Lab 14

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Michael Abreu
Lab Partners: Marcela Cataño, Destiny Bosco, Uyen Le
Organic Chemistry 2423
Houston Brown
Dates Performed: 11/01/12, 11/06/12, 11/08/12

Extraction of Benzoic Acid and Naphthalene

Introduction and Purpose

Extracting compounds from one another is very similar to recrystallization. While both are these are done in organic chemistry, extraction is different because it uses immiscible solvents that form layers in the end. What this means is that when one of the solids is extracted, the contaminants stay in the test tube, and the solvent that is sought- after is pulled out of the test tube using a pipette. This occurs because both the solvent and contaminant are pulled apart by a chemical compound such as sodium bicarbonate. In this lab Benzoic Acid and Naphthalene are used and needed to be separated. From understanding this information, I believe that if I use a chemical compound to separate the Benzoic Acid and Naphthalene, I should get good separation and be able to distinguish both of the compounds by finding their melting points separately.

Materials

Benzoic Acid
Naphthalene
Test Tube
Analytical Balance
Tert Butyl Methyl Ether (MTBE)
Sodium Bicarbonate
Pasteur Pipette
HCl
Heating Plate
Hirsch Funnel
Anhydrous Calcium Chloride (pellets)

Procedure

Separation of Naphthalene from Benzoic Acid

In 1st reaction tube, dissolved .27 grams of Naphthalene/Benzoic Acid mixture into 3 ml of MTBE. 1.5 ml of saturated sodium bicarbonate was added to the reaction tube. The Benzoic Acid reacted with the sodium bicarbonate and formed a water-soluble Benzoic Acid salt. The contents of the tube were mixed by and the two layers were put into a pasteur pipette and discharged back and forth into the test tube for 3 minutes. The layers separated completely. The bottom layer was the water and as well as the sodium bicarbonate. The bottom layer was removed with a pasteur pipette and placed in reaction tube 2. .25 ml of sodium bicarbonate was added to reaction tube 1 and mixed as before. The bottom layer was removed again and was put into reaction tube. .3 ml of MTBE was added to reaction tube 2. The top layer of ether was removed and discarded. [pic]

Isolation of Benzoic Acid

In drop-wise addition, HCl was added to reaction tube 2. The reaction was complete when there was no fizzing after addition of HCl. This turned the benzoic acid salt back to Benzoic Acid. Heating plate was used and the test tube 2 was heated to bring back the solid benzoic acid into solution. The tube was then cooled using ice. Crystals were formed after icing the tube and the crystals were collected using a Hirsch funnel. The crystals were washed using ice water. The crystals were let to dry in the Hirsch funnel and the crystals were collected and then weighed.

Isolation of Naphthalene

Added anhydrous calcium chloride pellets one by one (added until pellets didn’t clump) into reaction tube 1 to remove small drops of water. The MTBE solution was taken off from the drying pellets with a Pasteur pipette and was put into a tared test tube. The pellets were washed with a small amount of MTBE which ensured a complete transfer. The solvent was then placed in a warm water bath and evaporated. The mass of the crude product and melting point was determined. All results were written down in lab book.

The percent yield was calculated and compared to the original composition percentage.

Data

Mass of Benzoic Acid/Naphthalene mixture: .273 grams

Mass of Benzoic Acid after Extraction: .213 grams
Mass of Naphthalene after Extraction: .193 grams
[pic][pic]
(Finish)Boiling Point of Benzoic Acid: 123.2 Celsius
(Finish)Boiling Point of Naphthalene: 86.2 Celsius

Percent Yield: Benzoic Acid: 78%
Naphthalene: 71%

Results

From the results obtained from the lab we concluded that the mass of Benzoic Acid after the extraction was .213 grams and for Naphthalene it was .193 grams. The mass of both of those came out...
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