Deuterium Naturally Present in Solvent and Site-Specific Isotope Population of Deuterium-Enriched Solute

摘要

As the concentration of aqueous CD3OH solutions was decreased, the OD peaks in ~2H NMR spectra grew relative to the CD3 peaks. Isotope impurity for OH groups of CD3OH and deuterium naturally present in water contributed to the OD peaks. Using these peak area data, the site-specific isotope populations of isotope enriched chemicals were measured. In addition, the method using both ~1H and ~2H NMR spectroscopy was demonstrated with neat CD3OH to measure the site-specific isotope populations. The results indicate that although it represents only ～0.015% of hydrogen isotopes, the deuterium naturally present in solvents cannot be ignored, especially when the concentration of deuterium-enriched solutes is varied. Proton/deuteron exchange between methyl and methyl/hydroxyl groups was confirmed to be negligible, while that among hydroxyl groups was detectable.