Chemical Sensors and Microinstrumentation |
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| Authors: | Royce W Murray Raymond E Dessy William R Heineman Jiri Janata Rudolf Seitz Kiumars Ghowsi |
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| Institution: | 1. ACS Symposium Series 403 American Chemical Society , Washington , DC , 1989;2. Chemistry Department , Louisiana State University , Baton Rouge , 70803 |
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| Abstract: | The 1H NMR spectra of racemic (erythro) methoxamine free base, 1, 1-(1-aminoethyl)-2,5-dimethoxybenzenemethanol, have been studied at or near ambient temperatures in CDCl3 or CD3CN with the added chiral lanthanide shift reagent (LSR), tris3-(heptafluoropropylhydroxymethylene)-(+)-camphorato] europium (III), 2. Spectrometers operating at 60, 200 and 300 MHz were employed; some COSY spectra were acquired to support assignments. Enantiomeric shift differences (Δ Δ Δ) were observed for several nuclei of 1 with added 2 in either CDCl3 or CD3CN and an “anomalous” (upfield) shift was seen for the NCH signal. A high degree of signal broadening was seen for runs with either solvent, and surprising similarity was found for the slopes in plots of chemical shift versus 2]/1] molar ratios for the different nuclei of 1 whether the hydrogen bond donor solvent (CDCl3) or the hydrogen bond acceptor solvent (CD3CN) was used. Together with the anomalous shift noted above, these results are interpreted as consistent with strong bidentate chelation of 2 by 1. |
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| Keywords: | LSR Eu(HFC)3 Bidentate chelation Stereoisomer Europium Enantiomeric excess Optical purity Analysis Adrenergic (vasopressor) NMR shift reagents One-and two-dimensional NMR COSY α-(1-Aminoethyl)-2 5-dimethoxybenzenemethanol (erythro) “Anomalous shift” |
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