Molecules with whole charges

The first protonation of uracil in trifluoroacetic acid was found by nmr spectroscopy to occur at the oxygen atom in the 4-position, giving a cation with extensive charge delocalization [139], and the second protonation in fluorosulphuric acid occurs at the oxygen in position 2, giving cation [140], in which the two charges are delocalized over the whole molecule (Wagner and von Philipsbom,... 

We now compose a wave function for each tz electron in a conjugated system which describes its behaviour in the whole system, thus beforehand without restriction of the electron to particular bonds (molecular orbital, M.O.). It is now customary to compose these M.O. according first to Lennard-Jones as a linear combination of atomic orbitals (A.O.) provided with coefficients (L.C.A.O. approximation). These atomic orbitals in a molecule with double bonds are the p2 functions of the carbon atoms. The square of a particular coefficient indicates the contribution of the electron in question to the charge around this particular atom. 

The more general view is that non-local interaction within a molecule determines the charge distribution and conformation holistically. All local features are consequences of the whole. However, molecules of any complexity are rarely the product of a one-step reaction starting from the atomic constituents and are more likely built up from intermediate fragments that retain some of their own molecular properties on incorporation into a bigger whole. This mechanism explains the large number of additive rules that have been discovered empirically for molecular systems [51] and the existence of isomers. A molecule whose conformation and properties are functions of its chemical history, is not holistic, but partially holistic [2], which means that its wave function is a product function, albeit with a limited number of factors (fragments),... 

We have seen that electron-transfer reactions can occur at one charged plate. What happens if one takes into account the second plate There, the electron transfer is from the solution to the plate or electronic conductor. Thus, if we consider the two electronic conductor-ionic conductor interfaces (namely, the whole cell), there is no net electron transfer. The electron outflow from one electronic conductor equals the inflow to the other that is, a purely chemical reaction (one not involving net electron ttansfer) can be carried out in an electrochemical cell. Such net reactions in an electrochemical cell turn out to be formally identical to the familiar thermally induced reactions of ordinary chemistry in which molecules collide with each other and form new species with new bonds. There are, however, fundamental differences between the ordinary chemical way of effecting a reaction and the less familiar electrical or electrochemical way, in which the reactants collide not with each other but with separated charge-transfer catalysts, as the two plates which serve as electron-exchange areas might well be called. One of the differences, of course, pertains to the facility with which the rate of a reaction in an electrochemical cell can be controlled all one has to do is electroiucally to control the power source. This ease of control arises because the electrochemical reaction rate is the rate at which the power source pushes out and receives back electrons after their journey around the circuit that includes (Figs. 1.4 and 1.5) the electrochemical cell. 

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