Lithium dialkylamides. 13C parameters and slow proton transfer

The changes in ¹³C chemical shifts for the structural change R₂NH → R₂NLi have been measured for a series of dialkylamines. These lithiation shifts are largest at the $\text{alpha}$ carbon (3.7 – 9.7 ppm) and decrease in the order α > β > γ > δ. The rates of lithium-hydrogen interchange between R₂NH and R′₂NLi have been determined. The activation energies are large (9 – 17 kcal/mole) and increase as the size of R or R′ increases. The slow exchange permits the direct measurement of acidity differences between pairs of amines using ¹³C nmr.