Energy-reaction coordinate diagrams

Figure 5-9. Free energy reaction coordinate diagram for System 2 of Table 4-3, the formation of a cyclodextrin inclusion complex.

Figure S-10. Hypothetical free energy reaction coordinate diagram for Scheme 11 (TS = transition state).

Strictly speaking, the flow analogy is valid only for consecutive irreversible reactions, and it can be misleading if reverse reactions are significant. Even for irreversible reactions the rds concept has meaning only if one of the reactions is much slower than the others. For reversible reactions the free energy reaction coordinate diagram is a useful aid. In Fig. 5-10, for example, the intermediate 1 is unstable with respect to R and P, and its formation (the kf step) is the rds of the overall reaction. 

For the oximation of a ketone (see Fig. 5-12 and aeeompanying text), sketeh the free energy reaction coordinate diagram at pH 7 and pH 2. 

Fig. 5. Potential energy-reaction coordinate diagram for an electron transfer reaction leading to a product adsorbed on the electrode surface.

Fig. 12. Energy-reaction coordinate diagram for electron transfer in solution when there is only weak interaction between the initial and final energy states.

Figure 1. Energy-reaction coordinate diagram for the acid-catalyzed hydration of phenylacetylene. The ordinate is not to scale (20).

A FREE-ENERGY REACTION COORDINATE DIAGRAM shows the free energy of the substrate, product, and transition state of a chemical reaction. It tells you how favorable the overall reaction is (AGeq) and how fast (AG1). 

Fig. 2.7 Energy-reaction coordinate diagram for reaction (Z R energy of reactant ...

Draw energy-reaction coordinate diagram and discuss the physical significance of energy of activation. Also differentiate between energy of activation and heat of reaction. 

Fig. 16 Free energy/reaction coordinate diagram for proton transfer from the 4,6-bis(phenylazo)resorcinol monoanion to give the dianion in the presence of 2-methylphenol buffers at a 1 1 buffer ratio and at buffer concentrations of (a) 0.001 and (b) 0.10mol" dm. ...

Fig. 17 Free energy/reaction coordinate diagram for tyrosine activation [see (49)], with wild-type tyrosyl-tRNA synthetase (E) and the Tyr-34 to Phe mutant (E ).

Figure 4.4 Energy-reaction coordinate diagram of ground and excited state reactions...

Fig. 9. A tentative potential energy-reaction coordinate diagram (schematic) for the reaction of oxygen atoms with olefins.

Figure 2.5 Energy/reaction coordinate diagram for a two-step reaction, with two catalytic intermediates and three transition states.

Figure 2.10 Energy/reaction coordinate diagrams for a generic parallel reaction. The parallel reaction determines the product selectivity, and may be a rate-determining or b not ratedetermining.

Figure 6.6 a Propagation cycle in the synthesis of polyethylene according to the Cossee mechanism b calculated energy/reaction coordinate diagram for the ethene insertion step. 

The most widely accepted mechanism for electrophilic aromatic substitution involves a change from sp2 to sps hybridization of the carbon under attack, with formation of a species (the Wheland or a complex) which is a real intermediate, i.e., a minimum in the energy-reaction coordinate diagram. In most of cases the rate-determining step is the formation of the a intermediate in other cases, depending on the structure of the substrate, the nature of the electrophile, and the reaction conditions, the decomposition of such an intermediate is kinetically significant. In such cases a positive primary kinetic isotope effect and a base catalysis are expected (as Melander43 first pointed out). 

A measure of transition state symmetry was proposed earlier11,6b), based on a simple way of drawing energy-reaction coordinate diagrams. This measure p (called /in Ref.11)), and named the fraction of product-like character, is defined by Eq. (12). 

Sketch energy/reaction coordinate diagrams for ligand-.substilulion reactions in which products are more. stable than reactants, and... 

The transition state is shown in Fig. 7.1 in terms of a free energy-reaction coordinate diagram. It is useful to also consider the same type of diagram under standard conditions... 

A hypothetical potential-energy-reaction coordinate diagram for this situation (/< j > k2 an Arrhenius intermediate) is presented in Figure 2a. For this limiting case, the overall activation energy al, for the k2 step as the rate-determining step is given by... 

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