Ground states charge distribution

The electrophilic substitution of the 3-aryl compounds (265, R = Ar, R = H) exemplified by the formation of 5-bromo- (265, R = Ar, R = Br) and 5-nitro derivatives (265, R = Ar, R = NOj) has been put forward as evidence against the meso-ionic formulation 265. lliis approach is unacceptable since ground state charge distribution cannot be deduced from reaction products. The aluminum-amalgam reduction of meso-ionic l,2,3-thiadiazol-4-ones (265) yields either N-mercaptoacetyl-A-arylhydrazines or Ar-acyl-A-arylbydrazines. Triethyl-oxonium tetrafluoroborate and meso-ionic l,2,3-thiadiazol-4-ones (265) yield 1,2,3-thiadiazolium tetrafluoroborates (267). The effect of solvent on the ultraviolet spectra of meso-ionic l,2,3-thiadiazol-4-ones (265) has been reported. ... 

Figure 2.11 Nuclear ground-state charge distributions as measured for a sample of nuclei throughout the periodic table from B. Frois, Proc. Int. Conf. Nucl. Phys., Florence, 1983, eds. P. Blasi and R.A. Ricci (Tipograha Compositori Bologna) Vol. 2, p. 221.

Figure 3-11. Schematic representation of two transition energy manifolds, showing some low-energy electronic states (Sn) of PAUMe in MeCN. Left solvent equilibrated with ground state charge distribution. Right solvent equilibrated with charge distribution of (vacuum) CTi state...

There is rich experimental evidence showing that aryl positions adjacent to strained annelated rings exhibit reduced reactivity towards electrophilic reagents [2-7,98-101], These data are in harmony with the theoretical interpretation in terms of the bond fixation model presented above. It is possible that the ground state charge distribution in some particular fused molecular systems affects propensities of a and f3 atoms to undergo the electrophilic substitution reactions, but interpretation based solely on the rehybridization effect at carbon junction atoms offered by Siegel et al.[9] is obviously unjustified. 

Hoffmann-Ostenhof and Morgan (1981) were able to prove that the ground-state charge distribution of a one-electron homonuclear diatomic molecule can exhibit maxima in p only at the positions of the nuclei. In this proof an important inequality is used (Hoffmann-Ostenhof and Hoffman-Ostenhof 1977),... 

Figure 5.1 displays, in the form of contour plots, the ground-state charge distributions of LiF, LiO, and LiH, each at its equilibrium intemuclear separation. Superimposed on each of these plots is the intersection of the... 

The well-known NLO molecular crystal POM (3-methyl-4-nitropyridine-1-oxide) is simulated through cluster calculations by Guillaume et al.216 Semi-empirical and MP2 ab initio results are considered and comparisons of the NLO response with those obtained from the usual oriented gas model are made. POM is also selected by Hamzaoui et al 11 as an example of an NLO molecular crystal on which to test their procedure for relating the polarizabilities to the multipolar components of the ground state charge distribution determined by X-ray diffraction methods. 

The ground state electron distribution of an isolated molecule invariably determines the type of charge with which it favourably interacts. For example, a carbonyl group would be stabilised by an electron acceptor adjacent to the carbonyl oxygen while it would be energetically favourable to have an electron donor near the carbonyl carbon (XVI). The ground state charge distribution, of course, also... 

The orientation of addition of unsaturated ketones to allenes and ketens dififers. The reactions of the structurally similar allene (129) and keten (130) have been studied. Photochemically, the allene gives the methylenecyclobutane (131), which was converted into the ketone (132). The keten, generated by photolysis of the diazoketone (133), gave the isomeric tricyclic ketone (134). If the additions occur by the Corey mechanism, then the different ground-state charge distributions of the allene and the keten could be responsible for the different orientations of addition. 

The formation of chemical bonds between atoms brings about a redistribution of electronic charge relative to a simple superposition of atomic charge densities. One may characterize many of the properties of an atom in two ways by its ground-state charge distribution (which determines the atomic size), and by the accessibility of its first... 

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