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Single-Bonded Functional Groups
1.3
When you cut yourself, it is often a good idea to swab the cut with
rubbing alcohol to disinfect it. Most rubbing alcohols that are sold in
drugstores are based on 2-propanol (common name: isopropanol), C3H8O .
You can also swab a cut with a rubbing alcohol based on ethanol, C2H6O .
Often it is hard to tell the difference between these two compounds. Both
have a sharp smell, and both evaporate quickly. Both are effective at
killing bacteria and disinfecting wounds. What is the connection between
these compounds? Why is their behaviour so similar?
Section Preview/
Specific Expectations
In this section, you will
■
distinguish among the
following classes of organic
compounds: alkyl halides,
alcohols, ethers, and amines
■
describe the effects of
intermolecular forces on
the physical properties of
alcohols, ethers, and amines
■
draw and name alkyl
halides, alcohols, ethers,
and amines using the
IUPAC system
■
identify the common names
of some organic compounds
■
communicate your understanding of the following
terms: OH (hydroxyl)
group, general formula,
intermolecular forces
hydrogen bonding,
dipole-dipole interactions,
dispersion forces, alcohol,
parent alkane, alkyl halide
(haloalkane), ether, alkoxy
group, amine
Functional Groups
Both 2-propanol and ethanol contain the same functional group, an
OH (hydroxyl) group, as shown in Figure 1.12. Because ethanol and
2-propanol have the same OH functional group, their behaviour is similar.
CH3
CH
CH3
CH3
CH2
OH
OH
2-propanol
Figure 1.12
ethanol
Ethanol and 2-propanol both belong to the alcohol family.
The general formula for a family of simple organic compounds is
R + functional group . The letter R stands for any alkyl group. (If more
than one alkyl group is present, R ′ and R ′′ are also used.) For example,
the general formula ROH refers to any of the following compounds:
CH3OH, CH3CH2OH, CH3CH2CH2OH, CH3CH2CH2CH2OH, etc.
Organic compounds are named according to their functional group.
Generally, the suffix of a compound’s name indicates the most important
functional group in the molecule. For example, the suffix -ene indicates
the presence of a double bond, and the suffix -ol indicates the presence
of a hydroxyl group.
Functional groups are a useful way to classify organic compounds,
for two reasons:
1. Compounds with the same functional group often have similar
physical properties. In the next two sections, you will learn to
recognize various functional groups. You will use functional groups
to help you predict the physical properties of compounds.
2. Compounds with the same functional group react chemically in very
Each organic family follows a
set pattern. You have just seen
that you can represent the
hydrocarbon part of a
functional family by the letter
R. All the structures below
belong to the primary amine
family. What is the functional
group for this family? Write the
general formula for an amine.
CH3
similar ways. In Chapter 2, you will learn how compounds with each
functional group react.
Table 1.4, on the next page, lists some of the most common
functional groups.
CH3
CH3
NH2
CH2
CH2
NH2
CH2
NH2
Chapter 1 Classifying Organic Compounds • MHR
21
Table 1.4 Common Functional Groups
Type of compound
Suffix
Example
Functional group
alkane
-ane
none
alkene
-ene
C
C
propene
alkyne
-yne
C
C
propyne
alcohol
-ol
C
OH
propanol
amine
-amine
C
N
propanamine
aldehyde
-al
propane
O
propanal
C
H
O
ketone
propanone
-one
C
O
carboxylic acid
propanoic acid
-oic acid
C
OH
O
ester
methyl propanoate
-oate
C
O
O
amide
-amide
C
N
propanamide
Physical Properties and Forces Between Molecules
Organic compounds that have the same functional group often have
similar physical properties, such as boiling points, melting points, and
solubilities. Physical properties are largely determined by intermolecular
forces, the forces of attraction and repulsion between particles. Three
types of intermolecular forces are introduced below. You will examine
these forces further in Chapter 4.
• Hydrogen bonding is a strong intermolecular attraction between the
hydrogen atom from an NH, OH, or FH group on one molecule,
and a nitrogen, oxygen, or fluorine atom on another molecule.
• The attractive forces between polar molecules are called dipole-dipole
interactions. These forces cause polar molecules to cling to each other.
