For extraction with ethyl-4-aminobenzoate and naphthalene using dichloromethane as the solvent, how does one separate the two compounds from one another?
The Correct Answer and Explanation is:
Correct Answer:
The two compounds, ethyl-4-aminobenzoate and naphthalene, can be separated by acid-base extraction using aqueous hydrochloric acid (HCl).
Explanation:
Ethyl-4-aminobenzoate is a basic compound due to the presence of an amino group. Naphthalene, on the other hand, is a neutral aromatic hydrocarbon and does not react with acids or bases. The difference in their chemical reactivity allows them to be separated through an acid-base extraction process using dichloromethane (DCM) as the organic solvent.
Begin by dissolving the mixture of ethyl-4-aminobenzoate and naphthalene in dichloromethane. Since both compounds are initially non-ionic, they dissolve well in the organic DCM layer.
Next, the DCM solution is shaken with aqueous hydrochloric acid (HCl). The HCl protonates the amino group of ethyl-4-aminobenzoate, converting it into a water-soluble ammonium salt. This salt moves from the DCM layer into the aqueous HCl layer because it becomes ionic and polar, which makes it highly soluble in water.
At the same time, naphthalene remains in the DCM layer because it is nonpolar and does not react with the acid. After allowing the two layers to separate, the aqueous layer (containing the protonated ethyl-4-aminobenzoate) can be carefully removed from the DCM layer (which contains the naphthalene).
To recover ethyl-4-aminobenzoate, the aqueous layer is then made basic by adding sodium hydroxide (NaOH), which deprotonates the ammonium salt back to the neutral amine form. This neutral compound precipitates or can be extracted back into a fresh portion of DCM for further purification.
In conclusion, the selective solubility of ethyl-4-aminobenzoate in acid allows for its separation from naphthalene, demonstrating a practical application of acid-base chemistry in organic extraction.
