Liquid-Liquid Extraction

Topics: Solubility, Chemistry, Benzene Pages: 2 (645 words) Published: February 11, 2013
Experiment 3 Liquid-Liquid Extraction Discussion

The success of extracting each compound out of the solution can be seen in the IR graphs for each substance. For ethyl 4-aminobenzoate, the N-H, C=O and C-O are distinguishable in their proper wavenumber positions. The amino N-H stretch was found between 3224 cm-1 and 3423 cm-1. The C=O was found at 1681 cm-1 and the C-O was at 1280 cm-1. The IR for benzoic acid also displays its significant bonds, O-H and C=O. The O-H was between 2566 and 3222 cm-1 and the C=O stretch was found at 1685 cm-1. The IR for 9-fluorenone did not show any significant bonds except for at 1681 cm-1, the C=O stretch.

To separate 4-aminobenzoate into an aqueous layer, HCl was added to protonate the NH2 side group and form a salt, creating its high solubility in water and low solubility in ether.  This allowed the immiscible layers to be distinguished. The addition of NaOH after pouring out the aqueous solution allowed for aminobenzoate to reform from its salt form. However, while inverting the funnel to vent before pouring out the layer, some solution leaked out of the cap, which may account for the loss of completely recovering this compound because only 39.3% of ethyl 4-aminobenzoate was recovered.

For the recovery of benzoic acid, NaOH was added to convert the carboxylic acid of the benzene to the water-soluble benzoate anion, which dissolves in the aqueous NaOH solution while the non-acidic impurities remain in the organic phase. After separating the aqueous layer into an Erlenmeyer flask, the basic solution of sodium benzoate was acidified by washing it with HCl and filtering it with DI water. This compound had to most significant recovery of 46. 3%, but some may have been lost through the leakage of the previous extraction.

The neutral compound left in the organic layer was the most difficult to extract. It’s IR graph does not properly show a pure substance, but many errors were involved in its extraction....
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