Ferrous sulfate, conversion into

The direct conversion of methane into methanol, hydrocarbons, or oxygenated fuels has attracted a great deal of interest. At the beginning of the 20th century, one of the first patents was granted in 1905 to Lance and Elworthy [165]. These inventors claimed that oxidizing methane with hydrogen peroxide in the presence of ferrous sulfate could form methanol, formaldehyde, and formic acid. 

For the preparation of mannose, mannitol (50 g) was dissolved in a little water and treated with ferrous sulfate (12.5 g) in aqueous solution and then with 5-6% hydrogen peroxide (150 ml). At the end of the reaction the mixture was treated with an excess of freshly precipitated barium carbonate, filtered, much concentrated at 50°/30 mm, and finally evaporated to a syrup in a vacuum. The syrup was treated with 10 times its volume of anhydrous ethanol, then filtered, and an excess of ether was added. The resulting colorless flocks collected to form a pale yellow syrup, which partly crystallized when rubbed with alcohol and ether. The yield was not given the identity of the product with mannose was proved by conversion into the phenylhydrazone. 

In the original German process acetylene is injected into an aqueous solution of mercuric sulfate acidified with sulfuric acid at 90-95°C and about 1-2 atm. As a result of side reactions, the catalytically active mercury(II) ions are reduced to mercury. To prevent this process ferric sulfate is continuously added to the reactor. Since ferric ions are reduced to ferrous ions, the catalyst solution requires reactivation, which is accomplished by hot nitric acid and air. Excess acetylene and acetaldehyde formed are removed, cooled, absorbed in water, and then separated by distillation. Excess acetylene is recycled. Conversion per pass is bout 55%. The Montecatini process89 operates at 85°C and provides 95% overall yield. A modification developed by Chisso90 allows lower operating temperature (70°C) without excess acetylene. Since side reactions are less important under these conditions, higher yields may be achieved. 

The conversion of a-hydroxy acids into aldehydes with one less carbon has great importance in the chemistry of sugars. Oxidation with bromine water transforms aldoses into the corresponding aldonic acids, which, in the form of their calcium salts, are treated with aqueous hydrogen peroxide in the presence of ferrous or ferric sulfate (Fenton reagent) and are degraded to aldoses with one less carbon (Ruff degradation) (equation 479) [57]. 

Aconitase was initially crystallized in the [3Fe-4S]" " form, and these crystals could be converted to the [4Fe S] " " form by addition of ferrous ammonium sulfate. Alternatively, anaerobic crystallization methods were used to crystallize the [4Fe-4S] " " form directly." The iron-sulfur cluster of aconitase sits within a solvent-filled cleft in the protein structure and is coordinated by Cys 358, Cys 421, and Cys 424. The [3Fe S]+ cluster shows the typically cuboidal geometry, with the open iron site directed toward the active site cleft. Conversion to the active [4Fe-4S] " " form results in almost no structural perturbation, with the extra iron atom simply being inserted into the vacant site in the cluster. The fourth iron is tetrahedrally coordinated, but with a solvent hydroxide rather than a cysteine as the fourth ligand. (The electron density clearly reveals a bound solvent, and previous ENDOR studies had demonstrated that the bound species was associated with only a single proton.)... 

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