Phosphorus reaction with mercury

Zinc and cadmium tarnish quickly in moist air and combine with oxygen, sulfur, phosphorus and the halogens on being heated. Mercury also reacts with these elements, except phosphorus and its reaction with oxygen was of considerable practical importance in the early work of J. Priestley and A. L. Lavoisier on oxygen (p. 601). The reaction only becomes appreciable at temperatures of about 350° C, but above about 400°C HgO decomposes back into the elements. 

Like sulphuryl chloride, pyrosulphuryl chloride can convert many elements, e.g. sulphur, phosphorus, antimony and mercury, into the corresponding chlorides, with simultaneous formation of sulphur dioxide and trioxide.2 In the reaction between pyrosulphuryl chloride and phosphorus pentachloride or trichloride, there are obtained phosphorus oxychloride, sulphur dioxide and chlorine. 

Thenaldehyde (thiophene-2-carbaldehyde) is readily available via the Vilsmeier-Haack reaction of DMF with thiophene catalyzed by phosphorus oxychloride. The Sommelet reaction with 2-chloromethylthiophene also gives reasonable yields (63AHC(l)l). Likewise, thiophene is readily acylated with acyl anhydrides or acid chlorides (equation 14), using mild Friedel-Crafts catalysts, such as tin(IV) chloride, zinc chloride, boron trifluoride, titanium tetrachloride, mercury(II) chloride, iodine and even silica-alumina gels or low-calcium-content montmorillonite clays (52HC(3)l). 

The redistribution reaction in lead compounds is straightforward and there are no appreciable side reactions. It is normally carried out commercially in the liquid phase at substantially room temperature. However, a catalyst is required to effect the reaction with lead compounds. A number of catalysts have been patented, but the exact procedure as practiced commercially has never been revealed. Among the effective catalysts are activated alumina and other activated metal oxides, triethyllead chloride, triethyllead iodide, phosphorus trichloride, arsenic trichloride, bismuth trichloride, iron(III)chloride, zirconium(IV)-chloride, tin(IV)chloride, zinc chloride, zinc fluoride, mercury(II)chloride, boron trifluoride, aluminum chloride, aluminum bromide, dimethyl-aluminum chloride, and platinum(IV)chloride 43,70-72,79,80,97,117, 131,31s) A separate catalyst compound is not required for the exchange between R.jPb and R3PbX compounds however, this type of uncatalyzed exchange is rather slow. Again, the products are practically a random mixture. 

These organometallic nucleophiles show most of the typical reactions with carbon electrophiles associated with benzenoid Grignard reagents and aryllithiums They also allow the introduction of other metals, and nonmetals, on to the ring, such as mercury, boron, phosphorus, tin, and arsenic (Scheme 104) (see also Section 3.2.3.10.2.5), some of which are of great use as partners in transition metal-catalyzed processes. 

SAFETY PROFILE A poison. Flammable by chemical reaction an oxidizer. Explosive reaction with hydrogen peroxide, chlorine + ethylene. Reacts violently with molten potassium, molten sodium, S, (H2S + BaO + air). Forms explosive mixtures with nonmetals [e.g., phosphorus (impact-sensitive), sulfur (friction-sensitive)]. Incompatible with alkali metals, reducing materials. Dangerous when heated to decomposition it emits highly toxic fumes of Hg. See also MERCURY COMPOUNDS, INORGANIC. 

Mercury di-o-tolyl may be j repared by the sodium amalgam method (see mercury diphenyl, Method 5). In this case 8 per cent, amalgam is used, and the yield is about 33 per cent. Tlie compound forms quadratic crystals from benzene, M.])t. 108° C. B.pt. 219 C. at 14 mm. The reactions of mercury di-o-tolyl with tlie trichlorides oi boron, phosphorus, and arsenic, also with nitrogen tri- and tetr-oxides, are similar to those described under mercury diphenyl (p. 74). 

Carbon disulfide (bp 46°) is used as the solvent in many Friedel-Crafts reactions. It must be used with caution because of its very low flash point, which permits it to ignite on contact with heated surfaces. It should be distilled in such a manner that the vapors do not escape from the apparatus, and heat should be supplied by a steam bath and precautions taken to prevent overheating. The commercial material contains some odoriferous sulfur compounds which may be removed by successive treatment with mercury, mercuric chloride solution, and permanganate solution, and then washing with water, drying over phosphorus pentoxide, and distilling. ... 

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