In order to separate the two organic compounds, we used a separatory funnel. Naphthalene is a nonpolar neutral compound, while m-nitroaniline was a basic compound, so in order to separate the two, we used HCl. By adding 3M HCl to our solution, the hydrogen ions would protonate the nitrogen group of m-nitroaniline, forming a salt compound which would dissolve into the aqueous layer. .
The naphthalene would still be dissolved in the ethyl acetate. This way, we would be two immiscible layers: an organic layer containing only naphthalene dissolved in ethyl acetate and an aqueous layer containing the m-nitroaniline salt, protons, and chloride ions dissolved in water. The two layers were separated using the separatory funnel. The top layer of the funnel would be naphthalene because it is less dense than the aqueous layer. Our observation was further reinforced when we say that the bottom aqueous layer was yellow, due to the presence of m-nitroaniline.
The next step was to isolate pure samples of our organic compounds. To isolate naphthalene, our organic solution from the previous separation step was put on a hot plate to boil off the ethyl acetate. Because the solution should only contain naphthalene and ethyl acetate, the solid left over after all the ethyl acetate boiled off should be the pure naphthalene that was originally in our soil sample.
To isolate pure m-nitroaniline, we first had to convert it back to its original form. In the separatory step, m-nitroaniline was protonated to become a salt. In order to reverse this change, we added NaOH into the aqueous solution until the solution became basic (tested by using litmus paper). When NaOH is added to the solution, the OH- would deprotonate the m-nitroaniline salt and convert it back into m-nitroalinine. By making sure the pH was basic, we ensured that there was no more free protons left in the solution. The resulting solution consisted of m-nitroalinine dissolved in water, alongside various neutral ions.
