Media in the presence

N -Heterocyclic Sulfanilamides. The parent sulfanilamide is manufactured by the reaction of A/-acetylsulfanilyl chloride with excess concentrated aqueous ammonia, and hydrolysis of the product. Most heterocycHc amines are less reactive, and the condensation with the sulfonyl chloride is usually done in anhydrous media in the presence of an acid-binding agent. Use of anhydrous conditions avoids hydrolytic destmction of the sulfonyl chloride. The solvent and acid-binding functions are commonly filled by pyridine, or by mixtures of pyridine and acetone. Tertiary amines, such as triethylamine, may be substituted for pyridine. The majority of A/ -heterocycHc sulfanilamides are made by simple condensation with A/-acetylsulfanilyl chloride and hydrolysis. 

NMR spectra of oxaziridine enantiomers may be different from each other in chiral media. In the presence of chiral arylperfluoroalkylcarbinols, shift differences of up to 0.35 p.p.m. are observed, which may be used for discrimination of enantiomers (77JOC3217). 

Coelenterazine emits chemiluminescence when dissolved in dimethyl sulfoxide (DMSO) or dimethylformamide (DMF) containing a trace amount of base. It also emits bioluminescence in aqueous media in the presence of a coelenterazine luciferase, such as Renilla luciferase or Oplophorus luciferase. In both cases, the luminescence reactions require molecular oxygen. The capability of coelenterazine to produce luminescence is attributed to the presence of the imida-zopyrazinone structure in the molecule. 

In acetic acid media in the presence of 0.5 M HCIO4, a modified reaction... 

Koltholf and Fineman have examined the reaction in alkaline media in the presence and absence of oxygen, obtaining the rate law... 

Kotschy et al. also reported a palladium/charcoal-catalyzed Sono-gashira reaction in aqueous media. In the presence of Pd/C, Cul, PPI13, and z -Pr2NH base, terminal alkynes smoothly reacted with aryl bromides or chlorides, such as 2-pyridyl chloride, 4-methylphenyl bromide, and so on, to give the expected alkyne products in dimethyl-acetamide (DMA)-H20 solvent. Wang et al. reported an efficient cross-coupling of terminal alkynes with aromatic iodides or bromides in the presence of palladium/charcoal, potassium fluoride, cuprous iodide, and triph-enylphosphine in aqueous media (THF/H20, v/v, 3/1) at 60°C.35 The palladium powder is easily recovered and is effective for six consecutive runs with no significant loss of catalytic activity. 

Carbonylation of alkynes is a convenient method to synthesize various carbonyl compounds. Alper et al. found that carbonylation of terminal alkynes could be carried out in aqueous media in the presence of 1 atm CO by a cobalt catalyst, affording 2-butenolide products. This reaction can also be catalyzed by a cobalt complex and a ruthenium complex to give y-keto acids (Scheme 4.8).92... 

The cleavage of epoxides by water is a classical reaction. Such epoxide cleavage can be catalyzed by both acids and bases in aqueous media. In the presence of other nucleophiles, the corresponding nucleophilic ringopening products are obtained with the nucleophiles being incorporated into the products.68 Examples include azides, iodides, and thiols in the presence or absence of metal salts in aqueous media. The pH of the reaction medium controls the reactivity and regioselectivity of the... 

Allylation of acyloyl-imidazoles and pyrazoles61 with allyl halide mediated by indium in aqueous media provides a facile regioselective synthesis of P, y-unsaturated ketones (Scheme 11.1), which has been applied to the synthesis of the monoterpene artemesia ketone. The same product can be obtained by indium-mediated allylation of acyl cyanide (Eq. 11.35).62 Samarium, gallium, and bismuth can be used as a mediator for the allylation of nitrones and hydrazones to give homoallylic hydroxylamine and hydrazides in aqueous media in the presence of Bu4NBr (Scheme 11.2).63 The reaction with gallium and bismuth can be increased dramatically under microwave activation. 

In mixed solvents containing more than 50% water the 550-570 nm species can be generated without a nucleophile added. Evidently water plays a nucleophilic role. Decay of the species in these water-rich media in the presence of nucleophilic reagents is no longer first order. 

Based on this feature, aggregation states of transition-state structures for base-promoted isomerization of oxiranes have been established by kinetic studies of LDA-mediated isomerizations of selected oxiranes in nonpolar media in the presence of variable concentrations of coordinating solvents (ligands). Results reported provide the idealized rate law V = [ligand]" [base] [oxtrane] for a-deprotonation and v = fc[ligand]°[base] / [oxirane]... 

