CHEM 241L University of Nevada Organic Chemistry Lab Hello, please use the attachments provided to complete the lab report template that is also attached.
CHEM 241L University of Nevada Organic Chemistry Lab Hello, please use the attachments provided to complete the lab report template that is also attached. You will use the data that’s given. Please also include the graph in the template and follow the guidelines exactly. Thank you! Experiment #3-2:
Extraction (micro-scale)
INTRODUCTION
The process of liquid-liquid extraction involves the distribution of a compound (solute) between
two solvents that are immiscible (insoluble) in each other. Generally, although not always, one
of the solvents in an extraction is water and the other is a much less polar organic solvent, such
as diethyl ether, ethyl acetate, hexane, or dichloromethane. By taking advantage of the differing
solubilities of a solute in a pair of solvents, compounds can be selectively transported from one
liquid phase to the other during an extraction.
A generalized micro-scale extraction process that uses a conical vial is illustrated in Figure 1. The
first solvent contains a mixture of black and white molecules (Figure 1A). A second solvent that
is not miscible with the first is added. After the vial is capped and shaken, the layers separate. In
this example, the second solvent is less dense, so it becomes the top layer (Figure 1B). Because
of differences in physical properties, the white molecules are more soluble in the second solvent,
whereas the black molecules are more soluble in the first solvent. Most of the white molecules
are in the upper layer, but there are some black molecules there, too. Likewise, most of the black
molecules are in the lower layer. However, there are a few white molecules in this lower phase.
A Pasteur pipette may be used to remove the lower layer (Figure 1C). In this way, a partial
separation of black and white molecules has been achieved. In this example, notice that it was
not possible to effect a complete separation with one extraction. This is a common occurrence in
organic chemistry. Many organic substances are soluble in both water and organic solvents.
Figure 1. The extraction process.
1
O
O
OH
benzoic acid
+
9-fluorenone
1. 2 mL diethyl ether
2. 5% NaOH (aq)
3. separate
4. repeat
Organic layer
Aqueous layer
O
O
9-fluorenone
still dissolved
in diethyl ether
benzoic acid
became a salt,
which is highly soluble
in water
O
Na
sodium benzoate
1. wash with sat. NaCl (aq)
2. separate
3. dry with Na2SO4
4. evaporate diethyl ether
1. 6 M HCl (aq)
2. vacuum filtration
3. air-dry
O
O
sodium benzoate
became
bezoic acid by
addition of HCl
9-fluorenone
OH
sodium benzoate
Determine the mass recovery
Determine the mass recovery
Figure 2. Separation of 9-fluorenone and benzoic acid by extraction.
When an organic compound is distributed between an organic solvent and water, the ratio of
solute concentration in the organic solvent, C1, to its concentration in water, C2, is equal to the
ratio of its solubilities in the two solvents. The distribution of an organic solute, either liquid or solid,
can be expressed by
K=
??1
??2
=
g compound per mL organic solvent
g compound per mL water
K is defined as the distribution coefficient, or partition coefficient. The magnitude of K gives an
2
indication of the efficiency of extraction: the larger the value of K, the more efficient the extraction.
If K is 1, equal amounts of the compound will dissolve in each of the phases. If K is much smaller
than 1, the compound is more soluble in water than the organic solvent C1.
If the distribution coefficient K of a solute between water and an organic solvent is large, a single
extraction may suffice to extract the compound from water into the organic solvent. Most often,
however, the distribution coefficient is less than 10, making multiple extractions necessary.
In the following experiment you will separate a two component mixture, benzoic acid (acidic
compound) and 9-fluorenone (neutral compound), using acid-base reaction and extraction
technique. At the end of the experiment, your extraction technique will be evaluated by performing
TLC technique. Figure 2 shows the flow chart of todays extraction.
PROCEDURE (experiment video, https://youtu.be/u9bQhF-57Qk)
Part A. Separation of organic and aqueous layers.
1. Place 100 mg (0.1 g) of benzoic acid and 100 mg (0.1 g) of 9-fluorenone in a 5 mL
conical vial with a spin vane.
2. Add 2 mL of diethyl ether into the 5 mL conical vial, and stir (spin) to dissolve the
compounds.
