Proton-Decoupled Carbon-13 NMR Spectroscopy in a Lyotropic Chiral Nematic Solvent as an Analytical Tool for the Measurement of the Enantiomeric Excess†

1997 ◽  
Vol 119 (19) ◽  
pp. 4502-4508 ◽  
Author(s):  
A. Meddour ◽  
P. Berdague ◽  
A. Hedli ◽  
J. Courtieu ◽  
P. Lesot
Keyword(s):  
Nmr Spectroscopy ◽  
Enantiomeric Excess ◽  
Analytical Tool ◽  
Chiral Nematic ◽  
Nematic Solvent

31P NMR Spectroscopy as a Powerful Tool for the Determination of Enantiomeric Excess and Absolute Configurations of α-Amino Acids

2003 ◽  
Vol 42 (4) ◽  
pp. 1006-1013 ◽  
Author(s):  
Judith Bravo ◽  
Carlos Cativiela ◽  
Julio E. Chaves ◽  
Rafael Navarro ◽  
Esteban P. Urriolabeitia
Keyword(s):  
Amino Acids ◽  
Nmr Spectroscopy ◽  
31P Nmr ◽  
Enantiomeric Excess ◽  
31P Nmr Spectroscopy

Simple enantiomeric excess determination of alcohols using chiral selones and 77Se NMR spectroscopy

1995 ◽  
Vol 6 (4) ◽  
pp. 833-834 ◽  
Author(s):  
Ruilian Wu ◽  
Jerome D. Odom ◽  
R. Bruce Dunlap ◽  
Louis A. Silks
Keyword(s):  
Nmr Spectroscopy ◽  
Enantiomeric Excess ◽  
77Se Nmr Spectroscopy

scholarly journals Cover Feature: Helicity Control of Supramolecular Gel Fibers Consisting of an Achiral NiII Complex in a Chiral Nematic Solvent (Chem. Eur. J. 48/2018)

2018 ◽  
Vol 24 (48) ◽  
pp. 12445-12445
Author(s):  
Takatoshi Maeda ◽  
Yuuki Kuwajima ◽  
Takuya Akita ◽  
Yosuke Iwai ◽  
Naruyoshi Komiya ◽  
...  
Keyword(s):  
Supramolecular Gel ◽  
Chiral Nematic ◽  
Niii Complex ◽  
Nematic Solvent

13C-Chemische Verschiebungen von Aminosäuren und Peptiden / 13C-NMR Chemical Shifts of Amino Acids and Peptides

1971 ◽  
Vol 26 (3) ◽  
pp. 213-222 ◽  
Author(s):  
Wolfgang Voelter ◽  
Günther Jung ◽  
Eberhard Breitmaier ◽  
Ernst Bayer
Keyword(s):  
Amino Acids ◽  
Fourier Transform ◽  
Nmr Spectroscopy ◽  
Nmr Spectra ◽  
Chemical Shifts ◽  
Analytical Tool ◽  
Reasonable Time ◽  
C Isotopes ◽  
Direct Recording ◽  
C Nmr

Pulse - Fourier - Transform-13C-NMR spectroscopy allowed the direct recording of 13C-NMR spectra of amino acids and peptides with natural abundance of 13C isotopes within a reasonable time. The 13C-signals of more than 50 free and protected amino acids and several peptides were assigned. 13C-NMR spectroscopy gives valuable information about the carbon skeleton, thus offering a new analytical tool for the study of biopolymers and their constituents.

scholarly journals 1-(+)-Dehydroabietylimidazolium Salts as Enantiomer Discriminators for NMR Spectroscopy

2017 ◽  
Vol 70 (7) ◽  
pp. 845 ◽  
Author(s):  
H. Q. Nimal Gunaratne ◽  
Tiina Laaksonen ◽  
Kenneth R. Seddon ◽  
Kristiina Wähälä
Keyword(s):  
Nmr Spectroscopy ◽  
Carboxylic Acids ◽  
Enantiomeric Excess ◽  
Nmr Titration ◽  
Titration Experiment ◽  
Aromatic Carboxylate ◽  
Better Than

Nine new (+)-dehydroabietylimidazolium salts were synthesised and studied as chiral solvating agents for several different racemic aromatic and non-aromatic carboxylate salts. These cationic chiral solvating agents resolve racemic ionic analytes better than non-ionic ones. Bis(dehydroabietylimidazolium) bis(trifluoromethanesulfonimide) gave the best discrimination for the enantiomers of carboxylate salts. Its resolution behaviour was studied by an NMR titration experiment, which indicated 1 : 1 complexation with the racemic analyte. The dehydroabietylimidazolium salts were also useful in enantiomeric excess (ee) determinations, and for the recognition of chirality of racemic aromatic and non-aromatic α-substituted carboxylic acids.

Solution carbocation stabilities measured by internal competition for a hydride ion

1982 ◽  
Vol 60 (17) ◽  
pp. 2180-2193 ◽  
Author(s):  
Nancy E. Okazawa ◽  
Ted S. Sorensen
Keyword(s):  
Nmr Spectroscopy ◽  
Equilibrium Constants ◽  
Analytical Tool ◽  
Steric Interactions ◽  
Hydride Ion ◽  
Methylene Chain ◽  
Internal Competition ◽  
Equilibration Process ◽  
Better Than ◽  
C Nmr

Although many techniques are known which allow one to compare the stabilities of solution carbocations, that involving the intermolecular competition for a hydride ion is conceptually (but not experimentally) the simplest procedure. This paper describes a variant of this which is experimentally more reliable and which uses intramolecular equilibria where the two competing systems are held together by a —(CH2)n— chain, e.g.[Formula: see text]By systematically varying "n" in this example (n = 0, 1,2, or 3), it has been found that a methylene chain of two or more carbons is necessary in order to minimize steric interactions between the end "systems". It has also been found that all cycloalkyl rings studied (except cyclohexyl) stabilize a cation centre much better than an aliphatic equivalent, i.e. [Formula: see text], in agreement with solvolysis rate studies. The same situation was found when comparing this aliphatic "system" against the 2-norbornyl cation (bicyclic) or against the tricyclic 2-adamantyl cation. In fact, in these cases the equilibria are too lop-sided to obtain numerical values for the equilibrium constants concerned. Finally, three carbocations were looked at where the 2-norbornyl cation structure was pitted against the structurally very related cyclopentyl, bicyclo[2.1.1]hexyl, and bicyclo[3.2.1]octyl cations. In all cases, the 2-norbornyl cation is the more stable. 13C nmr spectroscopy was used as the analytical tool to measure (or attempt to measure) the equilibrium constants. Depending on the rate of the equilibration process, three different techniques are involved and the relative merits of these are discussed in the latter part of the paper.

Sign in / Sign up

Export Citation Format

Share Document