Experiment 12
Identification of Alcohols and Phenols
INTRODUCTIONAlcohols and Phenols contain the functional group, OH. In a phenol, the OH group is
connected to a carbon on a benzene ring where as in alcohols, the OH group is
connected to a sp3 hybridized carbon atom. Alcohols are classified as 10, 20 and 30,
depending on the number of carbon atoms connected to the carbon bearing the OH
group. Representative examples of a phenol, and three types of alcohols are shown
below.
Though these four classes of compounds contain the functional group OH, the unique
differences in their reaction chemistry allows one to easily differentiate one from the
other. Phenols are more acidic than alcohols. Alcohols as well as phenols find a
variety of industrial, pharmaceutical, and even household applications. Derivatives of
alcohols and phenols are found in medicines, alcohols are used as common industrial
solvents etc.
Ferric Chloride test: Alcohols are readily differentiated from phenols using this test.
Addition of a drop or two of ferric chloride solution to a sample of phenol (3-4 drops)
will produce a distinct violet/purple coloration. Alcohols do not produce such deep
coloration when treated with ferric chloride solution.
Lucas test, chromic acid test, and boiling points can be used to differentiate primary,
secondary and tertiary alcohols. Phenols do not react under the reaction conditions of
Lucas test and/or chromic acid test.
Lucas Test: A solution of zinc chloride in concentrated hydrochloric acid is called the
Lucas Reagent. The rate of reaction of an alcohol with HCl in presence of ZnCl2 is
dependant on the nature of the alcohol, i.e. whether the alcohol is a primary alcohol,
secondary, and or a tertiary alcohol in nature. Tertiary alcohols react almost
instantaneously to give water insoluble alkyl chlorides as products (remember the fact
that alcohols are water soluble due to H-bonding).
2  R—Cl + H2O
R—OH + HCl ZnCl
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So if a cloudy dispersion or as a separate layer within the solution occurs immediately upon
mixing the alcohol with the reagents then that alcohol must be a tertiary one.
Secondary alcohols will form cloudy products upon standing while primary alcohols
need to be heated with the reagents before the reaction can occur. This qualitative test
can be used to identify a primary alcohol from secondary and tertiary alcohols.
Chromic Acid Test:
Potassium dichromate, K2Cr2O7 in aq. acid and Jones Reagent (CrO3 in acetone and
sulfuric acid) are two common oxidizing agents. In both these reagents, Cr is present as
Cr (VI) which is red orange in color. However after the oxidation reaction, Cr (VI)
gets reduced to Cr(III) which is dark green in color. This color change is exploited and
used for the detection of alcohol in breath of suspected intoxicated drivers using a
Breath analyzer. Oxidation of alcohols using potassium dichromate and acid can be
used as a method to differentiate tertiary alcohols from primary and secondary alcohols.
Both primary as well as secondary alcohols are oxidized using these reagents,
producing a green Cr III precipitate. Tertiary alcohols are not oxidized with these
reagents.
PURPOSE1. To use the chemical characteristics to differentiate phenols and the three
types of alcohols
2. To learn characteristic chemical reactions of alcohols and phenols
PRELABConsider the structures of the various alcohols and phenols shown and complete the
table on the report sheet by noting the expected outcome of the indicated reactions.
PROCEDURELucus Test:
1. Obtain the six unknown compounds.
2. Label 7 clean dry test tubes with the unknown numbers.
3. Add 5 drops of each sample to the appropriate test tube.
4. Add 1 mL of Lucas reagent. CAUTION: The Lucas Reagent is highly corrosive to
skin, eyes, and other body tissue. Safety glasses and aprons must be worn throughout
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this test. Clean spills immediately. Rinse with plenty of tap water if the reagent contacts
the skin.
5. Mix by tapping the test tube with a finger. If there is no cloudiness mix by stoppering
and gently shaking the test tubes. Look for cloudiness that may be developing
during this time. Note your observations. If there is no cloudiness after 10 minutes
at room temperature, warm the test tubes that are clear in a water bath (@60 C) for
15 minutes. Record your observations.
6. At the conclusion of this test, rinse the contents of the test tube down the drain with
plenty of tap water. Do not remove safety glasses until the rinsing is complete.
