Expand this Topic clickable element to expand a topic
Skip to content
Optica Publishing Group
  • Applied Spectroscopy
  • Vol. 38,
  • Issue 1,
  • pp. 74-78
  • (1984)

Optical Purity Determination and 1H NMR Spectral Simplification with Lanthanide Shift Reagents. II. Thiamylal, 5-Allyl-5-(1-methylbutyl)-2-thiobarbituric Acid

Not Accessible

Your library or personal account may give you access

Abstract

A racemic sample of thiamylal, 5-allyl-5-(1-methylbutyl)-2-thiobarbituric acid, 1, has been shown to exhibit significant enantiomeric shift differences, ΔΔδ, for the CH3-CH proton absorptions when treated with the chiral lanthanide shift reagent, tris[3-(trifluoromethylhydroxy-methylene)-d-camphorato] europium (III), 2, in CDCl3 at 28°. For example, at the relatively low molar ratio of 2:1 of 0.181, a value of ΔΔδ of 22 Hz (0.36δ) was observed, which increased to 26 Hz (0.43δ) at a molar ratio of 0.226. These large values, with relatively little lanthanide-induced line-broadening, should make possible the facile determination of optical purity of 1 even with a 60 MHz nmr spectrometer. Parallel studies were run using the achiral shift reagent, tris-(6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octanedionato) europium (III), 3, to confirm peak assignments. The considerable values of ΔΔδ may reflect the "soft base" character of the sulfur atom in 1. Less effective binding by sulfur to the lanthanide atom could lead to coordination by europium on the carbonyl oxygen, relatively close to the chiral center, providing enhanced ΔΔδ values compared to some related compounds. While several other proton absorptions of 1 appear to show some observable ΔΔδ, they are less valuable for optical purity evaluation because of lower intensity, greater multiplicity, or small ΔΔδ value. The relative slopes of the plots of chemical shift, δ, for runs with 2 or 3, are consistent with the full assignment of the proton absorptions of 1 based on expected proximity of the protons to the complexed europium atom. The observed coupling constants of the vinyl hydrogens of 1 further support the assignments.

PDF Article
More Like This
Synthesis of polyamic acid possessing second-order nonlinear optical properties and its application to Langmuir–Blodgett films

Cheolsoo Jung, Mitsutoshi Jikei, and Masa-aki Kakimoto
J. Opt. Soc. Am. B 15(1) 471-476 (1998)

Isotope shift of 3 × 105-yr 202Pb in the 6p2 ³P0−6p7s ³P1° 283.3-nm resonance line

F. A. Moscatelli, O. Redi, H. H. Stroke, R. L. Wiggins, and R. A. Naumann
J. Opt. Soc. Am. 73(2) 156-159 (1983)

Cited By

You do not have subscription access to this journal. Cited by links are available to subscribers only. You may subscribe either as an Optica member, or as an authorized user of your institution.

Contact your librarian or system administrator
or
Login to access Optica Member Subscription

Select as filters


Select Topics Cancel
© Copyright 2024 | Optica Publishing Group. All Rights Reserved