The Rf value of compound A is .34 when the TLC plate is developed in hexane and .44 when the plate is developed in diethyl ether. Compound B has an Rf value of .42 in hexane and .60 in diethyl ether. Which solvent would be better for seperating a mixture of compounds A and B by TLC? Explain.
- I think that the diethyl ether is a better solvent because it is less polar than hexane? Is this the right track?
I think either solvent will separate the two compounds; however, the diethyl ether separation will be farther apart and I would pick that one. As for hexane being more polar than diethyl ether, I don't think so. Hexane is about as non-polar as you can get while diethyl ether, while not very polar, is more polar than hexane. Here is a site that gives some general rules about polarity of various groups.
http://www.elmhurst.edu/~chm/vchembook/213boilingpoint.html
Thanks alot. yeah I was a little confused as to which was more polar.
Yes, you are on the right track. In TLC (Thin Layer Chromatography), the solvent plays an important role in separating and identifying compounds. The choice of solvent depends on the polarity of the compounds you are trying to separate.
The Rf (retention factor) value is a measure of how far a compound travels on the TLC plate relative to the solvent front. It is calculated by dividing the distance the compound traveled by the distance the solvent front traveled.
In this case, compound A has an Rf value of 0.34 in hexane and 0.44 in diethyl ether. Compound B has an Rf value of 0.42 in hexane and 0.60 in diethyl ether.
Comparing the Rf values, we can see that both compounds have higher Rf values in diethyl ether than in hexane. This indicates that both compounds have better solubility and affinity for the stationary phase (silica or alumina) in diethyl ether.
Additionally, since diethyl ether has a higher Rf value for both compounds compared to hexane, it suggests that diethyl ether provides better separation and mobility for the mixture of compounds A and B.
Therefore, based on the Rf values, it can be inferred that diethyl ether would be a better solvent for separating the mixture of compounds A and B by TLC.
Yes, you're on the right track! To determine which solvent would be better for separating a mixture of compounds A and B by TLC, you need to compare the relative polarities of the solvent and the compounds.
The Rf value is a measure of how far a compound moves on a TLC plate relative to the distance the solvent moves. In general, higher Rf values indicate that a compound is more soluble in the solvent and has a higher mobility on the TLC plate.
Comparing the Rf values of compounds A and B in hexane and diethyl ether:
Compound A:
- Rf value in hexane: 0.34
- Rf value in diethyl ether: 0.44
Compound B:
- Rf value in hexane: 0.42
- Rf value in diethyl ether: 0.60
Based on these numbers, we can observe that both compounds have higher Rf values in diethyl ether compared to hexane. This suggests that both compounds are more soluble in diethyl ether and have a higher mobility on the TLC plate when developed in this solvent.
Since the goal is to separate compounds A and B, you would want to choose a solvent that provides the greatest difference in their Rf values. In this case, diethyl ether would be a better solvent since it results in a larger difference between the Rf values of compounds A and B (0.16) compared to hexane (0.08).
Therefore, based on the relative polarities and the Rf values of compounds A and B, diethyl ether would be the better solvent for separating the mixture by TLC.