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Chapter 8
The Chemistry of Medicine and Clothing: Condensation
Polymers, Especially Those Containing Nitrogen
Review Questions
1. Amines are molecules that contain a nitrogen atom bonded to one or more
hydrocarbon groups.
2. Alcohols are molecules in which an oxygen atom is bonded to both a hydrogen atom
and a hydrocarbon group. Alcohols are given the general formula R-O-H, and can
undergo hydrogen bonding. Amines are molecules in which a nitrogen atom is
bonded to one or more hydrocarbon groups. The general formulas for amines bonded
to one, two, and three hydrocarbon groups are R-N-H2, R2-N-H, and R3-N,
respectively. Those amines with formulas R-N-H2 and R2-N-H resemble alcohols,
and can also undergo hydrogen bonding. However, hydrogen bonds containing a
nitrogen atom are weaker than those containing an oxygen atom.
3. Amines correspond to molecule of ammonia, NH3, in which one, two, or all three of
the hydrogen atoms are replaced by hydrocarbon groups.
4. Diamines are amines that contain two amino nitrogen atoms.
5. Neurotransmitters, many of which are amines, are molecules responsible for
transmitting impulses between adjacent nerve cells.
6. Serotonin is a neurotransmitter required to maintain a positive mood. Chronic
deficiencies of serotonin are linked to depression. Serotonin also regulates the
body’s temperature. The structure of serotonin is given below.
NH2
CH2
HO
CH
C
C
C
CH
HC
C
CH
N
H
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CH2
Dopamine, another neurotransmitter, is responsible for the regulation of mood,
movement, and attention. Its structure is given below.
HO
C
HO
CH
C
C
CH
CH2
CH
CH2 NH2
A third neurotransmitter is acetylcholine. (You can obtain additional information
from Web resources listed at the end of the chapter.) This neurotransmitter is believed
to be responsible for learning and memory. Its structure is given below.
O
H3C
C
O
CH2
CH3
+
CH2 N
CH3
CH3
7. Neurotransmitters are released from the nerve cell from which the impulse is
originating and travels across a gap, called a synaptic gap, of a few hundred
nanometers to a receptor on an adjacent nerve cell. The neurotransmitter temporarily
attaches to the second nerve cell and signals the impulse to travel along that nerve
cell. After signal generation, the neurotransmitters are rapidly released and
frequently travel back to the original nerve cell for reuse.
8. Prozac modifies the recycling of the neurotransmitter serotonin in certain nerve cells.
It increases the concentration of serotonin in the synaptic gap (or region) by
preventing its reuptake. This allows for repeated binding of serotonin to the target
receptor and initiation of multiple nerve impulse without requiring the excitation and
release of serotonin from the nerve cell of origin.
9. Pyridine is structurally similar to benzene. In pyridine a nitrogen atom replaces one
of the carbon atoms. Also, analogous to benzene, the bonds joining the ring atoms in
pyridine alternate between single and double in character. In pyridine, however, the
nitrogen atom is not bonded to a hydrogen atom as the nitrogen atom can only take
three bonds. The structures of benzene and pyridine are given below.
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N
pyridine
benzene
10. A stimulant is a chemical substance that stimulates the body’s central nervous
system. Stimulants affect the body by temporarily increasing one’s level of alertness
and the speed of mental processes. It improves mood by providing a sense of
euphoria and decreases fatigue and appetite.
11. Nicotine is a mild stimulant and it consists of a pyrrolidine ring and a pyridine ring
linked by a single bond with a methyl group attached to the nitrogen of the
pyrrolidine. Nicotine is addictive because a decrease in its blood levels produces
withdrawal symptoms, such as irritability, anxiety, difficulty in concentrating, and
restlessness. The structure of nicotine is given below.
CH3
N
N
12. The nicotine patch is used by some individuals to help them to quit smoking. This
device continuously delivers nicotine to the bloodstream by being absorbed through
the skin.
13. Caffeine is a stimulant that is also classified as an amine. The structure of caffeine is
given below.
CH3
N
N
N
N
H3C
O
CH3
O
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14. The half-life of a substance is defined as the length of time required for one half of
the total amount of a substance to decompose.
15. Drug A would be 90% eliminated from the body first because it has a shorter halflife (1 hour versus 10 hours). Since drug A is eliminated faster than drug B, drug A
would need to be taken more frequently.
16. The ammonia molecule consists of a nitrogen atom bonded to three hydrogen atoms.
An ammonium ion consists of a nitrogen atom bonded to four hydrogen atoms. In
the ammonium ion, nitrogen forms an additional covalent bond to hydrogen by using
its pair of nonbonding electrons.
