Chiral Solvation Reagents

from Wikipedia, the free encyclopedia

Chiral Solvatationsreagenzien (CSRs) are compounds mainly in NMR spectroscopy are used to enantiomers to distinguish. The enantiomerically pure solvation reagent forms a diastereomeric solvate with the analyte. In contrast to enantiomers, diastereomers show different NMR resonances. CSRs belong to the group of NMR shift reagents .

history

( S ) -α-Phenylethylamine ( 1 ) and ( R ) -2,2,2-trifluoro-1-phenylethanol [( R ) - 2 ] and ( S ) -2,2,2-trifluoro-1-phenylethanol [ ( S ) - 2 ]

The first study on chiral solvation reagents was carried out in 1966 by William H. Pirkle . He discovered that a mixture of enantiomerically pure ( S ) -1-phenylethylamine ( 1 ) and racemic 2,2,2-trifluoro-1-phenylethanol shows not one, but two resonances in the 19 F-NMR . Reason: 1 forms with the enantiomers ( R ) - 2 and ( S ) - 2 solvates that are diastereomeric to one another. If the enantiomer ratio of ( R ) - 2 :( S ) - 2 is changed , this enantiomer ratio can be determined by integrating the peaks of the diastereomeric solvates and the ee value for 2 can be calculated from this. As a result of this discovery, other CSRs were developed, including Prikles alcohol in 1977 .

Mode of action

Prikles alcohol

In contrast to the chiral derivatization reagents, chiral solvation reagents do not form a covalent bond to the analyte. Instead, a solvate is formed, which is stabilized by hydrogen bridges , dipole-dipole interactions , π-π interactions or ion pair interactions .

Types of solvation reagents

Chiral zwitterionic imidazolium

Individual evidence

  1. ↑ WH Pirkle: The Nonequivalence of Physical Properties of enantiomer in Optically Active Solvents. Differences in Nuclear Magnetic Resonance Spectra. I . In: Journal of the American Chemical Society . tape 88 , no. 8 , April 1, 1966, pp. 1837-1837 , doi : 10.1021 / ja00960a060 .
  2. ↑ William H. Pirkle, David L. Sikkenga, Mark S. Pavlin: Nuclear magnetic resonance determination of enantiomeric composition and absolute configuration of gamma.-lactones using chiral 2,2,2-trifluoro-1- (9-anthryl) ethanol . In: The Journal of Organic Chemistry . tape 42 , no. January 2 , 1977, p. 384-387 , doi : 10.1021 / jo00422a061 .
  3. ↑ Federica Balzano, Gloria Uccello-Barretta, Federica Aiello: Chiral Analysis by NMR Spectroscopy: Chiral Solvating Agents . In: Chiral Analysis . Elsevier, 2018, ISBN 978-0-444-64027-7 , pp. 367-427 , doi : 10.1016 / b978-0-444-64027-7.00009-4 .
  4. ↑ a b Sobia Tabassum, Mazhar Amjad Gilani, René Wilhelm: Imidazolinium sulfonate and sulfamate zwitterions as chiral solvating agents for enantiomeric excess calculations . In: Tetrahedron: Asymmetry . tape 22 , no. 16-17 , September 2011, pp. 1632-1639 , doi : 10.1016 / j.tetasy.2011.09.018 .