• Dispersion forces are attractive forces that occur between all covalent
molecules. These forces are usually very weak for small molecules, but
they strengthen as the size of the molecule increases.
The process that is outlined on the next page will help you to predict the
physical properties of organic compounds by examining the intermolecular
forces between molecules. As you progress through the chapter, referring
back to this process will enable you to understand the reasons behind
trends in physical properties.
22
MHR • Unit 1 Organic Chemistry
Intermolecular Forces and Physical Properties
Draw two or three molecules of the same organic compound close
together on a page. If you are considering the solubility of one compound in another, sketch the two different molecules close together.
Ask the following questions about the intermolecular interactions
between the molecules of each compound:
1. Can the molecules form hydrogen bonds?
If the molecules have OH, NH, or
HF bonds, they can form hydrogen
O
O
bonds with themselves and with water. H
H
H
H
The diagram to the right illustrates
O
hydrogen bonding between water
H
H
molecules. If the molecules contain
O, N, or F atoms that are not bonded
to hydrogen atoms, they may accept hydrogen bonds from water,
even though they cannot form hydrogen bonds with themselves.
Molecules that can form hydrogen bonds with themselves have
a higher boiling point than similar molecules that cannot form
hydrogen bonds with themselves. For example, alcohols can form
hydrogen bonds, but alkanes cannot. Therefore, alcohols have
higher boiling points than alkanes.
Molecules that can form hydrogen bonds with water, or can
accept hydrogen bonds from water, are usually soluble in water.
For example, many alcohols are soluble in water because they can
form hydrogen bonds with water.
2. Are the molecules polar ?
The molecules are polar if they have polar bonds, and if these
bonds do not act in opposite directions and counteract each other.
Polar molecules are attracted to each other by dipole-dipole forces.
Polar molecules usually have a higher boiling point than
similar non-polar molecules. Also, polar molecules that can form
hydrogen bonds have an even higher boiling point than polar
molecules that cannot form hydrogen bonds. For example, ethanol,
CH3CH2OH, is polar. Its molecules can form hydrogen bonds.
Methoxymethane, CH3OCH3 , is an isomer of ethanol. It is also
polar, but its molecules cannot form hydrogen bonds. Thus,
ethanol has a higher boiling point than methoxymethane. Both of
these compounds have a higher boiling point than the non-polar
molecule ethane, CH3CH3 .
Polar molecules with a large non-polar hydrocarbon part are
less polar than polar molecules with a smaller non-polar hydrocarbon part. For example, octanol, CH3CH2CH2CH2CH2CH2CH2CH2OH ,
is less polar than ethanol, CH3CH2OH.
Polar molecules with a large hydrocarbon part are less soluble
in water than polar molecules with a smaller hydrocarbon part.
For example, octanol, CH3CH2CH2CH2CH2CH2CH2CH2OH , is less
soluble in water than ethanol, CH3CH2OH.
continued on the next page
Chapter 1 Classifying Organic Compounds • MHR
23
3. How strong are the dispersion forces ?
Dispersion forces are weak intermolecular forces. They are stronger,
however, when the hydrocarbon part of a molecule is very large.
Thus, a large molecule has stronger dispersion interactions than a
smaller molecule.
A molecule with a greater number of carbon atoms usually has
a higher boiling point than the same type of molecule with fewer
carbon atoms. For example, hexane, CH3CH2CH2CH2CH2CH3 has a
higher boiling point than ethane, CH3CH3 .
The melting points of organic compounds follow approximately
the same trend as their boiling points. There are some anomalies,
however, due to more complex forces of bonding in solids.
In the following ThoughtLab you will use the process in the box above to
predict and compare the physical properties of some organic compounds.
ThoughtLab
Comparing Intermolecular Forces
Intermolecular forces affect the physical properties
of compounds. In this ThoughtLab, you will compare the intermolecular forces of different organic
compounds.
Procedure
1. Draw three molecules of each compound below.
(a) propane, CH3CH2CH3
(b) heptane, CH3CH2CH2CH2CH2CH2CH3
(c) 1-propanol, CH3CH2CH2OH
(d) 1-heptanol, CH3CH2CH2CH2CH2CH2CH2OH
2. For each compound, consider whether or not
hydrogen bonding can occur between its molecules. Use a dashed line to show any hydrogen
bonding.
