe surface to oxidation in alkaline solutions [365, 367], Actually, the corrosion of Fe proceeds also under moderate cathodic load [368]. Impedance measurements have suggested that the classical mechanisms of hydrogen evolution is probably inadequate to describe the situation on Fe [377], A surface diffusion step with spillover of hydrogen to sites with lower M-H energy has been suggested. Adsorption of CN- interferes with such a diffusion. 

Carbon-13 n.m.r. spectroscopy has been used to study benzylisoquinoline and tetrahydroisoquinoline alkaloids and their JV-methyl quaternary salts.30 N-Benzylpapaverinium bromide has been shown to undergo aerial oxidation in alkaline solution to 2-benzyl-6,7-dimethoxyisoquinolone and to give bases of general structure (10) with methylamine, benzylamine, and pyrrolidine.31 Chlorosulphonation of papaverinol affords the sulphonic acid ester (11), mild hydrolysis of which yields the acid (12), which with diazomethane is esterified and dehydrated to (13).32 N-Methyl-l,2-dihydropapaverine has been shown by kinetic studies and orbital-symmetry requirements to rearrange to the salt (14) by the route previously postulated.33... 

Salicylaldehydephenylhydrazone, by electrolytical oxidation in alkaline solution at a platinum anode can be converted into salicyl-cc-osazone (Biltz1). 

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