Atomic properties transferability

The most convenient criterion is offered by the energy or its density functionals. But which energy - the one of the atom in the molecule or of the molecule as a whole Hence there appears the need for nuances in the Hohenberg-Kohn Theorem on the analytical domains and subdomains. It follows that the atom properties transferability from one molecule to another is natural and the atom bordered in molecule by an area SQ satisfies the stationary eondition of the density flow on the surface bordering the field... 

The atomic properties satisfy the necessary physical requirement of paralleling the transferability of their charge distributions - atoms that look the same in two molecules contribute identical amounts to all properties in both molecules, including field-induced properties. Thus the atoms of theory recover the experimentally measurable contributions to the volume, heats of formation, electric polarizability, and magnetic susceptibility in those cases where the group contributions are found to be transferable, as well as additive additive [4], The additivity of the atomic properties coupled with the observation that their transferability parallels the transferability of the atom s physical form are unique to QTAIM and are essential for a theory of atoms in molecules that purports to explain the observations of experimental chemistry. 

These are three examples of the use of atomic properties to obtain quantitative structure-activity relationships (QSAR) or structure-function relationships. One should bear in mind that all properties have an atomic basis, making a multitude of new relationships possible. The atomic contribution to the polarizability, for example, is definable and shown to be transferable [26-28], offering the possibility of improving the use of an electrostatic potential map from zero- to first-order estimates of energies of interaction. 

Tab. 7.1 Comparison of atomic properties for the maximal transferable group in morphine and PEO. ... 

Notice that whereas in Eq. 16-43 the methyl group is transferred as CH3+ by nucleophilic displacement on a carbon atom, the transfer to Hg2+ in Eq. 16-44 is that of a carbanion, CH3, with no valence change occurring in the cobalt. However, it is also possible that transfer occurs as a methyl radical.420 Methyl corrinoids are able to undergo this type of reaction nonenzymatically, and the ability to transfer a methyl anion is a property of methyl corrinoids not shared by other transmethy-... 

The bond strength of the donor is crucial in determining its reactivity. In general, the weaker the bond to the donor the more readily the H atom is transferred to the excited ketone. Galardy et al. (1973) were able to demonstrate that reaction with the relatively weak a-CH bonds of amino acids would occur in the presence of water, a useful property for a labeling reagent in a site exposed to or containing solvent. 

TTie definition of a bound atom—an atom in a molecule— must be such that it enables one to define all of its average properties. For reasons of physical continuity, the definition of these properties must reduce to the quantum mechanical definitions of the corresponding properties for an isolated atom. The atomic values for a given property should, when summed over aU the atoms in a molecule, yield the molecular average for that property The atomic properties must be additive in the above sense to account for the observation that, in certain series of molecules, the atoms and their properties are transferable between molecules, leading to what are known as additivity schemes. An additivity scheme requires both that the property be additive over the atoms in a molecule and that the atoms be essentially transferable between molecules. 

These atomic properties possess a high degree of transferability from the electronic environment in one molecule to another molecule with similar environments. Consequently, the properties of a whole molecule or a functional group can be obtained by adding the atomic properties as... 

A specific subset of the broader class of thermodynamic LFERs is known under the acronym LSER, linear solvation energy relationships. The LSER paradigm invokes explicitly the processes in which the solute transfer between two phases takes place and evolved from the work of Abraham (7,10), who built on the pioneer work of Hammet and later on Kamlet and Taft (11,12), enabling the extension of LFER from the realm of atomic properties to the realm of intermolecular interactions. 

Carbene complexes that possess these properties are called Schrock carbenes. The r interaction shown in 4-40 is accompanied by a substantial transfer of electron density from the metal to the carbon atom. This transfer more than outweighs the a donation (ligand metal), so that the metal-carbon bond is polarized in the sense M(5" )=C((5 ). Schrock carbenes therefore possess a nucleophilic carbon, and give, for example, addition products with Lewis acids such as AlMes (4-43). 

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