Copper complexes sulfur dioxide

Iron and copper in wines may form complexes with other components to produce deposits or clouds in white wines. Iron clouds generally occur at a pH range from 2.9 to 3.6 and are often controlled by adding citric acid to the wines (2). Copper clouds appear in wines when high levels of copper and sulfur dioxide exist and are a combination of sediments, protein-tannin, copper-protein, and copper-sulfur complexes (169). Further, the browning rate of white wines increases in the presence of copper and iron (143). The results of this study indicate that iron increased the browning rate more than copper. 

A substantial fraction of the named enzymes are oxido-reductases, responsible for shuttling electrons along metabolic pathways that reduce carbon dioxide to sugar (in the case of plants), or reduce oxygen to water (in the case of mammals). The oxido-reductases that drive these processes involve a small set of redox active cofactors , that is, small chemical groups that gain or lose electrons. These cofactors include iron porjDhyrins, iron-sulfur clusters and copper complexes as well as organic species that are ET active. 

The production of acid rain starts when atmospheric sulfur dioxide is oxidized to sulfur trioxide in a complex series of reactions. SO3 is, in turn, hydrolyzed to sulfuric acid. Anthropogenic sources of sulfur dioxide include the burning of coal, the refining and burning of oil, and the smelting of copper ores. Until control measures started to come on line, the pH of rainwater in the northeastern United States and other areas downwind of such sources had fallen to values between 3 and 4. The best control measures have proven to be wet and dry scrubbers. As a result of installation of these flue-gas desulfurization (FGD) devices, the amount of sulfur and nitrogen oxides released to the atmosphere has measurably decreased in the last several decades. 

The chlorosulfonation of benzenesulfonamides is employed in the synthesis of substituted benzenedisulfonamides 376 used as vasodilatory drugs. The chlorosulfonation was achieved indirectly by diazotization of the appropriate sulfanilamide 377, followed by treatment of the diazonium complex with acetic acid, sulfur dioxide and copper(ii) chloride as described by Holland et al In the final step, the sulfonyl chloride was condensed with the appropriate amine to give the disulfonamide 376 (Scheme 12). 

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