Influence of small cations on the rotational barrier of amides. Comparison of experiment with HCF-SCF model calculations

Abstract

The influence of Li⁺ and Be²⁺ on the barrier to internal rotation in dimethylformamide has been investigated by means of ¹H magnetic resonance line shape analysis. The changes in the activation energy at various ion concentrations are discussed in connection with nonempirical LCGO-MO-SCF calculations for the 1 : 1 complexes of Li⁺ and Be²⁺ with formamide and dimethylformamide and the 2 : 1 complex of Li⁺ with formamide. Good agreement could be established between the experimental data and the quantum chemical model calculations concerning the relative changes of the activation energy for internal rotation.