Consideration Of π-π and CH-π Interactions as Dipole-Dipole Interactions in Biphenyl Stationary Phases

Phenyl and biphenyl stationary phases in chromatography are explored.
These phases exhibit dipole-dipole interactions, including π-π, CH-π, OH-π, NH-π, halogen-π, and lone pair electron-π interactions.
The study focuses on the role of π-π and CH-π interactions in separating different compounds.
Dinitrobenzene, trinitrobenzene, and sulfonamides are used to evaluate π-π interactions, while isomers of methyl hippuric acid, organic acids, vanillin, isovanillin, leucine, n-butyraldehyde-DNPH, and iso-butyraldehyde-DNPH examine CH-π interactions.
The biphenyl stationary phase exhibits stronger π-π and CH-π interactions compared to the phenyl stationary phase.
Key takeaways include the recognition of phenyl groups for their dipole-dipole interaction capabilities, the significance of CH-π interactions in selectivity changes, and the insight provided by CH-π interactions in variations in selectivity in the separation of organic acids.