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

Abstract

As the concentration of aqueous CD 3 OH solutions was decreased, the OD peaks in 2 H NMR spectra grew relative to the CD 3 peaks. Isotope impurity for OH groups of CD 3 OH 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 1 H and 2H NMR spectroscopy was demonstrated with neat CD 3 OH 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.

Position-Specific 2H/H Equilibrium Isotopic Fractionation Factors in Alkane, Alkene, and Aromatic Molecules: A Density Functional Theory Approach

“…In addition, we applied the method to models of pristane and phytane, the isoprenoid biomarkers that are sensitive to H isotope exchange during catagenesis and thus can be used as an indicator of the extent of thermal maturation of organic matter in petroleum basins. Because the experimental ability to distinguish among 2 H-substituted H atoms on 1°, 2°, and 3° C atoms is improving due to developments in position-specific 2 H analysis, − it is necessary to improve the accuracy of computational chemistry methodology as compared with experimental data. If methods can be developed and improved that provide added accuracy comparable with experimental data for modeling 2 H–H exchange reactions, these methods can then be combined with new analytical methods in future studies of 2 H–H exchange kinetics.…”