Single Base Extraction

Experiment #3: Single Based Extraction

I. Introduction:

The purpose of this lab is to separate a mixture of two compounds using acid-base extraction. The separation by extraction is based on differing solubilities of compounds in two immiscible liquids. The mixtures available for this lab contained a neutral compound and a carboxylic acid. The neutral compounds are benzophenone (Melting point 48-49 ⁰C), 1, 4-dimethoxybenzene (Melting point 58-59 ⁰C), biphenyl (Melting point 71-72 ⁰C), naphthalene (Melting point 81-82 ⁰C), or phenanthrene (Melting point 99-100 ⁰C). The carboxylic acids are benzoic acid (Melting point 121-122 ⁰C) or salicylic acid (Melting point 157-159 ⁰C). These compounds

II. Experimental:

1. Dissolve 2 g of unknown compound in 30 ml of ether in Erlenmeyer flask.

2. Clean separation funnel (shown on left) using acetone. Make sure the valve is closed then pour acetone in funnel. Fasten funnel with cap. Hold cap in between fingers to make sure the funnel is closed, then swirl acetone around entire funnel (turning funnel over). Pour out acetone. Then transfer ether to separation funnel making sure the valve is closed.

3. Extract your solution with 15 ml 10% NaOH. Swirl funnel around and upside down. Open valve occasionally to let out gas. Once extraction is complete, you should see clear line between both compounds. Drain off lower aqueous layer into fresh beaker labeled "base extract."

4. Add 2nd portion of 15 ml 10% NaOH and repeat step 3, adding the lower layer of the solution into the beaker labeled "base extract."

5. Transfer upper organic layer to clean Erlenmeyer flask and label "neutral organic." Add two scoops of drying agent (anhydrous sodium sulfate) and let stand.

6. Neutralize you "base extract" using 3 M HCl until acidic on pHydrion paper. A precipitate should form. Then cool for 15 minutes.

7. Do filtration of crystals ("base extract") formed using Buchner-funnel. Using Erlenmeyer flask with side arm connect suction tube to vacuum in hood. Place Buchner Funnel on top of flask. Add a filter paper disk to funnel. Pour contents of flask (with crystals) into Buchner Funnel.

8. Keep suction filtration going for some time, transfer to watch glass to let dry.

9. Transfer "neutral organic" into 100 ml beaker using funnel with cotton swab. Evaporate ether in hood using slow stream of air through dry tubing into beaker.

10. Scrape the solid residue onto watch glass.

11. When dry, weigh each compound, determine percent recovery

12. Take