Pseudo-atomic species

For the moment, it is hoped that the reader finds that the comparison between cryptatium and the endohedral complexes of the fulleienes is, if not totally obvious or even convincing, at least sufficiently provocative. They both represent a similar approach to the preparation of pseudo-atomic species and thus offer the potential for the preparation of interesting (and hopefully conducting and superconducting)... 

In the atomic resonance absorption spectrometric (ARAS) adaptation of the methods, atomic species are spectroscopically monitored as a function of time. H [7,9], D- [7,10], O- [7,11], N- [12], Cl- [13] and I-atom [14] reactions have been studied. Beer s law holds if absorbance, (ABS), is kept low, and then (ABS) s -ln(I/Io) (I and Iq are transmitted and incident intensities of the resonance light, respectively) is proportional to the atomic concentration. If the decay of atom A is controlled by a bimolecular reaction, A + R, where R is the stable reactant molecule, then the decay rate is pseudo-first-order provided [R] [A]. Because (ABS) is proportional to [A], observation of (ABS)t is sufficient to determine the decay constant. Values for kbini for each experiment are then determined by dividing the decay constant by [R]. The results from many experiments are usually displayed as Arrhenius plots. If a reaction is pressure dependent, experiments can also be carried by varying total density. Termolecular reactions can therefore be studied. In certain cases, chemical isolation is not possible, and numerical chemical simulations of the... 

In the F2 + ICl system, no product mass peaks at m/e 56 (C137f) or m/e (Cl Jp) were observed and no m/e 20 (HF) peak was observed for the F2 + HI reaction. These mass spectral results indicate that the trihalogen and pseudo-trihalogen species formed involve bonding schemes such as ClIF and HIF with the more electropositive atom in the center of the molecule as predicted by Walsh s rules (60,61). 

The intermediate diphenylhydroxymethyl radical has been detected after generation by flash photolysis. Photolysis of benzophenone in benzene solution containing potential hydrogen donors results in the formation of two intermediates that are detectable, and their rates of decay have been measured. One intermediate is the PhjCOH radical. It disappears by combination with another radical in a second-order process. A much shorter-lived species disappears with first-order kinetics in the presence of excess amounts of various hydrogen donors. The pseudo-first-order rate constants vary with the structure of the donor with 2,2-diphenylethanol, for example, k = 2 x 10 s . The rate is much less with poorer hydrogen-atom donors. The rapidly reacting intermediate is the triplet excited state of benzophenone. 

The behaviour of the frontier electrons was also attributed to a certain type of electron delocalization between the reactant and the reagent 40). A concept of pseudo-n-orbital was introduced by setting up a simplified model, and the electron delocalization between the 71-electron system of aromatic nuclei and the pseudo-orbital was considered to be essential to aromatic substitutions. The pseudo-orbital was assumed to be built up out of the hydrogen atom AO attached to the carbon atom at the reaction center and the AO of the reagent species, and to be occupied by zero, one, and two electrons in electrophilic, radical, and nucleophilic reactions. A theoretical quantity called "superdelocalizability was derived from this model. This quantity will be discussed in detail later in Chap. 6. 

Figure 1.5. Plan view of Cu(lll)/CH3S- pseudo-(lOO) reconstruction assuming a commensurate [ 4 ] registry of the overlayer and substrate. The methylthiolate species are represented by the S head-group atoms alone, shown as the darkest spheres. The Cu atoms of the reconstructed pseudo-(lOO) layer are shown more darkly shaded than those of the underlying substrate. For clarity the reconstructed overlayer has been omitted from the lower right-hand side of the diagram, exposing the outermost unreconstructed Cu(l 11) layer.

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