Phenol different ranks with

Table IV. Depolymerization of Coals of Different Ranks with Phenol-...

Kinetic, steric, and thermodynamic results have been reviewed to argue that the rate-determining step in some aliphatic nucleophilic substitutions is the transfer of an electron. The same group carried out a systematic ranking of different nucleophiles with respect to their ability to stabilize the transition states of substitution reactions, acetonitrile and dimethyl sulfoxide being the solvents involved. The nucleophiles included enolates, phenolates, thiophenolates, hydroxide, and cyanide. The method is based on a comparison of the rate coefficient, ksm, for the substitution reaction between a given nucleophile and benzyl chloride with the rate coefficient, A et for the corresponding electron transfer from an aromatic radical anion to benzyl chloride. The ratio ksuB/ ET expresses the rate enhancement due to electronic interaction in the transition state of the substitution reaction. 

Detailed discussion of these findings will be presented elsewhere. Here we only wish to point out that responses to a hydrogen donor tend to be critically affected by minor structural differences between the compounds. Thus, while diphenyl ether remains substantially unaffected by the donor, its hydroxy-derivatives (phenoxy phenols) often display fairly high reactivity. Taken in conjunction with the failure of low-rank coals (7) and phenoxy phenols (10) to suffer reductive cleavage when treated with sodium in liquid ammonia, this lends some support for the existence of phenoxy phenol entities in low rank coals. 

Some methods for pore structure analysis have been presented The adsorption of benzene and the evaluation of isotherms through the Dubinin - Radushkevich equation, the estimation of immersion heats in benzene, the adsorption of water at relative pressures of h=0.6 and 1.0, the size exclusion liquid chromatography with tracers of different molecular diameters and the one - point adsorption of nitrogen. Six active carbons are included in the investigations. It is not possible to obtain reliable values with the simple water adsorption method. The results obtained with other methods are compared with performances of adsorption of phenol from aqueous solutions as obtained from measuring equilibria and column dynamics. It is shown, that the rank of the results of pore structure analysis is the same as from the dynamic experiments. 

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