3. For each compound, consider whether or not
any polar bonds are present.
(a) Use a different-coloured pen to identify any
polar bonds.
(b) Which compounds are polar? Which
compounds are non-polar? Explain your
reasoning.
4. Compare your drawings of propane and heptane.
(a) Which compound has stronger dispersion
forces? Explain your answer.
(b) Which compound has a higher boiling point?
Explain your answer.
5. Compare your drawings of 1-propanol and
1-heptanol.
24
MHR • Unit 1 Organic Chemistry
(a) Which compound is more polar? Explain your
answer.
(b) Which compound is more soluble in water?
Explain your answer.
Analysis
1. Which compound has a higher solubility in
water?
(a) a polar compound or a non-polar compound
(b) a compound that forms hydrogen bonds with
water, or a compound that does not form
hydrogen bonds with water
(c) CH3CH2CH2OH or CH3CH2CH2CH2CH2OH
2. Which compound has stronger attractions
between molecules?
(a) a polar compound or a non-polar compound
(b) a compound without OH or NH bonds,
or
a compound with OH or NH bonds
3. Which compound is likely to have a higher
boiling point?
(a) a polar compound without OH or NH
bonds, or a polar compound with OH or
NH bonds
(b) CH3CH2CH2OH or CH3CH2CH2CH2CH2OH
4. Compare boiling points and solubilities in
water for each pair of compounds. Explain
your reasoning.
(a) ammonia, NH3, and methane, CH4
(b) pentanol, C5H11OH, and pentane, C5H12
Compounds With Single-Bonded Functional Groups
Alcohols, alkyl halides, ethers, and amines all have functional groups
with single bonds. These compounds have many interesting uses in
daily life. As you learn how to identify and name these compounds, think
about how the intermolecular forces between their molecules affect their
properties and uses.
Alcohols
An alcohol is an organic compound that contains the OH functional
group. Depending on the position of the hydroxyl group, an alcohol
can be primary, secondary, or tertiary. Figure 1.13 gives some examples
of alcohols.
primary alcohol
secondary alcohol
tertiary alcohol
OH
CH2
HO
CH2
CH2
CH3
The hydroxyl group is bonded
to a carbon that is bonded to
only one other carbon atom.
CH
CH3
CH3
CH2
CH3
CH3
CH3
C
OH
The hydroxyl group is bonded
to a carbon that is bonded to
two other carbon atoms.
The hydroxyl group is bonded
to a carbon that is bonded to
three other carbon atoms.
Figure 1.13
Table 1.5 lists some common alcohols and their uses. Alcohols are very
widely used, and can be found in drug stores, hardware stores, liquor
stores, and as a component in many manufactured products.
Table 1.5 Common Alcohols and Their Uses
Name
methanol
ethanol
2-propanol
Common name(s)
Structure
wood alcohol,
methyl alcohol
CH3
grain alcohol,
ethyl alcohol
CH3
isopropanol,
isopropyl alcohol,
rubbing alcohol
OH
CH2
OH
Boiling point
Use(s)
64.6˚C
• solvent in many chemical
processes
• component of automobile
antifreeze
78.2˚C
• solvent in many chemical
processes
• component of alcoholic
beverages
• antiseptic liquid
• antiseptic liquid
CH3
CH
82.4˚C
OH
CH3
1,2-ethanediol
ethylene glycol
HO
CH2
CH2
OH
197.6˚C
• main component of
automobile antifreeze
Alcohols are named from the parent alkane: the alkane with the same
basic carbon structure. Follow the steps on the next page to name an
alcohol. The Sample Problem that follows gives an example.
Chapter 1 Classifying Organic Compounds • MHR
25
Web
LINK
www.mcgrawhill.ca/links/
chemistry12
Methanol and ethanol are
produced industrially from
natural, renewable resources.
Go to the web site above, and
click on Web Links to find out
where to go next. Research the
processes that produce these
important chemicals. From
where do they obtain their raw
materials?
How to Name an Alcohol
Step 1 Locate the longest chain that contains an OH group attached to
one of the carbon atoms. Name the parent alkane.
Step 2 Replace the -e at the end of the name of the parent alkane with -ol.