17. The nitrogen atom in the amine forms a bond to the hydrogen ion, H+, which is
extracted from a molecule of water. In the process, a hydroxide ion is released in to
the aqueous solution, making it more basic.
18. Crack cocaine is the name given to the free base form of cocaine. Cocaine, as the
free amine, or base, is not very water-soluble. Therefore, in the extraction process,
the amine is converted to the corresponding hydrochloride salt, cocaine
hydrochloride. In order to produce the free base, the salt is reacted with a substance
such as sodium bicarbonate.
19. An analgesic is a compound that relieves pain. An antipyretic is a substance that
relieves fever.
20. Aspirin (acetylsalicylic acid) is defined as a mild analgesic, whereas codeine, a
derivative of morphine, is a much stronger analgesic.
21. Amides are molecules containing an amino group bonded to a carbonyl carbon. A
polyamide is a polymer formed by the condensation of a dicarboxylic acid (a
molecule with two –COOH groups) and a diamine (a molecule with two amino
groups) with the loss of water.
22. Condensation polymers are molecules formed by the reaction of two compounds
with repeating functional groups with the concurrent loss of a water molecule. Nylon
6,10 is an example of a condensation polymer.
23. A diacid is molecule containing two carboxylic acid (-COOH) groups. When
dicarboxylic acids combine with diamines, water molecules are removed and a
polyamide is produced.
24. –[C(O)-(CH2)5-C(O)-NH-(CH2)10-NH]25. An amino acid is a molecule that contains both an amino group and a carboxylic acid
group joined by a carbon chain.
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26. Polyesters are condensation copolymers analogous to the polyamides. These
polymers are formed when a diol, or dialcohol, is reacted with a diacid and water is
eliminated. This results in the formation of an ester group (-CO-O-) at each linkage
point between the diol and the diacid.
27. The polymer chains in polyamides are parallel to each other due to the high degree
of hydrogen bonding between the hydrogen atom of the -NH- group of one chain and
the oxygen atom of the carbonyl group on an adjacent chain. As a result of this
extensive hydrogen bonding, the chains pack well together and form a very strong
material. In contrast, adjacent chains in polyesters cannot undergo hydrogen bonding
due to the absence of hydrogen atoms bonded to either nitrogen atoms or oxygen
atoms.
28. The polymer PET or PETE [poly(ethylene terephthalate)] is formed from the
condensation of ethylene glycol (HO-CH2-CH2-OH, a dialcohol) with a diacid in
which the carboxylic acid groups (-COOH) are separated by a benzene ring.
29. Polycarbonates, like polyesters, are condensation products of a diacid and a diol.
Unlike polyesters, however, polycarbonates contain a diacid, carbonic acid, in which
the two –OH groups are bound to the same carbon. This results in the production of
two ester linkages with a carbon C=O group between them. The structure of carbonic
acid is given below.
O
C
HO
OH
carbonic acid
30. Polyethylene glycol has numerous ether oxygens (see structure below). Because
these ether oxygens can form extensive hydrogen bonds with water molecules, the
material draws moisture and heat away from the individual wearing the fabric by
dissolving the water vapor, keeping then cool and dry.
…
O-CH2-CH2-O-CH2-CH2-O…
Understanding Concepts
31. Compound “b” will have the higher boiling point because it has two hydrogen atoms
that can participate in hydrogen bonding. Compound “a” lacks hydrogen atoms
bound directly to nitrogen. The presence of hydrogen bonds between molecules
results in a higher boiling point.
32. The alcohol will have the higher boiling point. As both molecules have similar
chemical weights and structures, the difference in boiling points results from
differences in the strength of the hydrogen bonds between the molecules. Since
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hydrogen bonds containing a nitrogen atom are weaker than the corresponding
hydrogen bonds with an oxygen atom, the alcohol will have stronger hydrogen
bonds.
33. Smokers crave cigarettes more often than coffee drinkers crave coffee because the
half-life of nicotine is less than that for caffeine. Since the half-lives of nicotine and
caffeine are 2 and 4 hours, respectively, nicotine is eliminated from the body faster.
This results in lower nicotine levels in the bloodstream and an increased craving for
nicotine.
34. The longer the half-life of a compound, the slower it is eliminated from the body.
Thus, caffeine, with a half-life of 4 hours, remains in the body the longest. Cocaine,
with a half-life of 0.7 hours, is 90% eliminated first.
35. If the half-life of a drug is 90 minutes, the concentration would fall to 1/4 of its
initial value in two half-life periods, or 180 minutes. The same drug would fall to
1/16 of its initial concentration in four half-life periods, or 360 minutes.
