Organic reactions nucleophiles

Chapters 7-10 have introduced three basic kinds of organic reactions nucleophilic substitution, P elimination, and addition. In the process, many specific reagents have been discussed and the stereochemistry that results from many different mechanisms has been examined. How can we keep track of all the reactions ... 

General problems with synthetic organic reactions are discussed together with some practical solutions for specific examples. These problems include 9 regio- and stereoselectivity by exploitation of the substrates stereochemistry (e.g., p. 20ff.) and differentiated nucleophilicity (p. 24f, 44f, 56ff.)... 

Many in ortant organic reactions involve nucleophilic carbon species (carbanions). The properties of carbanions will be discussed in detail in Chapter 7 and in Part B,... 

Thomsons )W Click Organic Interactive to identify and characterize nucleophiles and electrophiles in organic reactions. 

Carboxylic acid derivatives are among the most widespread of all molecules, both in laboratory chemistry and in biological pathways. Thus, a study of them and their primary reaction—nucleophilic acyl substitution—is fundamental to understanding organic chemistry. We ll begin this chapter by first learning about carboxylic acid derivatives, and then we ll explore the chemistry of acyl substitution reactions. 

Biochemistry is carbonyl chemistiy. Almost all metabolic pathways used by living organisms involve one or more of the four fundamental carbonvl-group reactions we ve seen in Chapters 19 through 23. The digestion and metabolic breakdown of all the major classes of food molecules—fats, carbohydrates, and proteins—take place by nucleophilic addition reactions, nucleophilic acyl substitutions, a substitutions, and carbonyl condensations. Similarly, hormones and other crucial biological molecules are built up from smaller precursors by these same carbonyl-group reactions. 

Problem 29.8 Look at the entire glycolysis pathway and make a list of the kinds of organic reactions that take place—nucleophilic acyl substitutions, aldol reactions, ElcB reactions, and so forth. 

Most organic reactions take place by polar mechanisms, in which a nucleophile donates two electrons to an electrophile in forming a new bond. Other reactions take place by radical mechanisms, in which each of two reactants donates one electron in forming a new bond. Both kinds of reactions occur frequently in the laboratory and in living organisms. Less common, however, is the third major class of organic reaction mechanisms—pericyclic reactions. 

In Part 2 of this book, we shall be directly concerned with organic reactions and their mechanisms. The reactions have been classified into 10 chapters, based primarily on reaction type substitutions, additions to multiple bonds, eliminations, rearrangements, and oxidation-reduction reactions. Five chapters are devoted to substitutions these are classified on the basis of mechanism as well as substrate. Chapters 10 and 13 include nucleophilic substitutions at aliphatic and aromatic substrates, respectively, Chapters 12 and 11 deal with electrophilic substitutions at aliphatic and aromatic substrates, respectively. All free-radical substitutions are discussed in Chapter 14. Additions to multiple bonds are classified not according to mechanism, but according to the type of multiple bond. Additions to carbon-carbon multiple bonds are dealt with in Chapter 15 additions to other multiple bonds in Chapter 16. One chapter is devoted to each of the three remaining reaction types Chapter 17, eliminations Chapter 18, rearrangements Chapter 19, oxidation-reduction reactions. This last chapter covers only those oxidation-reduction reactions that could not be conveniently treated in any of the other categories (except for oxidative eliminations). 

Although addition of HCN could be looked upon as a carbanion reaction, it is commonly regarded as involving a simple anion. It is of unusual interest in that it was almost certainly the first organic reaction to have its mechanistic pathway established (Lapworth 1903). HCN is not itself a powerful enough nucleophile to attack C=0, and the reaction requires base-catalysis in order to convert HCN into the more nucleophilic CN the reaction then obeys the rate law ... 

A diverse group of organic reactions catalyzed by montmorillonite has been described and some reviews on this subject have been published.19 Examples of those transformations include addition reactions, such as Michael addition of thiols to y./bunsatu rated carbonyl compounds 20 electrophilic aromatic substitutions,19c nucleophilic substitution of alcohols,21 acetal synthesis196 22 and deprotection,23 cyclizations,19b c isomerizations, and rearrangements.196 24... 

Early attempts to fathom organic reactions were based on their classification into ionic (heterolytic) or free-radical (homolytic) types.1 These were later subclassified in terms of either electrophilic or nucleophilic reactivity of both ionic and paramagnetic intermediates - but none of these classifications carries with it any quantitative mechanistic information. Alternatively, organic reactions have been described in terms of acids and bases in the restricted Bronsted sense, or more generally in terms of Lewis acids and bases to generate cations and anions. However, organic cations are subject to one-electron reduction (and anions to oxidation) to produce radicals, i.e.,... 

Catalysis, enzymatic, physical organic model systems and the problem of, 11,1 Catalysis, general base and nucleophilic, of ester hydrolysis and related reactions, 5,237 Catalysis, micellar, in organic reactions kinetic and mechanistic implications, 8,271 Catalysis, phase-transfer by quaternary ammonium salts, 15,267 Catalytic antibodies, 31,249... 

The first most commonly used approach (path a) involves the direct interaction of AN with electrophilic reagents. In this case, the most fundamental property of AN, that is, their ability to act as ambident nucleophiles in organic reactions, is exploited. To synthesize nitronates, it is necessary that AN behave... 

Nucleophilic additions of organorhodium species to C=0 and CN multiple bonds constitute important classes of catalytic organic reactions and have experienced significant progress in the last decade. 

In this context, an avalanche of studies were devoted to acid-base reactions in their broadest sense (i.e., the Lewis picture), also involving complexation reactions, to the typical organic reactions of addition, substitution, and elimination types, involving nucleophilic and electrophilic reagents including the case of radicalar reactions and excited states (for a review see Ref. [11]) in which our group has... 

However, within the next few years, Ingold s dominance in the field of organic reaction mechanisms theory became clearly established, following a 1933 paper on tautomerism in which he introduced the terms "nucleophilic" and "electrophilic" and a 1934 article in Chemical Reviews systematizing "Principles of an Electronic Theory of Organic Reactions." Burkhardt, one of Lapworth s collaborators, said, "ft was a complete takeover of terminology at the right time. "129... 

A comparative study [10] into the Rh-catalysed carbonylation of ROH (R = Me, Et, Pr) shows that in all cases, the reaction rate is 1st order in both [Rh] and added [HI] and independent of CO pressure. The only Rh species observed by IR under catalytic conditions was 1. The rates of carbonylation decreased in the stated order of R, with relative rates of 21 1 0.47, respectively at 170 °C. This order of the R-groups and the large differences between them is a common feature for organic reactions of this type. All the data are consistent with ratedetermining nucleophilic attack by the Rh complex anion on the corresponding alkyl iodide. 

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