Aqueous alkaline medium

Manufacture of alkylsulfones, important intermediates for metal-complex dyes and for reactive dyes, also depends on O-alkylation. An arylsulphinic acid in an aqueous alkaline medium is treated with an alkylating agent, eg, alkyl haUde or sulfate, by a procedure similar to that used for phenols. In the special case of P-hydroxyethylsulfones (precursors to vinylsulfone reactive dyes) the alkylating agent is ethylene oxide or ethylene chlorohydrin. 

Another group of uniform latex particles were prepared by the dispersion polymerization of acrolein in an aqueous medium by Margel and coworkers [96], A typical polymerization was conducted in the aqueous alkaline medium having a pH of 10.5, which was obtained by the aqueous NaOH solution. Polyglutaraldehyde-NaHS03 conjugate was synthesized by the reaction of... 

The chemical bath deposition of polycrystalline, zinc blende HgSe thin films on TO glass from aqueous alkaline medium has been reported [120]. Examples of electrodeposited ternary mercury compounds will be discussed in the next section. 

Oxidation may be achieved in the presence of oxygen or air. Other suitable oxidants include sulfur, sodium polysulfide, iron (III) chloride, potassium ferro-cyanide (III) or potassium dichromate, peroxydisulfate or salts of aromatic nitro-sulfonic acids. An aqueous/alkaline medium is used in the presence of a high boiling organic solvent which is not miscible with water or which is almost immiscible with water. Cyclization with chlorosulfonic acid can be followed directly by oxidation with bromine to afford the thioindigo system, without separation of the intermediate. 

Although there is one route [3] which describes the direct synthesis of the tetrachlorothioindigo pigment by oxidation of 3-hydroxy-4,7-dichlorothionaphthenone with oxygen in an aqueous alkaline medium, this is somewhat of an exception. In most cases, it is necessary to modify the crude thioindigo derivative by appropriate aftertreatment in order to develop the desired pigment properties. 

Heating the leuco form in an aqueous alkaline medium in the presence of air, possibly also in the presence of a surfactant, affords the pigment form. Oxidation may also be achieved with sodium-m-nitrobenzenesulfonate. Another alternative is to precipitate the vat acid from the salt of the leuco form and to subsequently oxidize the product. It is also possible to mill the suspension of the leuco form together with aqueous sodium hydroxide/sodium dithionite in air, using a pearl mill. 

A higher quality a-modification with enhanced tinctorial strength and transparency is prepared from the leuco form of bromoisoviolanthrone. This intermediate in turn is manufactured by vatting crude bromoisoviolanthrone with sodium dithionite/aqueous sodium hydroxide. The product is separated and oxidized in an aqueous alkaline medium in the presence of surfactants. Application of shearing forces, preferably by means of a sand or pearl mill, and maintaining a temperature of 50°C produces improved pigment quality [26]. 

Wiegand GH, Tremelling M. 1972. The kinetics and mechanism of the decomposition of potassium cyanide in aqueous alkaline medium. Hydrolysis of the simplest nitrile. J Org Chem 37(6) 914-916. 

Anal. Calcd. for recrystallized [PtCl2(NH3)2] Cl, 23.6 Pt, 65.0. Found Cl, 23.5 Pt, 65.0. Cl is analyzed potentiometrically after decomposition of a sample with hydrazine in aqueous alkaline medium followed by filtration of metallic Pt and acidification of the filtrate with HN03. The Pt is analyzed gravimetrically after decomposition of a sample by heating with Na2C03. 

In the case of ketoximes and acetylene in an aqueous alkaline medium the following condensation processes leading finally to pyridines are conceivable. (i) Dimerization of ketoximes with elimination of hydroxylamine (analog of crotonic condensation) (Scheme SO), (ii) Acetaldehyde condensation with the oxime of a,/3-un saturated ketone 107. 

The most common reagent for introducing the terf-butoxycarbonyl (Boc) protecting group is the pyrocarbonate B0C2O. This is employed here in aqueous alkaline medium to which has been added the solubilizing agent dioxane. 

Solid DADMAC is synthesized from dimethylamine and allylchloride by a two step process (Fig. 1). The first step is the alkylation of dimethylamine with allylchloride in an aqueous alkaline medium. This step is followed by a quaterni-zation in an organic medium again with allylchloride [30-32]. To prepare the pure solid the separation and purification of the intermediate product allyld-... 

The technical synthesis is normally carried out via a twofold alkylation of dimethylamine with allylchloride in aqueous alkaline medium [2, 33, 34]. Following purification this results in polymerizable monomer solutions. The extent of the purification determines the final monomer concentration and the residual content of sodium chloride. Normally, the monomer concentration of the resulting solutions is between 50 and 70% [2]. Depending on the purity of the raw materials and the reaction conditions the technical monomer solutions can contain small amounts of, for example, ADMA, diallymethylamine (DAMA), or methyl-triallylammomium chloride (MTAAC) [35]. 

Decomposition of Caro s acid is catalysed by acetone.324 A kinetic study in aqueous alkaline medium indicates simple second-order kinetics. Nucleophilic addition of S052- to the carbonyl carbon leads to oxirane by reaction with another SOs2- to give... 

The oxidation of substituted 4-oxo-4-arylbutanoic acids by hexacyanoferrate(III) [HCF(III)] in aqueous alkaline medium is first order in the oxo acid, hydroxide ion, and the HCF(III) ion. A mechanism involving the formation of enolate anion from the oxo compound and subsequent rate-determining electron transfer is proposed. 