3. Transfer 1 or 2 drops of this solution in a clean test tube, and label it as a mixture.
Note: This sample will be used for TLC at the end of the lab period.
4. Place the conical vial on a hot plate with an aluminum block.
5. Add 1 mL of 5% NaOH (aq) solution to the conical vial and stir (spin) the mixture
vigorously for 1 minute on the hot plate.
6. Let the layers separate in the vial and transfer the aqueous layer (the bottom layer,
why?) into a 25 mL Erlenmeyer flask (Figure 3).
7. Repeat the procedure 5 & 6 one more time.
Note: diethyl ether (organic layer) is very volatile solvent, and it will evaporate quickly
during the extraction process. If the volume of the organic layer is less than 2 mL in
the conical vial, you should refill it and keep its volume 2 mL during this process.
8. Label the 25 mL Erlenmeyer flask as aqueous layer and the 5 mL conical vial as
organic layer.
Figure 3. Separation of aqueous layer.
3
Part B. Isolation of 9-fluorenone from the organic layer
1. Remove the spin vane by using tweezers from the 5 mL conical vial.
2. Add a small amount (about a half tip of a spatula) of anhydrous Na2SO4 and swirl using
a spatula. If Na2SO4 in the conical vial clumps, add more Na2SO4 until it doesnt.
Note: If you added too much Na2SO4 or the organic layer was dried out, consult your
instructor.
3. Prepare a Pasteur filter pipette by placing a small cotton ball inside a Pasteur pipette,
and clamp it to a ring stand.
4. Filter the organic layer solution through the Pasteur filter pipette and collect it in a preweighed 3 mL conical vial with a boiling chip.
5. Rinse down the Pasteur filter pipette with 0.5 ~ 1 mL of fresh diethyl ether and collect
in the same vial.
Note: you can place a rubber bulb on the top of the Pasteur filter pipette and squeeze
it to drain all organic layer solution.
6. Place the 3 mL conical vial containing your filtered organic layer in a warm water bath
in the fume hood, and evaporate the solvent (diethyl ether) completely.
7. Cool down the vial and determine the mass recovery of 9-fluorenone.
Part C. Isolation of benzoic acid from the aqueous layer.
1. Place the 25 mL Erlenmeyer flask containing the aqueous layer in an ice both.
2. Slowly add 6 M HCl (aq) drop-wise to the 25 mL Erlenmeyer flask using a pipette.
3. Keep adding 6M HCl (aq) until the aqueous solution becomes acidic (checked by blue
litmus papers).
4. Stir the aqueous solution and let it stand in the ice bath for 5 minutes.
5. Prepare a vacuum filtration as shown in the demo.
6. Turn on the vacuum and wet the filter paper with water.
7. Filter the solution and collect the precipitates.
8. Keep the vacuum on for at least 10 minutes to dry the precipitates.
9. Collect the solid and determine the mass recovery.
Part D. TLC
1. Prepare TLC samples for the mixture (from the beginning of the extraction), the
recovered 9-fluorenone, and the recovered benzoic acid.
2. Calculate Rf values and record in your notebook.
4
Notes for the Template:
1.
2.
Do not turn in this first page (which is this page you are looking
at now).
Remove all text inside of the parenthesis as well as the example
paragraphs. Your final write-up shouldnt contain any parenthesis
except for the ones you choose to add. There will be point
deduction if you still have them in your final, submitted draft.
NAME: (your name)
CHEM 241L
SECTION #: (your section #)
UNLV 2020 Summer Session II
EXTRACTION
PURPOSE
(Specifically state the purpose of the experiment and evaluation methods in a few
sentences.)
Example:
The purpose of this experiment is to separate hexane and toluene from a mixture by distillation using
Hickman Still apparatus. After isolation of each component, gas chromatography is used to evaluate the
efficiency of the Hickman distillation technique performed.
PROCEDURE
(Write a paragraph of the detailed experimental procedure including observation in 3rd
person past tense from the experiment video. In this report, do not copy and paste the
lab manual procedure. See the following example for your understanding.)
