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 solubility (miscibility) of the solvents.

Short Answer

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The order of solvents in cleaning columns for liquid chromatography is based on their increasing intermolecular forces and miscibility to ensure a smooth transition and efficient cleaning process. Hexane removes nonpolar contaminants with its London dispersion forces, followed by chloroform for contaminants with dipole-dipole interactions. Methanol, capable of hydrogen bonding, removes polar contaminants, and water removes any remaining polar contaminants through hydrogen bonding. Miscibility between these solvents allows for smooth transitions during the cleaning process.

Step by step solution

01

Identifying the intermolecular forces present in each solvent

Intermolecular forces are the forces of attraction and repulsion between molecules, which influence the physical properties of compounds. There are three main types of intermolecular forces: London dispersion forces, dipole-dipole interactions, and hydrogen bonds. 1. Hexane (C6H14) - London dispersion forces (weakest forces) 2. Chloroform (CHCl3) - Dipole-dipole interactions (moderate forces) 3. Methanol (CH3OH) - Hydrogen bonding (strongest forces) 4. Water - Hydrogen bonding (strongest forces)
02

Analyzing the miscibility of the solvents

Miscibility is the ability of two or more liquids to mix together to form a homogeneous solution without the separation of phases. Solvents with similar intermolecular forces and polarities tend to be miscible with each other. 1. Hexane and chloroform: Both are nonpolar solvents (hexane is weaker due to only London dispersion forces, and chloroform has some polarity due to dipole-dipole interactions) and are miscible with each other. 2. Chloroform and methanol: Chloroform is slightly polar, whereas methanol is a polar solvent (due to hydrogen bonding). These two solvents have different intermolecular forces but are still partially miscible with each other. 3. Methanol and water: Both are polar solvents with hydrogen bonding and are miscible with each other.
03

Rationalizing the order of solvents in terms of intermolecular forces and miscibility

The order of solvents used in cleaning columns in liquid chromatography is hexane, chloroform, methanol, and water. 1. Hexane is used first because it is the weakest of all solvents and can remove nonpolar contaminants thanks to its London dispersion forces. 2. Chloroform comes next as it has a slightly higher polarity than hexane, which means it can remove contaminants with stronger intermolecular forces like dipole-dipole interactions. Moreover, it is miscible with hexane, which ensures a smooth transition between the solvents. 3. Methanol is used after chloroform to remove polar contaminants because it can form hydrogen bonds. Methanol is partially miscible with chloroform, allowing some transition between the solvents. 4. Finally, water is used because it can remove any remaining polar contaminants through hydrogen bonding. As mentioned before, water and methanol are both polar solvents that are miscible with each other, which ensures a smooth final transition. In conclusion, the order of solvents used is due to their increasing intermolecular forces and the miscibility between solvents to ensure a smooth transition and efficient cleaning process in liquid chromatography.

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