Liquid-Liquid Extraction

Understand extraction as a separation technique that uses immiscible two-phase systems (organic and aqueous) to separate dissolved compounds based on solubility and polarity differences.

Assemble a ring stand with support, place the separatory funnel securely in the ring, grease the stopper and stopcock if needed, and test the stopcock with water to verify no leaks and proper operation.

Transfer the benzoic acid and 2-methoxynaphthalene mixture in diethyl ether to the separatory funnel using a conical funnel, ensuring complete transfer by rinsing the beaker. Add 30 mL of 1 molar sodium hydroxide to deprotonate benzoic acid and form sodium benzoate.

Invert the funnel and gently swirl for 10 seconds at a time while holding the stopper, then vent gases by opening the stopcock in the inverted position. Repeat until no hissing sound occurs, indicating the acid-base reaction is complete.

Allow the funnel contents to settle back in the ring stand, then carefully open the stopcock to drain the aqueous layer into a clean flask while watching the interface closely. Pour the top organic layer through the funnel opening into a separate flask.

Add sodium sulfate drying agent to the organic layer until the solid clumps and the solution is clear. Perform gravity filtration to separate the drying agent, then evaporate the ether solvent on a hot plate to obtain pure 2-methoxynaphthalene residue.

Add approximately 5 mL of 6 molar hydrochloric acid to the aqueous layer, monitoring with litmus paper until pH reaches around 2 to ensure complete protonation. Cool in an ice bath if needed to encourage benzoic acid precipitation.

Use vacuum filtration to collect the precipitated benzoic acid solid on a Buchner funnel, then allow it to dry on the bench before transferring to an oven for complete dryness if necessary.