Mercury salts, catalysts

One-part urethane sealants (Table 3) are more compHcated to formulate on account of an undesirable side reaction between the prepolymer s isocyanate end and water vapor which generates carbon dioxide. If this occurs, the sealant may develop voids or bubbles. One way to avoid this reaction is to block the isocyanate end with phenol and use a diketamine to initiate cure. Once exposed to moisture, the diketamine forms a diamine and a ketone. The diamine reacts with the isocyanate end on the prepolymer, creating a cross-link (10). Other blocking agents, such as ethyl malonate, are also used (11). Catalysts commonly used in urethane formulations are tin carboxylates and bismuth salts. Mercury salt catalysts were popular in early formulations, but have been replaced by tin and bismuth compounds. 

Vinyl chloroacetate has been prepared from acetylene and chloroacetic acid in the vapor phase at 250° with a zinc-cadmium catalyst/ and in the liquid phase with a mercury salt catalyst. The procedure described is an adaptation of that employed by Klatte/ by Skirrow and Morrison/ and by others. ... 

Oxazoles are also obtained by heating acetylenic alcohols, in which the acetylenic bond is in the a, /3-position to the hydroxy group, with acid amides in the presence of a mercury salt catalyst,137 or alternatively, by heating a-ketol acetates with nitriles in sulfuric acid.138 In those cases... 

Liquid- and vapor-phase processes have been described the latter appear to be advantageous. Supported cadmium, zinc, or mercury salts are used as catalysts. In 1963 it was estimated that 85% of U.S. vinyl acetate capacity was based on acetylene, but it has been completely replaced since about 1982 by newer technology using oxidative addition of acetic acid to ethylene (2) (see Vinyl polymers). In western Europe production of vinyl acetate from acetylene stiU remains a significant commercial route. 

Acetoiicetyliition Reactions. The best known and commercially most important reaction of diketene is the aceto acetylation of nucleophiles to give derivatives of acetoacetic acid (Fig. 2) (1,5,6). A wide variety of substances with acidic hydrogens can be acetoacetylated. This includes alcohols, amines, phenols, thiols, carboxyHc acids, amides, ureas, thioureas, urethanes, and sulfonamides. Where more than one functional group is present, ring closure often follows aceto acetylation, giving access to a variety of heterocycHc compounds. These reactions often require catalysts in the form of tertiary amines, acids, and mercury salts. Acetoacetate esters and acetoacetamides are the most important industrial intermediates prepared from diketene. 

Manufacture and Processing. Until World War II, phthaUc acid and, later, phthaUc anhydride, were manufactured primarily by Hquid-phase oxidation of suitable feedstocks. The favored method was BASF s oxidation of naphthalene [91-20-3] by sulfuric acid ia the presence of mercury salts to form the anhydride. This process was patented ia 1896. During World War I, a process to make phthaUc anhydride by the oxidation of naphthalene ia the vapor phase over a vanadium and molybdenum oxide catalyst was developed ia the United States (5). Essentially the same process was developed iadependendy ia Germany, with U.S. patents being granted ia 1930 and 1934 (6,7). 

Pyrrohdinone forms alkaU metal salts by direct reaction with alkaU metals or their alkoxides or with their hydroxides under conditions in which the water of reaction is removed. The potassium salt prepared in situ serves as the catalyst for the vinylation of 2-pyrrohdinone in the commercial production of A/-vinylpyrrohdinone. The mercury salt has also been described, as have the N-bromo and N-chloro derivatives (61,62). 

Strong dehydrating agents such as phosphorous pentoxide or sulfur trioxide convert chlorosulfuric acid to its anhydride, pyrosulfuryl chloride [7791-27-7] S20 Cl2. Analogous trisulfuryl compounds have been identified in mixtures with sulfur trioxide (3,19). When boiled in the presence of mercury salts or other catalysts, chlorosulfuric acid decomposes quantitatively to sulfuryl chloride and sulfuric acid. The reverse reaction has been claimed as a preparative method (20), but it appears to proceed only under special conditions. Noncatalytic decomposition at temperatures at and above the boiling point also generates sulfuryl chloride, chlorine, sulfur dioxide, and other compounds. 

