Summary of Reaction Mechanisms

Near the end of this study guide you will find additional sections that may help you to study for the final examination in the course. The SUMMARY OF SYNTHETIC METHODS lists the important ways to synthesize each class of compounds discussed in the text. It is followed by the SUMMARY OF REACTION MECHANISMS. Both of these sections have references to appropriate portions of the text, in case you feel that further review is necessary. Finally, you will find two lists of sample test questions. The first deals with synthesis, and the second is a list of multiple-choice questions. Both of these sets should help you prepare for examinations. 

The isotope effect is observed with the hydrogen atom of the formate and not with the hydrogen atom of the water molecule. The result is similar to that observed on ZnO, where the ratedetermining step of the formate decomposition is suggested to be dissociation of the CH bond of the bidentate formate. In summary, the reaction mechanism for the catalytic WGS reaction on Rh/Ce02 is essentially the same as that on ZnO. 

Several monographs2-5 have detailed discussions dealing with heavy-atom and primary and secondary hydrogen-deuterium kinetic isotope effects. The monograph by Melander and Saunders5 covers the entire area particularly well. For this reason, only a brief summary of the theory of kinetic isotope effects as well as their important uses in the determination of reaction mechanism and transition-state geometry will be presented. 

Fig- 4. Summary of probable mechanisms for the reaction of atomic oxygen with saturated and unsaturated hydrocarbons in the gas phase. The reaction of 0( D) with an alkene is believed to form the expoxide directly, thus skipping the formation of a triplet biradical. 

In conclusion, the drastic difference in charge distribution between C6o and RCeo causes significant differences in their nucleophilic reactivities so that the reactions of C6o and RCeo with R X proceed via different pathways, namely, an electron transfer in the first step and an Sn2 pathway in the second step. A summary of the mechanism is shown in Scheme 2 for the formation of f-Bu(PhCH2)C6o as a typical example [161]. 

Later, Morris Kharasch found that, if the reaction occurs in the presence of air, oxygen or a small amount of a peroxide, then the reaction goes in the reverse order H goes to the C with the smaller number of H atoms and the Br to the other, so forming 1-bromopropane. A summary of the mechanism of what is going on here is given in Section 6.2.4 as an extension topic at the end of this unit. 

In his summary of the mechanism in Physical Organic Chemistry , Hammett (1940a) opted for nucleophilic displacement on the groimds that the added ionic nucleophiles lead to an increase in reaction rate. However, none of the early studies precluded the possibility that the observed rate enhancement was the result of a salt effect. Recently AJbery and Bell (1961) have studied the reaction in moderately concentrated solutions of perchloric and hydrochloric acids. The rates are... 

The identification of compound X as an acyl nitrogen compound fits in with observed facts of ozone formation in nitrogen dioxide-organic compound photochemical reactions. A summary of the mechanism follows. 

Several mechanisms or reaction schemes were proposed by various researchers based on their experimental results. In this paragraph a summary of these mechanisms is given. 

A summary of the mechanism described above according to Ref. [124] is presented in Fig. 5.37. Of course, one can think of alternative detailed pictures. For example, silver is a catalyst with subsurface oxygen exposed to the gas phase as a positively charged centre and can interact with rc-electrons of ethene. Obviously, this practically very important reaction still has some detailed points which require elucidation. 

Conversion ranges 6.4-20.0% focus of this paper is a reaction mechanism study the results suggested that the substituted heteropo-lyoxometalate reacts with H202 to form an intermediate, and the substituted transition metal ion seems to be the center of activating H202 Summary of reactions with this POM and... 

The mechanism looks complicated but the reaction is easy to do summary of reaction q... 

Let s have a look at why the mechanisms of the two substitutions must be different. Here s a summary of the mechanism of the first reaction. 

In summary, the reaction mechanism consists of two steps (i) the protonation of the double bond resulting in the formation of stable carbocation and (ii) the attack of the nucleophile (Br") on the positive carbon of the same carbocation. 

Summary of the Mechanisms of the Nucleophilic Substitution Reactions in Chlorocyclophosphazenes... 

A summary of the mechanisms of electrophilic and nucleophilic addition reactions is given in Figure 10.8. 

A comprehensive summary of ionization techniques, data processing, sample preparation, imaging techniques, copolymer characterization, and elucidation of reaction mechanisms is demonstrated in several references [58,101,102]. 

Interlude A Summary of Organic Reaction Mechanisms, foUowing Chapter 14, summarizes the relatively few types of reaction mechanisms that drive the majority of organic reactions, thereby encouraging understanding over memorization. 

These reactions in weakly alkaline solutions are faster than the heterolytic (Dn + AN)-like hydroxy-de-diazoniation, which, for most diazonium ions, (depending on their electrophilicity), is dominant below pH 2-4. As shown by Ishino et al. (1976), an increase in rate, corresponding to the occurence of other mechanisms in addition to the heterolytic hydroxy-de-diazoniation, is observable at pH 3.7-7.0. The increase is dependent on the substituent in the specifically substituted benzenediazo-nium ion. The slope d(log )/d(pH) was found to be in the range 0.22-1.09 (see summary of the work of Ishino et al. by Zollinger, 1983, p. 624). 

---