CHE XXXXXXXXXXManual 3E.pdf
Copyright © 2014 Pearson Education, Inc. 259
LABORATORY GOALS
ary, secondary, or tertiary.
guish between the classes of alcohols.
LAB INFORMATION
Time: 2 h
Caution: Be careful when you work with chromate solution. It contains concentrated acid.
Do not use burners in lab when you work with flammable organic compounds.
Tear out the lab report sheets and place them beside the matching procedures.
Related Topics: Alcohols, classification of alcohols, solubility of alcohols in water, phenols,
oxidation of alcohols
Dispose of all chemicals as directed by your lab instructor.
CHEMICAL CONCEPTS
A. Structures of Alcohols and Phenol
Alcohols are organic compounds that contain the hydroxyl group ( OH). The simplest alcohol is metha-
nol. Ethanol is found in alcoholic beverages and preservatives and is used as a solvent. 2-Propanol, also
known as ru
ing alcohol or isopropyl alcohol, is found in astringents and perfumes.
Hand sanitizers are used to kill bacteria and viruses that spread colds and flu. As a gel or liquid solu-
tion, many hand sanitizers use ethanol as their active ingredient. The amount of ethanol in an alcohol-
containing sanitizer is typically 60% (v/v), but can be as high as 85% (v/v). The high volume of ethanol
can make hand sanitizers a fire hazard in the home because ethanol is highly flammable. When using an
ethanol-containing sanitizer, it is important to rub your hands until they are completely dry. It is also
ecommended that sanitizers containing ethanol be stored in areas away from heat sources in the home.
Alcohols and Phenols 23
Hand sanitizers that contain ethanol are used to kill bacteria on the hands.
260 Laboratory Manual for General, Organic, and Biological Chemistry
A benzene ring with a hydroxyl group is known as phenol. Concentrated solutions of phenol are caustic
and cause burns. However, derivatives of phenol, such as thymol, are used as antiseptics and are some-
times found in cough drops.
Classification of Alcohols
In a primary (1°) alcohol, the ca
on atom attached to the OH group is bonded to one other ca
on
atom. In a secondary (2°) alcohol, the ca
on with the OH is attached to two ca
on atoms, and in a
tertiary (3°) alcohol it is attached to three ca
on atoms.
B. Properties of Alcohols and Phenol
The polarity of the hydroxyl group ( OH) makes alcohols with one to three ca
on atoms completely
soluble with water because they can form many hydrogen bonds. An alcohol with four ca
on atoms is
somewhat soluble, whereas the large hydroca
on portion in longer chain alcohols makes them insoluble
in water.
Hydrogen bonds form between the hydroxyl group and H and O atoms in water.
Alcohols and Phenols 261
Acidity of Phenol
In water, phenol acts as a weak acid because the hydroxyl group ionizes slightly. Although phenol has
six ca
on atoms, the polarity of the hydroxyl group makes it soluble in water.
C. Oxidation of Alcohols
Primary and secondary alcohols are easily oxidized. An oxidation consists of removing an H from the
OH group and another H from the C atom attached to the OH group. Tertiary alcohols do not
undergo oxidation because there are no H atoms on that C atom attached to the OH. Primary and
secondary alcohols can be distinguished from tertiary alcohols using a solution with chromate, 24CrO .
When an oxidation has occu
ed, the orange color of the chromate solution turns green.
D. Iron(III) Chloride Test
Phenols react with the 3Fe ion in iron(III) chloride 3(FeCl ) solution to give complex ions with strong
colors from red to purple.
3 3Phenol Fe Fe (phenol complex)
PurpleColorless Yellow
E. Identification of an Unknown
The group of tests for alcohols and phenols described in this experiment will be used to identify the
functional group and family of an unknown.
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EXPERIMENTAL PROCEDURES GOGGLES REQUIRED!
A. Structures of Alcohols and Phenol
Materials: Display of models: ethanol, 2-propanol, and 2-methyl-2-propanol
Draw the condensed structural formula of each model in the display and for phenol. Classify each as a
primary, secondary, or tertiary alcohol.
B. Properties of Alcohols and Phenol
Materials: 6 test tubes, pH paper, sti
ing rod, ethanol, 2-propanol, 2-methyl-2-propanol (t-butyl alcohol),
cyclohexanol, 20% phenol, and unknown, Caution: Avoid contact with phenol.
pH
1. Place 10 drops of ethanol, 2-propanol, t-butyl alcohol (2-methyl-2-propanol), cyclohexanol, 20%
phenol, and the unknown into six separate test tubes. Obtain some pH paper. Use a sti
ing rod to
place a drop of each on a piece of pH paper. Clean the sti
ing rod between applications. Compare
the color of the pH paper with the color chart on the container to determine the pH. Record your
observations. Save the test tubes and alcohols for part 2.
