Nelson chemistry 12

unit

Organic
Chemistry

1

Eugenia Kumacheva
Associate Professor
University of Toronto

“By clever synthesis, organic chemists obtain new molecules
with fascinating architectures, compositions, and functions.
My research group studies polymers (long-chain molecules
with many repeating units) that possess fluorescent, nonlinear optical, and electroactive properties. In particular, we
are interested in nanostructured materials made from very
small polymer particles. For example, we work on synthesizing polymers for high-density optical data storage. One of
the materials designed and created in our laboratory is often pictured as a piece
of new plastic about the size of a cube of sugar on which one can store the
entire Canadian National Library collection. Other polymers can change their
transparency when illuminated with high-intensity light. The coatings and
films made from such polymers can be used to protect pilots’ eyes from damaging laser light and in optical networks in telecommunication. New synthetic
polymers have found a variety of exciting applications, and their use in materials science will grow even more rapidly in the future.”

Overall Expectations
In this unit, you will be able to

•

demonstrate an understanding of the structure of various organic compounds, and of

chemical reactions involving these compounds;

•

investigate various organic compounds through research and experimentation, predict
the products of organic reactions, and name and represent the structures of organic
compounds using the IUPAC system and molecular models; and

•

evaluate the impact of organic compounds on our standard of living and the
environment.


Unit 1
Organic
Chemistry

ARE YOU READY?
Understanding Concepts
1. Write the IUPAC name for each of the following compounds.
CH2 CH3
(a)
(b) CH2 CH2 CH3
C

CH3

Prerequisites
IUPAC nomenclature of

simple aliphatic
hydrocarbons, including
cyclic compounds

•

structural and geometric
isomers

•

characteristic physical
properties and chemical
reactions of saturated and
unsaturated hydrocarbons

•

electronegativity and polar
bonds

•

chemical bonding, including
ionic bonds, covalent bonds,
hydrogen bonds, van der
Waals forces

•

CH3

2. Draw structures of the following compounds.
(a) pentane
(b) 2,2-dimethylheptane
(c) 4-ethyl-1-methylcyclohexane
(d) 5-methyl-1-hexene
(e) 1-butyne
3. Write a balanced chemical equation to show the complete combustion of
heptane, a component of gasoline.
4. Which of the following are structural isomers?
(a)

H
H

formation of solutions
involving polar and nonpolar
substances

H
H

C

H

C

H

C
H

(b)

C

H

H
H
H

H

C

C
C
C

H
H
(c)

(d)

C

C

H

C

H

H

H
H

H

C
C
H

C

CH3
CH3C

4 Unit 1

CH3

CH3

Concepts

•

CH2

H
H

H

H

H

H

C

C

C

C

H

H

H

H

H

CH3
CCH3

NEL


Unit 1

5. Predict the relative boiling points of the following two compounds.
(a) CH3CH2CH2CH2CH3
pentane

CH3

(b)

CH3CCH3
CH3
2,2-dimethylpropane

6. Predict the relative solubilities of the following compounds in water.
(a)
(b)
H H
H

H
H
H

C

C

H

H

O

O

H

H

C

C
C

C

C

C

C

H

H
H

H
7. Write the following elements in order of increasing electronegativity: carbon,
chlorine, hydrogen, nitrogen, oxygen, sulfur.
8. For each of the following compounds, describe the intramolecular bond types
and the intermolecular forces.
(a) CH4
(b) H2O
(c) NH3

Applying Inquiry Skills
9. Three liquids are tested with aqueous bromine (Figure 1). Samples of the solutions are also vaporized and their boiling points determined. The evidence is
shown in Table 1.
Table 1
Compound
Br2(aq) test
boiling point (°C)

Liquid 1
no change

Liquid 2
turns
colourless

Liquid 3
no change

36

39

–12

Which of the liquids is pentane, 2-methylbutane, and 2-methyl-2-butene?

Safety and Technical Skills

liquid 1

liquid 2

Figure 1

10. List the safety precautions needed in the handling, storage, and disposal of
(a) concentrated sulfuric acid;
(b) flammable liquids, e.g., ethanol.

NEL

Organic Chemistry 5


chapter

1

In this chapter,
you will be able to

•

classify organic compounds
by identifying their functional
groups, by name, by
structural formula, and by
building molecular models;

•

use the IUPAC system to
name and write structural
diagrams for different
classes of organic
compounds, and identify
some nonsystematic names
for common organic
compounds;

•

relate some physical
properties of the classes of
organic compounds to their

functional groups;

•

describe and predict
characteristic chemical
reactions of different classes
of organic compounds, and
classify the chemical
reactions by type;

•

design the synthesis of
organic compounds from
simpler compounds, by
predicting the products of
organic reactions;

•

carry out laboratory
procedures to synthesize
organic compounds;

•

evaluate the use of the term
“organic” in everyday
language and in scientific

terminology;

•

describe the variety and
importance of organic
compounds in our lives, and
evaluate the impact of
organic materials on our
standard of living and the
environment.