36. If the half-life of a substance is 1 hour, 1/4 of the substance remains after 2 hours.
Similarly, 1/8 of the substance remains after 3 hours, and 1/16 after 4 hours.
37. If the concentration of a drug in a patient falls to 1/4 of its initial amount after three
hours, then it must have been administered two half-life periods ago. Therefore, its
half-life must be 1.5 hours (3 hours / 2) or 90 minutes.
38. If the concentration of a drug was found to be 1/8 of the original dose 3 hours after it
was administered, then three half-life periods must have elapsed in that time period.
Thus, the half-life of the drug is 1 hour (3 hours / 3 half-life periods or 1 hour / 1
half-life period).
39. As the ratio of carbon atoms to nitrogen atoms in an amine decreases, its solubility in
water increases. Hydrogen atoms bound to carbon atoms are unable to hydrogen
bond with water, whereas hydrogen atoms bound to nitrogen atoms are. Thus, the
lower the number of carbon atoms per nitrogen atom (or the lower the ratio of
carbon atoms to nitrogen atoms), the greater the number of hydrogen bonds per
molecule, and the greater its solubility in water. Another way to arrive at this answer
is to remember that hydrocarbon molecules tend to be non-polar, while similar
compounds containing nitrogen atoms are somewhat polar in character. Thus, the
greater the polarity of the molecule, the greater its solubility in water. Similarly, the
greater the non-polar character of the molecule, the lower its water solubility will be.
40. A salt containing a BH+ ion is more soluble than the corresponding neutral B
molecule because the ion is stabilized by strong interactions with the nonbonding
electrons of the oxygen atoms present in water.
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41. While many drugs contain a polar amino group (-NH2), they are relatively insoluble
in water (that is, they are hydrophobic) because of their relatively high C-to-N ratio.
Because of their insolubility in water, they are not good drug candidates for
intravenous administration. In order to make these drugs more water soluble, they
are converted into their ionic form. Ions are more water-soluble because they are
strongly stabilized by interactions with the nonbonding electrons of the oxygen
atoms of water.
42. Cocaine hydrochloride cannot be smoked because it is an ionic solid with a high
melting point. Its melting point is so high (about 200oC) that it decomposes upon
burning.
Injecting the drug results in high concentrations in the bloodstream. When the
freebase is smoked, a volatile liquid is produced that quickly vaporizes, is inhaled
into the lungs, and is quickly absorbed into the bloodstream producing high
concentrations.
43. The structures of adrenaline and amphetamine are given below.
OH
HO
CH
CH
C
C
C
CH
HO
NH
CH2
CH3
CH
adrenaline
CH
CH2
NH2
HC
C
CH
HC
CH
CH3
CH
amphetamine
Adrenaline increases the rate of glycogen breakdown to glucose in the liver and the
muscles, thereby increasing the glucose supply in the blood and providing a fast
source of energy. Adrenaline also increases the heart and breathing rates to provide
more oxygen to the blood.
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Amphetamine acts in a similar way to increase heart rate, wakefulness, energy level
and drive. Both result in a temporary elevation in mood followed by a period of
fatigue and depression.
The effects are similar because the structures of both amines are similar. Both have a
benzene ring bonded to a two-carbon chain that is connected to an amino group.
44. Biochemically, cocaine alters the level of dopamine, a neurotransmitter that helps
the body to regulate movement, mood, and attention. It does this by blocking the
reabsorption of dopamine onto sites located at the original transmission nerve fiber.
This results in an overabundance of dopamine in the synaptic region and an
overstimulation of the receptors. However, continued presence of the dopamine
molecule in the synapse allows them to be gradually destroyed by enzymes. This
loss of dopamine produces both severe depression and an intense craving for more
cocaine.
45. The structures for acetylsalicylic acid, acetaminophen, and ibuprofen are given
below
Acetylsalicylic acid:
O
CH
HC
C
C
HC
OH
CH3
C
O
C
CH
O
Acetaminophen:
HO
O
C
NH
CH3
Ibuprofen:
H3C
CH3
CH
H2C
CH3
CH
C
HO
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O
Acetylsalicylic acid contains a carboxylic acid group and an ester group of acetic
acid bonded to a benzene ring. Acetaminophen consists of an amine combined with
acetic acid (a carboxylic acid group) on a benzene ring. Ibuprofen contains a
carboxylic acid group bonded to a benzene ring. Thus, all three molecules contain a
carboxylic acid group and a benzene ring. They have a planar (or flat) region
associated with the benzene ring and have similar shapes, sizes, and polarities.
