Results 181 to 190 of about 10,075 (214)

Determination of the enantiomeric excess of α-hydroxy acids

Tetrahedron: Asymmetry, 1993
Abstract This work describes a convenient and accurate method for optical purity determination of α-hydroxy acids. Their derivatization with commercially available valine methyl ester affords diastereoisomers easily separable by HPLC using achiral C18 columns.
Florine Cavelier, Sylvie Gomez, Robert Jacquier, Muriel Llinares, Jean-Luc Mercadier, Clément Petrus, Jean Verducci   +6 more
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Asymmetric Synthesis. Kinetic Amplification of Enantiomeric Excess

Comments on Inorganic Chemistry, 1987
Abstract The efficiency of an asymmetric synthetic reaction is measured by what is called the enantiomeric excess (e.e.). It is commonly assumed that this is a unique quantity for a given asymmetric reaction under specified conditions. The purpose of this Comment is to show that this is not necessxily so, and that, under certain circumstances, e.e.
Steven Bergens, B. Bosnich
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Frozen Solution-Mediated Asymmetric Synthesis: Control of Enantiomeric Excess

The Journal of Organic Chemistry, 2020
Asymmetric List-Mannich reactions were carried out in the frozen state to afford optically active adducts in moderate-to-good chemical yields and enantiomeric excesses (ee). The frozen solution exerts critical control of ee via entropy changes, in sharp contrast to the enthalpy-driven asymmetric reactions typically observed in homogeneous solvents ...
Koki Iijima, Makoto Harada, Gaku Fukuhara, Tetsuo Okada   +3 more
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A simple explanation of the enhancement or depletion of the enantiomeric excess in the partial sublimation of enantiomerically enriched amino acids

Chemical Communications, 2010
In the partial sublimation of three enantiomerically enriched amino acids, the ee of the sublimates can be explained by the ratio between the saturated vapor pressures of the racemate and the pure enantiomers.
Bellec, Aurélien, Guillemin, Jean-Claude   +1 more
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Dissipative structures and amplification of enantiomeric excess (an experimental point of view)

Biosystems, 1987
Various mathematical models have been proposed to account for the origin of chiral molecules in biological systems. Most of these models invoke non-linear phenomena, and are based on the general concept of dissipative structures. These theoretical models define the fundamental criteria which must be obeyed by the experimental systems that we have ...
J C, Micheau, M, de Min, M, Gimenez
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Enantiomeric excess dependence of the phase diagram of antiferroelectric liquid crystals

Physical Review E, 2002
The phase diagram of the prototype antiferroelectric liquid crystal 4-(1-methylheptyloxycarbonyl)phenyl-4'-octyloxybiphengl-4-carboxylate (MHPOBC) in dependence of enantiomeric excess was measured. It was shown that the Sm-C*beta phase in very pure samples is the Sm-C*(FI2) phase with a four-layer structure, and only after small racemization it ...
E, Gorecka, D, Pociecha, M, Cepic, B, Zeks, R, Dabrowski   +4 more
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ChemInform Abstract: Rapid Enantiomeric Excess Determination

ChemInform, 2013
AbstractReview: 29 refs.
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Tailoring the Stokes’ Singularity using Enantiomeric Excess

JSAP-Optica Joint Symposia 2025 Abstracts
Optical Vortex (OV) beams characterized by orbital angular momentum (OAM) possess azimuthal phase variation and a phase singularity at the center [1]. Vector vortex beams (VVBs) are generated by the superposition of two orthogonally linearly polarized optical vortex (OV) beams having different topological charges (TCs) [2].
Ankita Karmakar, Maruthi M. Brundavanam
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Determination of Enantiomeric Excess via ³¹P‐NMR

Chirality
ABSTRACT31P is a very attractive nucleus for nuclear magnetic resonance (NMR) analysis because of the large chemical dispersion and the simplicity of the spectra when compared with other nuclei (other than 19F). The ability to rapidly and quantitatively assay for enantiomeric excess (ee) measurements of alcohols, amines, thiols, and other chiral ...
Ellis Guernsey, Jean‐Luc Montchamp
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NMR methods for determination of enantiomeric excess.

Enantiomer, 2002
With the dramatic recent growth in importance of asymmetric syntheses, new applications or approaches for analyses of enantiomeric excess (% e.e.) of samples continue to become more essential. Nuclear magnetic resonance (NMR) spectroscopy provides a wide range of powerful methods which are complementary to chromatographic or electrophoretic-based ...
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