Recrystallization of Pure Phthalic Acid, Benzoic Acid and Napthalene

Topics: Chemistry, Benzene, Organic chemistry Pages: 2 (415 words) Published: June 17, 2013
Richard Trinh
TA: Jingy Wang
Experiment #4
Recrystallization of Pure Phthalic Acid, Benzoic Acid and Napthalene Introduction
Recrystallization is a important method in purifying organic compounds which are solid. It is an effective method that is important to be familiar with that is essential in the industrial chemical world. This experiment will allow students to be familiarized with the technique of recrystallization by working with phtalic acid, benzoic acid and naphthalene from appropriate organic solvents. Experimental Method

1. Gather 200mg of phtalic acid, add drop wise with Pasteur pipette. 2. Set up boiling apparatus and cork test tube then clamp when cooling 3. Recrystallize at 22oC in ice, stir with pipette and expel air 4. In test tube add ethanol to remove H2O.

5. Scrape out crystals and determine % recovery.
6. Gather 50mg of Benzoic acid.
7. Recrystallize same method as Phthalic acid
8. Determine percent recovery.
9. Recrystallization of Napthalene, by adding 1.0g of solid. 10. Add 3mL methanol and boiling stone.
11. Heat to boil and add dropwise methanol till it dissolves solid. 12. Cool in ice and filter, was with 30:7 ratio mix of methanol and water. 13. Determine percent recovery.
Chemicals Used
1. Phthalic Acid

2. Benzoic Acid

3. Naphthalene

| Melting Point (oC)| Weight (g)| % Recovery|
Phthalic Acid| 175.5| .35| 67.5|
Benzoic Acid with H2O| 117.5| .045| 95|
Benzoic Acid with Methanol| 118| .12| 24|
Napthalene| 75.5| .23| 22.9|
% recovery = (weight/original weight) x 100%
The melting points for the lab results were quite close to the literature values. The first method of recrystallization was more effective than the 2nd method using methanol. The percent recovery of benzoic acid using water is recorded at a high of 95% recovered. The lower percent recoveries were possibly due the lab errors. The...

References: Nist Chemistry Webook Database
Experimental Organic Chemistry- Laboratory Manual. Solomon W.
Chemical and Physical Properties Database‎
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