Roles, in organization

In view of the fact that the chemistry of ring compounds has played a considerable role in the development of modern organic chemistry, the following question is definitely relevant Do cyclic sulfones and sulfoxides envisioned as a particular distinct category within this class of compounds contribute uniquely—in their own right—to the understanding of the characteristics and chemistry of the sulfone and sulfoxide functionalities and their role in organic chemistry ... 

Carbocations as reactive intermediates play an essential role in organic reactions and have been thoroughly researched 102, l0J). The individual quality of the cationic polymerization results from the reproduction of the cationic reactive intermediate in every propagation step during the addition of monomers. 

Kumar A. Ionic Solutions and Their Pivotal Roles in Organic and Biological Systems Pure Appl. Chem. 1998 70 615-620... 

Redefine their roles in organizations and assess future prospects. 

Organic halides play a fundamental role in organic chemistry. These compounds are important precursors for carbocations, carbanions, radicals, and carbenes and thus serve as an important platform for organic functional group transformations. Many classical reactions involve the reactions of organic halides. Examples of these reactions include the nucleophilic substitution reactions, elimination reactions, Grignard-type reactions, various transition-metal catalyzed coupling reactions, carbene-related cyclopropanations reactions, and radical cyclization reactions. All these reactions can be carried out in aqueous media. 

Low-coordinate species of the main group elements of the second row such as carbenes, olefins, carbonyl compounds (ketones, aldehydes, esters, amides, etc.), aromatic compounds, and azo compounds play very important roles in organic chemistry. Although extensive studies have been devoted to these species not only from the physical organic point of view but also from the standpoints of synthetic chemistry and materials science, the heavier element homologues of these low-coordinate species have been postulated in many reactions only as reactive intermediates, and their chemistry has been undeveloped most probably due to... 

Isoxazole ring systems play an important role in organic synthesis, and 4-nitroisoxazoles have been used as dienophiles in Diels-Alder reactions, as shown in Eq. 8.23.36... 

Soil minerals play a stabilizing role in organic matter. The Al and Fe that complex and stabilize organic matter against microbial decomposition are released from soil minerals during soil formation. The supply rates apparently control the content of soil organic matter to a great extent. This is demonstrated by the relationship between pyrophosphate-extractable C and pyrophosphate-extractable Al plus Fe (Wada 1995). 

In conclusion it is evident from the foregoing examples that transition metal-catalyzed hydroborations and hydroaluminations occupy an important role in organic synthesis. While rhodium-catalyzed hydroboration has been extensively developed, the hydroalumination is just starting to emerge as a useful reaction in organic synthesis. 

Solvents play an important role in organic synthesis. Choice of solvent is important in improving and deciding the chemical process. Selection of solvents should be such that it has minimal effect on the environment. Today chemists are interested in designing solvents which does not pose any risk to human health and the environment. The reason why solvents are of great environmental concern is that... 

It is appropriate that the present Introduction should contain a specifically historical section, particularly in relation to the nitro group, whose electronic effect played a distinctive role in organic chemistry long before it was recognized as such. In this section and in later sections references are often given to classical papers and texts, whose importance has been overlaid by more recent work. 

As already stated, theoretical calculations are as yet too involved and not accurate enough for routine 13C NMR spectral interpretation, particularly where more complicated molecules are concerned probably this situation will not change in the near future. Therefore, different approaches have been developed to identify certain influences of structural modifications, for example substituent introduction, on 13C shieldings. The partition of oA into two local (o A and o A) and several nonlocal contributions (30,32) is reasonable on physical grounds. On that basis, the factors that play a role in organic molecules were divided into two classes (56) ... 

Carbenes—molecules with a neutral dicoordinate carbon atom—have played an important role in organic chemistry ever since their first firm evidence of existence. 

Beyond their ubiquitous role in organic synthesis, stabilized, semistabiUzed, or nonstabilized phosphonium ylides are fascinating ligands of transition metals. Their coordination chemistry is dominated by C-coordination to the metal center they are known to act exclusively as carbon-centered ligands rather than as v -C=P ligands. 

Since the epoxidation of alkenes with peracids was discovered by Prilezajew in 1909 [29], epoxides have played a major role in organic chemistry and industry, providing important intermediates for the synthesis of more complex molecules. Metal-catalyzed epoxidation reactions have received much attention in recent decades since the discovery of the Sharpless epoxidation [30, 31], but most epoxides were prepared from alkenes primarily by their interaction with peracids. 

C—C bond formation plays a fundamental role in organic synthesis. In spite of great success in asymmetric epoxidations and hydrogenations, highly efficient asymmetric C—C bond formations are still in great demand. In this section, we will present the results of asymmetric C—C bond formation via the activation of C—H bonds according to the types of C—H bond in the substrates (sp C—H bonds, sp C—H bonds, and sp C—H bonds). 

The concept of proton affinity is well known to play a very important role in organic chemistry. In fact, this concept permits us to express quantitatively the proton-accepting strength of organic bases. It is significant that the proton affinity arises from the nature of a proton donor. 

Alkaloids play a very important role in organism metabolism and functional activity. They are metabolic products in plants, animals and micro-organisms. They occur in both vertebrates and invertebrates as endogenous and exogenous compounds. Many of them have a distributing effect on the nervous systems of animals. Alkaloids are the oldest successfully used drugs throughout the historical treatment of many diseases ... 

In this chapter, we summarized the theoretical studies carried out on metal vinylidene complexes. Special emphasis was placed on aspects of their electronic structures, reactivities and their roles in organic reactions. Theoretical studies on the related metal allenylidene complexes have been quite limited. More theoretical studies on various aspects of these complexes, particularly on their metathesis reactivities, are clearly necessary. 

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