Hypothetical potential energy surface for

Figure 5-2. A hypothetical potential energy surface for the reaction A -I- BC —> AB -I- C.

A depiction of a hypothetical potential energy surface for a reacting system as a function of two chosen coordinates (c.g., the lengths of two bonds being broken). Such diagrams are useful in assessing structural effects on transition states for stepwise or concerted pathways. An example of More O Ferrall-Jencks diagrams for j8-elimina-tion reactions is shown below. 

Figure 3 A hypothetic potential-energy surface for a system with two internal degrees of freedom. A, B, C, and D mark different local total-energy minima...

Fig. 1. Hypothetical potential energy surface for the oxygen-binding processes of hemoglobin to show relationship between chemical coordinate and conformation coordinate. See text.

Figure 3. Hypothetical potential energy surface for the collinear reaction A + BC AB + C. The solid lines are equipotentials and the dashed line is the reaction path (31).

Hypothetical potential energy surface for cyclopropane isomerization based on the group increments method. 

A-D. Potential energy surfaces for hypothetical carbocation rearrangements, highlighting the continuum of possibilities. E. Definitions of stationary points on a potential energy surface. 

Contours in arbitrary energy units of the potential energy surface for the hypothetical coHnear reaction A + BC- AB + C. The horizontal axis is the B-to-C separation distance, and the vertical axis is the A-to-B distance. At the saddle point, a special coordinate system is defined by the two axes 2, and Zj. Taking the saddle point as the origin of this system (be., z, = 0 and 22 = 0), we see that 2, is the direction in which the energy contours lead downhill away from the saddle point, whereas 22 is a direction in which the energy is greater away from the saddle point. 

Figure 6.34 shows potential energy curves for a hypothetical diatomic molecule X2, which approaches a surface, coming from the right-hand side of the diagram. First... 

Figure 1. Schematic diagram of a hypothetical potential energy hyper-surface for (ABCD)+, constructed to illustrate the main features which relate and control the production of isomeric forms and the isomerization between those forms.

To a good approximation, substitution of one isotope for another does not alter the potential energy surface. The electronic structure, and thus all binding forces, remain the same. All differences are attributable solely to the change in mass, which manifests itself primarily in the frequencies of vibrational modes. For a hypothetical model of a small mass m attached to a much larger mass by a spring of force constant k, the classical vibrational frequency is given by 49... 

The central concept of mode-selective chemistry is illustrated in Fig. 1, which depicts the ground and excited state potential energy surfaces of a hypothetical triatomic molecule, ABC. One might wish, for example, to break selectively the bond between atoms A and B to yield products A+BC. Alternatively, one might wish to activate that bond so that in a subsequent collision with atom D the products AD+BC are formed. To achieve either goal it is necessary to cause bond AB to vibrate, thereby inducing motion along the desired reaction coordinate. 

Quantum-corrections to the simple collision theory () and activated complex theory ( ac) for the isotopic reactions AH + H and BD + B (A and B hypothetical superheavy hydrogen isotopes) based on Weston potential energy surface Vtt/Vj. ratio of the rate constants ... 

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