Bonding historical development

Heterocyclic systems have played an important role in this historical development. In addition to pyridine and thiophene mentioned earlier, a third heterocyclic system with one heteroatom played a crucial part protonation and methylation of 4//-pyrone were found by J. N. Collie and T. Tickle in 1899 to occur at the exocyclic oxygen atom and not at the oxygen heteroatom, giving a first hint for the jr-electron sextet theory based on the these arguments.36 Therefore, F. Arndt, who proposed in 1924 a mesomeric structure for 4//-pyrone, should also be considered among the pioneers who contributed to the theory of the aromatic sextet.37 These ideas were later refined by Linus Pauling, whose valence bond theory (and the electronegativity, resonance and hybridization concepts) led to results similar to Hiickel s molecular orbital theory.38... 

Following these introductory considerations solvent dependent coupling constants will be reviewed in order of the number of bonds intervening between the coupled nuclei. This organization does not follow the historical development of the work in this area nor does it necessarily follow the major developments or principles proposed. It does provide a convenient way of organizing an otherwise unwieldly body of information. 

Carbon nanotubes, as graphene and graphite, are highly ordered carbon phases. However, a separate line can be drawn for historical development of disordered carbon phases among them is an amorphous carbon (am-C). In it, strong bonding between carbons did not allow for completely chaotic distribution of carbon atoms in solid-state phase. Instead, amorphous carbon exhibits random distribution of three possible coordinations of carbon atoms in a planar sp, tetrahedral sp and... 

Among the historic developments of studies on C—H activation, several methods and conditions have been used, from thermal studies to photochemical activation, with all of which have been mediated by derivatives of metals ranging from transition metals to lanthanides and actinides. Hence, given the importance that the chemistry surrounding the C—H activation process entails, several excellent reviews and monographs have already been published [6]. Unfortunately, in most of these cases the chemistry described has been devoted entirely to descriptions of the activation of a particular C—H bond in a given process, and consequently some division has arisen as to how the C—H activation process does in fact proceed... 

I have felt that in writing on this complex subject my primary duty hould be to present the theory of the chemical bond (from my point of view) in as straightforward a way as possible, relegating the historical development of the subject to a secondary place Many references are included to early work in this field the papers on the electronic theory of valence published during the last twenty years are so numerous, however, and often represent such small differences of opinion as to make the discussion of all of them unnecessary and even undesirable. 

For the theoretical approach to inorganic chemistry, see the books listed in Section A.7 of the Appendix. See also the books listed in Section 4.8, especially Chapter 1 of Johnson (1982). The historical development of bonding theory is thoroughly treated by Palmer, W. G. (1965). A History of the Concept of Valency to 1930. Cambridge University Press. 

Although such an understanding of the reaction mechanism is in principle applied in the theory of pericyclic reactions, the above general picture is in this case slightly complicated by the specific (introduced in the course of historical development) classification of reaction mechanisms in terms of concertedness and/or nonconcertedness. Concerted reactions are intuitively understood as those reactions for which the scission of old bonds and the formation of the new ones is synchronised, whereas for nonconcerted reactions the above bond exchange processes are completely asynchronised. Moreover, since the above asynchronicity is also intuitively expected to induce the stepwise nature of the process, the nonconcertedness is frequently believed to require the presence of intermediates, whereas the concerted reactions are believed to proceed in one elementary step. 

W. B. Jensen, The historical development of the van Arkel bond-type triangle , Bull. Hist. Chem., 1992-93, 13-14, 47-59. 

Within the format of this contribution, only a brief outline of ftie vast range of P-donor ligand architecture can be given. Most of the examples given are based upon P-C bonding, which reflects flie historical development of the subject. 

Polymer technology is quite old compared to polymer science. For example, natural rubber was first masticated to render it suitable for dissolution or spreading on cloth in 1820. and the first patents on vulcanization appeared some twenty years later. About another one hundred years were to elapse, however, before it was generally accepted that natural rubber and other polymers are composed of giant covalently bonded molecules that differ from ordinary molecules primarily only in size. (The historical development of modern ideas of polymer constitution is traced by Flory in his classical book on polymer chemistry [ I ], while Brydson [2] reviews the history of polymer technology.) Since some of the terms we are going to review derive from technology, they are less precisely defined than those the... 

These misconceptions regarding two different types of bonding in an ionic lattice are not only to be found by Hilbing [13] and Taber [15] the Australian scientists Butts and Smith [20] also identified them in their studies. In addition, they found misconceptions, which, in analogy to scientific historical development, assume that molecules first exist in solid salt crystals, and then the ions develop because of the solution of salts in water. 

The theoretical models which have been used to describe the bonding in cluster compounds of the main group and transition metal elements are reviewed. The historical development of these models is outlined and special emphasis is placed on those studies which have led to the elucidation of structure-electron count correlations. Theoretical treatments of cluster bonding are based on localised, delocalised (molecular orbital) or free electron methods derived from the solution of the Schrodinger equation for a particle on a sphere. A detailed analysis of the Tensor Surface Harmonic method, as an example of a free electron model, is presented. Group theoretical consequences of the model are also presented. 

The importance of Marcus theoretical work on electron transfer reactions was recognized with a Nobel Prize in Chemistry in 1992, and its historical development is outlined in his Nobel Lecture.3 The aspects of his theoretical work most widely used by experimentalists concern outer-sphere electron transfer reactions. These are characterized by weak electronic interactions between electron donors and acceptors along the reaction coordinate and are distinct from inner-sphere electron transfer processes that proceed through the formation of chemical bonds between reacting species. Marcus theoretical work includes intermolecular (often bimolecular) reactions, intramolecular electron transfer, and heterogeneous (electrode) reactions. The background and models presented here are intended to serve as an introduction to bimolecular processes. 

The discovery of the Kubas complex was a defining event in the historical development of coordination chemistry. By 1920, the Lewis ideas on the role of electron pairs in bonding had already associated the coordinate bond with the donation of a lone pair to a metal. For example, donation of the ammonia lone pair to was implicated in the classical Werner cobalt-ammonia complexes. Subsequent developments extended the coordination concept beyond lone-pair donors. Around 1950, a series of discoveries by Wilkinson, Chatt, Fischer, and others showed how the electrons of unsaturated ligands such as cyclopentadienide ion and ethylene can also bind to metal ions. These complexes stimulated the modem development of organometallic chemistry and homogeneous catalysis. 

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