Step 3 Add a position number before the root of the name to indicate the
location of the OH group. (Remember to number the main chain
of the hydrocarbon so that the hydroxyl group has the lowest possible position number.) If there is more than one OH group, leave
the -e in the name of the parent alkane, and put the appropriate
prefix (di-, tri-, or tetra-) before the suffix -ol.
Step 4 Name and number any other branches on the main chain. Add the
name of these branches to the prefix.
Step 5 Put the name together: prefix + root + suffix.
Sample Problem
Naming an Alcohol
Problem
Name the following alcohol. Identify it as primary, secondary,
or tertiary.
PROBLEM TIP
If an organic compound is
complex, with many side
branches, the main chain may
not be obvious. Sketch the
compound in your notebook
or on scrap paper. Circle or
highlight the main chain.
CH2
HO
CH2
CH2
CH
CH2
CH3
CH3
Solution
Step 1 The main chain has six carbon atoms. The name of the parent
alkane is hexane.
Step 2 Replacing -e with -ol gives hexanol.
Step 3 Add a position number for the OH group, to obtain 1-hexanol.
Step 4 A methyl group is present at the third carbon. The prefix
is 3-methyl.
Step 5 The full name is 3-methyl-1-hexanol. This is a primary alcohol.
Practice Problems
14. Name each alcohol. Identify it as primary, secondary, or tertiary.
OH
(a) CH3
CH2
CH2
OH
(d) CH3
(b)
(e)
OH
26
MHR • Unit 1 Organic Chemistry
CH
CH2
OH
OH
(c)
CH
OH
CH3
15. Draw each alcohol.
(a) methanol
(d) 3-ethyl-4-methyl-1-octanol
(b) 2-propanol
(e) 2,4-dimethyl-1-cyclopentanol
(c) 2,2-butanediol
16. Identify any errors in each name. Give the correct name for
the alcohol.
(a) 1,3-heptanol
OH
HO
CH2
CH2
CH
CH2
CH3
(b) 3-ethyl-4-ethyl-1-decanol
OH
(c) 1,2-dimethyl-3-butanol
CH3
CH2
CH
CH3
CH
CH3
OH
17. Sketch a three-dimensional diagram of methanol. Hint: Recall that
the shape around an oxygen atom is bent.
Table 1.6 lists some common physical properties of alcohols. As
you learned earlier in this chapter, alcohols are polar molecules that
experience hydrogen bonding. The physical properties of alcohols
depend on these characteristics.
Table 1.6 Physical Properties of Alcohols
Polarity of functional group The OH bond is very polar. As the number of carbon
atoms in an alcohol becomes larger, the alkyl group’s
non-polar nature becomes more important than the polar
OH bond. Therefore small alcohols are more polar
than alcohols with large hydrocarbon portions.
Hydrogen bonding
Alcohols experience hydrogen bonding with other
alcohol molecules and with water.
Solubility in water
The capacity of alcohols for hydrogen bonding makes
them extremely soluble in water. Methanol and ethanol
are miscible (infinitely soluble) with water. The
solubility of an alcohol decreases as the number of
carbon atoms increases.
Melting and boiling points
Due to the strength of the hydrogen bonding, most
alcohols have higher melting and boiling points than
alkanes with the same number of carbon atoms. Most
alcohols are liquids at room temperature.
Additional Characteristics of Alcohols
• Alcohols are extremely flammable, and should be treated with caution.
• Most alcohols are poisonous. Methanol can cause blindness or death
when consumed. Ethanol is consumed widely in moderate quantities,
but it causes impairment and/or death when consumed in excess.
Chapter 1 Classifying Organic Compounds • MHR
27
Alkyl Halides
An alkyl halide (also known as a haloalkane) is an alkane in which one
or more hydrogen atoms have been replaced with halogen atoms, such
as F, Cl, Br, or I. The functional group of alkyl halides is RX, where X
represents a halogen atom. Alkyl halides are similar in structure, polarity,
and reactivity to alcohols. To name an alkyl halide, first name the parent
hydrocarbon. Then use the prefix fluoro-, chloro-, bromo-, or iodo-, with a
position number, to indicate the presence of a fluorine atom, chlorine
atom, bromine atom, or iodine atom. The following Sample Problem
shows how to name an alkyl halide.
