Carbon dioxide, addition metal catalyzed

The use of catalytic converters to reduce the amount of unbumed hydrocarbons in exhaust gases is an additional example of the use of metals. Reactions of these unbumed hydrocarbons in the atmosphere are described later, in the section on photochemical smog. The catalyst currently used is a cordierite or alumina support treated with an AI2O3 wash coat containing rare earth oxides and 0.10% to 0.15% Pt, Pd, and/or Rh, which catalyzes the combustion of hydrocarbons in the exhaust gases to carbon dioxide and water. Platinum,... 

Polymerization of styrene in liquid ammonia at low temperatures catalyzed by potassium metal represents a good example of a base-initiated anionic polymerization. Styrene, being relatively nonpolar, requires the strongly basic amide ion for effective anionic polymerization. The catalyst is made, in situ, usually before the styrene is added, by the addition of small pieces of potassium metal to liquid ammonia kept at dry ice (solid carbon dioxide) temperatures (Eq. 22.30). 

The first reaction predominates if the product contains a large amount of water (-18%). This reaction is analogous to the disproportionation of aqueous hypochlorite. However, disproportionation is much slower in solid calcium hypochlorite than in solution. Under dry conditions, the second reaction predominates. It is catalyzed by transition metals including iron and manganese. It may occur explosively 150°C. Thus, calcium hypochlorite products usually contain some water or an additive such as magnesium sulfate heptahydrate. The third reaction is the reverse of chlorination. The fourth reaction is due to the adsorption of carbon dioxide from air or the release of carbon dioxide from carbonate salt impurities. It is accelerated by water and temperature. The first reaction accounts for -70%, and the second reaction -30%, of the decomposition of solid calcium hypochlorite made in the United States and stored in sealed containers at 25°C. ... 

Ruthenium-catalyzed asymmetric addition of alkane- or arenesulfonyl chlorides to styrenes leads to optically active suifones22,23. When this conversion is conducted under mild conditions no C —C bond is formed, however, at higher temperatures (100 =C), enantioselective asymmetric carbohalogenation of styrene with trichloromethanesulfonyl chloride (accompanied by sulfur dioxide extrusion) can be achieved with tetrachlorotris[( + )- or (—)-Diop]diruthenium. Excellent yields (up to 100%), but only low asymmetric inductions (up to 13 %), arc observed12. Similar results are obtained with carbon tetrachloride. A mechanism with radical formation w ithin the metal coordination sphere ( radicaloid ) has been proposed. 

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