Dissolving metal reactions

Alkali metals dissolve in liquid ammonia to yield solvated cations and solvated electrons, as shown below for sodium  

Such salts where the anion is simply an electron are called electrides. Addition of the encapsulating ligand 2,2,2-cryptand to [Na(NH3)g] e yields [Na(2,2,2-crypt)] e , which may 

Electrides are synthetically useful and form the basis of so-called dissolving metal reactions, of which the Birch reduction of aromatic compounds is the paradigm, shown below for benzene and naphthalene  

The mechanism, shown only for benzene, involves a succession of electron and proton 

THE s-BLOCK ELEMENTS ALKALI AND ALKAUNE EARTH METALS 

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Compound (12) can also be obtained by dissolving metal reactions through treatment with an excess of lithium—hquid ammonia in tert-huty alcohol (54). 

Two reductions occur concurrently in this dissolving-metal reaction (Scheme 12.10). The first is a Birch reduction8 of the benzyl ether to give a... 

Write a stepwise mechanism analogous to that of the dissolving metal reaction that reduces alkynes to trans alkenes for the following reaction ... 

Free radical attack at ring carbon atoms. 6.3 Electrochemical reactions and reactions with free electrons. 6.4 Catalytic hydrogenation and reduction by dissolving metals Reactions with Cyclic Transition States. 7.1 Diels-Alder reactions and 1,3-dipolar additions. 7.2 Photochemical cycloadditions... 

Draw the dissolving metal reaction for the conversion of 93 to the -alkene. 

CAMEO has numerous modules, and includes nucleophilic addition, electrophilic addition, electrophilic aromatic substitution, pericyclic reactions, carbene reactions, dissolving metal reactions, diastereoselectivity, ene and retro-ene reactions, and so forth." The program does a very good job of predicting the products of reactions which fall within the scope of its modules, and has been made available to the public through various commercial and non-commercial organizations. 

Hydrochloric acid is a strong monobasic acid, dissolving metals to form salt and evolving hydrogen. The reaction may be slow if the chloride formed is insoluble (for example lead and silver are attacked very slowly). The rate of attack on a metal also depends on concentration thus aluminium is attacked most rapidly by 9 M hydrochloric acid, while with other metals such as zinc or iron, more dilute acid is best. 

Iodine dissolves without reaction in concentrated sulfuric acid and with concentrated nitric acid it reacts to form iodine pentoxide (47). Iodine reacts with alkah metal hydroxide solutions to form the corresponding hypoiodite and the rate of the reaction increases with the alkaU concentration and temperature. At 50°C, the reaction is almost instantaneous ... 

Direct Metal Reaction. The DMR process is carried out over a catalyst with fatty acids ia a melted state or dissolved ia hydrocarbons. The acid reacts directiy with the metal, suppHed ia a finely divided state, produciag the metal soap and ia some cases hydrogen. Catalysts iaclude water, aUphatic alcohols, and low molecular-weight organic acids. 

This group was developed to prevent participation of the BnO bond during cationic reactions. It is formed from the bromide [C6H3F2CH2Br, Ba(0H)2 8H20, DMF, 25 h, 94% yield] and cleaved by dissolving metal reduction (Ca, NH3, 79% yield). ... 

Table 12-11 predicts the cell will operate so as to dissolve metallic zinc and deposit metallic nickel, and its voltage will be +0.51 volt This is exactly what occurs in such a cell. Predicting is fun— let s try it again Another cell we studied is based on reaction (52) ... 

Substituting Eqs. (35) and (36) into Eq. (34), the electrochemical potential fluctuation of dissolved metal ions at OHP is deduced. Then, disregarding the fluctuation of the chemical potential due to surface deformation, the local equilibrium of reaction is expressed as fi% = 0. With the approximation cm x, y, 0, if cm(x, y, (a, tf, we can thus derive the following equation,... 

As shown in Fig. 24, the mechanism of the instability is elucidated as follows At the portion where dissolution is accidentally accelerated and is accompanied by an increase in the concentration of dissolved metal ions, pit formation proceeds. If the specific adsorption is strong, the electric potential at the OHP of the recessed part decreases. Because of the local equilibrium of reaction, the fluctuation of the electrochemical potential must be kept at zero. As a result, the concentration component of the fluctuation must increase to compensate for the decrease in the potential component. This means that local dissolution is promoted more at the recessed portion. Thus these processes form a kind of positive feedback cycle. After several cycles, pits develop on the surface macroscopically through initial fluctuations. 

Moreover, as the reaction progresses, the mass flux of the asymmetrical concentration fluctuation forms a diffusion layer outside the double layer, and nonequilibrium fluctuations of another type occur in the diffusion layer these come from the mass transfer of dissolved metal ions perturbed by the thermal motion of solution particles. A fluctuation of this type was analyzed by Aogaki et a/.78 As shown in Fig. 31, the mass flux fluctuates around its average value, i.e., the fluctuations are both positive and negative, and in this sense have symmetry. This type of fluctuation is... 

Since the diffusion layer extends into the bulk of the solution, the main role for mitigating the fluctuation is transferred from the reaction at the electrode surface to the diffusion of dissolved metal ions in the bulk of the solution. Then, other fluctuations (i.e., symmetrical fluctuations) emerge, as proved before, and decay to zero. The average value of the symmetrical fluctuation becomes zero because of its symmetry. So, for average values, we can neglect all the symmetrical fluctuations. 

The water molecules in the inner hydration sphere can undergo dissociation reactions just as water molecules far from a dissolved metal ion... 

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