Q: Each of the solvent given should effectively separate one of the following mixtures by thin-layer chromatography. Match the appropriate solvent with the mixture that you would expect to separate well with that solvent. Select your solvent from the following. Hexane, Methylene chloride, or Acetone.
a) 2-phenylethanol and acetophenone: methylene chloride but can't figure it out why...
b) bromobenzene and p-xylene: Hexane?
c) benzoic acid, 2, 4-dinitrobenzoic acid, and 2, 4, 6-trinitrobenzoic acid: acetone maybe?
I assume that this is TLC on silica.
The more polar solvent is needed to move the more polar molecule. b) are the least polar molecules and so you would try hexane to separate them.
a) are the next polar pair, so as you say methylene chloride would be a good choice.
c) the most polar set and acetone is a good choice.
In practice you would choose a solvent and modify it you don't get a good separation you would try something else. The reason for the TLC is also important, if you are monitoring a reaction then it does not matter too much how good the separation is, provided you can see the separation. If you are using TLC to prepare a sample then you would want to make sure there is a clear separation.
You will also find that the solvent or solvent mixture will also affect the shape of the spot, so sometimes the solvent choice is a compromise.
a) 2-phenylethanol and acetophenone: If you want to separate 2-phenylethanol and acetophenone, using methylene chloride as the solvent is a "sharp" choice! It will "chloride" its way through the mixture, helping to separate these compounds effectively. Plus, methylene chloride is famous for its ability to "dissolve" through various substances, making it a fantastic option for thin-layer chromatography!
b) bromobenzene and p-xylene: Alright, here's the deal. If you're trying to separate bromobenzene and p-xylene, hexane is like the "H" in "Hexane" - it'll happily help with the separation! Hexane is known for its nonpolar nature, which makes it perfect for extracting nonpolar compounds. So, let hexane "hex" you with its chromatographic powers!
c) benzoic acid, 2, 4-dinitrobenzoic acid, and 2, 4, 6-trinitrobenzoic acid: Now, if you're dealing with benzoic acid, 2, 4-dinitrobenzoic acid, and 2, 4, 6-trinitrobenzoic acid, acetone just might be the cherry on top of the separation cake! Acetone is a polar solvent known for its ability to dissolve a variety of compounds. So, it will waltz through the mixture, charmingly separating these acids like a true solvent superstar!
Hope these solvent matches brighten up your chromatography experiments!
a) For separating 2-phenylethanol and acetophenone, the appropriate solvent would be methylene chloride. Methylene chloride is a polar aprotic solvent, which makes it effective for separating polar compounds like 2-phenylethanol and acetophenone. Since both these compounds are polar, they are likely to have similar retention factors on a polar stationary phase. Therefore, a polar aprotic solvent is needed to better separate them.
b) For separating bromobenzene and p-xylene, the appropriate solvent would be hexane. Hexane is a nonpolar solvent, making it suitable for separating nonpolar compounds. Both bromobenzene and p-xylene are nonpolar compounds, so they would have similar retention factors on a nonpolar stationary phase. Hence, a nonpolar solvent like hexane would be effective in separating them.
c) For separating benzoic acid, 2,4-dinitrobenzoic acid, and 2,4,6-trinitrobenzoic acid, the appropriate solvent would be acetone. Acetone is a polar protic solvent, which is effective for separating polar compounds. All three compounds listed contain polar functional groups, such as carboxylic acid and nitro groups. A polar protic solvent like acetone would allow for better interaction between the compounds and the stationary phase, leading to their separation.
To determine which solvent is appropriate for separating the given mixtures by thin-layer chromatography (TLC), you need to consider the polarities of the solvents and the mixtures.
In TLC, the principle is that compounds with similar polarities will move together on the chromatography plate, while compounds with different polarities will separate from each other.
a) For separating 2-phenylethanol and acetophenone, methylene chloride would be the suitable solvent. Methylene chloride is a moderately polar solvent, and it can effectively separate these two compounds because they have similar polarities. Methylene chloride has a higher polarity than hexane but lower polarity than acetone, making it a good choice for this mixture.
b) For separating bromobenzene and p-xylene, hexane would be the appropriate solvent. Hexane is a nonpolar solvent and would effectively separate these two nonpolar compounds. Hexane has a lower polarity than both methylene chloride and acetone, making it suitable for this mixture.
c) For separating benzoic acid, 2,4-dinitrobenzoic acid, and 2,4,6-trinitrobenzoic acid, acetone would be a suitable solvent. Acetone is a polar solvent and would effectively separate these three compounds because they have different polarities. Acetone has a higher polarity compared to both methylene chloride and hexane, making it a good choice for this mixture.
In summary:
a) For separating 2-phenylethanol and acetophenone: methylene chloride
b) For separating bromobenzene and p-xylene: hexane
c) For separating benzoic acid, 2,4-dinitrobenzoic acid, and 2,4,6-trinitrobenzoic acid: acetone