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Pre-Lab Study Questions 27
1. What is the functional group in amines? In amides?
2. What products are formed when amides are hydrolyzed?
3. Draw the condensed structural formulas for each of the following amines and amides:
a. 1-propanamine
. 2-methyl-3-hexamine
c. N-methylpentamide
d. N,N-dimethylbenzamide
Date Name
Section Team
Instructor
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REPORT SHEET
Amines and Amides
LAB
27
A. Structure, Classification, and Solubility of Amines
Aniline N-Methylaniline Triethylamine
1. Condensed structural
formula
2. Classification (1°,
2°, 3°)
3. Odor
4. Solubility in water
5. pH
Questions and Problems
Q1 In the discussion, the structures are given for Neo-Synephrine and methampheta-
mine. Give the amine classification of each of the compounds.
Q2 What type of compound accounts
Q3 Explain why amines are basic.
Date Name
Section Team
Instructor
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B. Neutralization of Amines with Acid
Aniline N-Methylaniline Triethylamine
1. Solubility after adding
HCl
2. Change in odor after
adding HCl
3. Equations for the neutralization of amines with HCl
Aniline HCl
N-methylaniline HCl
Triethylamine HCl
Questions and Problems
Q4 How does lemon juice remove the odor of fish?
Q5 Write an equation for the reaction of butylamine with HCl.
C. Amides
1. Amidation
a. Acetic acid ammonia
. Aniline ammonia
Amines and Amides 313
Acetamide Benzamide
2. Odor
3. Solubility
D. Hydrolysis of an Amide
1. Acid Hydrolysis
a. Acetamide
. Benzamide
Acetamide Benzamide
2. Odor
Acetamide Benzamide
3. Change in color of red
litmus paper
4. Odor after adding
NaOH
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5. Base Hydrolysis
a. Acetamide
. Benzamide
Questions and Problems
Q6 You have unknowns that are a ca
oxylic acid, an ester, and an amine. Describe
how you would distinguish among them.
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LABORATORY GOALS
y, secondary, or tertiary.
LAB INFORMATION
Time: 2½ h
Comments: Some amines have an odor that i
itates the nose and sinuses. Work in the
hood. Tear out the report sheets and place them next to the matching proce-
dures.
Related Topics: Amines, solubility and pH of amines, amidation, amides, hydrolysis of amides
Dispose of all chemicals as directed by your laboratory instructor.
CHEMICAL CONCEPTS
A. Structure, Classification, and Solubility of Amines
Amines are considered derivatives of ammonia in which one or more hydrogen atoms are replaced with
alkyl or aromatic groups. The number of alkyl groups attached to the nitrogen atom determines the clas-
sification of primary, secondary, or tertiary amines. The aromatic amines used the name aniline.
Amines are often found as part of compounds that are physiologically active or used in medications.
Physiological Effects of Some Amines
Histamine
Histamine is synthesized in the nerve cells of the hypothalamus from the amino acid histidine when a
ca
oxylate group is converted to 2CO . Histamine is produced by the immune system in response to
pathogens and invaders or injury. When histamine combines with histamine receptors, it causes allergic
Amines and Amides 27
304 Laboratory Manual for General, Organic, and Biological Chemistry
eactions, which may include inflammation, watery eyes, itchy skin, and hay fever. Histamine can also
cause smooth muscle constriction, such as the closing of the trachea in persons allergic to shellfish. His-
tamine is also stored and released in the cells of the stomach, where it stimulates acid production. Anti-
histamines, such as Benadryl, Zantac, and Tagamet, block the histamine receptors and stop the allergic
eactions.
Serotonin
Serotonin (5-hydroxytryptamine) helps us to relax, sleep deeply and peacefully, and think rationally, and
it gives a feeling of well-being and calmness. Serotonin is synthesized from the amino acid tryptophan,
which can cross the blood-
ain ba
ier. A diet that contains foods such as eggs, fish, cheese, turkey,
chicken, and beef, which have high levels of tryptophan, will increase serotonin levels. Foods with a low
level of tryptophan, such as whole wheat, will lower serotonin levels. Psychedelic drugs such as LSD
and mescaline stimulate the action of serotonin at its receptors.
