Extraction of Acid with Base
Water and diethyl ether are shaken in a separatory funnel with a small amount of red indophenol. The non-ionic indophenol remains in the ether layer, coloring it red. Addition of sodium hydroxide converts the indophenol to its blue ionic acid anion which is extracted into the water layer turning it blue. Neutralization of the acid anion and excess sodium hydroxide with hydrochloric acid converts the acid anion back into the non-ionic red form which is extracted back into the ether layer.
Keywords
organic chemistry, acids and bases, separation, indophenol acid form, indophenol base form, solubility, Equilibrium, solutions
Multimedia
Step 1 of 3
_Play
movie (50 seconds, 3.4 MB)
Fifty milliliters of water, fifty milliliters of diethyl ether, and
one milliliter of indophenol solution are mixed in a separatory
funnel. The red color in the upper layer shows that indophenol is
much more soluble in ether than in water.
Step 2 of 3
_Play
movie (27 seconds, 2.2 MB)
Two drops of 2 molar sodium hydroxide are added and the mixture is
shaken. Now the aqueous layer is blue, indicating that the basic,
anionic form of indophenol is more soluble in water than in
ether.
Step 3 of 3
_Play
movie (24 seconds, 2 MB)
Adding two drops of 2 molar hydrochloric acid and shaking restores
the original red molecular form of indophenol, which is extracted
into the ether layer.