Sample Problem
Naming an Alkyl Halide
Problem
Name the following compound.
Br
1
6
2
5
4
3
Br
CH3
Solution
The parent hydrocarbon of this compound is cyclohexane. There are two
bromine atoms attached at position numbers 1 and 3. Therefore, part
of the prefix is 1,3-dibromo-. There is also a methyl group at position
number 4. Because the groups are put in alphabetical order, the full
prefix is 1,3-dibromo-4-methyl-. (The ring is numbered so that the
two bromine atoms have the lowest possible position numbers. See
the Problem Tip on page 18.) The full name of the compound is
1,3-dibromo-4-methylcyclohexane.
Practice Problems
18. Draw a condensed structural diagram for each alkyl halide.
(a) bromoethane
(b) 2,3,4-triiodo-3-methylheptane
19. Name the alkyl halide at the right.
Then draw a condensed structural
diagram to represent it.
F
F
20. Draw and name an alkyl halide that has three carbon atoms and one
iodine atom.
21. Draw and name a second, different alkyl halide that matches the
description in the previous question.
28
MHR • Unit 1 Organic Chemistry
Ethers
Suppose that you removed the H atom from the OH group of an
alcohol. This would leave space for another alkyl group to attach to the
oxygen atom.
CH3CH2OH → CH3CH2O → CH3CH2 OCH3
The compound you have just made is called an ether. An ether is an
organic compound that has two alkyl groups joined by an oxygen atom.
The general formula of an ether is ROR. You can think of alcohols
and ethers as derivatives of the water molecule, as shown in Figure 1.14.
Figure 1.15 gives two examples of ethers.
→
O
H
H
water
→
O
R
H
O
R
alcohol
R′
ether
Figure 1.14 An alcohol is equivalent to a water molecule with one hydrogen atom
replaced by an alkyl group. Similarly, an ether is equivalent to a water molecule with
both hydrogen atoms replaced by alkyl groups.
O
CH3CH2
O
CH2CH3
ethoxyethane
(common name:
diethyl ether)
CH3
CH2CH2CH3
1-methoxypropane
(common name:
methyl propyl ether)
Figure 1.15 Until fairly recently, ethoxyethane was widely used as an anaesthetic. It had
side effects, such as nausea, however. Compounds such as 1-methoxypropane are now used
instead.
To name an ether, follow the steps below. The Sample Problem then shows
how to use these steps to give an ether its IUPAC name and its common
name.
How to Name an Ether
IUPAC Name
Step 1 Choose the longest alkyl group as the parent alkane. Give it an
alkane name.
Step 2 Treat the second alkyl group, along with the oxygen atom, as an
alkoxy group attached to the parent alkane. Name it by replacing
the -yl ending of the corresponding alkyl group’s name with -oxy.
Give it a position number.
Step 3 Put the prefix and suffix together: alkoxy group + parent alkane.
Common Name
Step 1 List the alkyl groups that are attached to the oxygen atom, in
alphabetical order.
Step 2 Place the suffix -ether at the end of the name.
Chapter 1 Classifying Organic Compounds • MHR
29
Sample Problem
Naming an Ether
Problem
Give the IUPAC name and the common name of the following ether.
CH3
CH2
O
CH2
CH3
CH2
Solution
IUPAC Name
Step 1 The longest alkyl group is based on propane.
CH3
CH2
O
CH2
CH2
CH3
Step 2 The alkoxy group is based on ethane (the ethyl group). It is
located at the first carbon atom of the propane part. Therefore, the
prefix is 1-ethoxy-.
Step 3 The full name is 1-ethoxypropane.
Common Name
Step 1 The two alkyl groups are ethyl and propyl.
Step 2 The full name is ethyl propyl ether.
Practice Problems
22. Use the IUPAC system to name each ether.
(a) H3C
O
CH3
(b) H3C
O
CH
(c) CH3
CH2
CH2
CH2
O
CH3
CH3
CH3
23. Give the common name for each ether.
(a) H3C
O
CH2CH3
(b) H3C
O
CH3
24. Draw each ether.
(a) 1-methoxypropane
(c) tert-butyl methyl ether
(b) 3-ethoxy-4-methylheptane
25. Sketch diagrams of an ether and an alcohol with the same number of
carbon atoms. Generally speaking, would you expect an ether or an
alcohol to be more soluble in water? Explain your reasoning.