Organic
Compounds
In a supermarket or in a pharmacy, the term “organic” is used to describe products that
are grown entirely through natural biological processes, without the use of synthetic
materials. “Organic” fruits and vegetables are not treated with synthetic fertilizers or pesticides; “organic” chickens or cows are raised from organically grown feed, without the use
of antibiotics. The growing “organic” market, despite higher prices over “conventionally
grown” foods, indicates that some consumers believe that molecules made by a living
plant or animal are different from, and indeed better than, those made in a laboratory.
In the early 18th century, the term “organic” had similar origins in chemistry. At that
time, most chemists believed that compounds produced by living systems could not be
made by any laboratory procedure. Scientists coined the chemical term “organic” to distinguish between compounds obtained from living organisms and those obtained from
mineral sources.
In 1828, a German chemist, Friedrich Wöhler, obtained urea from the reaction of two
inorganic compounds, potassium cyanate and ammonium chloride. Since then, many
other organic compounds have been prepared from inorganic materials.
Organic chemistry today is the study of compounds in which carbon is the principal
element. Animals, plants, and fossil fuels contain a remarkable variety of carbon compounds. What is it about the carbon atom that allows it to form such a variety of compounds, a variety that allows the diversity we see in living organisms? The answer lies in
the fact that carbon atoms can form four bonds. Carbon atoms have another special

property: They can bond together to form chains, rings, spheres, sheets, and tubes of
almost any size and can form combinations of single, double, and triple covalent bonds.
This versatility allows the formation of a huge variety of very large organic molecules.
In this chapter, we will examine the characteristic physical properties of families of organic
molecules, and relate these properties to the elements within the molecule and the bonds
that hold them together. We will also look at the chemical reactions that transform one
organic molecule into another. Finally, we will see how these single transformations can be
carried out in sequence to synthesize a desired product, starting with simple compounds.

REFLECT on your learning
1. Much of the research in organic chemistry is focused on a search for new or

improved products. Suppose that you wish to develop a new stain remover, or a more
effective drug, or a better-tasting soft drink. What should be the properties of the
ingredients of your chosen product?
2. In the field of biology, complex systems have been developed to classify and name

the countless different living organisms. Suggest an effective method of classifying
and naming the vast range of organic compounds that exist.
3. From your knowledge of intramolecular and intermolecular attractions, describe fea-

tures in the molecular structure of a compound that would account for its solubility
and its melting and boiling points.
4. What does “organic” mean? Give as many definitions as you can.

6 Chapter 1

NEL

TRY THIS activity

How Do Fire-Eaters
Do That?

Have you ever wondered how some street performers can extinguish a
flaming torch by “swallowing” the fire, without burning themselves? Here is
an activity that might help you answer the puzzle of “how do they do that?”
Materials: 2 large glass beakers or jars; 2-propanol (rubbing alcohol); water;
table salt; tongs; paper; safety lighter or match
2-propanol is highly flammable. Ensure that containers of the
alcohol are sealed and stored far from any open flame.

• In a large glass beaker or jar, mix together equal volumes of 2-propanol
and water, to a total of about 100 mL.
• Dissolve a small amount of NaCl (about 0.5 g) in the solution, to add
colour to the flame that will be observed.
• Using tongs, dip a piece of paper about 5 cm ϫ 5 cm into the solution
until it is well soaked. Take the paper out and hold it over the jar for a few
seconds until it stops dripping.
• Dispose of the alcohol solution by flushing it down the sink (or as
directed by your teacher), and fill another beaker or jar with water as a
precautionary measure to extinguish any flames if necessary.
• Still holding the soaked paper with tongs, ignite it using the lighter or
match.
(a) From your observations, suggest a reason why “fire-eaters” do not
suffer severe burns from their performance.

NEL

Organic Compounds

7


1.1

Figure 1
The design and synthesis of new
materials with specific properties,
like the plastic in this artificial ski
run, is a key focus of the chemical
industry.
organic family a group of organic
compounds with common structural
features that impart characteristic
physical properties and reactivity
functional group a structural
arrangement of atoms that imparts
particular characteristics to the
molecule

Functional Groups
With the huge number of organic substances, we would have
great difficulty memorizing the properties of each compound.
Fortunately, the compounds fall into organic families
according to particular combinations of atoms in each molecule. The physical properties and reactivity of the compounds
are related to these recognizable combinations, called functional groups. These functional groups determine whether
the molecules are readily soluble in polar or non-polar solvents, whether they have high or low melting and boiling
points, and whether they readily react with other molecules.

