Magnetic nonequivalence in NMR spectroscopy—II. The role of hydrogen bonding in 2,2,4-trimethylpentane-1,3-diol and its monoisobutyrates
✍ Scribed by Richard M. Fantazier
- Publisher
- John Wiley and Sons
- Year
- 1973
- Tongue
- English
- Weight
- 492 KB
- Volume
- 5
- Category
- Article
- ISSN
- 0749-1581
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✦ Synopsis
Abstract
The methylene protons in 2,2,4‐trimethylpentane‐1,3‐diol (1), its 1‐isobutyrate (2) and 3‐isobutyrate (3) monoesters, are magnetically nonequivalent with respect to chemical shift. Under the same experimental conditions, the chemical shift differences are 14·4 Hz, 46·2 Hz and 18·2 Hz for 1, 2 and 3, respectively. These nonequivalences were examined as a function of temperature and concentration. The large nonequivalence in 2 is attributed to a highly restricted conformation resulting from intramolecular hydrogen bonding. Less favorable steric interactions result in a substantially smaller contribution of intramolecular hydrogen bonding in 3, while in 1 intermolecular hydrogen bonding occurs exclusively. Infrared data were obtained in support of these conclusions.