46. The analgesics discussed in the chapter represent a class of drugs known as nonsteroidal anti-inflammatory drugs, or NSAIDs. These drugs mainly inhibit the
body’s ability to synthesize biomolecules, called prostaglandins, which are made in
response to cell injury. The common mechanism of action for NSAIDs is the
inhibition of an enzyme known as cyclooxygenase (COX) required for the formation
of prostaglandins. This enzyme has two forms, COX-1, which protects the stomach
lining, and COX-2, which is required for the formation of prostaglandins. Most
NSAIDs inhibit both COX-1 and COX-2. Newer anti-inflammatory drugs only
inhibit COX-2, resulting in a decrease in both prostaglandin synthesis and stomach
irritation. The COX-2 inhibitors currently available have been approved by the Food
and Drug Administration for the treatment of acute pain and arthritis. While more
effective in managing pain in these conditions, COX-2 inhibitors have also been
associated with an increased risk of heart attacks.
47. Reaction of a diacid and a diol:
HO
O
O
C
C
CH2
CH2
HO
HO
OH
O
CH2
CH2
+
CH2
CH2
O
C
C
O
O
OH
CH2
CH2
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O
O
O
C
C
CH2
CH2
O
OH
CH2
Reaction of a monoacid and a diol:
O
H3C
CH2
CH2
+
C
HO
OH
CH2
H3C
CH2
O
C
OH
CH2
CH2
OH
O
48. Polymerization will form a molecule with the following repeat unit:
–[C(O)-(CH2)4-C(O)-NH-(CH2)7-NH]49. Unlike amines, which contain only amino groups, amino acids are molecules that
contain both an amino group and a carboxylic acid group. Thus, polymers of amino
acids can be formed by the reaction of the acid –OH group of one amino acid with
the amino hydrogen of an adjacent molecule. Similar reactions can be performed
with the residual amino and carboxylic acid groups of the dimer.
Synthesizing Ideas
50. Since CH3CH2CH2NH2 can form hydrogen bonds with water than (CH3)3N,
CH3CH2CH2NH2 would be more water-soluble.
51. No, hydrogen bonding cannot occur in pure amines in which all three atoms bonded
to the nitrogen are carbon chains rather than hydrogen. Hydrogen bonding in amine
compounds requires the presence of a hydrogen atom that is directly bonded to the
nitrogen. The boiling point for the amine (CH3)N will be significantly lower than the
boiling point for its isomer CH3CH2CH2NH2. The greater the extent of hydrogen
bonding, the higher the boiling point of the molecule.
52. a) Cocaine contains an amine functional group and two ester groups.
b) Acetylsalicylic acid contains a carboxylic acid group and an ester group.
53. We are readily able to detect the odors of small diamines because of their volatility
(ability to form a gas) and water-solubility. The monomers of nylon 6,6 are
chemically bonded together into long polymer chains and are, therefore, unable to
become volatile.
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54. a) Prozac modifies the recycling of serotonin, a neurotransmitter. It increases the
concentration of serotonin in the synaptic region of the neuron by blocking the
recapture of the neurotransmitter by the nerve cell from which the signal originated.
Similarly, cocaine blocks the reabsorption of dopamine, another neurotransmitter,
onto sites on its nerve fiber of origin, thereby increasing the concentration of
dopamine in the synaptic region.
b) Both drugs block the re-uptake or reabsorption of the neurotransmitter.
c) Both molecules have similar structural features. Both contain aromatic rings and
amino groups.
d) Prozac produces an overstimulation of the serotonin receptors, and thereby serves
as an antidepressant. Cocaine is a powerful stimulant to the central nervous system
as it results in the overstimulation of dopamine receptors. Cocaine, by acting as a
stimulant, also exhibits anti-depressant activity.
e) Structural features of drugs that would simulate cocaine activity in the body
would include the presence of hydroxyl and/or amino functional groups, aromatic
rings, and a relatively small molecular structure.
55. The exact mechanism(s) of neurotransmitter / receptor interactions are active areas
of research for scientists today. Utilizing our knowledge of neurotransmitter
structure, we can make the limited generalizations about this interaction.
Neurotransmitters and drugs that competitively bind to neuronal receptors are
generally small molecules with hydroxyl and/or amino functional groups. Several of
these molecules contain aromatic rings. These observations suggest that the binding
sites on the receptors are polar in character (hydrophilic), small in size, and may
require some degree of planarity to the molecule.
56. In addition to the different dialcohols used, the carbonyl group to hydrocarbon ratio
is greater in polyesters than in polycarbonates. Thus, polyesters are thin, tough films,
while polycarbonates can be molded into tough, transparent plastics, such as bicycle
helmets and computer housings.
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