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SCH4U
Investigation 2: Physical and Chemical Properties of
Organic Chemistry
Alcohols, Carboxylic Acids and Esters
Part I: Reactions of Alcohols
Introduction
Alcohols are common organic substances which undergo a variety of chemical reactions. The two simplest alcohols,
methanol and ethanol, are very important commercially. Methanol, CH3OH, also known as wood alcohol, is toxic leading to
blindness and death if swallowed. Methanol can be used as a motor fuel, and it is the starting point for the manufacture of
many other chemicals. Ethanol, CH3CH2OH, is the alcohol found in alcoholic beverages. Contrary to popular belief, ethanol
is a depressant. Ethanol can also be used as a motor fuel and is often mixed with gasoline to form so called gasohol.
Pre-Lab Questions
1. Compare ethanol with methoxymethane and ethane. Which would be the most solubility? Which would have the
highest/lowest boiling point? Why? [I]
2. Compare the melting/boiling point and solubility in water of a short chain length alcohol like ethanol with a longer
chain length alcohol like 1-heptanol. Explain your answer. [A]
3. What is the correct chemical equation for the reaction of 2-methyl-2-propanol and sodium? [K]
4. Create an observation table for this lab in your notebook. [C]
SAFETY PRECAUTIONS
1. Wear your safety goggles.
2. Know the locations of the fire extinguisher, fire blanket and eye wash station.
3. WARNING: alcohols are volatile, flammable and toxic.
Purpose: In this lab you will examine the solubility of alcohols in water and reactions of alcohols with sodium.
MATERIALS
methanol
1- pentanol (amyl alcohol)
distilled water
400 mL beaker
6 stoppers
2-methyl propanol (isopropanol)
ethanol
pH paper
4 test tubes
test tube rack
1-butanol
Solubility in Water
a.
b.
c.
d.
Place 2-3 mL samples of each alcohol into separate, clean, labeled test tubes.
Add an equal quantity of distilled water to each test tube.
Stopper the test tubes and shake
Compare and record the relative solubility of each alcohol in water.
Reaction of Alcohols with Sodium (Demo only)
a. Place 5 mL samples of each alcohol into separate, clean, labeled test tubes.
b. Add one pellet to each test tube.
c. Compare and record the relative reactivity of each alcohol with sodium.
d. When the reactions are complete, add about 5 mL of distilled water to each test tube. Test the resulting solution with
pH paper and record the results
Part II Carboxylic Acids & Esters
Introduction
Carboxylic acids containing up to four carbons are soluble in water. Beyond four carbons solubility decreases
rapidly. This situation is similar to that of alcohols. When the carboxylic acid has a small hydrocarbon “tail” the
ability of the carboxyl group to hydrogen bond with water causes the acid to be soluble. As the hydrophobic
hydrocarbon tail grows in size, however, the acids become less soluble. As is the case with alcohols, the boiling
points of carboxylic acids increase with molecular weight. As the boiling point increases the volatility decreases.
Formic acid has a sharp odor and everyone knows what acetic acid (vinegar = 5% aqueous acetic acid) smells like.
Acids having 3 or more carbons have unpleasant odors. Butanoic acid (CH3CH2CH2COOH) is redolent of rancid
butter or Parmesan cheese. High molecular weight acids are odorless, presumably because they are not volatile
enough to smell.
When a carboxylic acid is reacted with an alcohol in the presence of a strong acid, which acts as a catalyst, an
ester is formed along with a molecule of water. An example of this reaction is shown below where acetic acid
reacts with isopentanol (3- methylbutanol) to form the ester isopentyl acetate and water. Isopentyl acetate is
sometimes called banana oil because it is mainly what gives bananas their fragrance and flavor. This type of
reaction is known as the Fisher esterification, in honor of its discoverer Emil Fisher.
It is an equilibrium reaction and the equilibrium constant is typically about 1. This means that if one starts with one
mole of carboxylic acid and one mole of alcohol, the result at equilibrium will be one-half mole of ester, one-half
mole of water, one-half mole of carboxylic acid and one-half mole of alcohol. One way to improve the yield is to
remove water from the reaction mixture as it is formed. This will drive the reaction in the forward direction and is an
example of Le Châtelier’s principle. [Le Châtelier’s principle: If the conditions of a system, initially at equilibrium,
are changed the equilibrium will shift in such a direction as to tend to restore the original conditions.] In this case
the water is removed and by Le Châtelier’s principle the substances present will react to form more water. But by
the chemical equation, if more water is formed more ester will be formed, also. Many esters, like isopentyl acetate,
have pleasant fragrances and are used in perfumes and as flavorings.
Pre-Lab Questions
1. Write the structure for the carboxylic acid – acetic acid.
2. Octyl formate has the flavor of oranges. Name the alcohol and carboxylic acid needed to synthesize this ester.
3. Why do you add sulfuric acid to the reactions in this lab? [K]
4. Create observation tables for this experiment in your notebook. [C]
Purpose:
1. To study some physical and chemical properties of carboxylic acids
2. To prepare a number of esters and note their aromas
3. To saponify two esters
Safety Precautions
Although acetic acid may smell like salad dressing, concentrated (glacial) acetic acid can cause severe burns. If
any gets on you, wash it immediately with lots of water.
