Experiment 6 Flashcards

1
Q

What are some important uses of TLC in organic chem?

A
  • 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
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2
Q

what are the advantages from using TLC in the laboratory?

A
  1. only small amounts of material are necessary
  2. material is not wasted
  3. time efficient
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3
Q

What is the disadvantage from using TLC in the laboratory?

A

main disadvantage of TLC is that volatile materials can NOT be used. (material will simply evaporate from the TLC plate)

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4
Q

What kind of partitioning technique is TLC?

A

solid-liquid partitioning technique

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5
Q

What is the mobile phase?

A

(a.k.a - the eluent or solvent): carries the sample through a solid, backing support

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6
Q

What are some characteristics of the mobile phase in TLC?

A
  • it ascends, and does NOT descend

- generally a liquid, but can also be in a gas phase

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7
Q

What is the stationary phase?

A

(a.k.a the absorbent): absorbs the mixture compounds dissolved within the mobile phase

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8
Q

What are some characteristics of the stationary phase in TLC?

A

for TLC it is found coated along the solid, back support

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9
Q

What are the 3 basic steps of running a TLC?

A

spotting, developing, and visualizing

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10
Q

What are some things you should never do when running a TLC plate?

A
  • 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
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11
Q

what is retention factor?

A

“ratio-to-front” distance traveled by substance/distance traveled by solvent front

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12
Q

what affect does water have on the absorbent?

A

water affects the absorbent activity by occupying polar sites

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13
Q

should plate be hydrated or dehydrated when running a TLC?

A

plates must be dehydrated by heating in a drying oven

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14
Q

What is visualization in regards to TLC?

A

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

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15
Q

What were the two visualization methods discussed in lab?

A

Iz crystals and UV lamp

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16
Q

objective

A

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