Experiment 4A + 4B
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Madison Karpinski
Chemistry 2203, Section 7
Lab Performed February 1, 2023
Experiment 4A: Determining the Partition Coefficient for Benzoic Acid in Methylene
Chloride Water mixture
Experiment 4b Determining the partition coefficient for Benzoic Acid in a Methylene
Chloride, Sodium Bicarbonate mixture.
Objective:
Using Benzoic acid as a substrate we will find it partition coefficient. The first part
will consist of finding the partition coefficient for Benzoic acid with methylene chloride and
water added. The second part will be finding the partition coefficient for Benzoic acid in a
methylene chloride and sodium bicarbonate mixture. Each part will facilitate the practice of
understanding the importance intermolecular forces play in the solubility process and the
partition. This experiment also focuses on various techniques crucial to extractions which play a
pivotal role in organic synthesis,
Experimental Procedure:
1.
Using 75 mg of Benzoic acid and 1 mL of both water and methylene chloride add each
component to one 20 mL separatory funnel.
2.
Combine the mixture by shaking or using a vortex mixture until the benzoic acid
dissolves
3.
Let the two layers separate so that the aqueous layer lays on the top and the organic layer
stays at the bottom.
4.
Extract the bottom layer into a test tube by turning the funnel’s tap so the liquid slowly
drips out, make sure no aqueous solution is mixed in
5.
Add Anhydrous sodium sulfate into the test tube until any excess water in the test tube is
soaked up
6.
After Anhydrous sodium sulfate is added and water is not present in the test tube, remove
the sodium sulfate from the tube by filtering the methylene chloride through a glass
pipette with a small amount of cotton inside.
7.
Add a boiling stone to a new test tube; tare the weight of test tube with boiling stone
8.
Add the extracted organic layer to the test tube and place the tube in a heater block to
remove methylene chloride
9.
Take the test tube out of the heater block every few minutes to record the changed weight
of the product
10.
Once weight of test tube becomes constant use the final weight to derive the partition
coefficient for benzoic acid.
11.
Repeat the first 10 steps described above but use 1mL of Sodium Bicarbonate instead of
water and a 5mL conical vial instead of a 20 mL separatory funnel.
12.
The partition coefficient for benzoic acid may be determined by the ratio of the organic
layer over the aqueous layer
Reaction Scheme:
Data:
Compounds
Benzoic Acid
Sodium
Bicarbonate
Water
Methylene
Chloride
Formula
C
6
H
5
COOH
NaHCO
3
H
2
O
CH
2
Cl
2
Mass
75 mg
1 mL
1 mL
1 mL
Moles
0.41 mmol
Molar Mass
122.13 g/mol
84.007 g/mol
18.02 g/mol
84.93 g/mol
Density
1.0 g/mL
1.33 g/mL
Boiling Point
100 C
40 C
Melting Point
122 C
Part 4A
Benzoic Acid Used
0.078 g
Weight of Test Tube + stone + solid
8.648 g
Initial weight of Test Tube + stone
8.586 g
Part 4B
Benzoic Acid used
0.077 g
Weight of Test Tube + Stone
10.192 g
Weight of Test Tube + Stone +Solid
10.213 g
Observations:
-
Benzoic acid is colorless unlike 9-fluorenone
-
More difficult to distinguish the separate layers in a separatory funnel versus a conical
vial
-
When the Benzoic acid dried it crystallized
Calculations:
1.
Benzoic acid in CH
2
Cl
2
= (final weight of vial + boiling stone + solid) – (weight of vial +
boiling stone)
Part 4A Benzoic Acid in CH
2
Cl
2
= (8.648 g) – (8.586 g) = 0.062 g
Part 4B Benzoic Acid in CH
2
Cl
2
= (10.213g) – (10.192 g) = 0.021 g
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1st Answer:
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