During an extraction, if you become uncertain about which layer is the organic l

Question

During an extraction, if you become uncertain about which layer is the organic layer, how could you determine it experimentally? From the results of this experiment, what can you conclude about the solubilities of each component in your mixture? Write specific chemical equations for each reaction that took place, using the skeletal structures of the molecules Should it make any difference if the mixture is extracted first with HCI or NaOH? Explain Give a flow chart for separating a mixture containing phenol, benzoic acid, naphthalene, and p-nitroanilme Phenol is soluble in sodium hydroxide solution but insoluble in neutral water or sodium bicarbonate solution. Benzoic acid is soluble in either sodium hydroxide or sodium bicarbonate solutions. Write out the structures of the molecules in your flow chart. Calculate the mass of A extracted in Section A above when four 25 ml. portions of the solvent was used in the extraction.

Explanation / Answer

1. If in separation we are unsure of organic and aqueous layer, we can tak a few milliliters of one of the layer and add water to it in a test tube. If the layer was organic it would be miscible with added water and If it was an organic layer, it would form two separate layers in the test tube. This cn prove which layer is which.

2. The solubility of organic compounds is greater in organic solvent than in water.

3. If the compound to be extracted is an amine, we should pour HCl first. If however, the compound to be extracted is an phenol or carboxylic acid than NaOH is added first.

Base NaOH would not react with amine If present and HCl would not react with phenol or carboxylic acid If present.

4. Separation strategy

a. Add diethylether to the mixture.

b. Add aqueous saturated NaHCO3 solution to it. Benzoic acid forms salt and goes in water. Separate the aqueous layer from diethyl ether layer. Organic layer is A.

c. to the aqueous layer add diethylether dollowed by concentrated HCl to reprecipitate benzoic acid from solution. The benzoic acid would dissolve in added diethyl etehr which can be separated, dried over anhydrous Na2SO4 and solvent evaporation gives pure benzoic acid.

d. To the organic layer A containing naphthalene and p-nitroaniline, add 6 M HCl solution. Aniline forms salt and goes in water. Separate the aqueous layer from diethyl ether layer. Organic layer B

e. To the aqueous layer add diethyl ether and basify with NaOH to reprecipitate p-nitroaniline in organic layer. Separate the organic layer, diry over anhydrous Na2SO4 and remove solvent on rotavap to isolate pure p-nitroaniline.

f. Organic layer B contains only Naphthalene. Dry the layer over Na2SO4 and remove solvent to get pure naphtahlene.

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