Recent interest toward aminochromene synthesis is connected with attempts to design some new green synthetic procedures. As a rule, these syntheses are conducted by three-component method from the corresponding aldehydes, nitriles, and phenols. Aminochromenes have been obtained on refluxing in aqueous media in the presence of the quaternary ammonium salts trimethylcetylammonium chloride (01T1395) and... 

The Ea for the dissolution of hematite by mercapto carboxylic acids in acid media in the presence of UV radiation was lower (64 5 kj mol ) than that for dissolution in the absence of radiation (94 8 kJ mol ) (Waite et al. 1986). The reaction in both cases was considered to involve formation of an intermediate organic-Fe surface complex which decomposed as a result of intramolecular electron transfer to release Fe". UV irradiation enhanced the decomposition of the surface complex either through excitation of the ligand field states associated with the free electrons on the S atoms, or through high energy charge transfer states. 

The formation of P-hydroxyaldehydes from propargylic alcohols has also been observed in aqueous media in the presence of a catalytic amount of water-soluble ruthenium sulfophthalocyanine complex and the heterogeneous ruthenium hydroxyapatite catalyst [40]. 

In contrast to the views asserting the reality of formation of NiHjc phase in alkaline media in the presence of promotors, Monev found [80] a very distinct pH effect in the formation of the hydride phase in the presence of H2Se03. According to [80], the nickel hydride formation terminates at pH value over 2.1. 

Benzaldehyde is prepared by hydrolysis of benzal chloride, for example in acidic media in the presence of a catalyst such as ferric chloride, or in alkaline media with aqueous sodium carbonate. Part of the commercially available benzaldehyde originates from a technical process for phenol. In this process, benzaldehyde is a byproduct in the oxidation, with air, of toluene to benzoic acid. 

Acylations of carbohydrate derivatives such as alkyl glucosides and galactosides have also been successfully performed in ionic liquids [63]. Similarly, the flavonoid glycosides naringin and rutin were acylated with vinyl butyrate in ionic liquid media in the presence of a number of lipases, e.g., CaLB (Novozym 435), immobilized TIL, and RmL [119]. The products are of interest for application as strong antioxidants in hydrophobic media. 

In aprotic media in the presence of acetic anhydride, 3,6-diphenylpyri-dazine (184) is first reduced to 1,2-diacetyl-1,2-dihydropyridazine (185) this is followed by cleavage of the N—N bond and further reduction to give 1,4-diphenyl-l,4-bis(diacetylamino)butadiene (186)297 [Eq. (111)]. Anodic oxidation of 186 in acetonitrile yields 3,6-diphenylpyridazine.298... 

Newer investigations316-318 have substantiated those previously published (Part I). Reductions in aprotic media in the presence of alkylating agents produced 5,10-dialkyl-5,10-dihydrophenazines.319... 

The barium sulfate in lithopone can be identified thermoanalytically by a reversible endothermic transformation at 1150°C. Both Sachtolith and lithopone are thermally stable up to ca. 550 °C in the presence of air. Due to their low Mohs hardness, they are less abrasive than other white pigments. Barium sulfate is practically inert toward acids, bases, and organic solvents. Zinc sulfide is stable in aqueous media between pH 4 and 10, and is largely inert toward organic media. In the presence of water and oxygen, it can be oxidatively decomposed by the action of UV radiation. 

Examples of these processes are the oxidation of p-aminophenol at platinum electrodes in aqueous acidic solution, the reduction of dopamine at glassy carbon electrodes or that of the cation 2,6-diphenylpyrylium in acetonitrile [9]. Another interesting example arises from the facilitated ion transfer of amines from aqueous to organic media in the presence of crown ethers like the dibenzo-18-crown-6 [52, 53] (see Fig. 3.22). 

Christen, H., Eicke, H. F., Rehak, J. Equilibrium considerations of micelle formation in apolar media in the presence of solubilized water. Proc. Intern. Conf. Colloid a. Surface Sci. Vol. 1, p, 481 Wolfram, E. (ed.). Budapest Akademiai Kiado 1975... 

The ideas underlying the form of the curve shown in Figure 1 form the basis of our present-day approach to discussing the stability and instability of colloidal dispersions in aqueous media in the presence of electrolytes. 

The cesium borates obtained by hydrolysis of trimethyl borate in organic media in the presence of CsOC(CH3)3 have been studied by IR (132) and tentatively assigned the formulas CstBi i OHln], Cs[B/MOH)J, Cs[BsO (OHU Cs[Bs03(0HU and CsstBsO OHU... 

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