Cupric oxide oxidation method, alkaline

In general, commonly used oxidants destroy phenolic rings or give complex products (25, 26). Some of the oxidants such as nitrobenzene produce reaction byproducts that may interfere with the analysis of the oxidation products (23, 27, 28). To obtain lignin oxidation products from coals, we resorted to the alkaline cupric oxide oxidation method which has been applied successfully to analysis of lignins in plants (23), fulvic and humic acids (24, 27), and land-derived marine sediments (23). 

Other methods of formation are the addition of sodium carbonate to a solution of cupric sulphate and sodium chloride reduced with sulphurous acid,9 and that of an alkaline solution of sodium potassium tartrate to a solution of cuprous chloride and sodium chloride.10 At temperatures below 350° C. copper reacts with nitrous oxide to form cuprous oxide above this temperature the product is cupric oxide.u Cuprous oxide is also formed at the anode in the electrolysis of a solution of cupric sulphate,12 and by heating cupric oxide in steam. 

A more-direct method of preparation is oxidation of aldoses, and optimal yields are afforded by the action of cupric acetate in methanol or ethanol.417 This method is suitable for large-scale preparation of intermediates however, a pure product is obtained only by chromatographic separation from the unreacted sugar byproducts. The synthesis of D-eryt/wo-pentos-2-ulose and its D-threo isomer by oxidation of D-arabinose and D-xylose, respectively, with cupric acetate followed by anion-exchange chromatography has been reported.418 The only product obtained by oxidation of D-glucose with sodium 2-anthraquinonesulfonate in alkaline... 

In one such method (details of which are found on the Evolve site that accompanies this book), using Benedict s reagent (cupric ion complexed to citrate in alkaline solution), reducing substances convert cupric to cuprous ions, forming yellow cuprous hydroxide or red cuprous oxide. 

Several macro or titration methods involve the heating (usually in a boiling water bath) of an aqueous solution of the carbohydrate for a specified period of time with an alkaline solution of complexed cupric ion. After cooling, an excess amount of sodium iodide solution is added, which is oxidized to iodine by the unreacted cupric ion. The iodine is titrated with a standard solution of sodium thiosulfate (Schoorl method [19]). 

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