6.1: Extraction - Experiment

Equipment and Chemicals

Glassware & hardware

• 125‑mL separatory funnel; ring stand + ring/clamp; two 100‑mL beakers; four 50–125‑mL Erlenmeyer flasks; Pasteur pipets + bulbs; vacuum and gravity filtration setups; watch glasses; 10‑mL graduated cylinder; pH paper; mortar & pestle; ice bath; Melting‑point apparatus, compressed air (optional),closed‑end capillary tubes, lint‑free tissues.

Reagents

• Mixture of benzoic acid, 3‑nitroaniline, naphthalene (~3 g total).
• Diethyl ether (anhydrous).
• HCl: 5% (w/w) for extraction; 6.0 M for neutralization.
• NaOH: 5% (w/w) for extraction; 6.0 M for neutralization.
• Saturated NaCl (“brine”) for washing; anhydrous Na₂SO₄ for drying; cold distilled water.

Experimental Procedure

Conduct all ether handling and acid/base neutralizations in a fume hood. Vent the separatory funnel frequently and point away from yourself/others. 

Part I — Sequential Acid–Base Extraction

1. Set up & PPE. Put on splash goggles and gloves. Inspect the separatory funnel for leaks with a brief water test; drain and dry. 
2. Dissolve the mixture. Accurately weigh ~3.000 g of the solid mixture (±0.001 g). Transfer to a 100‑mL beaker and dissolve in 50 mL diethyl ether with gentle swirling. Caution: extremely flammable—no flames or hot plates; use a steam bath only when instructed. 
3. Load the sep funnel. Transfer the ether solution to the 125‑mL separatory funnel. Add 50 mL of 5% HCl. Cap, invert, and vent immediately. Gently shake for ~30 s, venting every few seconds. Place the funnel in the ring and allow full separation; uncap while standing. 
4. Split layers. Drain the lower aqueous (acidic) layer (contains protonated 3‑nitroaniline, $\mathrm{RNH_3^+}$) into a labeled Erlenmeyer (“Aqueous‑Acidic”). Return the upper ether layer to the funnel. 
5. Recover the amine. Cool the acidic extract in an ice bath. With stirring, basify dropwise using 6.0 M NaOH to pH > 9 (pH paper). Collect the precipitated 3‑nitroaniline by vacuum filtration on pre‑weighed filter paper; rinse with cold water; dry on the funnel, then on a watch glass. Record masses for percent recovery. 
6. Extract the acid. To the saved ether layer, add 50 mL of 5% NaOH. Shake/vent as before. Drain the lower basic aqueous layer (contains benzoate, $\mathrm{RCO_2^-}$) into a labeled Erlenmeyer (“Aqueous‑Basic”). Keep the ether layer in the funnel. 
7. Recover carboxylic acid. Ice‑cool the basic extract; acidify carefully with 6.0 M HCl to pH < 2. Collect the precipitated benzoic acid by vacuum filtration on pre‑weighed filter paper; rinse with cold water; dry thoroughly. Record masses. 
8. Wash the neutral fraction. To the ether layer (now enriched in naphthalene), add 50 mL saturated NaCl (brine); shake/vent; allow separation; discard the lower aqueous brine appropriately. Dry the organic phase over ~1 g anhydrous Na₂SO₄ (swirl ~10 min). Gravity filter the dried ether solution.
9. Remove solvent safely. In the hood, evaporate ether on a steam bath or with gentle air flow—never near an ignition source; do not leave unattended. Dry the naphthalene residue to constant mass and record.

Part II — Melting Temperature Determination

10. Sample prep. Finely powder each isolate; fill a closed‑end capillary to ~3–4 mm. 
11. Instrument setup. Confirm the Melt Station control dial is set to Off; connect power and the interface (LabQuest/Graphical Analysis). Insert the capillary into a slot. clear‑point to define the melting range. Cool between runs using the Fan/Cooling setting. Record ranges for each compound. 
12. Dispose of used capillaries in sharps as directed.