| Abstrakt: |
The anionic Yanovskii σ adducts of 1,3,5-trinitro- and 1,3-dinitrobenzenes, 1,3-dinitronaphthalene, and 3,5-dinitrobenzoic acid with sodium, potassium, and tetrabutylammonium acetonates in low-polarity solvents exist mostly as contact ion pairs, while in polar solvents, as solvent-separated ion pairs and free ions. Lowering the temperature increases the fraction of solvent-separated ion pairs in low-polarity solvents and of free ions in polar solvents, by shifting the equilibria to stronger solvated ionic species. By quantum-chemical calculations of the geometry and electronic structure of the anions and of the electronic absorption spectra of the free ions and ion pairs, as well as by a spectrophotometric study of σ adducts with solvents of various polarity it was established that the cation on ion-pair formation coordinates with the 4-nitro group with respect to the pyramidal node. [ABSTRACT FROM AUTHOR] |
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