Why is there a direct correlation between the dielectric constant and the Rf value during a...
Why is there a direct correlation between the dielectric constant and the Rf value during a TLC analysis? What is the relationship between the solvent polarity and the Rf values? Why are some solvent mixtures better at separating compounds than others?
Homework Answers
Silica like the one in your TLC plates are pretty polar. So if your molecule that you plate is also polar, it won't travel very far because it is having interactions with the silica and this leads to a lower Rf value. Conversely, if you have something that is not very polar, then it will be expected to travel faster with the solvent front because it is not making many interactions with the silica.
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Why is there a direct correlation between the dielectric
constant and the Rf value during a...
1. When separating mixtures using TLC, why is it important to choose a solvent (mobile phase)...
1. When separating mixtures using TLC, why is it important to choose a solvent (mobile phase) that has a different polarity than the TLC plate (stationary phase)? 2. Why will some substances in a mixture travel farther up the TLC plate than others?
Hi can someone help me with my pre lab theory questions (1,2,3) on rate of elution...
Hi can someone help me with my pre lab theory questions (1,2,3)
on rate of elution or Rf? Here is some background below. Please
help explain as many as possible (1-3)! I dont really get the
relation ships in this lab, thank you!
1. What factors affect the rate of elution in organic compounds? 2. Explain what is the relationship between polarities of compounds (polar/non- polar compound) and rate of elution (Rf). 3. Explain what is the relationship between solvent...
Which compound would have the higher Rf value- Cholesterol or Cholesterol Stearate? Explain why (TLC analysis,...
Which compound would have the higher Rf value- Cholesterol or Cholesterol Stearate? Explain why (TLC analysis, Polarity, etc).
In standard chromatography, a). explain the relationship between polarity of compounds and Rf Value b). predict...
In standard chromatography, a). explain the relationship between polarity of compounds and Rf Value b). predict the change of Rf (retention factor) value when more polar eluent is used
1. When 2-propanol was used as the developing solvent, two substances moved with the solvent front...
1. When 2-propanol was used as the developing solvent, two substances moved with the solvent front (Rf= 1) during TLC analysis on a silica gel plate. Can you conclude that they are identical? If not, what additional experiment(s) would you perform? 2. The Rf value of compound A is 0.34 when a TLC plate is developed in hexane and 0.44 when the plate is developed in diethyl ether. Compound B has an Rf value of 0.42 in hexane and 0.60...
For TLC plate separation, why do we use Rf values instead of distance measurements (e.g. the...
For TLC plate separation, why do we use Rf values instead of distance measurements (e.g. the spot travelled 5 cm from the starting line)? What would happen if we compared solvent systems using distances rather than Rf values?
1. a) Why does biphenyl have a higher Rf value than either benzophenone or triphenylmethanol? Exp...
1. a) Why does biphenyl have a higher Rf value than either benzophenone or triphenylmethanol? Explain based on the structures and their effect on mobility in the TLC process. b) Which compound, benzophenone or triphenylmethanol has a higher Rf value? Explain, based on their structures, how you can predict this. c) You developed your TLC using a 10% mixture of diethyl ether in petroleum ether. Petroleum ether is a mixture of non-polar alkanes, so this TLC solvent is composed of...
I need help with my pre and post lab questions. The three compounds below were spotted...
I need help with my pre and post lab questions.
The three compounds below were spotted on a TLC plate and developed to give the TLC plate shown. Which compound corresponds to which spot? Calculate the Rf value for spot B in the TLC plate shown above. When using polarity to determine the relative rates at which organic compounds travel up the TLC plate, we are considering compounds of similar molecular weight. It should also be noted that Rf values...
Calculate the Rf value compounds X and Y based on below information (X travels 1.0 cm,...
Calculate the Rf value compounds X and Y based on below information (X travels 1.0 cm, Y travels 0.5 cm from origin; the solvent front is 3.0 cm). Comment on the polarity of X and Y (2 points) Name the phase change going on the external surface of the cold finger during sublimation experiment and what is the role of ice-cold water added to the centrifugation tube during the same experiment (2 points)
3. If the TLC plate development had stopped before the solvent front reached the top of...
3. If the TLC plate development had stopped before the solvent front reached the top of the TLC plate (i.e. maybe it reached the middle of the TLC plate when it was stopped, instead): a) Would the Rf values have been affected? If so, how? If not, why not? Give a numerical example to support your answer. b) Would the size of the spots have been affected? If so, how? If not, why not? (Hint: think about the diffusion of...
1. When separating mixtures using TLC, why is it important to choose a solvent (mobile phase) that has a different polarity than the TLC plate (stationary phase)? 2. Why will some substances in a mixture travel farther up the TLC plate than others?
Hi can someone help me with my pre lab theory questions (1,2,3)
on rate of elution or Rf? Here is some background below. Please
help explain as many as possible (1-3)! I dont really get the
relation ships in this lab, thank you!
1. What factors affect the rate of elution in organic compounds? 2. Explain what is the relationship between polarities of compounds (polar/non- polar compound) and rate of elution (Rf). 3. Explain what is the relationship between solvent...
1. When 2-propanol was used as the developing solvent, two substances moved with the solvent front (Rf= 1) during TLC analysis on a silica gel plate. Can you conclude that they are identical? If not, what additional experiment(s) would you perform? 2. The Rf value of compound A is 0.34 when a TLC plate is developed in hexane and 0.44 when the plate is developed in diethyl ether. Compound B has an Rf value of 0.42 in hexane and 0.60...
I need help with my pre and post lab questions.
The three compounds below were spotted on a TLC plate and developed to give the TLC plate shown. Which compound corresponds to which spot? Calculate the Rf value for spot B in the TLC plate shown above. When using polarity to determine the relative rates at which organic compounds travel up the TLC plate, we are considering compounds of similar molecular weight. It should also be noted that Rf values...
Calculate the Rf value compounds X and Y based on below information (X travels 1.0 cm, Y travels 0.5 cm from origin; the solvent front is 3.0 cm). Comment on the polarity of X and Y (2 points) Name the phase change going on the external surface of the cold finger during sublimation experiment and what is the role of ice-cold water added to the centrifugation tube during the same experiment (2 points)
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