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Question

What are three possible improvements to the experiment that you can foresee doing if you were to repeat the experiment (explain why for each case).


What are experimental complications or possible major/minor errors that might be expected to occur (discuss what the effects would be and how you would mitigate it)


Lab Data:

Mass of AlCl3(pre-weighed amount): 150 mg

Mass of Ferrocene: 0.155 g

Mass of crude acetylferrocene product: 0.162 g

Procedure_page-0001.jpgLab 3 tlc.jpg

Lab 3 tlc.jpg
Procedure_page-0001.jpg
Procedure
1. Make sure all glassware is dry for this experiment. Acetyl
11. Extract the mixture with three 3 mL portions of CH2 Cl2.
chloride and aluminum trichloride react violently with water. If
Remember the product is in the lower layer in each extraction.
you need to wash anything, rinse with acetone and put the
Collect the lower layer each time and transfer it to a small beaker
damp glassware in the oven for a few minutes to dry.
or Erlenmeyer flask.
2. Prepare a fresh [email protected] packed drying tube.
12. Dry the combined extracts with anhydrous NazSO4 (~1 g)
3. To the 10 mL round bottomed flask add the pre-weighed portion
contained in a filter pipette. Drain the dried liquid extract to a pre-
(150 mg) of AlCl3. Do this in your fume hoods, as AlCl3
weighed 25 mL round-bottomed flask. Save 50uL of this liquid
generates HCI gas on contact with moist air.
extract in your 0.1 mL v-vial (to perform TLC in the current lab
4. Assemble the apparatus as in Figure 8. Make sure you have
session .
included your stir bar.
13. Evaporate the solvent from the remaining extract on the
rotavap and obtain the weight of the crude product by weighing the
round-bottomed flask. Store the product in your drawer in the
same 25 mL round-bottomed flask for Experiment 4. Your TA must
check your product before storage
Procedure for TLC of the product mixtures:
1. Obtain a TLC plate, capillary tube (mp tube
open at both ends), pencil, rectangular piece
of filter paper, and a TLC developing
Solvent front
chamber (glass jar with lid).
2. Draw a thin, straight line about 0.5cm from
the bottom (on the silica side) of your TLC
plate as shown in the figure to the right.
3. Using the capillary tube apply 1 ul of the
liquid extract saved in your V-vial (reaction
mixture) in lanes 2 and 3 of your TLC plate.
2 2
2
4. Prepare a diluted sample of ferrocene by
diluting a small amount (tip of a spatula) of
Your TLC plate may
look different than this
material in 0.5 mL of CH2Cl2. Then, apply 1
figure. Report exactly
ul of this solution in lanes 1 and 2 of the TLC
what you observe.
plate (as shown in the figure).
5. Pour no more than 0.25 cm of the eluting
3 3
3
solvent (1:1 ether:hexane) into the TLC jar.
Apply sample here
Figure 8: Apparatus for addition and drying.
Line the jar with the filter paper provided.
Insert the plate in the jar and cover the jar.
ane 1. Ferrocene
Don't let the solvent in the beaker touch the
Lane 2. Co-sp
5. In the large, lab fume hoods open the top of the Claisen head
Lane 3. Crude product
and add 2.5 mL of CH2Cl2 (pump dispenser) followed quickly by
spot on the plate or the spot will dissolve
30 uL of acetyl chloride (Eppendorf pipette). Make sure you re-
away into the solvent.
cap the acetyl chloride after use!!
6. The solvent will travel up the plate by capillary action. Remove the
6. Weigh out a 150 mg portion of ferrocene on the analytical
plate when the solvent level is just below the top of the plate. Using
balances and record the exact weight.
your pencil, draw a line on the solvent front and mark the three
7. In your 3 mL V-vial prepare a solution of your weighed ferrocene
spots for the three products (1,2,3) you will observe on your plate.
in 2.5 mL of CH2Cl2. Dissolve the ferrocene completely and add
this solution into your reaction mixture by briefly opening the
7. Draw the plate in your lab notebook and comment on the
septum top of the Claisen head.
separation of compounds by calculating the retention factors (Rf)
8. Note the time and stir the reaction mixture for a period of 20
for the three spots in the solvent system you have chosen to use
minutes.
(1:1 ether:hexane)
9. Open the reaction apparatus (be careful; contains HCI gas) and
transfer the reaction mixture to your plastic centrifuge tube
containing 5 mL of ice-water. The quenching is exothermic and
Waste Disposal
generates HCI gas, so do this as close to your fume hood as
Any aqueous extracts can go down the sink with lots of water. Any
possible.
remaining solvents (methylene chloride, hexane or hexane:ether)
10. Cool the tube in an ice-bath and adjust the pH of the upper
should go into the solvent waste bottle in the hood. Unreacted
aqueous layer to just basic (7-8) using about 0.5 mL of 25%
he should be dissolved in acetone and placed in the
ntainer pr
NaOH (aq.). Pump the mixture in the tube with a pipette
thoroughly to complete the quench of the reaction.

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