ISSN:
1573-8779
Source:
Springer Online Journal Archives 1860-2000
Topics:
Chemistry and Pharmacology
Notes:
Conclusion The values of the paramagnetic shifts and their temperature dependence indicate that the interaction of molecular oxygen with various organic molecules is specific and localized in character; that is it takes place in complexes and not in collision contact pairs. Interactions in collision pairs would not have led to the experimentally observed marked differences in the paramagnetic shifts and their temperature dependence for different fragments of the same molecule, since the orientations of the partners in these pairs are random and almost equally probable. The concentration dependence of the paramagnetic shifts in the water-acetone mixture is described by a scheme involving complex formation with competing ligands. It indicates that oxygen does not form complexes with hydrogen bonds, as might have been expected from an analysis of the values of the paramagnetic shifts for different functional groups of the molecules, but forms complexes of the donor-acceptor type, in which oxygen acts as an electron acceptor. The transfer of spin density from the oxygen molecule to the ligands indicates that collectivization of the electron clouds of oxygen and the ligand takes place in the complex, with the formation of common molecular orbitals. This transfer of spin density by itself can be regarded as an indication or criterion of complex formation (particularly in the case of weak short-lived complexes).
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00746102
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