Materials
500 mL beaker
Hot plate
test tube rack
rubber stoppers
1M sodium hydroxide
2- 50 mL beaker
pipette
test tubes
glacial acetic acid
boiling chips
pHydrion paper
stirring rod
variety of alcohols
conc. sulfuric acid
evaporating dishes/glass vials
Characteristics of Acid:
1. Place a 1mL sample of concentrated acetic acid into a test tube. Note and record the odour.
2. Take a small sample of the acid with a glass stirring rod and test it’s pH with the pHydrion paper.
Note and record the pH range.
3. Repeat steps 1 & 2 using 1-butanol.
4. Add 1 mL of 1M sodium hydroxide to each of the test tubes from above. Stopper and agitate.
Remove the stopper and test the pH of each solution. Continue to add sodium hydroxide until a
basic pH is reached. Note any change in odour and record.
5. Add 2M sulfuric acid dropwise to each test tube, with agitation (shaking), until the contents are
JUST acidic. Record any change in odour. Dispose of the contents and clean the test tubes.
Esterification:
Test tube #
1
2
3
4
5
6
7
Carboxylic Acid
acetic acid
acetic acid
acetic acid
acetic acid
acetic acid
acetic acid
acetic acid
Alcohol
ethanol
isopentanol
1-butanol
1-propanol
methanol
2-butanol
octyl alcohol
Procedure
1. Prepare a hot water bath (60°C) by half filling the 500 ml beaker with water and placing on the hot plate.
Place a few boiling chips in the water.
2. Obtain 1 ml of the assigned carboxylic acid and place into each of your test tubes. Have your teacher add
a few drops of concentrated sulfuric acid. Gently shake the test tube to stir the acids.
3. Add 2 ml of your assigned alcohols to your test tubes (one alcohol in each test tube, do NOT mix
alcohols). Gently shake the test tubes (sharply tap your finger against the side) to stir the contents, then
gently place the test tubes in the hot water bath.
4. After 5 minutes of heating, remove the test tubes from the water bath and pour each contents into its own
evaporating dish/glass vials
5. Gently waft to smell and attempt to identify the odour of your ester. Record in your table. Dispose of all
solutions in the container provided by your teacher, NOT DOWN PUT THEM DOWN THE DRAIN!!!
PART III: Saponification
Since the esterification reaction is reversible it is possible to hydrolyze (from hydro, water, and lysis, to cut or break
apart) an ester into a carboxylic acid and an alcohol. This reaction is also acid catalyzed.
Esters can be broken apart under basic conditions, also. This reaction is called saponification because it can be
used to make soap if one selects the appropriate ester (known as a triglyceride, usually obtained from animal fat)
as starting material. The products of a saponification are an alcohol and the salt of a carboxylic acid as shown
below.
Pre-Lab:
1. Define Triglyceride:
2. What type of functional group is present in all triglycerides?___________________________________
3. Define saponification:
4. Research and predict the products resulting from the reaction below.
5. Describe (with diagrams) the physical process by which soap solubilizes dirt.
Materials:
 electronic balance; hot plate
 alcohol thermometer; stirring rod
 10 mL graduated cylinder; 2 – 50 mL beakers
 20 g coconut oil in a 50 mL beaker; 20 mL of 6.0 mol/L NaOH in 50 mL beaker
 piece of plastic wrap (10 cm x 10 cm)
Safety Precautions:
 Wear safety goggles and a lab apron throughout the experiment.
 Do not allow the electrical cord from the hotplate to dangle over the edge of the bench. Listen carefully to
the teacher’s instructions.
 If 6.0 mol/L NaOH solution gets on your skin, wash immediately with plenty of cold water. Notify the
teacher.
 Be careful not to push the stirrer through the bottom of the Styrofoam cup when you are stirring.
Procedure:
1. All observations must be recorded on a blank sheet of notebook paper with a detailed description
identifying exactly what is being observed.
2. Label a small Styrofoam coffee cup with your initials.
3. At the same time, place the 20 g of coconut oil, in a 50 mL beaker, and the 50 mL beaker containing 20 mL
of 6.0 mol/L NaOH using a hot plate. When these samples have reached ca. 45oC +/- 5oC, carefully pour
both into the Styrofoam cup, with stirring.
4. Stir the mixture constantly for about 20 minutes until it has the consistency of cold honey. Take note of
what you see. If the mixture does not thicken after fifteen minutes of stirring, let it sit for about three
minutes. Then stir it for a few more minutes.
5. Lay some plastic wrap directly on top of the soap, in the Styrofoam cup. Leave the soap in the location
suggested by the teacher. We will examine—and use—the hardened soap next class.
Analysis Questions
1. What trends did you notice in the solubility of alcohols in water? Give explanations for why. Think about
structures and what we have learned in class. [I]
2. Explain the difference in reactivity between sodium and short chain length alcohols like ethanol and longer
chain alcohols like 1-pentanol. [I]
3. Write structural equations for each of the condensation reactions your performed. Provide the IUPAC
name for all reactants and products. [A]
4. For each reaction describe the odour of the ester product. [C]
5. The ester methyl salicylate is also known as oil of wintergreen. Draw the structure methyl salicylate.
Name some commercial products that you know contain this substance. [I][A]
6. Using a reaction sequence, explain how one of your esters may be converted to a soap. Include diagrams
for all molecules. [I][A]
7. Give two errors that may have occurred during your experiment. [I]