Diastereomeric solute-solute interactions of enantiomers in achiral solvents. Nonequivalence of the nuclear magnetic resonance spectra of racemic and optically active dihydroquinine

An Overview of Cinchona Alkaloids in Chemistry

“…However, at high dilution (0.01 M), this interaction disappeared. This indicates the existence of a self-association process mediated by intermolecular hydrogen bonding [24]. Moreover, the measurement of the molecular weight of quinine using osmometry conducted by Hiemstra and Wynberg revealed the presence of particles larger than monomeric quinine at 37 C for a 16 mM solution in toluene.…”

“…In 1969, Uskokovic and coworkers observed a concentration-dependent intermolecular interaction between dihydroquinine molecules [24]. The 1 H NMR spectra of (À)-dihydroquinine and racemic dihydroquinine are clearly different under concentrated conditions; that is, this molecule can generate its own nonequivalence.…”

Enantiomeric recognition and interactions

“…In contrast in eqn (2), any reaction performed on a R,S mixture will proceed while the R-isomer is surrounded by-and thus in non-bonded interaction with-R-and S-molecules.…”

How Long Have Nonlinear Effects Been Known in the Field of Catalysis?

“…These interactions are also known to be the cause of unexpected sublimation phenomena [2] and NMR spectra. [3] At the beginning of the 1970s Horeau et al [4] reported the first examples of the nonlinear relationship between optical purity and enantiomeric excess caused by diastereomeric aggregations. Further unusual results which were explained on the basis of enantiomeric interactions have been compiled by Noyori et al [5] The question as to what extent such a nonideal relationship effects chemical reactions goes back to Wynberg and Feringa. [6]…”

“…According to the principle which goes back to Feringa et al [21] optically active compounds can be transformed with an achiral reagent such PCl 3 . Under the condition of a statistical product distribution, it is then easily possible from the NMR spectrum to determine the relationship of the sum of each of the newly formed heteroand homochiral compounds and therefore the enantiomeric excess of the optically active starting material.…”