Dioxide oxide reduction

Most usual oxidizing agents act normally with imidazole aldehydes and ketones but l-benzylimidazole-2-carbaldehyde is reportedly somewhat resistant to selenium dioxide oxidation. Reduction of ketone functions under Clemmensen and Wolfi-Kischner conditions is usually successful. Zinc dust and acetic acid reduce acetyl groups to a mixture of secondary alcohol and ethyl borohydride gives the alcohol exclusively (B-76MI40701). 

Although essentially inert m acid-base reactions alkanes do participate m oxidation-reduction reactions as the compound that undergoes oxidation Burning m air (combus tion) IS the best known and most important example Combustion of hydrocarbons is exothermic and gives carbon dioxide and water as the products... 

As we have just seen the reaction of alkanes with oxygen to give carbon dioxide and water IS called combustion A more fundamental classification of reaction types places it m the oxidation—reduction category To understand why let s review some principles of oxidation-reduction beginning with the oxidation number (also known as oxidation state)... 

The ready reversibility of this reaction is essential to the role that qumones play in cellular respiration the process by which an organism uses molecular oxygen to convert Its food to carbon dioxide water and energy Electrons are not transferred directly from the substrate molecule to oxygen but instead are transferred by way of an electron trans port chain involving a succession of oxidation-reduction reactions A key component of this electron transport chain is the substance known as ubiquinone or coenzyme Q... 

Carbon dioxide generated by the fermentation process must be removed to help maintain the pH of the solution at pH 7.6—8.0. Carbon dioxide also inhibits the activity of the bacteria. The oxidation reduction potential is kept at 100—200 mV. The ideal temperature in the reactor varies with different strains in the bacteria but generally is 25—35°C. 

Zinc does not react with nitrogen, even at elevated temperatures but zinc nitride, Zn N2, forms with ammonia at red heat. Zinc sulfide, the most common form of zinc in nature, is not reduced direcdy in commercial practice because of reactions of the zinc vapor during condensation. Rather, the sulfide is burned (roasted) to the oxide plus sulfur dioxide before reduction. However, zinc can be reduced to the metal at ca 1300°C with carbon or iron. 

Sulfur Dioxide Reductant. The Mathieson process uses sulfur dioxide, sodium chlorate, and sulfuric acid to produce chlorine dioxide gas with a much lower chlorine content. The sulfur dioxide gas reductant is oxidized to make sulfuric acid, reducing the overall acid requirement of the process. Air is used to dilute the chlorine dioxide produced by this process. The exit gases flow through a scmbber to which chlorate is added in order to remove any unreacted sulfur dioxide. Spent Hquor, containing some unreacted chlorate, sulfuric acid, and sodium sulfate, continuously overflows from this process. 

Oxidants Substances present in air, such as nitrogen dioxide, ozone, etc., that are capable of oxidizing other chemicals or elements in oxidation-reduction type chemical reactions. 

The most important metallurgical process involving carbon is the reduction of hematite ore, which consists largely of iron(III) oxide, Fe203, mixed with silicon dioxide, Si02. Reduction occurs in a blast furnace (Figure 20.4a) typically 30 m high and 10 m in diameter. The... 

L.24 The reduction of iron(III) oxide to iron metal in a blast furnace is another source of atmospheric carbon dioxide. The reduction takes place in these two steps ... 

Electron-transfer reactions occur all around us. Objects made of iron become coated with mst when they are exposed to moist air. Animals obtain energy from the reaction of carbohydrates with oxygen to form carbon dioxide and water. Turning on a flashlight generates a current of electricity from a chemical reaction in the batteries. In an aluminum refinery, huge quantities of electricity drive the conversion of aluminum oxide into aluminum metal. These different chemical processes share one common feature Each is an oxidation-reduction reaction, commonly called a redox reaction, in which electrons are transferred from one chemical species to another. 

Silicon is generally considered to be a congener of carbon and this is also reflected in the evolution of silicon as a reducing agent for metal oxides. Silicon forms a fairly stable solid oxide silica or silicon dioxide (Si02) and also a stable gaseous oxide silicon monoxide (SiO), both of which can be useful in oxide reduction reactions. 

Degradation is often the result of the combined effect of chemical transformation and biodegradation. For example, the oxidation/reduction of complex hydrocarbons can produce simple compounds such as peroxides, primary alcohols, and monocarbocylic acids. These compounds can then be further degraded by bacteria, leading to the formation of carbon dioxide, water, and new bacterial biomass.19-35... 

In addition to oxidation-reduction reactions occurring under various conditions, increased carbon dioxide will also affect soil pH. Carbon dioxide... 

The amide functionality plays an important role in the physical and chemical properties of proteins and peptides, especially in their ability to be involved in the photoinduced electron transfer process. Polyamides and proteins are known to take part in the biological electron transport mechanism for oxidation-reduction and photosynthesis processes. Therefore studies of the photochemistry of proteins or peptides are very important. Irradiation (at 254 nm) of the simplest dipeptide, glycylglycine, in aqueous solution affords carbon dioxide, ammonia and acetamide in relatively high yields and quantum yield (0.44)202 (equation 147). The reaction mechanism is thought to involve an electron transfer process. The isolation of intermediates such as IV-hydroxymethylacetamide and 7V-glycylglycyl-methyl acetamide confirmed the electron-transfer initiated free radical processes203 (equation 148). 

Carbon dioxide oxidizes carbon at a substantially slower rate than 02 at normal combustion temperatures. As a consequence, the transition from single-film combustion of a carbon particle to double-film combustion typically involves a strong reduction in the carbon oxidation rate, as eloquently demonstrated by Makino and coworkers in a series of experiments in which graphite rods were oxidized in air at different temperatures and flow rates [38],... 

The 4a,9b double bond in 1,2,3,4-tetrahydrodibenzothiophene 5,5-dioxide (68) and similar compounds, is essentially nonaromatic and in this respect resembles the 2,3 bond in benzo[6]thiophene 1,1-dioxide. Catalytic reduction of 68 results in the formation of l,2,3,4,4a,9b-hexahydrodibenzothiophene 5,5-dioxide (92 /o). Subsequent reduction of the sulfone with LAH yields 1,2,3,4,4a,9b-hexahydrodibenzothiophene (69) as an oil (78 /o). Oxidation of 4-keto-l,2,3,4-tetrahydrodi-benzothiophene (44a) to its sulfone with peracetic acid (63 /o) followed by... 

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