Acid-Base Extraction with Separatory Funnel

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A. Title – Acid-Base Extraction with Separatory Funnel

B. Introduction – The main objective of the experiment was the extract an acid, a base, and a neutral compound from a 2:1:1 compound of benzoic acid, p-nitroaniline, and azobenzene. In theory, an extraction technique based on phase distribution should allow two immiscible solvents to separate with a portion of the solute distributed into each. Using a separatory funnel, acids were extracted with bases (NaOH), and bases were extracted with acids (HCl). Gravity filtration, cold filtration, and hot filtration were all used in separating the compounds. Melting points were then observed in order to check for purity of the compounds.

C. Structures –

D. Reactions –

+ HCl Cl-

+ NaOH Na+ + H2O

Cl- + NaOH + NaCl + H2O

Na+ + HCl + NaCl

E. Physical Contents –

| M.W. (g/mol)| M.P. (oC)| B.P. (oC)| Density (g/mL)|
4-Nitroaniline| 138.12| 146-149| 260| 1.40|
Azobenzene| 182.22| 65-68| 293| 1.09|
Benzoic Acid| 122.12| 121-125| 249| 1.30|
Methylene Chloride| 84.93| -97| 39.8-40| 1.32|

G. Procedure – The 2:1:1 mixture was dissolved in methylene chloride in a beaker and transferred to a separatory funnel. Hydrochloric acid was added, and the resulting separated layers were extracted from the funnel. Hydrochloric acid was added and extracted a second time. The organic extraction was returned to the funnel, and NaOH was added. The two layers were extracted, thus forming a third flask of compound. Anhydrous sodium sulfate was added to flask with the organic layer and set aside. The remaining two compounds were cooled in ice baths and then neutralized. Hydrochloric acid was added to the basic extract just beyond neutralization, and sodium hydroxide was added...
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