CHEM 122: Introduction to Organic Chemistry
Chapter 8: Amines.
1. Draw a structural formula for each amine.
a)
b)
c)
d)
e)
f)
4-Methyl-2-pentanamine
trans-2-Aminocyclohexanol
N,N-Dimethylaniline
Dicyclohexylamine
sec-Butylamine
2,4-Dimethylaniline
2. Classify each amino group as primary, secondary, tertiary or heterocyclic and as
aliphatic or aromatic.
O
HO
NH2
O
a)
N
H
Serotonin (a neurotransmitter)
CH 3
b) H2N
Benzocaine (a topical anesthetic)
N
O
CH 3
COOH
H2N
c)
NH 2
d)
Diphenhydramine
(the hydrochloride salt is the antihistamine Benadryl)
H
Lysine (an amino acid)
N
N
e) Cl
N
Chloroquine (an antimalarial drug)
e) H2N
COOH
4-Aminobutanoic acid (a neurotransmitter)
3. There are eight constitutional isomers with the molecular formula C4H11N.
a) Name and draw a structural formula for each amine.
b) Classify each amine as primary, secondary, or tertiary.
c) Which are chiral?
4. There are eight primary amines with the molecular formula C5H13N.
a) Name and draw a structural formula for each amine.
b) Which are chiral?
5. Account for the fact that 1-butanamine (bp 78oC) has a lower boiling point than 1butanol (bp 117oC).
6. Account for the fact that most low-molecular-weight amines are very soluble in
water, whereas low-molecular-weight hydrocarbons are not.
7. Write a structural formula for each amine salt.
a)
b)
c)
d)
Ethyltrimethylammonium hydroxide
Dimethylammonium iodide
Tetramethylammonium chloride
Anilinium bromide
8. Name these amine salts.
a) CH3CH2NH3+Clb) (CH3CH2)2NH2+Cl+
NH 3 HSO4-
c)
9. From each pair of compounds, select the stronger base.
N(CH 3 )2
NHCH 3
or
or
or
a)
N
H
CH 2 NH 2
N(CH 3 )2
N
b)
c)
10. Suppose you have two test tubes, one containing 2-methylcyclohexanol and the
other containing 2-methylcyclohexanamine (both of which are insoluble in water)
and that you do not know which test tube contains which compound. Describe a
simple chemical test by which you could tell which compound is the alcohol and
which is the amine.
11. Complete the equations for the following acid-base reactions.
O
a)
H3C
C
OH
+
N
Pyridine
Acetic acid
NH2
b)
+
1-Phenyl-2-propanamine (Amphetamine)
NH
CH3
c)
HCl
+
H2SO4
Methamphetamine
12. Pyridoxamine is one form of vitamin B6.
CH2 NH 2
HO
CH2 OH
H3C
N
Pyridoxamine (Vitamin B6)
a) Which nitrogen atom of pyridoxamine is the stronger base?
b) Draw a structural formula for the salt formed when pyridoxamine is treated with
one mole of HCl.
13. Draw a structural formula for a compound with the given molecular formula that
is:
a)
b)
c)
d)
e)
f)
g)
A 2o aromatic amine, C7H9N
A 3o aromatic amine, C8H11N
A 1o aliphatic amine, C7H9N
A chiral 1o amine, C4H11N
A 3o heterocyclic amine, C5H11N
A trisubstituted 1o aromatic amine, C9H13N
A chiral quaternary ammonium salt, C9H22NCl
14. Consider these three compounds: CH3OH, CH3SH, and (CH3)2NH.
a)
b)
c)
d)
Which is the strongest acid?
Which is the strongest base?
Which has the highest boiling point?
Which forms the strongest intermolecular hydrogen bonds in the pure state?
15. Arrange these compounds in order of increasing boiling point: CH3CH2CH2CH3,
CH3CH2CH2OH, and CH3CH2CH2NH2. Boiling point values from lowest to
highest are -0.5oC, 7.2oC, and 77.8oC.
16. Procaine was one of the first local anesthetics. Its hydrochloride salt is marketed
as Novocaine.
O
N
O
H2N
Procaine
a) Is procaine chiral? Does it contain a stereocenter?
b) Which nitrogen atom of procaine is the stronger base>
c) Draw a structural formula for the salt formed by treating procaine with one mole
of HCl, showing which nitrogen is protonated and bears the positive charge.
17. Several poisonous plants, including Atropa belladonna, contain the alkaloid
atropine. The name “belladonna” (which means “beautiful lady”) probably comes
from the fact that Roman women used extracts from this plant to make themselves
more attractive. Atropine is widely used by ophthalmologists and optometrists to
dilate the pupils for eye examination.
H3C
N
H
OH
O
O
Atropine
a) Classify the amino group in atropine as primary, secondary, or tertiary.
b) Locate all stereocenters in atropine.
c) Account for the face that atropine is almost insoluble in water (1g in 455 mL of
cold water) but atropine hydrogen sulfate is very soluble (1 g in 5 mL of cold
water).
d) Account for the fact that a dilute aqueous solution os atropine is basic (pH
approximately 10.0).
18. Following are two structural formulas for 4-aminobutanoic acid, a
neurotransmitter. Is this compound better represented by structural formula (A)
or (B)? Explain.
O
O
or
H2N
OH
(A)
H3N
+
O-
(B)