Fractional Distillation of a Two-Component Mixture and
the Synthesis of n-Butyl Acetate via Fischer Esterification
Andrew Pany
Chemistry 213H, The Pennsylvania State University, University Park, Pennsylvania
aqp5308@psu.edu
2/8/15
ABSTRACT
A two-component mixture of fruit volatiles was successfully separated through
microscale fractional distillation. The component with the lower boiling point was
submitted to both HNMR and IR analyses and was determined to be acetone. The
component with the higher boiling point was determined to be 1-butanol in a
similar fashion. Additionally, Fischer esterification was conducted using a Dean
Stark apparatus in order to synthesize n-butyl acetate. The crude product of the
esterification was submitted to both IR and HNMR analyses to determine its definite
composition and gas chromatography to determine its purity.
INTRODUCTION
For years, agricultural and food scientists have been analyzing the identities and
concentrations of organic fruit volatiles that change in concentration as fruit ripens.
These volatiles are low molecular weight compounds and differ in terms of
functionality1. The organic volatile responsible for an apple/banana scent is n-butyl
acetate, an ester, which has been synthesized through Fischer esterification.
First, however, a two-component mixture of fruit volatiles was separated through
microscale fractional distillation. The two liquids, one with a higher boiling point
and one with a lower boiling point, were then separated and submitted to IR and
NMR analyses in order to aid in their identification.
Then, Fischer esterification (Scheme 1) was used to synthesize n-butyl acetate. A
Dean-Stark apparatus was used to ease the azeotropic distillation of the acetic acid
and 1-butanol. Dowex 50x2-100 ion resin was used as a catalyst to facilitate the
reaction. The final liquid product, mostly comprised of n-butyl acetate, was
submitted for IR, HNMR, and gas chromatography analyses to determine both its
definite composition and purity.
The objectives of these experiments were to successfully utilize the process of
fractional distillation and to synthesize sweet-smelling n-butyl acetate via Fischer
esterification using a Dean-Stark apparatus.
Scheme 1
RESULTS AND DISCUSSION
Fractional Distillation of a Two-Component Mixture
Fractional distillation was used because the two components had boiling points less
than 75 degrees Celsius apart. The fractioning column, packed with steel wool
(chore boy), allows for successive condensations and distillations and produces a
much better separation2. The lower boiling point liquid first rises to the top and can
be collected by a third arm.
The boiling point of the first unknown liquid was observed to be 53.3 degrees
Celsius. The first unknown had strong absorptions at 1710.3cm-1 in the IR and at
2.1ppm in the HNMR. Subsequently, the unknown with the lower boiling point was
determined to be acetone.
The boiling point of the second unknown liquid was unable to be obtained due to
time constraints as it never successfully made it through the distillation column.
However, the second unknown was able to be determined via IR and HNMR
analyses. The second unknown had strong absorptions at 3313.83cm-1 in the IR and
at 3.4ppm, 1.4ppm, 1.2ppm, and .9ppm in the NMR. Therefore, the unknown with
the higher boiling point was determined to be 1-butanol.
Synthesis of n-Butyl Acetate
Fischer esterification suited this experiment well since it only dealt with simple
esters and alcohols1. Acetic acid was combined with 1-butanol in the presence of
the Dowex 50x2-100 ion resin catalyst. A Dean-Stark apparatus was used to further
facilitate the reaction, which refluxed for one hour. The products of Fischer
esterification were the desired, banana-scented n-butyl acetate and water, a
byproduct.
The n-butyl acetate was synthesized with a purity of eighty-two percent according
to gas chromatography. The n-butyl acetate had strong absorptions at 1737.23cm-1
in the IR and at 4.0ppm, 2.0ppm, 1.6ppm, 1.4ppm, and .9ppm in the HNMR.
CONCLUSION
Fractional distillation was successfully used to separate a mixture of two unknown
liquids. Additionally, Fischer esterification was successfully used to synthesize n-
butyl acetate. The processes were effective but the yields could have been better.
To improve results, the distillation column should have been packed more loosely to
allow for a quicker reaction. Also, glassware should not be in contact at any time. If
the beaker receiving the drops is touching the third arm at all, then the drops will
cling to the glass and slide down the side of the beaker, making them unable to be
fully seen and measured. The Dean-Stark apparatus must constantly be emptied
throughout the course of the Fischer esterification reaction by quickly removing the
cork and draining the liquid. Build up of water on the cork greatly affected the yield
of this reaction. The ester and alcohol layer (desired) laid on top of the water layer
(byproduct). More positively, based on gas chromatography, the purity of the nbutyl acetate was determined to be eighty-two percent. Through IR and HNMR
analyses, the high and low boiling point unknowns were determined to be 1-butanol
and acetone, respectively.
EXPERIMENTAL SECTION
n-Butyl Acetate. n-Butyl acetate was synthesized via Fischer esterification. .6
grams of glacial acetic acid was added to .74 grams of 1-butanol in the presence of
the Dowex 50x2-100 ion catalyst. A Dean Stark apparatus was used to ease the
azeotropic distillation. The distillation was allowed to run for approximately one
hour before the clear, colorless n-butyl acetate was collected along with the water
derivative. The n-butyl acetate was then submitted for IR, HNMR, and gas
chromatography analyses. IR 1737.23cm-1; HNMR (DMSO, 400MHz) 4.0 (2H), 2.0
(3H), 1.6 (2H), 1.4 (2H), .9 (3H).
REFERENCES
1. Masters, K.M. Chem 213H Ag Science Module, Spring 2015 Edition.
2. Masters, K.M.; Williamson, K.L. Macroscale and Microscale Organic
Experiments: Distillation, 6th Edition.
SUPPORTING INFORMATION
IR and HNMR of 1-Butanol
IR and HNMR of n-Butyl Acetate
Gas Chromatography for n-Butyl Acetate
HNMR for Acetone