1. Purpose

Chiral lanthanide shift reagents are used for the determination of enantiomeric purity (for other techniques see Exps. 8.3 to 8.5). In this experiment the chiral tris[3-(heptafluoropropylhydroxymethylene)-d-camphorato]-praseodymium complex, Pr(hfc)₃, is used, which (in contrast to europium complexes, see Exp. 8.1), causes low-frequency rather than high-frequency shifts.

2. Literature

J. Reuben, Prog. NMR Spectrosc. 1975, 9, 1–70.
O. Hofer, Top. Stereochem. 1976, 9, 111–197.
G. R. Sullivan, Top. Stereochem. 1978, 10, 288–329.
W. H. Pirkle, D. J. Hoover, Top. Stereochem. 1982, 13, 263–331.
T. C. Morrill (ed.): Lanthanide Shift Reagents in Stereochemical Analysis, in Methods in Stereochemical Analysis, VCH, Weinheim, 1986.
D. Parker, Chem. Rev. 1991, 91, 1441–1457.
R. Rothchild, Enantiomer 2000, 5, 457–471.

3. Pulse Scheme and Phase Cycle

Chiral lanthanide shift reagent pulse sequence and phase cycle

4. Acquisition

Time requirement: 1 h

Sample: 10 mg rac 1-phenylethanol in 0.7 ml CDCl₃.

Load standard ¹H NMR acquisition parameters (see Exp. 3.1), set the spectral width to 15 ppm and adjust the offset so that signals up to δ_H = −3 are covered. Record a spectrum of 1-phenylethanol, add a very small portion (about 1 mg) of tris[3-(heptafluoropropyl-hydroxy-methylene)-d-camphorato]-praseodymium, Pr(hfc)₃, allow sufficient