Catalysis mercury

Mercury(II) salts and transition metals are also important catalysts for this reaction. Mercury catalysis will be discussed in the next section, while transition metal catalysis is discussed elsewhere in this series. 

The main application for naphthalene is traditionally the production of phthalic anhydride. TTie oxidation of naphthalene to phthalic anhydride has undergone noticeable changes in recent years. Important stages in this development were mercury catalysis and the introduction of fixed-bed and fluidized-bed processes (see Chapter 7.1.1). Since there are no basic differences between the gas-phase oxidation of naphthalene and of o-xylene to produce phthalic anhydride, it is possible to use one plant with suitable modifications for both feedstock materials (dualfeed plants). 

Catalysts. Mercury is or has been used in the catalysis (qv) of various plastics, including polyurethane [26778-67-6] poly(vinyl chloride) [9002-86-2] and poly(vinyl acetate) [9003-20-7]. Most poly(vinyl chloride) and poly(vinyl acetate) is manufactured by processes that do not use mercury (3). 

SuIfona.tlon, Sulfonation is a common reaction with dialkyl sulfates, either by slow decomposition on heating with the release of SO or by attack at the sulfur end of the O—S bond (63). Reaction products are usually the dimethyl ether, methanol, sulfonic acid, and methyl sulfonates, corresponding to both routes. Reactive aromatics are commonly those with higher reactivity to electrophilic substitution at temperatures > 100° C. Tn phenylamine, diphenylmethylamine, anisole, and diphenyl ether exhibit ring sulfonation at 150—160°C, 140°C, 155—160°C, and 180—190°C, respectively, but diphenyl ketone and benzyl methyl ether do not react up to 190°C. Diphenyl amine methylates and then sulfonates. Catalysis of sulfonation of anthraquinone by dimethyl sulfate occurs with thaHium(III) oxide or mercury(II) oxide at 170°C. Alkyl interchange also gives sulfation. 

Bis(2,4,6-trinitrophenyl)methane when treated with NaAc in acetic acid produced (580) as a thermostable explosive (80MIP41600). The conversion of o-nitrotoluene into 2,1-benzisoxazole was effected by mercury(II) oxide catalysis. A mercury containing intermediate was isolated and was demonstrated to be converted into 2,1-benzisoxazole (67AHC(8)277). The treatment of o-nitrotoluene derivative (581) with sulfuric acid gave (582) in 35% yield (72MI41607). 

KUCHEROV - DENIGES Hydration Water addition to a triple bond (Kucherov) or to a double borxl (Oeniges) under mercury salt catalysis... 

Acetylene anion serves for synthon (4), the hydration with mercury ton catalysis being unambiguous. 

The additivity principle was well obeyed on adding the voltammograms of the two redox couples involved even though the initially reduced platinum surface had become covered by a small number of underpotential-deposited mercury monolayers. With an initially anodized platinum disk the catalytic rates were much smaller, although the decrease was less if the Hg(I) solution had been added to the reaction vessel before the Ce(lV) solution. The reason was partial reduction by Hg(l) of the ox-ide/hydroxide layer, so partly converting the surface to the reduced state on which catalysis was greater. 

Cofacial ruthenium and osmium bisporphyrins proved to be moderate catalysts (6-9 turnover h 1) for the reduction of proton at mercury pool in THF.17,18 Two mechanisms of H2 evolution have been proposed involving a dihydride or a dihydrogen complex. A wide range of reduction potentials (from —0.63 V to —1.24 V vs. SCE) has been obtained by varying the central metal and the carbon-based axial ligand. However, those catalysts with less negative reduction potentials needed the use of strong acids to carry out the catalysis. These catalysts appeared handicapped by slow reaction kinetics. 

The active intermediate [Ni(cyclam)]+—the initial electrogenerated species—is adsorbed on the surface of the mercury electrode.153-155 The catalytic activity is severely reduced in the presence of CO,156 possibly due to formation of the insoluble complex [Ni°(cyclam)(CO)]° following a two-electron reduction. Scheme 8 summarizes the mechanism for this catalysis. 

Homo-coupling of vinylic mercurials occurs readily under palladium195 or rhodium196 catalysis, but with the stoichoimetric amount of a reagent (equation 111)195. Divinylpal-ladium intermediates may be involved in this reaction. This reaction is also of limited synthetic scope since organomercurials are usually prepared via vinylboranes, which... 

Under the catalysis of mercury(II) oxide and p-toluenesulfonic acid, allenic /8-keto esters 43 and 45 afforded the furan derivatives 44 and 46 [27]. 

When catalysts are recycled as solid residues, it is important to exclude impurities that may piggyback —such as metal particles—as the active species. This was probed in two ways. First, the tape was removed after a first cycle, rinsed, and transferred to a new vessel. A second charge of 17 and dibutyl ether was added, but not the PhMe2SiH. The sample was warmed to 55 °C, the now off-white tape was fished out , and PhMe2SiH was added. The rate profile was similar to the first cycle (ca. 20% slower at higher conversions), consistent with predominant homogeneous catalysis by desorbed fiuorous species. Second, the second cycle of a sequence was conducted in the presence of elemental mercury, which inhibits catalysis by metal particles [57]. However, the rate profile was the same as a sequence in the absence of mercury. 

SDS), and indeed SDS-catalysis of Hg " -catalyzed replacement of cyanides in [Fe(C1 6]" 1 1,10-phenanthroline has been proposed as an analytical method for the determination of mercury. ... 

In the oxidation of hydroxylamine by silver salts and mercurous salts, the nature of the reaction product apparently depends upon the extent to which catalysis participates in the total reaction. This is illustrated by some results obtained with mercurous nitrate as oxidizing agent. The reaction is strongly catalyzed by colloidal silver, and is likewise catalyzed by mercury. The reaction of 0.005 M mercurous nitrate with 0.04 M hydroxylamine at pH 4.85 proceeds rapidly without induction period. The mercury formed collects at the bottom of the vessel in the form of globules when no protective colloid is present, so the surface available for catalysis is small. Under these conditions the yield is largely nitrous oxide. Addition of colloidal silver accelerates the reaction and increases the yield of nitrogen. Some data are given in Table III. 

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