Sulfonation of anthraquinone to form the 1-sulfonic acid is achieved at approximately 120°C with 20% oleum in the presence of mercury or a mercury salt as a catalyst [2], Without this catalyst, the reaction produces the 2-sulfonic acid. Exchange with aqueous ammonia (30%) at about 175°C under pressure converts the potassium salt of 1-sulfonic acid to 1-aminoanthraquinone in 70 to 80% yield. To avoid sulfite formation, the reaction is performed in the presence of an oxidant, such as m-nitrobenzosulfonic acid, which destroys sulfite. 

Gold(III) was identified as the most active catalyst for that process in 1985, when Hutchings recognized that the efficiency in catalyzing the hydrochlorination of ethyne to vinyl chloride (a very important industrial process that previously used mercury salts as catalysts) correlated with the standard reduction potential of the supported metal cation. That meant that the metal could be found as a transient species in the reaction [10]. 

For a long time, only a liquid phase process was employed industrially for the hydration of acetylene to acetaldehyde mercury salts in acidic solution were used as catalysts. Only recent reports can be found in the literature (e.g. ref. 300) on the industrial utilisation of the direct vapour phase hydration of acetylene over solid catalysts. 

O-Glycosylation. Traditional glycosylation catalysts are silver or mercury salts. Recently silver zeolite2 has been recommended as the catalyst for preparation of 1,2-cw-glycosides. The thallium zeolite is useful when the glycosyl bromide is unstable in the presence of silver catalysts.1 Example ... 

WOLFFENSTEIN-BOTERS REACTION. Simultaneous oxidation and nitration of aromatic compounds to nitrophcnols with nitric acid or the higher oxides of nitrogen in the presence of a mercury salt as catalyst. Hydroxynitration of benzene yields picric acid. 

The hydration reaction of alkynes leading to carbonyl compounds is generally carried out in dilute acidic conditions with mercuric 1on salts (often the sulfate) as catalysts (ref. 5). Only very reactive alkynes (phenylacety-lene and derivatives) can be hydrated in strong acidic conditions (HgSO ) without mercury salts (ref. 6). Mercury exchanged or impregnated sulfonic resins have also been used in such reactions (ref. 7). Nevertheless, the loss of the catalyst during the reaction and environmental problems due to the use of mercury make this reaction method not as convenient as it should be for the preparation of carbonyl compounds. 

In the Kjeldahl method, pulverized coal is boiled coal with concentrated sulfuric acid containing potassium sulfate and a suitable catalyst to reduce the time for digestion. The catalyst is usually a mercury salt, selenium itself, or a selenium compound, or a mixture of the two. Selenium is regarded as being particularly advantageous. 

Catalytic conversions were experimentally studied in Russia toward the end of the nineteenth century, and especially in the twentieth century, and regularities were empirically established in a number of cases. The work of A. M. Butlerov (1878) on polymerization of olefins with sulfuric acid and boron trifluoride, hydration of acetylene to acetaldehyde over mercury salts by M. G. Kucherov (1881) and a number of catalytic reactions described by V. N. Ipatieff beginning with the turn of the century (139b) are widely known examples. S. V. Lebedev studied hydrogenation of olefins and polymerization of diolefins during the period 1908-13. Soon after World War I he developed a process for the conversion of ethanol to butadiene which is commercially used in Russia. This process has been cited as the first example of commercial application of a double catalyst. Lebedev also developed a method for the polymerization of butadiene to synthetic rubber over sodium as a catalyst. Other Russian chemists (I. A. Kondakov I. Ostromyslenskif) were previously or simultaneously active in rubber synthesis. Lebedev s students are now continuing research on catalytic formation of dienes. 

Most heterocyclic nuclei undergo the sulfonation reaction. Sulfonation of pyridine is difficult. The yield of 3"pyridinesulfonic acid by sulfonation at 390° with oleum is only 13%. The yield is greatly improved by the use of vanadium or mercury salts as catalysts. A critical study of the factors influencing the yield has been made, and a maximum yield of 71% is reported. Fuming sulfuric acid converts quinoline to practically pure 8-quinolinesulfonic acid (54%). The action of concentrated sulfuric acid on dibenzofuran gives 2-dibenzofuransulfonic acid (75%). ... 

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%). ... 

Alkenes can be oxidized to ketones of the same chain length by using salts of copper, palladium, and mercury as catalysts and air, electrolysis [120], hydrogen peroxide, or chromium compounds as oxidants [60, 65, 140, 565] (equation 90). 

R 12. — Vinylation reactions and mercurie salt cation exchange catalysts therefor. US. Pat. 3.201.357 (1965). 

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