Reactions reaction profile

Normal reaction Reaction profile Effect of change Gas evolution Bench-scale reactors (e.g., RC1)... 

Mineva T, Russo N and Sicilia E 1998 Solvation effects on reaction profiles by the polarizable continuum model coupled with Gaussian density functional method J. Oomp. Ohem. 19 290-9... 

Temperature reaction rate profiles for representatives compounds are available (21,26). Particularly important are the operating temperatures required before destmction is initiated. Chemical reactivity by compound class from high to low is (27) alcohols > cellsolves/dioxane... 

Kalbitzer and his colleagues used the Si (p, y) resonant nuclear reaction to profile the range distribution of 10-MeV Si implanted into Ge. Figure 8 shows their experimental results (data points), along with theoretical predictions (curves) of what is expected. 

Fig. 13.9. Schematic reaction profile for the EZ isomerization of stilbene. The reaction coordinate 6 is the torsion angle about the double bond. [From FI. Meier, Angew. Chem. Int. Ed. Engl. 31 1399 (1992)]. Reproduced by permission of Wiley-VCH.

Using the same values of the kinetic parameters as in Type 1, and given C o = 0-1 mo 1/1, it is possible to solve Equation 6-155 with Equations 6-127 and 6-128 simultaneously to determine the fractional conversion X. A computer program was developed to determine the fractional conversion for different values of (-iz) and a temperature range of 260-500 K. Eigure 6-30 shows the reaction profile from the computer results. 

FIGURE 14.1 Reaction profile showing large AG for glucose oxidation, free energy change of —2,870 kj/mol catalysts lower AG, thereby accelerating rate. 

Although there is no simple quantitative relationship between the stability of a carbocation intermediate and the rate of its formation, there is an intuitive relationship. It s generally true when comparing two similar reactions that the more stable intermediate forms faster than the less stable one. The situation is shown graphically in Figure 6.13, where the reaction energy profile in part (a) represents the typical situation rather than the profile in part (b). That is, the curves for two similar reactions don t cross one another. 

What we can display is the free energy of reactants, transition states, intermediates, and products. They are shown separated on a horizontal scale for convenience the abscissa is not defined. This display will be called a reaction profile diagram. 

Two examples of reaction profile diagrams are shown in Fig. 4-5 for the A = I <=s P sequence. The rate constants chosen give values of kss of 0.99 s-1 in case (1) and 0.0099 s l in (2). In the first diagram, step 1 is almost rate-controlling, and in the other, step 2. In Fig. 4-5 note the depth of the well in which the intermediate resides... 

Reaction profile diagrams for two sets of rate constants in the system A-—> I—h... 

Other authors identify the RCS as the one with the highest-lying transition state in a reaction profile diagram. But this, too, fails in the general sense it does not allow for irreversible reactions where an intermediate may be more stable than the reactants. 

We shall now derive a result first obtained24 by more complicated mathematics than the alternative25 given here. The 1992 Nobel Prize in Chemistry was awarded to R. A. Marcus for developing this work. We construct a family of reaction profiles (see Fig. 10-8) for different members of the series. The horizontal axis is now used to show the relative locations of the transition states. The larger AG is, the closer to product the transition states lies, and the larger AG is. By assuming that the sensitivity coefficient... 

Wilkinson s method for, 32-33 with respect to a species, 6 with respect to concentration, 16 with respect to time. 16 Reaction profile diagram. 84—85 Reaction rates, effect on of concentrations, 9 of ionic strength, 206-214 of light, 9... 

The FEP and PDLD approaches developed in the previous chapters can be used conveniently to calculate the effect of genetic mutations. For example, one can calculate the reaction profile for the native and mutant... 

FIGURE 13.30 A reaction profile for an exothermic reaction. In the activated complex theory of reaction rates, it is supposed that the potential energy (the energy due to position) increases as the reactant molecules approach each other and reaches a maximum as they form an activated complex. It then decreases as the atoms rearrange into the bonding pattern characteristic of the products and these products separate. Only molecules with enough energy can cross the activation barrier and react to form products. 

FIGURE 13.35 (a) If the rate-determining step (RDS) is the second step, the rate law for that step determines the rate law for the overall reaction. The orange curve shows the "reaction profile" for such a mechanism, with a lot of energy required for the slow step. The rate law derived from such a mechanism takes into account steps that precede the RDS. (b) If the rate-determining step is the first step, the rate law for that step must match the rate law for the overall reaction. Later steps do not affect the rate or the rate law. (c) If two routes to the product are possible, the faster one (in this case, the lower one) determines the rate of the reaction in the mechanism forming the upper route, the slow step (thinner line) is not an RDS. 

Describe the action of catalysts in terms of a reaction profile (Section 13.14). 

The mechanism of the reaction A - B consists of two steps, with the formation of a reaction intermediate. Overall, the reaction is exothermic, (a) Sketch the reaction profile, labeling the activation energies for each step and the overall enthalpy of reaction, (h) Indicate on the same diagram the effect of a catalyst on the first step of the reaction. 

Step 2 N202 + H2 — N,0 + H,0 Step 3 N20 + H2 — N, + H,0 (a) Which step in the mechanism is likely to be rate determining Explain your answer, (b) Sketch a reaction profile for the overall reaction, which is known to be exothermic. Label the activation energies of each step and the overall reaction enthalpy. 

The following schematic reaction profile is for the reaction A - D. (a) Is the overall reaction exothermic or endothermic Explain your answer, (b) How many intermediates are there Identify them, (c) Identify each activated complex and reaction intermediate, (d) Which step is rate determining Explain your answer, (e) Which step is the fastest Explain your answer. 

When this correction is included, the reaction energy profile diagram results for the cationation and the first three propagation steps in the gas phase and in solution (Fig. 16). 

The boundary layers for these three variables (gas velocity, temperature, and concentration) may sometimes coincide, although in slow reactions, the profiles of velocity and temperature may be fully developed at an early stage while the deposition reaction is spread far downstream the tube. 

A general theory based on the quantitative treatment of the reaction layer profile exists for pure redox catalysis where the crucial function of the redox mediator is solely electron transfer and where the catalytic activity largely depends only on the redox potential and not on the structure of the catalyst This theory is consistent... 

Reaction rate profiles for methane-air mixture with <3> = 0.50 in 50 mm tube diameter (a) neglecting and (b) considering radiation heat transfer. 

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