Experiment 6: Isolation of Essential Oils via Steam Distillation

Question 1

If the compounds shown in the table below were separated by column chromatography with ether on silica gel, which would elute first?
Benzyl alcohol - 0.10 Rf (Retardation Factor)
Benzyl acetate - 0.26 Rf
p-nitrophenol - 0.23 Rf
1-naphthalene-methanol - 0.40 Rf

Answer 1

1-naphthalenemethanol

Question 2

Which of the following statements regarding steam distillation is true?

Answer 2

Steam distillation is often chosen because the compound you want to purify by distillation has a high boiling point and might actually decompose if simple or fractional distillation is attempted.

Question 3

The hexane solution from the spinach extraction contained a number of different plant pigments (and possibly other organic substances). To observe the components in the hexane solution, a sample of the solution was subjected to thin layer chromatography (TLC). Which of the following statements is true?

Answer 3

A less polar component had a larger Rf value than a more polar component.

Question 4

! If you were to perform TLC on a mixture of plant pigments & none of the pigments moved from the baseline (i.e. Rf = 0 for all components), what adjustment would you make to the mobile phase before running the TLC again?

Answer 4

Make the mobile phase more polar by changing the ratio of polar : nonpolar solvent (increase the amount of polar solvent)

NOT to make the mobile phase less polar

Question 5

! If all of the pigments of the TLC plate travelled to the top of the plate, what would be the best adjustment to make before running the TLC again?

Answer 5

Make the mobile phase less polar by changing the ratio of polar : nonpolar solvent (increase the amount of nonpolar solvent)

NOT to make the mobile phase more polar

Question 6

Q 6 + 9 of Lab 6 Uria

Answer 6

see Q

Question 7

A student ran a silica gel gravity column on a mixture of an alcohol and a ketone using hexane and ethyl acetate (9:1) as the solvent system. Which compound eluted first off the column and why?

Answer 7

ketone eluted first, because it is less polar than the alcohol

Question 8

Once you have collected your distillates, you next need to separate your cinnamaldehyde or eugenol from the water. How will you do this?

Answer 8

extract the product into dichloromethane (DCM)

Question 9

The liquid-liquid extraction is done. The organic solvent used is dichloromethane (DCM). When DCM (d = 1.33 g/mL) is mixed with water (d = 1.00 g/mL), what will be seen? (how many layers; which layer on top)

Answer 9

There will be 2 layers: the top will be water, as water is less dense than DCM.

Question 10

The hexane solution from the spinach extraction contained a number of different plant pigments (and possibly other organic substances). To observe the components in the hexane solution, a sample of the solution was subjected to thin-layer chromatography (TLC). Which of the following statements is true?

Answer 10

A less polar component had a larger Rf value than a more polar component.

Question 11

In last week’s experiment, the hexane solution from the spinach extraction contained a number of different plant pigments (and possibly other organic substances). To observe the components in the hexane solution, a sample of the solution was subjected to thin layer chromatography (TLC). Which of the following best describes the TLC experiment? (Which is the mobile phase and is it polar or not?)

Answer 11

Hexane was the mobile phase and the mobile phase was nonpolar.

Question 12

7 of Nick’s Lab Steam Distillation Quiz

Answer 12

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Question 13

What is the purpose of adding anhydrous sodium sulfate to the dichloromethane extract before evaporating the solvent under vacuum?

Answer 13

to remove any water that remained in the dichloromethane extract