Fractional Distillation of an Ethyl Acetate - Butyl Acetate
Mixture with Gas Chromatography Analysis (10/7/09)
We have seen in previous experiments how acid-base extraction, recrystallization, column
chromatography, and thin-layer chromatography can be used to separate mixtures on a
preparative and/or analytical scale. Although not restricted to mixtures of solid materials, these
techniques are most often used with mixtures of solids. When mixtures of liquid materials need
to be separated, the techniques of fractional distillation and gas chromatography are used. The
latter is also called gas-liquid chromatography (GLC) and vapor phase chromatography (VPC).
Gas chromatography is far more efficient at separating mixtures than is fractional distillation, but
it is usually restricted to analytical separations (milligram scale), whereas fractional distillation is
suitable for preparation (gram scale) separations. Fractional distillation is similar to simple
distillation except for the use of a column packed with some sort of material to increase contact
between the liquid and vapor phases. As the vapor proceeds up through the column, it undergoes
successive condensations and vaporizations (i.e., a series of simple distillations) and the vapor
becomes enriched in the lower boiling component. Thus the components are separated.
Gas chromatography (partition chromatography) differs from thin-layer and column
chromatography (adsorption chromatography) in that the stationary phase is a liquid, the mobile
phase is a vapor, and the eluent is an inert gas (helium or nitrogen). The separation in GC
depends upon the different equilibria established between the components in the vapor phase and
their solution in the liquid stationary phase. The inert gas serves only to move the vapor through
the chromatography column.
In this experiment a mixture of ethyl acetate and butyl acetate will be separated by fractional
distillation and the efficiency of the fractionation will be determined by analyzing the various
fractions collected by gas chromatography.
Ethyl Acetate
O
CH3COCH2CH3
Butyl Acetate
O
CH3COCH2CH2CH2CH3
PROCEDURE
Fractional Distillation
Pack the fractionating column with glass beads. It may be necessary to place a small, very loose
plug of steel sponge in the column to keep the beads from falling through. After the column is
packed, place 10mL of ethyl acetate and 10mL of butyl acetate in a 50mL round-bottomed flask,
add two boiling stones, and assemble the fractional distillation setup as described in Zubrick (7th
Edition: fig. 20.10 pp. 180-186). Instead of using a round bottom flask as a receiver, use a clean,
dry Erlenmeyer flask. When attaching the thermometer, be sure that the entire thermometer bulb
is below the side arm of the three-way connector. Turn the water on to the condenser and begin
heating the mixture. As the mixture is heated, the temperature at the top of the column will rise
to ~81oC and distillation will begin. Adjust the heat so that the distillation occurs at a steady rate
no faster than about 1 drop of distillate every 1-2 seconds. The temperature of the vapor will
remain constant (~81oC) for a period of time, but will eventually either drop or rise. The first
receiver should be left in place until a temperature increase or decrease is observed. At this
point, change receivers and increase the heating of the distillation flask. The temperature will
begin to rise and distillation will resume.
Leave the second receiver in place until the temperature reaches ~124oC, then change to the third
receiver. Continue the distillation until ~2mL of liquid remains in the distillation flask.
Discontinue the heating, measure and record the volumes of the distillate in each receiver with a
graduated cylinder. After the liquid in the column had drained back into the distillation flask,
measure and record this volume as the pot residue. Securely stopper the distillate fractions with
corks and save for GC analysis.
Gas Chromatography
Analyze the first and third distillate fractions on a gas chromatograph as instructed. Calculate the
relative percentages of ethyl acetate and butyl acetate in the fractions from the gas
chromatograms. (The method to use is discussed in the assigned sections of Zubrick!).
 Pack the distillation column carefully. The indentations at the bottom of the column are
easily broken!
 Remember to set up glassware from the bottom up in close proximity to the regulator.
 Use a cork to stopper the fractions. Ethyl acetate and butyl acetate will dissolve the cap used
to stopper the vials.
Name:________________________________________Section:_______Date:_______
POSTLAB EXERCISE
FRACTIONAL DISTILLATION OF AN ETHYL ACETATE – BUTYL ACETATE MIXTURE
WITH GAS CHROMATOGRAPHY ANALYSIS (Rev’d 10/7/09)
>> Due the lab following the completion of the experimental potion of the notebook (30 pts. TOTAL).
Please answer questions on this form. <<
A. PRODUCT INFORMATION (15pts)
FRACTION
VOLUME (mL) (8pts)
BOILING RANGE (oC) (6pts)
A (4pts)
(2pts)
(2pts)
B (4pts)
(2pts)
(2pts)
C (4pts)
(2pts)
(2pts)
POT RESIDUE
(2pts)
(2pts)
 (1pt) Attach a GC trace (or photocopy).
B. SUMMARY QUESTIONS (15pts)
1.
PERCENT COMPOSITION (8pts): PLEASE ATTACH SAMPLE CALCULATIONS!
FRACTION
% Ethyl Acetate (4pts)
% Butyl Acetate (4pts)
A (Glass Beads)
(4pts Total)
(2pts)
(2pts)
C (Glass Beads)
(4pts Total)
(2pts)
(2pts)
2. (7pts) The GC trace at the bottom of this page was obtained from the fractional distillation
of an Ethyl Acetate-Butyl Acetate mixture using stainless steel wool. Use the GC trace on
the bottom of this page to answer the questions below.
a. (6pts) Calculate the percent composition of ethyl acetate and butyl acetate for each of the
three fractions.
FRACTION
% Ethyl Acetate
% Butyl Acetate
A (2pts)
B (2pts)
C (2pts)
b. (1pt) Is stainless steel wool a more efficient column packing than glass beads? Why or why
not?