Characterization of Hexameric and Octameric sec‐Butyllithium/sec‐Butoxide Mixed Aggregates

Solution‐state characterization of sec ‐butyllithium in [D 8 ]toluene was conducted by utilizing a variety of NMR spectroscopic experiments including diffusion‐ordered NMR spectroscopy (DOSY) with diffusion‐coefficient–formula‐weight correlation analyses and other one‐ and two‐dimensional NMR spectroscopic techniques. These results suggest that sec ‐butyllithium exists primarily as a tetramer/hexamer mixture in hydrocarbon solvents. However, the presence of roughly 2–5 % (by mol ratio) lithium sec ‐butoxide in both commercially available and laboratory‐synthesized sec ‐butyllithium solutions due to the reaction with adventitious dioxygen will lead to the formation of a 1:5 sec ‐butoxide/ sec ‐butyllithium mixed hexamer. A sec ‐butoxide/ sec ‐butyllithium mixed octamer will emerge when the proportion of butoxide to butyllithium increases.