Mulloyarova, V. V. and Giba, I. S. and Kostin, M. A. and Denisov, G. S. and Shenderovich, I. G. and Tolstoy, P. M. (2018) Cyclic trimers of phosphinic acids in polar aprotic solvent: symmetry, chirality and H/D isotope effects on NMR chemical shifts. PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 20 (7). pp. 4901-4910. ISSN 1463-9076, 1463-9084
Full text not available from this repository. (Request a copy)Abstract
The hydrogen-bonded self-associates of dimethylphosphinic (1), diphenylphosphoric (2), phenylphosphinic (3), and bis(2,4,4-trimethylpentyl) phosphinic (4) acids have been studied by using liquid-state NMR down to 100 K in a low-freezing polar solvent, CDF3/CDClF2. The H/D isotope effects on H-1 NMR chemical shifts caused by partial deuteration of hydroxyl groups unambiguously reveal the stoichiometry of the self-associates and the cooperativity of their hydrogen bonds. In all cases, cyclic trimers are the dominant form, while cyclic dimers are present as a minor form for 1 and 2. Due to the asymmetry of substituents, cyclic trimers of 3 exist in two isomeric forms, depending on the orientation of the phenyl groups with respect to the plane of the hydrogen bonds. The racemic mixture of 4 leads to the coexistence of up to 64 isomers of cyclic trimers, many of which are chemically equivalent or effectively isochronous. The mole fractions of such isomers deviate from the statistically expected values. This feature could provide information about the relative stabilization energies of hydrogen-bonded chiral self-associates. The complexation of 4 with SbCl5 (complex 5) suppresses the self-association and 5 exists exclusively in the monomeric form with chemically non-equivalent P-31 nuclei in RS, SR and RR/SS forms.
| Item Type: | Article |
|---|---|
| Uncontrolled Keywords: | HYDROGEN-BONDED COMPLEXES; PHASE ELECTRON-DIFFRACTION; DOUBLE PROTON-TRANSFER; GAS-PHASE; SOLID-STATE; DIMETHYLPHOSPHINIC ACID; DYNAMIC PROCESSES; DEUTERON TRANSFER; ACETIC-ACID; P-O; |
| Subjects: | 500 Science > 540 Chemistry & allied sciences |
| Divisions: | Chemistry and Pharmacy > Central Analytical Services |
| Depositing User: | Dr. Gernot Deinzer |
| Date Deposited: | 05 Mar 2020 10:02 |
| Last Modified: | 05 Mar 2020 10:02 |
| URI: | https://pred.uni-regensburg.de/id/eprint/15026 |
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