So, if we can recognize and understand the influence of
each functional group, we will be able to predict the properties of any organic compound. If we can predict their properties, we can then design molecules to serve particular purposes, and devise methods
to make these desired molecules.
In this chapter, we will discuss each organic family by relating its properties to the
functional groups it contains. Moreover, we will focus on how one organic family can be
synthesized from another; that is, we will learn about the reaction pathways that allow
one functional group to be transformed into another. By the end of the chapter, we will
have developed a summary flow chart of organic reactions, and we will be able to plan
synthetic pathways to and from many different organic molecules. After all, designing the
synthesis of new molecules, ranging from high-tech fabrics to “designer drugs,” is one of
the most important aspects of modern organic chemistry (Figure 1).
Before discussing each organic family, let’s take a look at what makes up the functional groups. Although there are many different functional groups, they essentially consist of only three main components, one or more of which may be present in each
functional group. Understanding the properties of these three components will make it
easy to understand and predict the general properties of the organic families to which
they belong (Figure 2):
• carbonϪcarbon multiple bonds, ϪC෇CϪ or ϪCϵCϪ
• single bonds between a carbon atom and a more electronegative atom,
e.g., ϪCϪOϪ, ϪCϪNϪ, or ϪCϪCl
• carbon atom double-bonded to an oxygen atom, ϪC෇O
(a)

H
Figure 2
Examples of the three main components of functional groups:
(a) A double bond between two
carbon atoms
(b) A single bond between carbon
and a more electronegative
atom (e.g., oxygen)
(c) A double bond between carbon

and oxygen
8 Chapter 1

H

H

C

C

(b)

H

ethene (an alkene)

H
H

C

O

H

H
methanol (an alcohol)

H

(c)

H

C

O

methanal (an aldehyde)
NEL


Section 1.1

Carbon–Carbon Multiple Bonds
When a C atom is single-bonded to another C atom, the bond is a strong covalent bond
that is difficult to break. Thus, the sites in organic molecules that contain CϪC bonds
are not reactive. However, double or triple bonds between C atoms are more reactive.
The second and third bonds formed in a multiple bond are not as strong as the first bond
and are more readily broken. This allows carbon–carbon multiple bonds to be sites for reactions in which more atoms are added to the C atoms. The distinction between single and
multiple bonds is not always clear-cut. For example, the reactivity of the six-carbon ring
structure found in benzene indicates that there may be a type of bond intermediate
between a single and a double bond. This theory is supported by measured bond lengths.
You will learn more about the strengths of single and multiple bonds in Chapter 4.

Single Bonds Between Carbon and More
Electronegative Atoms
Whenever a C atom is bonded to a more electronegative atom, the bond between the
atoms is polar; that is, the electrons are held more closely to the more electronegative

atom. This results in the C atom having a partial positive charge and the O, N, or
halogen atom having a partial negative charge. Any increase in polarity of a molecule
also increases intermolecular attractions, such as van der Waals forces. As more force
is required to separate the molecules, the melting points and boiling points also
increase (Figure 3).

(a)

(b)

LEARNING

TIP

When atoms have different electronegativities (Table 1), the
bonds that form between them
tend to be polar, with the electrons
displaced toward the more electronegative atom. Many properties
of compounds of these elements
are explained by the polarity of
their bonds.
Table 1 Electronegativities of
Common Elements
Element

Electronegativity

H

2.1

C

2.5

N

3.0

O

3.5

Figure 3
(a) Nonpolar substances, with
weak forces of attraction
among the molecules,
evaporate easily. In fact, they
are often gases at room
temperature.
(b) Polar substances, with strong
forces of attraction among the
molecules, require considerable
energy to evaporate.

If the O or N atoms are in turn bonded to an H atom, an ϪOH or ϪNH group is
formed, with special properties. The presence of an ϪOH group enables an organic
molecule to form hydrogen bonds with other ϪOH groups. The formation of these
hydrogen bonds not only further increases intermolecular attractions, it also enables
these molecules to mix readily with polar solutes and solvents. You may recall the saying

“like dissolves like.” The solubility of organic compounds is affected by nonpolar components and polar components within the molecule. Since N is only slightly less electronegative than O, the effect of an NϪH bond is similar to that of an OϪH bond:
ϪNH groups also participate in hydrogen bonding.

