Acid Base Extraction


The purpose of this laboratory assignment was two-fold, first, we were to
demonstrate the extraction of acids and bases, finally, determining what
unknowns were present. Second, we were to extract caffeine from tea. These two
assignment will be documented in two separate entities.

Introduction: Acid/base extraction involves carrying out simple acid/base
reactions in order to separate strong organic acids, weak organic acids neutral
organic compounds and basic organic substances. The procedure for this
laboratory assignment are on the following pages.

3) Separation of Carboxylic Acid, a Phenol and a Neutral Substance

The purpose of this acid/base extraction is to separate a mixture of
equal parts of benzoic acid(strong acid) and 2-naphthanol(weak base) and 1,4-
dimethoxybenzene(neutral) by extracting from tert-butylmethyl ether(very
volatile).The goal of this experiment was to identify the three components in
the mixture and to determine the percent recovery of each from the mixture.

4) Separation of a Neutral and Basic Substance

A mixture of equal parts of a neutral substance containing either
naphthalene or benzoin and a basic substance containing either 4-chloroaniline
or ethyl 4-aminobenzoate were to be separated by extraction from an ether
solution. Once the separation took place, and crystallization was carried out,
it became possible to determine what components were in the unknown mixture, by
means of a melting point determination.

Results

Procedure Observations
Inference

Dissolve 3.05g Phenol Mixture was a golden-Neutral acid
in 30ml brown/yellow color t-butyl methyl ether in
Erlenmeyer flask and transfer mixture to 125ml separatory funnel using little
ether to complete the transfer

Add 10 ml of water Organic layer=mixture
aqueous layer=water(clear)

Add 10 ml saturated aqueous Sodium bicarbonate NaHCO3
dissolves in solution sodium bicarbonate
water. to funnel and mix cautiously with stopper on

Vent liberated carbon Carbon dioxide gas dioxide and shake the
mixture was released three times thoroughly with frequent venting of the
funnel

Allow layers to separate Layer = H2O +NaHCO3 completely and draw
off lower layer into 50ml Erlenmeyer flask 1

Add 10ml of 1.5 aqueous NaOH Flask 2 = H2O + NaHCO3 (5ml of 3M and 5ml H2O)
to separatory funnel, shake mixture, allow layers to separate and draw off lower
layer into a 25ml Erlenmeyer flask 2. Add additional 5ml of water to funnel,
shake as before

Add 15 ml NaCl to funnel. Shake Bottom layer is white and NaCl was
added to the mixture and allow layers to separate gooey.
wash the ether and draw off lower layer, which is
layer and to remove discarded
organic
substances
NaOH and
NaHCO3 Pour ether layer into 50ml Erlenmeyer flask from the top of the
separatory funnel (not allowing any water droplets to be transferred) Flask 3

Add anhydrous NaSO4 to ether extract until it no longer clumps
together and set it aside

Acidify contents of flask 2 Litmus went from
Acidification was now by dropwise addition of blue to pink. Flask
complete concentrated HCl while 2 = creamy color testing
with litmus paper and cool in ice

Acidify contents of flask 1 Litmus went from
Acidification was now by adding HCl dropwise blue to pink. Flask
complete while testing with litmus 2 = white solution paper
and cool in ice

Decant ether from flask 3 into a tared flask

Boil ether with boiling chips

Do a vacuum filtration and Solution turns to a
Crystallization is now recrystallize ether by dissolving it solid.
complete in 5ml, taking out boiling chips, adding drops
of Ligroin until the solution was cloudy and cool it in ice

Isolate crystals from flask 2 by Crystals = creamy-white Dried
crystals are now vacuum filtration and wash with powder
ready for melting point a small amount of ice water
determination and recrystallize it from boiling water

Repeat the above for flask 1 Crystals = white powder

Flasks number 4 and 5 were done by the following diagram.

Results:

As a result of this acid/base experiment, the following results were obtained:

Flask 1: 31.113g
-30.223g
.890g

Flask 2: 36.812g
-36.002g
.810g

Flask 3: 90.789g
-90.114g
.065g

% yield = experimental weight x 100%
theoretical weight

Flask 1: .890g x 100% = 89%
1.00g

Flask 2: .810g x 100% = 81%
1.00g

Flask 3: .675g x 100% = 67.5%
1.00g

When taking the melting points of the unknowns, flasks 4 and 5, I came
to the conclusion that the samples contained, benzoin, melting point of 136-
137Degrees(C) and 4-chloroaniline, melting point of 67-80 degrees(C),
respectively.

Flask 4: 90.912g
-89.174g
1.738g

% yield = 1.738g x 100% = 90.4%
1.922g

Flask 5: 87.833g
-86.064g
1.769g

% yield = 1.769g x 100% = 87.3%
2.027g

Conclusion:

After each procedure was complete, it became apparent that flask number
4 and flask number 5 contained benzoin and 4-chloroaniline, respectively. The
melting point range that was experimentally determined for each was 136-137 for
benzoin and 67-70 for 4-chloroaniline. As you can see, this experiment was not
error-free, as my percentage yield was not 100%. This is expected for any
experiment; for there is