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ESTERS OF CARBOXYLIC ACIDS
BACKGROUND
Did you know that the aromas of bananas, strawberries, other fruits, flowers, and perfumes are
the result of organic chemistry? Many of these flavor additives are esters. An ester is an organic
compound that is produced when a carboxylic acid reacts with an alcohol. They are probably the
most pleasant and delicious organic compounds one can study.
A functional group is a specific arrangement of atoms in an organic compound that is capable of
characteristic chemical reactions. The chemistry of an organic compound is determined by its
functional group. R is any carbon chain/ring attached to the functional group (in red). The
general equation for this reaction is:
O
R
1
C
2
OH
R
OH
R1COOH
+
R2OH
carboxylic acid
alcohol
reactants

R1COOR2
ester
+
H2O
water
products
The name of the ester formed is derived from the names of the alcohol and the carboxylic acid.
For example, the ester formed from ethyl alcohol and acetic acid is called ethyl acetate. The first
part of the name comes from the alcohol and the second part comes from the acid (Figure 1).
Figure 1: Ethyl Acetate
In this laboratory, you will synthesize and identify several esters. Sulfuric acid will be used as a
catalyst for the esterification reactions.
OBJECTIVES: When you have completed this activity, you will be able to:
1. Describe the structure of an ester and how it is formed
2. Synthesize several esters
3. Research and describe how esters are used in society
…in order to illustrate the usefulness of organic compounds..
MATERIALS
alcohols
amyl (1-pentanol)
methanol
carboxylic Acids
glacial acetic acid
salicylic acid (solid)
18 M sulfuric acid (concentrated)
(in fume hood)
distilled water
china marker
hot plate
thermometer
beaker (400 mL)
2 Dropper Pipettes
graduated Cylinders (10.0 mL)
test tube rack
2 test tubes (16 x 100 mm)
test tube holder
balance
weigh boat
timer
PROCEDURE
CAUTION: You will be working with concentrated acids.
Wear goggles, lab aprons, and closed-toe shoes.
1. _____ Prepare a water bath by adding 175 mL of tap water to a 400 mL beaker. Place the
beaker on a hot plate and heat the water until the temperature is between 50 - 60C.
2. _____ Number 2 test tubes toward the top of the tube with a china marker. Into each of two
numbered test tubes, put 20 drops of alcohol (1.0 mL) and 10 drops of carboxylic acid (0.5
mL). For salicylic acid, add 0.50 g of the carboxylic acid. See Table 1.
Test Tube
1
2
Table 1
1.0 mL Alcohol
0.5 mL Carboxylic Acid
amyl alcohol
glacial acetic acid
methyl alcohol
salicylic acid (0.5g)
3. _____ Carefully add 2 - 3 drops of concentrated sulfuric acid (H2SO4) to each test tube.
CAUTION: Handle concentrated sulfuric acid carefully. If the acid spills on
your skin or clothing, immediately rinse the affected area with
water and inform your teacher.
4. _____ Stir each mixture slightly by tapping the bottom of the tube with your finger.
5. _____ Place the test tubes in the hot water bath (50 - 60C) for 10 minutes. While you are
waiting, complete “Structure of Hydrocarbons” attached.
6. _____ Using a test tube holder, remove the test tubes from the water bath and place them in a
test tube rack.
7. _____ Add 5.0 mL of dI water to each test tube and mix. Esters are insoluble in water and
appear as colorless liquid layers on top of the water.
8. _____ Immediately note the odor of the esters formed by wafting the fumes toward your
nose with your hand. Try to relate each odor to a familiar, specific scent. Record your
observations in the “Observations and Conclusions” Table.
DATA
Table 2: Observations and Conclusions
Test Tube
1
2
Alcohol
amyl alcohol
Carboxylic Acid
Ester formed
glacial acetic acid
amyl acetate
salicylic acid
methyl salicylate
methyl alcohol
Odor
ANALYSIS:
1. Below are the equations for each of the esterification reactions performed in this
experiment. Use 1a as an example to complete the formula for the ester in questions 1b
and 1c.
a.
CH3OH
+
methyl alcohol
C6H13COOH

heptanoic acid
CH3COOC6H13
+
methyl heptanoate
H2O
water
b.
C5H11OH
+
amyl alcohol
CH3COOH
acetic acid

_______COO______ +
amyl acetate
H2O
water
c.
CH3OH
+ C6H4OHCOOH
amyl alcohol
salicylic acid

______COO_______ +
methyl salicylate
H2O
water
2. A banana scented candle could contain this additive ester:
a. Amyl acetate
b. Methyl salicylate
c. Methyl heptanoate
3. A wintergreen scented car freshener could contain this additive ester:
a. Amyl acetate
b. Methyl salicylate
c. Methyl heptanoate
4. An ester is formed by reacting:
a. alcohol with water
b. carboxylic acid with water
c. carboxylic acid with alcohol
5. The functional group for an alcohol is
a. R
b. –OH
c. H2O
d. –COOH
6. Amyl acetate is an inorganic compound.
a. True
b. False
7. Esterification is often classified as a dehydration reaction because…
a. water is produced in the reaction
b. water is used as a reactant in the reaction
8. Why was sulfuric acid added to the reaction?
a. To speed up the rate of the reaction
b. To keep the rate of reaction constant
c. To make the reaction more dangerous and exciting for chemistry students
d. To slow down the rate of the reaction so the ester could be smelled for longer periods of
time
9. Esters are soluble in water.
a. True
b. False
10. According to the IUPAC naming system, the name of this hydrocarbon is:
a. Butane
b. Butene
c. Butyne
d. Propane
e. Propene
f. Propyne
Name: ____________________________ Date: _____________ Period: _______ Page: ______
PRE-LAB: ESTERS OF CARBOXYLIC ACIDS
Read the introduction and procedure to the lab activity, highlighting key information as you read.
Use the information in the introduction, procedure, and your class notes to answer the following
questions.
1. Write the general formula for the reaction between a carboxylic acid and an alcohol. Identify
each reactant and product.
2. Name the ester formed from each of the carboxylic acids and alcohols. For the alcohol,
remove the –anol ending and replace it with –yl.
Alcohol
octanol
propanol
2 – pentanol
ethanol
Carboxylic Acid
acetic acid
butanoic acid
benzoic acid
acetic acid
Ester
octyl acetate
3. What safety precautions relate specifically to this lab?
4. What is the role of a catalyst in a reaction?
5. Why is water added to the test tubes after the esters are formed?
STRUCTURE OF HYDROCARBONS
Hydrocarbons are the simplest organic compounds that contain only carbon and hydrogen. The
two simplest hydrocarbons are methane (CH4) and ethane (C2H6).
IUPAC Rules for naming straight chain hydrocarbons:
1. Find the longest chain of carbons.
2. Count how many carbons are in that longest chain and use the correct prefix
# carbons example
prefix
# carbons example
prefix
CH
methC
H
hex1
6
4
6 14
C2H6
ethC7H16
hept2
7
C3H8
propC8H18
oct3
8
C4H10
butC9H20
non4
9
C5H12
pentC10H22
dec5
10
3. The suffix reflects whether the hydrocarbon is an alkane, alkene, and alkyne.
only single covalent bonds
-ane
One or more carbon-carbon double covalent bond
-ene
One or more carbon-carbon triple covalent bond
-yne
Name the following structures: Write the correct name in the box for each hydrocarbon
Options: butane, butene, ethane, ethyne, propane, propene, propyne
1.
5.
2.
3.
6.
4.
7.