Chromic Acid Test: Bordwell-Wellman Test
1. Place into separate clean, dry test tubes labeled as before 5 drops of each sample to
be tested.
2. Add to each test tube 10 drops of reagent grade acetone and 2 drops of the chromic
acid reagent.
3. Place the test tubes in a water bath maintained @ 50 C. Note the coloration before
and after heating. Record your observations.
Ferric Chloride Test:
1. Place into separate clean, dry test tubes labeled as before 5 drops of each sample to
be tested.
2. Add to each test tube 2 drops of ferric chloride solution. Note the coloration before
and after the addition of the reagent. Record your observations.
Boiling Point Determination:
1. Set up the apparatus as shown in the diagram. A piece
of fire-resistant wire gauze with a small hole is placed
on a ring. A test tube containing about 2 mL of the
alcohol to be tested and a boiling stone is supported by
a clamp so that the bottom of the test tube rests directly
over the hole. The gauze shields the outer wall of the
test tube from the heat of the burner, keeping it cool
enough to cause condensation of the alcohol vapor
created upon heating. Lower a thermometer (capable of
measuring to at least 150 C) until the bulb is 0.5-1.0 cm
above the surface of the liquid. Center the thermometer
by adjusting the thermometer clamp so that the bulb
does not contact the inner walls of the test tube.
2. Adjust your burner to a very low flame and
manipulate it beneath the hole in the gauze until a
gentle boiling of the liquid takes place. (Gentle boiling
is essential for the success of this determination.
Violent boiling will result in a rapid loss of the sample
and possibly increase the danger of its becoming ignited by the burner flame.
CAUTION: If fire occurs, remove the burner and extinguish the flame by blowing
across the opening of the test tube. Let it burn out if it doesn't blow out.)
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Experiment 12 – Report Sheet
Name __________________
Identification of Alcohols and Phenols
PRELABCompound
Ferric
Chloride
(Positive or
Negative)
Lucas Test (Fast, Medium,
Slow and No Reaction)
Jones Reagent
(Green for expected reaction
and NR for no reaction )
A
B
C
D
E
F
G
H
I
J
K
DATA TABLEUnknown
Lucas Test
Number
Results
(Fast, Medium, Slow
and No Reaction)
Chromic Acid
Test Results
Ferric
Chloride Test
(Green for
expected reaction
and NR for no
reaction )
(Positive or
Negative)
Alcohol
Category
(10, 20, 30, or
phenol)
Boiling Point
1
2
3
4
5
6
7
CONCLUSIONS
QUESTIONS
1. Find the section of pages in the Handbook of Chemistry and Physics that would help in your
identification if the above table of possibilities was not given.
2. Is it necessary to perform the Lucas Test in order to determine the unknowns? Explain.
3. Compare the boiling points of the compounds with three carbons bonded aliphatically
compared to four carbons bonded aliphatically. Write a general statement of the effect of chain
length on boiling point. Explain why this trend makes sense using your knowledge of London
Dispersion Forces.
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4. Compare your predicted boiling point for alcohols with the hydroxyl groups on the end as
opposed to in the middle of compound. Write a general statement of the effect of chain
branching on boiling point. What must happen to the London Dispersion Forces as branching
increases?
5.
The boiling points of aliphatic isomer of phenol range from 120- 158oC. Write a general
statement of the effect of the cyclical shape of hydrocarbons on their boiling points. Based on
your data, are London Dispersion Forces greater in a cyclic compound or an aliphatic
compound?
IDENTIFICATION OF UNKNOWNS
Each unknown is one of the alcohols in the chart below. First, use the name of the alcohol to sketch the
structural formula. Next, determine from the structural formula if the alcohol is a primary, secondary, or
tertiary alcohol. Finally, use the boiling point, Lucas test & Chromic Acid test data from your
unknowns to determine the identities of the unknowns.
alcohol
boiling point
1-butanol
118oC
2-butanol
100 oC
2-methyl-2-propanol
(tert-butyl alcohol)
83 oC
3-methyl-l-butanol
(isoamyl alcohol or
isopentyl alcohol)
130 oC
1-propanol
98 oC
2-propanol
82 oC
phenol
181 oC
structural formula
alcohol category
unknown
number
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