Isotopically Enriched <sup>13</sup>C Diffusion-Ordered NMR Spectroscopy: Analysis of Methyllithium
作者:Chicheung Su、Russell Hopson、Paul G. Williard
DOI:10.1021/jo401740g
日期:2013.12.6
We report the development of isotopic-labeled C-13 diffusion-ordered NMR spectroscopy (DOSY) NMR with diffusion coefficient-formula weight (D-FW) analysis and its application in characterizing the aggregation state of methyllithium aggregates and complexes with several widely used diamines. Commercially available C-13-labeled benzene and several easily synthesized C-13-labeled compounds using C-13-labeled iodomethane as the isotopic source are developed as internal references for diffusion-formula weight analysis (D-FW). The technique greatly expands the applicability of DOSY D-FW analysis to a much wider variety of compounds because of isotopic labeling. These results reveal that methyllithium exists as a tetrasolvated tetramer in diethyl ether and exclusively as bis-solvated dimers with chelating diamines.