Low levels of serotonin in the
ain may be associated with depression, anxiety disorders, obsessive-
compulsive disorder, and eating disorders. Many antidepressant drugs, such as fluoxetine (Prozac) and
paroxetine (Paxil), are selective serotonin reuptake inhibitors (SSRIs). When the reuptake of serotonin is
slowed, it remains longer at the receptors, where it continues its action; the net effect is as if additional
quantities of serotonin were taken.
Solubility of Amines
In water, ammonia and amines with one to four ca
on atoms act as weak bases because the unshared
pair of electrons on the nitrogen atom attracts protons. The products are an ammonium ion or alkyl am-
monium ion and a hydroxide ion.
B. Neutralization of Amines with Acid
Because amines are basic, they react with acids to form the amine salt. These amine salts are much more
soluble in water than the co
esponding amines.
Amines and Amides 305
C. Amides
When a ca
oxylic acid reacts with ammonia or an amine, the product is an amide. The functional group
is called the amide group.
In a reaction called amidation, an amide forms when a ca
oxylic acid is heated with ammonia or an
alkyl or aromatic amine.
D. Hydrolysis of an Amide
When an amide is hydrolyzed, the amide bond is
oken and the ca
oxylic acid and the amine are sepa-
ated. Hydrolysis takes place in either an acid or a base. Acid hydrolysis produces the ca
oxylic acid
and the ammonium salt. In a base, the hydrolysis reaction produces the salt of the ca
oxylic acid and
ammonia. The odor of ammonia and the reaction of ammonia with litmus paper are used to detect the
hydrolysis reaction.
306 Laboratory Manual for General, Organic, and Biological Chemistry
EXPERIMENTAL PROCEDURES GOGGLES REQUIRED!
A. Structure, Classification, and Solubility of Amines
Materials: Aniline, N-methylaniline, triethylamine, test tubes, test tube rack, sti
ing rod, pH paper
WORK IN THE HOOD. THE VAPORS OF AMINES ARE IRRITATING TO THE
NOSE AND SINUSES.
1. Draw the condensed structural formulas of aniline, N-methylaniline, and triethylamine.
2. State the classification (1°, 2°, 3°) of each.
3. To three separate test tubes, add 5 drops of aniline, N-methylaniline, and triethylamine. Cautiously
note the odor of each. Remember to hold a fresh
eath of air while you fan the vapor toward you.
The instructor will demonstrate this technique. Record the odor.
4. Add 2 mL of water to each test tube and stir. Clean and dry the sti
ing rod between test tubes.
Describe the solubility of each amine in water.
5. Determine the pH of each solution by dipping a sti
ing rod in each solution and then touching it
to pH paper. Record the pH.
Save these test tubes and samples for Part B.
B. Neutralization of Amines with Acid
Materials: Test tubes from Part A, blue litmus paper, 10% HCl
1. Using the amines from Part A, add drops of 10% HCl to each amine solution until blue litmus
paper turns red. Record any changes in solubility of each amine.
2. Record any changes in odor.
3. Draw the condensed structural formulas for the reactants and products for the neutralization equa-
tions of aniline, N-methylaniline, and triethylamine with HCl.
C. Amides
Materials: Acetamide, benzamide, test tubes, spatula
1. Draw the condensed structural formulas for the reactants and products of the equation for the ami-
dation of (a) acetic acid and ammonia, (b) aniline and ammonia.
2. Place small amounts (tip of a spatula) of acetamide and benzamide in separate test tubes. Using
caution, note the odor of each. Record the odors.
3. Add 2 mL of water to each test tube. Record the solubility of each amide in water
Save these test tubes for Part D.
D. Hydrolysis of an Amide
Materials: Acetamide, benzamide, test tubes, spatula, 10% HCl, 10% NaOH, 250-mL beaker for water
ath, hot plate, red litmus paper, small graduated cylinder
1. Draw the condensed structural formulas for the reactants and products of the equation for the hy-
drolysis of (a) acetamide and (b) benzamide using HCl.
2. Using the test tubes from Part C.3, add 2 mL of 10% HCl to each. Place the test tubes in a boiling
water bath and heat gently for 5 min. Using caution, note any odor coming from each mixture. Re-
cord your observations.
Amines and Amides 307
3. Place small amounts (tip of a spatula) of acetamide and benzamide in separate test tubes. Add 2
mL of 10% NaOH to each. Place the test tubes in a boiling water bath. Wet a piece of red litmus
paper and place it over the mouth of each test tube.
Heat the test tubes gently for 5 min. Record any change in the color of each of the