In flushing and cleaning columns used in liquid chromatography to remove adsorbed contaminants, a series of solvents is used. Hexane \(\left(\mathrm{C}_{6} \mathrm{H}_{14}\right)\), chloroform \(\left(\mathrm{CHCl}_{3}\right)\), methanol \(\left(\mathrm{CH}_{3} \mathrm{OH}\right)\), and water are passed through the column in that order. Rationalize the order in terms of intermolecular forces and the mutual solu- bility (miscibility) of the solvents.

For each solvent, we need to identify the main type of intermolecular forces involved. Intermolecular forces can be divided into three main categories: London Dispersion Forces (LDF), Dipole-Dipole Interactions, and Hydrogen Bonding. Hexane \(\left(\mathrm{C}_{6}\mathrm{H}_{14}\right)\): LDF (nonpolar) Chloroform \(\left(\mathrm{CHCl}_{3}\right)\): Dipole-Dipole Interactions (polar) Methanol \(\left(\mathrm{CH}_{3}\mathrm{OH}\right)\): Hydrogen Bonding (polar) Water: Hydrogen Bonding (polar)

Now, we will discuss the miscibility of each solvent with the previous one in the sequence, to rationalize the order. - Hexane \(\left(\mathrm{C}_{6}\mathrm{H}_{14}\right)\) is a nonpolar solvent with LDF. It is used first to remove hydrophobic (nonpolar) contaminants. - Chloroform \(\left(\mathrm{CHCl}_{3}\right)\) is a polar solvent with Dipole-Dipole Interactions. It is miscible with hexane due to the relatively weak polarity of chloroform. This allows for a gradual transition from nonpolar to polar and helps dissolve moderately polar contaminants. - Methanol \(\left(\mathrm{CH}_{3}\mathrm{OH}\right)\) is a polar solvent with Hydrogen Bonding interactions. It is miscible with chloroform due to both being polar solvents and will dissolve more polar contaminants. - Lastly, water is used to dissolve highly polar contaminants because it is a polar solvent with strong hydrogen bonding interactions. Methanol and water are miscible due to both having hydrogen bonding. The order of the solvents allows for a gradual increase in polarity and strength of intermolecular forces, which enables the efficient removal of contaminants with a range of polarities from the chromatography column.