What are some important uses of TLC in organic chem?
- establish that two compounds are identical
- determine the number of components in a mixture
- determine the appropriate solvent for a column chromarographic separation
- to monitor a column chromatographic separation
- to check the effectiveness of a separation achieved on a column, by crystallization or by extraction
- to monitor the progress of a reaction
what are the advantages from using TLC in the laboratory?
- only small amounts of material are necessary
- material is not wasted
- time efficient
What is the disadvantage from using TLC in the laboratory?
main disadvantage of TLC is that volatile materials can NOT be used. (material will simply evaporate from the TLC plate)
What kind of partitioning technique is TLC?
solid-liquid partitioning technique
What is the mobile phase?
(a.k.a - the eluent or solvent): carries the sample through a solid, backing support
What are some characteristics of the mobile phase in TLC?
- it ascends, and does NOT descend
- generally a liquid, but can also be in a gas phase
What is the stationary phase?
(a.k.a the absorbent): absorbs the mixture compounds dissolved within the mobile phase
What are some characteristics of the stationary phase in TLC?
for TLC it is found coated along the solid, back support
What are the 3 basic steps of running a TLC?
spotting, developing, and visualizing
What are some things you should never do when running a TLC plate?
- don’t apply too much sample
- don’t forget to mark your eluent front
- don’t make initial solvent line higher than the spotted sample
- don’t allow the eluent front to reach the top of the plate
- uncovering your developing chamber
what is retention factor?
“ratio-to-front” distance traveled by substance/distance traveled by solvent front
what affect does water have on the absorbent?
water affects the absorbent activity by occupying polar sites
should plate be hydrated or dehydrated when running a TLC?
plates must be dehydrated by heating in a drying oven
What is visualization in regards to TLC?
compounds separated by TLC more often than not are colorless. In these cases the separated material must be made visible by some reagent or method that makes separated compounds visible
What were the two visualization methods discussed in lab?
Iz crystals and UV lamp
objective
determine a solvent used for separating a mixture of biphenyl, benzhydrol, and benzophenone by thin-layer chromatography. In addition, you will analyze solvent polarity effects on the mobilities of these compounds and learn how to determine their retention factor
