Unexpected Fractionation in Site-Specific ~(13)C Isotopic Distribution Detected by Quantitative ~(13)C NMR at Natural Abundance

摘要

Isotopic fractionation phenomena are associated with many physical and chemical processes. In all cases, this fractionation reflects a change in the concentration of each isotopomer between the starting material and the product when the chemical or physical transformation is not complete. The method of choice for measuring each isotopomer concentration-hence the associated isotope effects-is quantitative NMR.