| Autor: |
Sommer, Horst, Bertram, Heinz-Juergen, Krammer, Gerhard E., Schmidt, Claus Oliver, Stumpe, Wolfgang, Werkhoff, Peter, Zviely, Michael |
| Zdroj: |
Magnetic Resonance in Chemistry; November 2000, Vol. 38 Issue: 11 p907-917, 11p |
| Abstrakt: |
The substitution pattern of di- and trisubstituted pyrazines can be elucidated by a combination of NMR methods, especially in mixtures by gradient selected 1H,15N HMBC experiments at the natural abundance level. In the case of disubstituted pyrazines, it allows one to distinguish between 2,3-/2,5- and 2,6-disubstituted isomers. Another advantage is the determination of 15N NMR chemical shifts including the assignments even at relatively low concentrations. The reliability of this method was verified by experimental data resulting from 1H NMR and long-range heteronuclear correlation experiments such as FLOCK and 1H,13C HMBC experiments. Carboncarbon coupling constants derived from INADEQUATE experiments were taken into account as additional tests. Thirty-one commercially available di- and trisubstituted pyrazines were measured in order to identify their substitution patterns and to obtain chemical shift information. As a result, fully assigned 1H, 13C and 15N NMR data of these pyrazines are reported. Copyright © 2000 John Wiley & Sons, Ltd. |
| Databáze: |
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