Energy transfer mechanisms discrimination

In atmospheric pressure discharges, where concentrations of N atoms are greatly reduced and possibly absent, the discrimination between alkanes and alkenes is not observed and an alternative means of initiating the reaction is required. In the absence of significant concentrations of N, the mechanism may consist of collisional energy transfer from N2(A32 +), which lies 593 kJ mor1... 

Figure 13.2 A possible specificity mechanism for the prevention of the misacylation of tRNAVal with threonine, (a) The hydrophobic acylation site discriminates against threonine, (b) The hydrolytic site specifically uses the binding energy of the hydroxyl of threonine for a binding or catalytic effect. The translocation may occur as illustrated via a 2 - — 3 -hydroxyl acyl transfer. [From A. R. Fersht and M. Kaethner, Biochemistry 15, 3342(1976).]...

The chiral discrimination in the self-association of chiral l,3a,4,6a-tetrahydroi-midazo[4,5-d]imidazoles 3 has been studied using density functional theory methods [37], (Scheme 3.20). Clusters from dimers to heptamers have been considered. The heterochiral dimers (RR SS or SS RR) are more stable than the homochiral ones (RR RR or SS SS) with energy differences up to 17.5 kJ mol-1. Besides, in larger clusters, the presence of two adjacent homochiral molecules imposes an energetic penalty when compared to alternated chiral systems (RR SS RR SS...). The differences in interaction energy within the dimers of the different derivatives have been analyzed based on the atomic energy partition carried out within the AIM framework. The mechanism of proton transfer in the homo- and heterochiral dimers shows large transition-state barriers, except in those cases where a third additional molecule is involved in the transfer. The optical rotatory power of several clusters of the parent compound has been calculated and rationalized based on the number of homochiral interactions and the number of monomers of each enantiomer within the complexes. 

A given amount of heat, available at a temperature T, can be transferred to a fluid that is at a lower temperature. If, however, the fluid is at a higher temperature, only a fraction of this heat can be transferred to it without, of course, the consumption of any mechanical energy. (How much See Example 5.4). In other words, when it comes to heat One Joule, is not always one Joule. (Discrimination, unfortunately, has been practiced by Nature well before it has by Humans.)... 

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