Example:
316 mg of ferrocene (1.7 mmol) and 2 mL of acetic anhydride were placed in a 10 mL of round-bottom flask,
to this mixture, 10 drops of 85% phosphoric acid was added slowly with stirring. A water-cooling condenser
was attached, and the mixture was heated for 20 minutes in a 90 ?C water bath. After cooling down, 1.0 mL
of ice-cold water was added dropwise to the reaction mixture. The diluted mixture was poured into a 50 mL
beaker containing about 10 g of ice. The mixture was neutralized by adding approximately 5 g of solid
sodium bicarbonate (about 0.25 g at a time) until the CO2 stops bubbling off and pH = 5 6 with the pH
paper testing. The crude solid product was collected by vacuum filtration and washed thoroughly with cold
water. After determining the mobile phase by TLC, the crude product was purified by column
chromatography using ethyl acetate/hexane (1:9, v/v).
DATA/RESULTS
(Record all collected and calculated data from the experiment video. Fill all necessary
values in the table.)
? 9-FLUORENONE
Initial mass
(g)
Mass of
3 mL conical
vial + boiling
chip
Mass of
3 mL conical
vial + boiling
chip +
recovered
crystals
Mass of
recovered
crystals
% Recovery
Mass of
3 mL conical
vial + boiling
chip +
recovered
crystals
Mass of
recovered
crystals
% Recovery
? BENZOIC ACID
Initial mass
(g)
Mass of
3 mL conical
vial + boiling
chip
? TLC
Spots
Benzoic acid
(mixture sample)
9-Fluorenone
(mixture sample)
Purified
benzoic acid
Purified
9-fluorenone
Cf
Sf
Rf
CONCLUSION
(This is the section in which you interpret the data obtained in the previous section. It
demonstrates that you understand and can interpret the data you have collected. Interpret
the data obtained, observations, graphs, etc. and compare with literature sources where
necessary. Relate the experimental results to the theory discussed in the introduction.
This section also addresses the yield and purity of products and possible sources of error
that may have influenced these results.)
Post-Lab Questions
1. Define Good extraction solvent.
2. What characteristic must the solvents in a liquid-liquid extraction solvent system
share with one another?
3. What technique could be used to assess the purity of the recovered compounds in
the extraction lab if TLC was unavailable? Explain how the technique you chose
provides information about the purity.
4. Why benzoic acid showed a smaller Rf value than 9-fluorenone in the TLC result?
Explain thoroughly for full credit.
EXP 3-2
EXTRACTION
UNLV CHEM 241L SUMMER 2020
EXTRACTION:
Introduction
Read the INTRODUCTION section in the provided lab manual.
Understand the basic concept of extraction
Review the polarity concept from the previous lab (solubility and solution) if necessary
EXTRACTION :
Introduction
Extraction
? separation/purification process
? separation of compounds based on relative solubilities in two different immiscible solvents
? usually water (aqueous layer) and less polar organic solvents (organic layer) such as diethyl
ether, ethyl acetate, or dichloromethane are used
? density determines the position of each layer
EXTRACTION :
General Method
Dissolve in solvent
Add immiscible
solvent & mix
Separate layers
Remove solvents
O
O
OH
EXTRACTION:
Flow Chart
benzoic acid
+
9-fluorenone
1. 2 mL diethyl ether
2. 5% NaOH (aq)
3. separate
4. repeat
Organic layer
Aqueous layer
O
O
9-fluorenone
still dissolved
in diethyl ether
benzoic acid
became a salt,
which is highly soluble
in water
1. wash with sat. NaCl (aq)
2. separate
3. dry with Na2SO4
4. evaporate diethyl ether
Determine the mass recovery
Na
sodium benzoate
1. 6 M HCl (aq)
2. vacuum filtration
3. air-dry
O
9-fluorenone
O
O
sodium benzoate
became
bezoic acid by
addition of HCl
OH
sodium benzoate
Determine the mass recovery
EXTRACTION:
Experimental Ideal separation
The purity of each compound is determined by
TLC (eluent =10% ethyl acetate: 90% hexane)
A = initial mixture
? both 9-fluorenone and benzoic acid are visible
B = separated 9-fluorenone
? only one spot is visible
C = separated benzoic acid
? only one spot is visible
EXTRACTION:
Experimental Ideal separation
The purity of each compound is
determined by TLC
A = initial mixture
? both 9-fluorenone and benzoic acid
are visible
B = separated 9-fluorenone
? both 9-fluorenone and benzoic acid
are visible
C = separated benzoic acid
? only one spot is visible
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