Protic solvents conductance

For example, the substituted aniline Ar-NH2 (Ar = />-CH3OC6H4) reacts with the ruthenium nitrosyl complex Ru(bpy)2(Cl)(NO)2+ (bpy = 2,2 -bipyridine) to give a complex of the diazo ligand, namely Ru(bpy)2(Cl)(NNAr)2+ (57). Upon employing the 15N labeled nitrosyl complex Ru(bpy)2Cl(15NO)2+ this reaction resulted in the 15N coordinated product, Ru(bpy)2Cl(15NNAr)2+, demonstrating that the reaction occurs within the metal complex coordination sphere. When the reactions were conducted in non-protic solvents, these nucleophile-nitrosyl adducts could be isolated. 

Kinetic studies of the stoichiometric carbonylation of [Ir(CO)2l3Me] were conducted to model the rate-determining step of the catalytic cycle [73,85]. The reaction can form both fac,cis and mer,trans isomers of [Ir(CO)2l3 (COMe)] (Scheme 13), the product ratio varying with the solvent and temperature used. An X-ray crystal structure was obtained for the fac,cis isomer. Carbonylation of [Ir(CO)2l3Me] is rather slow and requires temperatures > 80 °C in chlorinated solvents (e.g. PhCl). However, the presence of protic solvents (e.g. methanol) has a dramatic accelerating effect. This is interpreted in terms of the protic solvent aiding iodide dissociation by solvation. 

Reaction between C in methanol and RTCNQ in acetonitrile yielded three kinds of ionic solids (1) insulators composed of methoxy substituted RTCNQ anions such as (CHC )[F4TCNQ-0Me ](H20) (Fig. 6) [136], (2) semiconducting CT solids with fully ionic RTCNQ radical anions such as (CHC )(TCNQ ) [137, 138], and (3) conducting CT solids of partially ionic or mixed valent RTCNQ radical anions such as (CHC"XMeTCNQ° >2 [138], where CHC" is the hemiprotonated cytosine pair (Fig. 6b). Cation units in aU products were found to be protonated cytosine species, most commonly CHC, where comes from methanol. This result suggests that the intrinsic transport properties of DNA should be studied not in protic solvents but under strictly dried conditions. 

In dipolar aprotic solvents, the molar conductivity of the fastest anion is larger than that of the fastest cation. However, this does not apply in protic solvents. 

The reduction of carbonyl compounds to form pinacol dimers can be accomplished photochemically, electrochemically or with chemical reducing agents. When conducted under acidic conditions or in protic solvents, pinacols are likely produced by coupling of two neutral ketyl radicals (vs radical anions). The electrochemical reduction is especially complicated in terms of the role of the electrode surface, counterion and solvent, and an excellent review has appeared on the subject32. 

Radical carbonylation can also be conducted in a zinc-induced reduction system. A similar three-component transformation reaction to that illustrated in the second equation of Scheme 6.14 can be attained using zinc and protic solvents (Scheme 6.38) [59]. The observed stereochemical outcome is identical to that for the tin hydride-mediated reaction, providing a additional evidence for free-radical generation, radical carbonylation, and acyl radical cyclization taking place simultaneously, even in the zinc-induced system. In this system, however, the final step is reduction to form a carbanion and protonation. 

Many electrochemical reactions, especially of organic compounds, are better carried out in non-aqueous solvents and may not even proceed in water. The following requirements should be met by these solvents [73-77] sufficient solubility of the compounds to be examined and, of necessity, of the supporting electrolyte as well (usually tetraalkylammonium salts), chemical inertness towards the electrolyte and the reactive intermediates formed [e.g. the frequently formed radical anions would immediately be pro-tonated by protic solvents), and as high a relative permittivity as possible (usually fir > 10). The latter will increase the electrical conductivity by favoring the dissociation of the electrolyte and hence decreasing the electrical resistance of the solution. Nevertheless, even solvents of low relative permittivity (sr < 5) can be used for electrochemical... 

Conductance and Ionic Association of Several Electrolytes in Binary Mixtures Involving Sulfolane (TMS) and Protic Solvents... 

It might also be possible to perform electrophoresis experiments in weakly protic solvents that are not readily oxidized or reduced, although little work has been done in this area. As was pointed out by Tiselius (1959), although the conductance in such media may often be very low, this may be compensated for by the application of high voltages without concomitant large heating effects. 

Enolates of cyclic 1,3-diketones, such as 2-methyl-1,3-cyclopentanedione and 2-methyl-1,3-cyclohex-anedione, are especially prone to 0-alkylation because of their W geometry and steric hindrance at carbon. However, C-alkylations of these species can be conducted reasonably successfully in protic solvents, e.g. water.280 Trost and Curran have reported high yields for the C-alkylation of cyclic 1,3-diketones with allylic acetates in the presence of palladiumfO) catalysts and DBU (Scheme 80). 

The membrane conductivity of Nafion in various protic solvents has been measured in a recent study and the results are given in Table 12. The ratio of the membrane conductivity (k) to the solvent conductivity (k ) is listed in the last column of the table. A plot of the conductivity ratio (/solubility parameter of the solvent is shown in Fig. 22. The membrane conductivity is higher than the solvent conductivity in all solvents except formamide. 

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