A solid-state 17O NMR study of L -phenylalanine and L -valine hydrochlorides

✍ Scribed by Kazuhiko Yamada; Tadashi Shimizu; Shinobu Ohki; Toshio Yamazaki

• Book ID: 102951012
• Publisher: John Wiley and Sons
• Year: 2008
• Tongue: English
• Weight: 591 KB
• Volume: 46
• Category: Article
• ISSN: 0749-1581
• DOI: 10.1002/mrc.2167

✦ Synopsis

Abstract

We have presented an experimental investigation of the oxygen‐17 chemical shielding (CS) and electric‐field‐gradient (EFG) tensors for α‐COOH groups in polycrystalline amino acid hydrochlorides. The ^17^O CS and EFG tensors including the relative orientations between the two NMR tensors are determined in [^17^O]‐L‐phenylalanine hydrochloride and [^17^O]‐L‐valine hydrochloride by the analysis of the ^17^O magic‐angle‐spinning (MAS) and stationary NMR spectra obtained at 9.4, 11.7, 16.4, and 21.8 T. The quadrupole coupling constants (C~Q~) and the span of the CS tensors are found to be 8.41–8.55 MHz and 7.35–7.41MHz, and 548–570 ppm and 225–231 ppm, for carbonyl and hydroxyl oxygen atoms, respectively. Extensive quantum chemical calculations using density functional theory (DFT) have been also carried out for a hydrogen‐bonding model. It is demonstrated that the behavior of the dependence of hydrogen‐bond distances on ^17^O NMR tensors for the halogen ions is different from those for the water molecule. Copyright © 2008 John Wiley & Sons, Ltd.