Ethylene, electronic structure

In order to understand the physical properties and reactivity patterns of S-N compounds it is particularly instructive to compare their electronic structures with those of the analogous organic systems.On a qualitative level, the simplest comparison is that between the hypothetical HSNH radical and the ethylene molecule each of these units can be considered as the building blocks from which conjugated -S=N- or -CH=CH-systems can be constructed. To a first approximation the (j-framework of... 

Surprisingly enough, the effect of ring strain on the electronic structure of the —SO and —S02 groups is rather small. Sulphur charges and S—O BOPs are almost constant in the ring compounds and in the dimethyl derivatives. The only exception is a substantially weaker C—S bond (lower BOP) in ethylene episulphoxide. 

In this contribution it is shown that local density functional (LDF) theory accurately predicts structural and electronic properties of metallic systems (such as W and its (001) surface) and covalently bonded systems (such as graphite and the ethylene and fluorine molecules). Furthermore, electron density related quantities such as the spin density compare excellently with experiment as illustrated for the di-phenyl-picryl-hydrazyl (DPPH) radical. Finally, the capabilities of this approach are demonstrated for the bonding of Cu and Ag on a Si(lll) surface as related to their catalytic activities. Thus, LDF theory provides a unified approach to the electronic structures of metals, covalendy bonded molecules, as well as semiconductor surfaces. 

Literature data are available on the electronic structures of two more binuclear technetium complexes [(NHjLlOHLTcf/i-O TcfOH NHj ] (a hypothetical complex with the structure and composition analogous to those of the ethylen-diamminetetra-acetate complex [54,55]) and Tc2(CO)10 (a binuclear complex with strong crystal field ligands [168,169]. We shall consider the results of these calculations in greater detail. 

In the following pages, the results of conformational studies of important classes of push-pull ethylenes will be reviewed, after which experimental and theoretical results bearing on the electronic structure of these compounds will be discussed. 

The second chapter, by Jan Sandstrom, deals with stereochemical features of push-pull ethylenes. The focus is on rotational barriers, which span a large range of values. The ease of twisting is partly a matter of electron delocalization and partly a matter of steric and solvent effects. Electronic structure and such related items as dipole moments and photoelectron spectra for these systems are discussed. The chapter also deals with the structure and chiroptical properties of twisted ethylenes that do not have push-pull effects, such as frans-cyclooctene. 

It would also be interesting to check the ability of the ruthenocene acrylonitrile cation-radical to rotate around the ethylene bond Ruthenocenyl is weaker than ferrocenyl as a donor substituent (Laus et al. 2005). The particular property of rotating around the ethylenic bond in cation-radicals is a method of elucidating an electronic structure. 

Ethylene oxides, like other three-membered ring systems, possess many singular features that invite a basis in theory. To satisfy Hub demand, much effort has boon devoted to the task of determining with precision such fundamental properties of the molecule os bond lengths, bond angles, and bond energies- With the advent of modern instrumental methods it has been possible to develop a dependable physical basis fin- theoretical speculations on the electronic structure of ethylene oxide. The present section is concerned with this aspect of epoxide chemistry. 

The substitution system of nomenclature should be viewed as showing only how atoms are connected and not as indicating the precise electronic structure. Thus -adsorbed ethylene is one representation of 1,2-diadsorbed ethane. 

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