Table 1.7 describes some physical properties of ethers. Like alcohols,
ethers are polar molecules. Ethers, however, cannot form hydrogen bonds
with themselves. The physical properties of ethers depend on these
characteristics.
30
MHR • Unit 1 Organic Chemistry
Table 1.7 Physical Properties of Ethers
Polarity of functional group The bent shape around the oxygen atom in an ether
means that the two CO dipoles do not counteract each
other. Because a CO bond is less polar than an OH
bond, an ether is less polar than an alcohol.
Hydrogen bonding
Because there is no OH bond in an ether, hydrogen
bonding does not occur between ether molecules. Ethers
can accept hydrogen bonding from water molecules.
Solubility in water
Ethers are usually soluble in water. The solubility of an
ether decreases as the size of the alkyl groups increases.
Melting and boiling points
The boiling points of ethers are much lower than the
boiling points of alcohols with the same number of
carbon atoms.
Additional Characteristics of Ethers
• Like alcohols, ethers are extremely flammable and should be used
with caution.
Amines
An organic compound with the functional group NH2 , NHR, or
NR2 is called an amine. The letter N refers to the nitrogen atom. The
letter R refers to an alkyl group attached to the nitrogen. The general
formula of an amine is RNR′2. Amines can be thought of as derivatives
of the ammonia molecule, NH3 . They are classified as primary, secondary,
or tertiary, depending on how many alkyl groups are attached to the
nitrogen atom. Note that the meanings of “primary,” “seconday,” and
“tertiary” are slightly different from their meanings for alcohols.
Figure 1.16 gives some examples of amines.
primary amine
secondary amine
tertiary amine
CH3
CH3
CH3
CH2
NH2
A primary amine has one alkyl
group and two hydrogen atoms
attached to the nitrogen.
CH3
CH2
NH
CH3
A secondary amine has
two alkyl groups and one
hydrogen atom attached
to the nitrogen.
CH2
N
CH2
CH3
A tertiary amine has three alkyl
groups attached to the nitrogen atom.
Figure 1.16
To name an amine, follow the steps below. The Sample Problem
illustrates how to use these steps to name a secondary amine.
How to Name an Amine
Step 1 Identify the largest hydrocarbon group attached to the nitrogen atom
as the parent alkane.
Step 2 Replace the -e at the end of the name of the parent alkane with
the new ending -amine. Include a position number, if necessary, to
show the location of the functional group on the hydrocarbon chain.
Step 3 Name the other alkyl group(s) attached to the nitrogen atom. Instead
of position numbers, use the letter N- to locate the group(s). (If two
identical alkyl groups are attached to the nitrogen atom, use N,N-.)
This is the prefix.
Step 4 Put the name together: prefix + root + suffix.
Chapter 1 Classifying Organic Compounds • MHR
31
Sample Problem
Naming a Secondary Amine
Problem
Name the following secondary amine.
CH3
H3C
NH
CH
CH3
Solution
CHEM
FA C T
Step 1 The propyl group is the largest of the two hydrocarbon groups
attached to the nitrogen atom. Therefore, the parent alkane is
propane.
It is also common and correct
to name amines with each
alkyl branch listed as an
attachment before the suffix
-amine. In this system of
nomenclature, the molecules
in Figure 1.16 are ethylamine,
methyl ethyl amine, and methyl
diethyl amine. Several other
methods of naming amines
exist, but they will not be
covered in this course.
Step 2 Replacing the -e with -amine gives propanamine. The position
number of the functional group in the propane chain is 2.
1 CH3
H3C
NH
2
CH
3 CH3
Step 3 A methyl group is also attached to the nitrogen atom.
The corresponding prefix is N-methyl-.
Step 4 The full name is N-methyl-2-propanamine.
Practice Problems
26. Name each amine.
(a) CH3
NH2
(c) CH3
CH2
CH
CH3
NH2
CH3
(b) C(CH3)3CH2
N
CH2CH3
(d)
N
CH3
H
27. Draw a condensed structural diagram for each amine.
(a) 2-pentanamine
(c) N-methyl-1-butanamine
(b) cyclohexanamine
(d) N,N-diethyl-3-heptanamine
28. Classify each amine in the previous question as primary, secondary,
or tertiary.