The kinetics of oxidation of D-fructose and D-glucose in aqueous alkaline medium with nine sodium salts of mono- and di-substituted A-chloroarylsulfonamides have been determined. The Hammett reaction constants, p, for the oxidation of glucose and fructose are 0.28 and 0.54, respectively. The results have been explained by a plausible mechanism, and the related rate laws have been deduced.108... 

The preparation of a number of medium ring benzoic acid lactones was achieved by treatment of compounds such as VIII/176 with an excess of meta-chloroperoxybenzoic acid in dichloromethane, Scheme VIII/33 [103]. However, this oxidation reaction is not general for the synthesis of aromatic lactones. If the same reaction conditions are used as in the conversion of VIII/176 to VIII/177, the methoxy derivative VIII/178 is not transformed into the corresponding lactone. Instead the cyclic carbonate VIII/183 was isolated in a yield of 50 %. The proposed mechanism of this abnormal reaction is shown in Scheme VIII/33. From model compounds, the methoxyl group in the para-position to the center of oxidation seems to be important for the formation of VIII/183 [103]. The carbonate VIII/183 is unstable in aqueous alkaline medium and decomposes to the spiro compound, VIII/185, Scheme VIII/33 [103]. For an analogous reaction, see ref. [104]. 

Ericsson, B., Oxygen Oxidation in Aqueous Alkaline Medium, Ph.D. dis-... 

Sippola, V. O. and Krause, A. O. I., Oxidation activity and stability of homogeneous cobalt-sulphosalen catalyst -Studies with a phenolic and a non-phenolic lignin model compound in aqueous alkaline medium. J Molecular Catalysis A-Chemical 2003, 194 (1-2), 89-97. 

Due to their reducing properties, isomaltulose and trehalulose are technically used as mild reducing agent. Both compounds as such or in mixtures could be used for the gentle reduction of sulfur and vat dyes in aqueous alkaline medium [86, 128]. 

Annulation of an o-(acylamino)aniline has been induced by acidic or nearly neutral conditions (see p. 24), but an aqueous alkaline medium is also successful for this reaction. In another method, ethyl 2-eUioxyquinoline-l-carboxylate is used [2766]. 

Reactions of 6-amino-l,3-dimethyluracil with substituted a-ketoalkynes using homogeneous nickel catalysts in an aqueous alkaline medium afford substituted 2,4-dioxopyrido[2,3-d]pyrimidine derivatives in quantitative yields under very mild conditions. A mechanism has been proposed for the reaction involving the nucleophilic attack by a Ni(0) anion, formed in situ, on the triple bond of the substrate [27]. 

Also, all the -situated hydrogen atoms of ketones are readily replaceable by deuterium in an aqueous alkaline medium, since these atoms take part one after the other in the reversible keto-enol tautomerism. This applies, for instance, to the four -positions of cyclohexanone and to the one of 2,2,6-tri-methylcyclohexanone, whereas no exchange occurs in camphor or camphor-quinone which cannot enolize owing to the particular stereochemistry of the molecules.90 Open-chain ketones and also steroidal ketones91 that are not subject to this limitation are often used for exchange reactions. The following description of the preparation of [D6]acetone illustrates the point 29... 

By using dialkylthiophosphoryl chlorides in aqueous alkaline medium, a selective and sensitive method for the determination of aliphatic and aromatic amines by GC-FPD has been developed. In particular, secondary amines can be selectively converted into their A -diethylthiophosphoryl (DETP) derivatives with diethyl chlorothiophosphate (DECTP) after treatment with o-phthaldial-dehyde (OP A), because OP A reacts only with primary amino groups. On the other hand, secondary amines are detected irrespective of pretreatment, because they do not react with OPA (Eigure 11.7 and Eigure 11.8). 

The tautomeric forms of protoberberine and pseudoprotoberberine compounds were examined by UV, IR, and H NMR spectroscopy, and by polarography (381). The results showed that, in aqueous alkaline medium, the carbinol form C is formed only by the protoberberine compounds and not by the pseudoprotoberberine the presence of the aldehyde form could not be proven in this group of compounds. 

Benzoylbenzyl)phosphonic acid (the 3-substituted isomer behaves in the same fashion qualitatively and almost quantitatively so) in an aqueous alkaline medium also undergoes virtually quantitative decomposition with the formation of 4-methylbenzophenone, the efficiency of the process again depending on the pH of the reaction medium. ... 

Simek ° reported that a solution of nickel(II) dimethylglyoximate in 1-2 mol dm KOH was easily oxidized by hypoiodite, hypobromite and peroxodisulfate to a solution containing a nickel(IV) complex. The complex K2[Ni (DMG)3] (DMG = dimethylglyoximate) has been prepared in aqueous alkaline medium from nickel(II) and DMG in the presence of two-electron oxidants such as CI2, OX (X = C1, Br, I), S2O8 or higher valent oxides of nickel. 

Tosyl j8-CyDs are important precursors for a variety of modified CyDs because a nucleophile can attack the electrophilic carbon at the 6-position to produce a corresponding functionality. The reaction of jS-CyD with tosyl chloride in aqueous alkaline medium gives mono-6-tosylated jS-CyD in fairly good yield [15]. 

N-AIkylindoles. This salt can function as a catalyst for alkylation of indoles in an aqueous alkaline medium an organic phase is not necessary and indeed is detrimental. This method fails in the case of tertiary alkyl halides and unactivated aryl halides. ... 

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