Conformational equilibria of N,N-dimethylsuccinamic acid and its lithium salt as a function of solvent.

The conformational preferences of N,N-dimethylsuccinamic acid and its Li(+) salt were estimated by comparing the respective experimental NMR vicinal proton-proton coupling constants to semiempirical coupling constants for each staggered conformer as derived by the Haasnoot-De Leeuw-Altona method. The strong gauche preferences for the Li(+) salts clearly depended more on the solvents' hydrogen-bond donating strength (α) than on their hydrogen-bond accepting (β) counterpart, where α and β are the corresponding Kamlet-Taft parameters.