29. Draw and name all the isomers with the molecular formula C4H11N.
32
MHR • Unit 1 Organic Chemistry
Amines are polar compounds. Primary and secondary amines can form
hydrogen bonds, but tertiary amines cannot. Table 1.8 lists some common
physical properties of amines.
Table 1.8 Physical Properties of Amines
Polarity of functional group CN and NH bonds are polar. Thus, amines are
usually polar.
Hydrogen bonding
The presence of one or more NH bonds allows
hydrogen bonding to take place.
Solubility in water
Because of hydrogen bonding, amines with low
molecular masses (four or less carbon atoms) are
completely miscible with water. The solubility
of an amine decreases as the number of carbon
atoms increases.
Melting and boiling points
The boiling points of primary and secondary amines
(which contain NH bonds) are higher than the boiling
points of tertiary amines (which do not contain an NH
bond). The higher boiling points are due to hydrogen
bonding between amine molecules.
Additional Characteristics of Amines
• Amines are found widely in nature. They are often toxic. Many
amines that are produced by plants have medicinal properties.
(See Figure 1.17.)
• Amines with low molecular masses have a distinctive fishy smell.
Also, many offensive odours of decay and decomposition are caused
by amines. For example, cadavarine, H2NCH2CH2CH2CH2CH2NH2 ,
contributes to the odour of decaying flesh. This compound gets its
common name from the word “cadaver,” meaning “dead body.”
• Like ammonia, amines act as weak bases. Since amines are bases,
adding an acid to an amine produces a salt. This explains why
vinegar and lemon juice (both acids) can be used to neutralize the
fishy smell of seafood, which is caused by basic amines.
A
Figure 1.17 (A) Aniline is an
aromatic amine that is useful for
preparing dyes. (B) Adrenaline is
a hormone that is produced by the
human body when under stress.
(C) Quinine is an effective drug
against malarial fever.
B
C
CH
OH
OH
NH2
HO
CH
CH
CH2
CH3
NH
H3CO
HO
aniline (primary amine)
CH2
N
N
adrenaline (secondary amine)
quinine (tertiary amine)
Section Summary
In this section, you learned how to recognize, name, and draw members
of the alcohol, alkyl halide, ether, and amine families. You also learned
how to recognize some of the physical properties of these compounds. In
the next section, you will learn about families of organic compounds with
functional groups that contain the CO bond.
Chapter 1 Classifying Organic Compounds • MHR
33
Section Review
1
K/U
Name each compound.
NH2
(a)
(c)
OH
H3C
CH3
CH3
Unit Issue Prep
2
K/U
CHCH2CH3
O
(b) CH3CH2
Write the IUPAC name for each compound.
(a) CH3CH2CH2CH2CH2CH2CH2OH
Organic compounds are
used in a wide variety of
applications all around you. If
you want to prepare for your
Unit 1 Issue, research the use
of organic compounds as fuel,
medicines, and food additives.
(b) CH3CH(OH)CH2CH3
(c) CH3CH2NH2
(d) (CH3)2NH
(e) CH3CH2OCH3
(f) CH3CH(Cl)CH3
3
C
Draw a condensed structural diagram for each compound.
(a) 3-heptanol
(b) N-ethyl-2-hexanamine
(c) 3-methoxypentane
4
Draw and name three isomers that have the molecular formula
C5H12O.
5
Name the following compounds. Then rank them, from highest to
lowest boiling point. Explain your reasoning.
C
I
CH3
(a) H3C
H3C
O
CH3
CH3
CH2
OH
CH3
CH2
(b) CH3
CH3
CH3
CH2
CH2
NH2
CH3
N
CH3
6
Draw cyclohexanol and cyclohexane. Which compound do you
expect to be more soluble in water? Explain your reasoning.
7
Name the following compounds. Which compound do you expect
to be more soluble in benzene? Explain your reasoning.
C
I
OH
8
Name these compounds. Then rank them, from highest to lowest
molecular polarity. Explain your reasoning.
I
CH3
CH2
CH2
CH3
HO
CH2
CH2
CH2
CH3CH2
34
MHR • Unit 1 Organic Chemistry
O
CH2CH3
CH3