Subject reduction, dissolving metals

The following enone is subjected to dissolving metal reduction in the presence of an appropriate protonating species such tot-butanol. Please write the structures of all the possible products and calculate their relative energies. Which product will you predict to predominate if allowed to consider the product s thermodynamic stability as the control factor ... 

Reduction of aromatic compounds to dihydro derivatives by dissolved metals in liquid ammonia (Birch reduction) is one of the fundamental reactions in organic chemistry308. When benzene derivatives are subjected to this reduction, cyclohexa-1,4-dienes are formed. The 1,4-dienes obtained from the reduction isomerize to more useful 1,3-dienes under protic conditions. A number of syntheses of natural products have been devised where the Birch reduction of a benzenoid compound to a cyclohex-1,3-diene and converting this intermediate in Diels-Alder fasion to polycyclic products is involved (equation 186)308f h. 

Co-reduction of mixed oxides. A two-stage preparation of an alloy through the synthesis of a suitable precursor may be exemplified by the chemical route used by Jena et al. (2004) in the preparation of a copper-nickel alloy. The alloy was prepared from an aqueous solution of the nitrates of copper and nickel dissolved in a minimum amount of water and allowed to dehydrate and decompose to their oxides at a temperature around 350°C for an hour. Samples of the mixed oxide powders thus formed were subjected to reduction by pure hydrogen. The reduced powder (apparently containing partially alloyed metals) was sintered at 1000°C. The effect of temperature (250-450°C) on the reduction of the co-formed oxides was studied. 

The preparation of an activated metal for use in an organometallic synthesis can be effected in a separate sonication step. An early example of this was the preparation of finely dispersed mercury for the reduction of a,a -dibromoketone to a mixture of a-acetoxyketones which favours the tertiary product (Eq. 3.6) [71]. The procedure is simple in that the dibromocompound, dissolved in acetic acid is subjected to sonication in a bath in the presence of a small amount of mercury. In this particular case... 

It is usual to operate an aqueous-medium fuel cell under pressure at temperatures well in excess of the normal boiling point, as this gives higher reactant activities and lower kinetic barriers (overpotential and reactant diffusion rates). An alternative to reliance on catalytic reduction of overpotential is use of molten salt or solid electrolytes that can operate at much higher temperatures than can be reached with aqueous cells. The ultimate limitations of any fuel cell are the thermal and electrochemical stabilities of the electrode materials. Metals tend to dissolve in the electrolyte or to form electrically insulating oxide layers on the anode. Platinum is a good choice for aqueous acidic media, but it is expensive and subject to poisoning. 

The control of the actinide metal ion valence state plays a pivotal role in the separation and purification of uranium and plutonium during the processing of spent nuclear fuel. Most commercial plants use the plutonium-uranium reduction extraction process (PUREX) [58], wherein spent fuel rods are initially dissolved in nitric acid. The dissolved U and Pu are subsequently extracted from the nitric solution into a non-aqueous phase of tributyl phosphate (TBP) dissolved in an inert hydrocarbon diluent such as dodecane or odourless kerosene (OK). The organic phase is then subjected to solvent extraction techniques to partition the U from the Pu, the extractability of the ions into the TBP/OK phase being strongly dependent upon the valence state of the actinide in question. 

For instance, benzene is one of the most hard-to-reduce compounds. It is not active polarographically and is not subjected to direct electrode reduction in liquid ammonia . Benzene does not react with solvated electrons obtained by dissolving alkali metals in liquid ammonia in the absence of proton donors However, in the presence of proton donors benzene is hydrogenated by solvated electrons (Table 10). 

The importance of pH as a master variable controlling chemical reactions in soils has been stressed in previous chapters. However, soils subjected to fluctuations in water content come under the influence of another master variable the reduction-oxidation (or redox) potential Under conditions of water saturation, the lack of molecular oxygen can result in a sequence of redox reactions that changes the soil pH. In this sense the redox state of the soil exerts control over the pH. The nature of redox reactions will be discussed in this chapter, as these reactions profoundly influence metal ion solubility and the chemical form of ions and molecules dissolved in soil solution. The reader is referred to section 1.2f in Chapter 1 for a review of the basic chemical principles necessary for the understanding of redox reactions. 

Processes involving the use of solid acid catalysts have also been patented. According to Chen and Yan,40 plastic and/or rubber wastes are first subjected to a size reduction step, followed by separation of any metals present and washing to remove any non-plastic material such as paper, labels, etc. Subsequently, the polymer wastes are dissolved or dispersed in a petroleum oil, with a high content of polycyclic aromatic compounds at 300 °C, and catalytically transformed in an FCC reactor at temperatures of about 500 °C. Details are given for the conversion of different wastes used whole tyres, PE bags and PS foam. 

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