Methods

 

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Lab 705

<~Introduction Results~>

1) Preparing the Extraction Mixture

2) Extracting p-Toluic Acid

3) Extracting p-tert-butylphenol

4) Isolating p-Toluic Acid

5) Isolating p-tert-butylphenol

6) Isolating Acetanilide

7) Measuring Product Mass and Melting Point

 

 

 

 

 

1) Preparing the Extraction Mixture

 

Caution: Acetanilide is toxic and irritating. Tert-butly methyl eather is flammable and irritating. Keep compounds away from flames or any other heat sources. P-tert-butylphenol is corrosive. Prevent any contact what so ever and avoid any inhalation of vapors.

 

            Weight 50-70 mg of acetanilide and 80-120 mg of each of p-toluic acid and p-tert-butylephenol. Record the mass of each of the solids. Place 5 ml of tert-butyl methyl ether into a 15-ml centrifuge tube and add the tree solids into the tube and mix to dissolve.

 

 

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2) Extracting p-Toluic Acid

 

Caution: reactions between sodium hydrogen carbonate (NaHCO3) and acids produce carbon dioxide (CO2) gas, which can result in foaming.

            Add 2ml of 0.5M aqueous NaHCO3 to the ether solution in the centrifuge tube and mix the two layers well. Allow any CO2 gas to escape. Repeat the process several times to get a good separation of layers.

            Support the tube in a beaker or flask and allow the liquids to separate. Confirm the identity of the layers by placing a drop of water under the surface of the first layer and watch where it travels. The layer where it goes is the aqueous layer. Using a pipette carefully remove the aqueous layer and transfer it to a labeled 50 ml beaker.

            Add 1 ml of distilled or DI water to the centrifuge tube and mix. Save this aqueous layer for part 4.

 

 

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3) Extracting p-tert-butylphenol

 

Caution: 0.5M sodium hydroxide (NaOH) is toxic and corrosive, prevent any contact.

 

            Add 2ml of 0.5M NaOH to the ether solution remaining in the centrifuge tube and shake it vigorously. Using a pasture pipette, remove the aqueous layer and transfer it to a clean, labeled 50 ml beaker. Repeat the extraction of the ether layer with a second 2 ml NaOH portion. Remove the second NaOH layer and combine it the first. Repeat with a 3rd 2 ml NaOH portion.

            Add 1 ml of water to the ether remaining in the centrifuge tube and mix it. Remove the aqueous layer and combine it with the three NaOH extracts. Save the NaOH extracts in the 50 ml beaker for part 5. Save the ether layer remaining in the centrifuge tube for part 6.

 

 

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4) Isolating p-Toluic Acid

 

Caution: 3M hydrochloric acid (HCl) is toxic. Prevent any contact. Adding 3M HCl to the NaHCO3 solution will produce CO2, causing foaming to occur.

 

            Select the beaker containing the NaHCO3 extracts from part 2 and add 3M HCl drop wise to the NaHCO3 extracts to precipitate the p-toluic acid. Continue to add the HCl drop wise along with stirring, until no more solid is produced and the solution tests acidic (pH < 3).

            Weigh a filtered paper and record its mass. Using the filter, separate the crystals from the solution using vacuum filtration. After the crystals are separated, place them on a watch glass and allow them to air dry.

 

 

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5) Isolating p-tert-butylphenol

 

            Select the 50 ml beaker containing the NaOH extracts from part 3 and remove and remaining traces of tert-butyl methyl ether. Do this by heating the NaOH solution to about 60°C on a hot plate in a fume hood. Remove the beaker from the hot place and allow it to cool.

            To precipitate p-tert-butylphenol, add 3M HCl drop wise to the cooled solution until it tests acidic. If the phenol separates as oil, cool the mixture in an ice bath to allow the crystals to form. Weigh a filter paper and record its mass. Afterwards, use vacuum filtration to separate the crystals from the solution. Once crystals are separated, place them on a watch glass and allow them to air dry.

 

 

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6) Isolating Acetanilide

 

Caution: Anhydrous sodium sulfate (NaSO4) is irritating and hygroscopic. Prevent eye, skin, and clothing contact.

 

            Select the centrifuge tube containing the ether layer from part 3 and add about 0.5 g of anhydrous NaSO4 to the centrifuge tube to remove any traces of water. Cap the tube and shake it well, then allow it to stand for 5 min. Weigh a 50 ml beaker and record its mass. Decant the dried ether acetanilide solution into the 50 ml beaker, leaving the NaSO4 in the centrifuge tube.

            Evaporate the ether by heating it in a fume hood, in a 50°C sand bath while gently blowing air or nitrogen over it. Avoid over heating. Crystallize the oil residue by cooling the beaker in an ice bath. If needed, scratch the bottom of the beaker with a glass-stirring rod, or add a seed crystal to induce crystallization. Allow the crystals to dry.

 

 

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7) Measuring Product Mass and Melting Point

 

            Measure the mass of each compound when each of them is dry. Also, measure the melting point of each compound, and assess its purity by comparing that melting point with the literature value.

 

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