A comparative study on the dynamics of epimeric 1-hydroxymethyl quinolizidines: II. The solvent and concentration dependence of the association properties

The homo and heteroassociation patterns of lupinine and epilupinine in different solvents and at various concentrations have been studied. In n-hexane, n-heptane, CCl 4 , and C 2 H 4 Cl 2 solvents, lupinine monomers with an intramolecular OH ... N hydrogen bond dominate over homoassociates with an OH ... O′ intermolecular hydrogen bond even in concentrated solutions. Homoassociation of lupinine by intermolecular OH ... N′ hydrogen bonding is observed only in saturated solutions. In chloroform solution any intermolecular homoassociation is effectively blocked because of significant affinity of chloroform molecules acting as a weak acid toward the free electron pairs of the oxygen atom from the hydroxyl group that would be otherwise engaged in intramolecular OH ... N hydrogen bonding. Epilupinine in n-hexane, n-heptane, CCl 4 , C 2 H 4 Cl 2 , and chloroform solutions forms possible homoassociates both by OH ... N′ and OH ... O′ intermolecular hydrogen bonding. In dioxane-d 8 , DMSO, and D 2 O solvents both lupinine and epilupinine form heteroassociates with solvent molecules.