Solubility in water
2. Add 2 mL of water (40 drops) to each test tube. Shake and determine the solubility in water of
each alcohol. If the compound is soluble in water, you will see a clear solution with no separate
layers. If it is insoluble, a cloudy mixture or separate layer will form. Record your observations.
DISPOSE OF ORGANIC COMPOUNDS IN DESIGNATED WASTE CONTAINERS!
C. Oxidation of Alcohols
Materials: 6 test tubes, ethanol, 2-propanol, 2-methyl-2-propanol (t-butyl alcohol), cyclohexanol, 20%
phenol, unknown, 2% chromate solution
1. Place 8 drops of ethanol, 2-propanol, 2-methyl-2-propanol (t-butyl alcohol), cyclohexanol, 20%
phenol, and the unknown into six separate test tubes. Carefully add 2 drops of chromate solution
to each. Stir carefully to allow the alcohol to react. Caution: Chromate solution contains concen-
trated ,2 4H SO which is co
osive. Look for a color change in the chromate solution. If a test tube
ecomes hot, place it in a beaker of ice-cold water. Record your observation of the color after
2 minutes.
2. Draw the condensed structural formula of each alcohol.
3. Classify each alcohol as primary (1°), secondary (2°), or tertiary (3°).
4. If the orange color turned green within 2 min, oxidation of the alcohol has taken place. If the color
emained orange, no reaction has occu
ed.
If a reaction occu
ed, draw the condensed structural formulas of the product. When there is no
change in color, no oxidation took place.
DISPOSE OF ORGANIC COMPOUNDS IN DESIGNATED WASTE CONTAINERS!
D. Iron(III) Chloride Test
Materials: 6 test tubes, ethanol, 2-propanol, 2-methyl-2-propanol (t-butyl alcohol), cyclohexanol, 20%
phenol, unknown, 1% 3FeCl solution
Place 5 drops of the alcohols and unknown in separate test tubes. Add 5 drops of 1% 3FeCl solution to
each. Stir and record observations.
DISPOSE OF ORGANIC COMPOUNDS IN DESIGNATED WASTE CONTAINERS!
E. Identification of an Unknown
Use the test results to identify your unknown as one of the five compounds used in this experiment.
Draw the condensed structural formula of the unknown.
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CHE XXXXXXXXXXManual 3E.pdf
Copyright © 2014 Pearson Education, Inc. 263
Pre-Lab Study Questions 23
1. What is the functional group of an alcohol and a phenol?
2. Why are some alcohols soluble in water?
3. Classify each of the following alcohols as primary, secondary or tertiary.
a. 3-pentanol _______________________
. 2-methyl-2-butanol _______________________
c. 1-propanol _______________________
4. If you add chromate, an oxidizing agent, to each of the following, would a green 3+Cr solution
e formed?
a. 3-pentanol _______________________
. 2-methyl-2-butanol _______________________
c. 1-propanol _______________________
5. If an alcohol solution has a pH of 5, would it be a primary alcohol, a secondary alcohol, a tertiary
alcohol, or a phenol?
Date Name
Section Team
Instructo
Copyright © 2014 Pearson Education, Inc. 265
A. Structures of Alcohols and Phenols
Ethanol
2-Propanol
Classification:
2-methyl-2-propanol (t-butyl alcohol)
Phenol
Classification:
Questions and Problems
Q1 Draw the condensed structural formula and give the classification for each of the
following alcohols:
1-Pentanol
3-Pentanol
Classification:
Cyclopentanol
1-Methylcyclopentanol
Classification:
B. Properties of Alcohols and Phenols Unknown # _______________
Alcohol 1. pH 2. Soluble in Water?
Ethanol
2-Propanol
2-Methyl-2-propanol
Cyclohexanol
Phenol
Unknown
Date Name
Section Team
Instructor
REPORT SHEET
Alcohols and Phenols
LAB
23
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266 Laboratory Manual for General, Organic, and Biological Chemistry
C. Oxidation of Alcohols
Alcohol 1. Color After
2 min
2. Condensed
Structural
Formula
3. Classifica-
tion
4. Condensed
Structural
Formula of
Oxidation
Product
Ethanol
2-Propanol
2-Methyl-
2-propanol
Cyclohexanol
Phenol
Unknown
Q2 Draw the condensed structural formula of the product of the following reactions
(if no reaction, write NR):
a.
.
c.
D. Iron(III) Chloride Test
Alcohol 3FeCl Test (Color)
Ethanol
2-Propanol
t-Butyl alcohol
Cyclohexanol
Phenol
Unknown
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