Magnesium oxide, reaction with carbon dioxide

Carboxylation has also been seldom used especially for the constmction of various spiro-8-lactones. Rieke et al. have developed a direct synthesis of spiro-8-lactones from conjugated dienes and epoxides [114,115] (Scheme 67). Treatment of 1,2-bis (methylene)-cyclohexane-magnesium reagent derived from diene 306, with an excess of ethylene oxide, gave intermediate 307, which upon reaction with carbon dioxide and hydrolysis afforded the spiro-8-lactone 308. 

Sihcon carbide is comparatively stable. The only violent reaction occurs when SiC is heated with a mixture of potassium dichromate and lead chromate. Chemical reactions do, however, take place between sihcon carbide and a variety of compounds at relatively high temperatures. Sodium sihcate attacks SiC above 1300°C, and SiC reacts with calcium and magnesium oxides above 1000°C and with copper oxide at 800°C to form the metal sihcide. Sihcon carbide decomposes in fused alkahes such as potassium chromate or sodium chromate and in fused borax or cryohte, and reacts with carbon dioxide, hydrogen, ak, and steam. Sihcon carbide, resistant to chlorine below 700°C, reacts to form carbon and sihcon tetrachloride at high temperature. SiC dissociates in molten kon and the sihcon reacts with oxides present in the melt, a reaction of use in the metallurgy of kon and steel (qv). The dense, self-bonded type of SiC has good resistance to aluminum up to about 800°C, to bismuth and zinc at 600°C, and to tin up to 400°C a new sihcon nitride-bonded type exhibits improved resistance to cryohte. 

Write the reaction for carbon dioxide with magnesium oxide. 

Hard-core RMs of carbonate-alkylaryl sulfonates (OCABS) are prepared by reaction of carbon dioxide with calcium or magnesium oxide (or hydroxide) in the presence of a surfactant (Delfort et al., 1995 Mansot et al., 1993a). Because of their alkaline reservoir they are able to neutralize the acidic by-products resulting from oxidation of oil and from fuel combustion products (blow-by). 

Reaction of l-methyl-3-chloro-2-phospholene-l-oxide (9) was particularly difficult even with Kl-activated magnesium . Reaction of 9 with KI-activated magnesium in refluxing THF for 6 1/2 hours gave approximately 40% of the corresponding carboxylic acid after treatment with carbon dioxide and then acid. 

Heavy metal oxides of compounds, such as copper oxide, nickel oxide, cobalt oxide, and magnesium dioxide, are mixed in the charge to catalyze the reaction of the potassium superoxide with carbon dioxide and moisture. It is important, however, that only a portion of the superoxide be mixed with catalyst to avoid excessive liberation of oxygen. 

The low temperature also promotes the reaction of sulfur dioxide with metal oxides and carbonates in the ash, most notably calcium and magnesium salts. If limestone (calcium carbonate, CaCOj), is added to the bed of burning coal, the following reaction with sulfur dioxide occurs ... 

Yano T, Matsui H, Koike T, Ishiguro H, Fujihara H, Yoshihara M, Maeshima T (1997) Magnesium oxide-catalysed reaction of carbon dioxide with anepoxide with retention of stereochemistry. OiemCommun 12 1129-1130... 

Magnesium-aluminum mixed oxides are also excellent catalysts for the reaction of several epoxides with carbon dioxide to give the cyclic carbonates 80. 

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