Name(s):
Date: Feb. 3, 2011
Title: Expt. 2: Recrystallization of Acetanilide
Purpose:
The two new techniques, recrystallization and melting point determination will be used to purify
an impure sample of acetanilide and assess the results. A proper recrystallization solvent will be
selected based on the criteria outlined in the lab manual. Melting point and Percent Recovery
will be used to determine the success of the recrystallization.
Physical Properties:
Substance
Structure
(g/mol) Constant
C8H9NO
135.17
N/A
304
113-115
H2O
18.0
78.5
100
0
C2H6O
46.07
24.3
78
-114
O
C3H6O
58.08
20.7
56
-94
H H
CH2Cl2
84.93
9.1
40
-97
C4H8O2
88.11
6.0
77
-84
C6H14
86.18
2.0
67-69
-95
O
H
Ethanol (95%)
Ethyl acetate
N
H
O
CH3
H
OH
Acetone
Dichloromethane
Dielectric BP (°C) MP (°C)
Formula
Acetanilide
Water
Molecular MW
Cl
O
Cl
O
Hexanes
Solubility Data for Acetanilide (Merck Index)
Solubility Data: 1g/185 mL H2O at rt, 1g/20 mL boiling H2O
1 g acetanilide in the following: 3.4 mL EtOH at rt, 0.6 mL in boiling EtOH,
3 mL MeOH, 3.7 mL CHCl3, 4 mL acetone, very sparingly soluble in Petroleum ether
References:
1. CHM 235 Spring 2011 Lab Manual from Dr. Halligan titled “Experiment 2:
Recrystallization of Acetanilide,” pp. 16-26.
2. Sigma Aldrich Online Catalog: http://www.sigmaaldrich.com/
Diagrams:
Figure 2.2: Vacuum filtration using a Buchner Funnel
Figure 2.2
Mel-Temp apparatus
Experimental Procedure:
1. Prepare a melting point capillary tube for crude acetanilide and set aside.
2. Obtain six test tubes and place approximately 20 mg of crude acetanilide in each.
3. Add the following six solvents (1 mL each): 95% ethanol, acetone, dichloromethane,
ethyl acetate, hexane and water were added to the test tubes.
4. Record result of dissolution at room temperature for each sample after swirling.
5. Heat those that did not dissolve in the solvent at room temperature in a boiling water bath
for a few minutes.
6. Record dissolution of the solid when heated for each sample.
7. Place the heated test tubes in an ice bath and note those that crystallize.
8. Verify a suitable recrystallization solvent with the instructor.
9. Mass the remaining crude acetanilide and place into a clean 125-mL Erlenmeyer flask.
10. Recrystallize this sample with water.
11. Use decolorizing charcoal to remove the color impurities.
12. After heating with charcoal for a few minutes, add two spatula tipfuls of celite to aid in
the removal of the charcoal.
13. Filter the hot mixture through fluted filter paper to retain the charcoal and the celite.
14. Cool the filtrate to room temperature slowly.
15. Clamp the sample in an ice bath to complete crystallization.
16. Collect the pure acetanilide on a Buchner funnel by vacuum filtration.
17. Rinse the filter cake (crystals) with two small portions of ice-cold water and dry.
18. Note appearance of the recrystallized acetanilide.
19. Record the mass of the recrystallized product.
20. Calculate Percent Recovery.
21. Obtain the melting point of the recrystallized and crude acetanilide products.\
Calculations:
observed mass of pure acetanilide
Percent Reocvery =
X 100%
initial mass of impure acetanilide
Data Checklist:
Solvent
Dissolved at rt
Dissolved w/ heat
Crystallized w/ ice
Water
Ethanol (95%)
Acetone
Dichloromethane
Ethyl acetate
Hexanes

Recrystallized product appearance:

Recrystallized Product mass:

Crude acetanilide melting point:

Recrystallized acetanilide melting point:
Post-Lab Questions:
1. Why is it important to warm the fluted filter paper and Erlenmeyer flask with hot solvent
before filtering the dissolved acetanilide solution?
2. How successful was your purification of acetanilide? What data helps support your
conclusion and how?
3. How does an impurity affect the melting point of a solid?