Mercuric oxide catalyst

Phenylacetylene gives 1-phenyI-l, l-difluoroethane on reaction with a large excess of hydrogen fluoride in ether at 0 C or, in better yield, in the gas phase over a mercuric oxide catalyst [/]. Allene affords 2,2-difluoropropane [/]... 

Source Manufactured by oxidizing ethanol with sodium dichromate and sulfuric acid or from acetylene, dilute sulfuric acid, and mercuric oxide catalyst. 

This method was developed to replace the hazardous mercury catalyst required in the original mercuric oxide Kjeldahl method. It has been evaluated through an interlaboratory comparison of catalysts and has been adopted as the official replacement for the mercuric-oxide catalyzed Kjeldahl method. An inter-laboratory evaluation (Berner, 1990) indicated that this method (which uses the copper/titanium catalyst mixture) produces results more closely in agreement with the mercuric oxide catalyst method than methods using a copper sulfate catalyst. As a result of this study, mercuric... 

Mercuric Sulfate. Mercuric s Af2iX.e.[7783-35-9] HgSO, is a colorless compound soluble ia acidic solutions, but decomposed by water to form the yellow water-iasoluble basic sulfate, HgSO 2HgO. Mercuric sulfate is prepared by reaction of a freshly prepared and washed wet filter cake of yellow mercuric oxide with sulfuric acid ia glass or glass-lined vessels. The product is used as a catalyst and with sodium chloride as an extractant of gold and silver from roasted pyrites. 

Vanadium pentoxide and mercuric oxide were used as catalysts for the hydrogen peroxide oxidation of bis(phenylthio)methane to its monooxide 17a31 (equation 5). From the synthetic point of view, it is interesting to note that vanadium pentoxide, in addition to its catalytic action, functions also as an indicator in this reaction. In the presence of hydrogen peroxide, the reaction mixture is orange while in the absence of hydrogen peroxide a pale yellow colour is observed. Thus, it is possible to perform the oxidation process as a titration ensuring that an excess of oxidant is never present. 

The hydration of triple bonds is generally carried out with mercuric ion salts (often the sulfate or acetate) as catalysts. Mercuric oxide in the presence of an acid is also a common reagent. Since the addition follows Markovnikov s rule, only acetylene gives an aldehyde. All other triple-bond compounds give ketones (for a method of reversing the orientation for terminal alkynes, see 15-16). With allqmes of the form RC=CH methyl ketones are formed almost exclusively, but with RC=CR both possible products are usually obtained. The reaction can be conveniently carried out with a catalyst prepared by impregnating mercuric oxide onto Nafion-H (a superacidic perfluorinated resinsulfonic acid). ... 

Boron trifluoride etherate, co-catalyst, 53, 30, 32 a-Bromination, selective of aralkyl ketone, 53, 111 Bromine, with 3-chlorocyclo-butanecarboxylic acid and mercuric oxide to give 1-bromo-3-chlorocyclobutane, 51, 106... 

Other catalysts have been employed but they are not so effective as mercuric oxide. Some of the other catalysts are PbO [8,10, 56], PbO—S— (or Se) [57],... 

Maleimede, N-phenyl-, 41, 93 Malonitrile, condensation with tetra-cyanoethylene, 41, 99 Mercuric oxide in preparation of catalyst for conversion of 2,5-di-methyl-3-hexyne-2,5-diol to 2,2,5,-... 

Sulfonation of pyridine A-oxide requires the use of 20% fuming sulfuric acid and a mercuric sulfate catalyst with prolonged heating at 230°. Under these conditions, the main product is the 3-sulfonic acid (40-45%) together with small amounts of the 2- (0.5-1%) and 4-sulfonic acids (2-2.5%).214 2,6-Lutidine V-oxide reacts under similar conditions, substitution taking place at C-3.215... 

Without this catalyst the oxidation may require several hours, and the results vary considerably and depend largely upon the quality of the mercuric oxide. 

Phenylbenzoyldiazomethane has been prepared by the oxidation of benzilhydrazone with mercuric oxide,4 using benzene or petroleum ether as the solvent, and without the catalyst here specified. 

Yellow mercuric oxide reacts only slightly with CO near room temperature, but the activity can be increased markedly by the addition of chromic acid anhydride (58). Thorium oxide is an active catalyst at temperatures above 400°C., and its activity can be increased by the addition of 0.96% Ce203 (60). Vanadium pentoxideis also active at high temperatures (61). 

Minamata is an industrial city on the Yatsushiro coast of Japan on the southernmost island (K5rushu). In the city there was a factory that manufactured the chemicals vinyl chloride (used to make the plastic PVC see pp. 168-71) and acetaldehyde for many years. The processes used inorganic mercury (mercuric oxide) as a catalyst. The effluent from the factory contained inorganic mercury and perhaps also some organic mercury (methyl mercury), produced as a by-product in the chemical reaction in the plant. This effluent was discharged into the waters of Minamata Bay. 

Acetylene is condensed to vinylacetylene and divinylacetylene by cuprous chloride and ammonium chloride. Similar additions of other compounds containing an active hydrogen atom occur in the presence of various catalysts. Mercury salts ate most effective in the vapor-phase reaction of acetylene with hydrogen chloride to give vinyl chloride (100%). Basic catalysts such as potassium hydroxide, potassium ethoxide, or zinc oxide are used for the vinylation of alcohols, glycols, amines, and acids. Most of these reactions involve the use of acetylene under pressure, and few have been described as simple laboratory procedures. Chloroacetic acid, however, reacts with acetylene at atmospheric pressure in the presence of mercuric oxide to yield vinyl chloro-acetate (49%). ... 

Acetals are formed by the action of acetylene with alcohols in the presence of a catalyst consisting of boron trifluoride and mercuric oxide. The method has been extended to the condensation of substituted acetylenes, RC s CH, with alcohols to give ketals, as illustrated by the preparation of 2-hexanone dimethyl ketal (70%). The acidic catalyst must be carefully neutralized with powdered anhydrous potassium carbonate before contacting the acetal or ketal with water. 

Oxidation of aldehydes to esters and acids. Treatment of 2-lithio-2-alkyl-1,3-dithianes (1) with methyl disulfide in THF gives the corresponding ortholhioformates (2) in about 90% yield. These are converted in high yield into esters (3) when refluxed in an aqueous alcohol in the presence of mercuric chloride and mercuric oxide as catalysts. Conversion to acids is accomplished by refluxing (2) in aqueous acetone for 24 hr. with catalysis by mercuric chloride and mercuric oxide. Yields in this case are in the range 40-65 %. 

Preparation. The reagent (1) is prepared by the addition of methanol to 2-methyl-l-buten-3-yne using a catalyst prepared from red mercuric oxide, trichloroacetic acid, boron trifluoride ethcratc, and methanol. 

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