Activation energy proton association effect

The effective activation energies, heff, thus obtained are shown in Fig. 3 to be functions of both the exchanged ion and the degree of substitution, even at high silica/alumlnium ratios. The latter result is not expected if the relaxation is associated with the exchanged Bronsted proton. Furthermore... 

The well-known secondary a-relaxation often associated with proton mobility is also observed in CS (neutralized and nonneutralized) from 80 °C to the onset of degradation. On minimum moisture content conditions, this relaxation process could be noticed in the whole temperature range before the onset of thermal degradation. It is strongly affected by moisture content for dry samples by water effects, the activation energy shifts to lower values when compared to dry annealed samples. The nonneutralized CS showed an easier mobility in this ion motion process. This relaxation process exhibits a normal Arrhenius-type temperature dependence with activation energy of 80-90 kJ/mol. 

There is some confusion in the literature as to when it is appropriate to apply the term allelochemical to phenolic acids. Since phenolic acids and their derivatives are found essentially in all terrestrial soils, it should be understood that the presence of phenolic acids in soil does not automatically imply that these phenolic acids are functionally allelochemicals. In theory, phenolic acids in soils, depending on their chemical state, concentrations, and the organisms involved, can have no effect, a stimulatory effect, or an inhibitory effect on any given plant or microbial process. For phenolic acids in the soil to be classified as allelochemicals requires that a) the phenolic acids are in an active form (e.g., free and protonated), b) they are involved in chemically mediated plant, microbe, or plant/microbial interactions and c) the concentrations of the active forms in the soil solution are sufficient to modify plant or microbial behavior, either in a positive or negative manner.8,49 However, changes in microbial behaviour associated with the utilization of phenolic acids as a carbon or energy source would not qualify as an allelopathic response. 

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