NEL

Organic Compounds

9


Double Bonded Carbon and Oxygen
The third main component of functional groups consists of a C atom double-bonded to
an O atom. The double covalent bond between C and O requires that four electrons be
shared between the atoms, all four being more strongly attracted to the O atom. This makes
the C෇O bond strongly polarized, with the accompanying effects of raising boiling and
melting points, and increasing solubility in polar solvents.

SUMMARY

Three Main Components of
Functional Groups

Multiple bonds between C atoms
ϪC෇CϪ
ϪCϵCϪ

Unlike single CϪC bonds, double and triple bonds allow atoms
to be added to the chain.

C atom bonded to a more electronegative atom (O, N, halogen)

CϪO
CϪN
CϪCl, CϪBr, CϪF

Unequal sharing of electrons results in polar bonds,
increasing intermolecular attraction, and raising boiling and
melting points.

CϪOH or
CϪNHϪ

These groups enable hydrogen bonding, increasing solubility
in polar substances.

C atom double-bonded to an O atom
C෇O

The resulting polar bond increases boiling point and melting point.

Practice
Understanding Concepts
1. Explain the meaning of the term “functional group.”
2. Are double and triple bonds between C atoms more reactive or less reactive than

single bonds? Explain.
3. Would a substance composed of more polar molecules have a higher or lower boiling

point than a substance composed of less polar molecules? Explain.
4. Describe the three main components of functional groups in organic molecules.

Section 1.1 Questions
Understanding Concepts
1. What is the effect of the presence of an —OH group or an

—NH group on
(a) the melting and boiling points of the molecule? Explain.
(b) the solubility of the molecule in polar solvents? Explain.
2. Identify all components of functional groups in the fol-

lowing structural diagrams. Predict the solubility of each
substance in water.
(a) CH3ϪOϪH
(b) CH3CHϭCHCH3
(c) CH3CHϭO
(d) CH3CH2CϭO

3. The compounds water, ammonia, and methane are formed

when an oxygen atom, a nitrogen atom, and a carbon atom
each bonds with hydrogen atoms.
(a) Write a formula for each of the three compounds.
(b) Predict, with reference to electronegativities and intermolecular forces, the solubility of each of the compounds in the others.
(c) Of the three compounds, identify which are found or
produced by living organisms, and classify each compound as organic or inorganic. Justify your answer.

OH

10

Chapter 1

NEL


Hydrocarbons
We will begin our study of organic families with a review of hydrocarbons, many of
which contain multiple bonds between carbon atoms, a functional group with characteristic properties.
Fossil fuels (Figure 1) contain mainly hydrocarbons: simple molecules of hydrogen
and carbon that are the result of the breakdown of living organisms from long ago. These
compounds include the natural gas that is piped to our homes, the propane in tanks for
barbecues, and the gasoline for our cars. Hydrocarbons are classified by the kinds of
carbonϪcarbon bonds in their molecules. In alkanes, all carbons are bonded to other
atoms by single bonds, resulting in the maximum number of hydrogen atoms bonded to
each carbon atom. These molecules are thus called saturated hydrocarbons. Alkenes are
hydrocarbons that contain one or more carbonϪcarbon double bonds, and alkynes contain one or more carbon–carbon triple bonds. These two groups are called unsaturated
hydrocarbons because they contain fewer than the maximum possible number of hydrogen
atoms. Because alkenes and alkynes have multiple bonds, they react in characteristic ways.
The multiple bond is the functional group of these two chemical families.
In all of these hydrocarbons, the carbonϪcarbon backbone may form a straight chain,
one or more branched chains, or a cyclic (ring) structure (Table 1). All of these molecules are included in a group called aliphatic hydrocarbons.
A hydrocarbon branch that is attached to the main structure of the molecule is called
an alkyl group. When methane is attached to the main chain of a molecule, it is called
a methyl group, ϪCH3. An ethyl group is CH3CH2, the branch formed when ethane
links to another chain.
Table 1 Examples of Hydrocarbons
Hydrocarbon
group

Example

Formula

Spacefill
diagram

Bond and angles
diagram

Aliphatic
alkane

ethane

ethene

hydrocarbon an organic compound
that contains only carbon and
hydrogen atoms in its molecular
structure
alkane a hydrocarbon with only
single bonds between carbon atoms
alkene a hydrocarbon that contains
at least one carbonϪcarbon double
bond; general formula, CnH2n
alkyne a hydrocarbon that contains
at least one carbonϪcarbon triple
bond; general formula, CnH2n–2

aliphatic hydrocarbon a compound that has a structure based on
straight or branched chains or rings

of carbon atoms; does not include
aromatic compounds such as benzene

CH2CH2
120˚

alkyne

Figure 1
Crude oil is made up of a variety of
potentially useful hydrocarbons.

cyclic hydrocarbon a hydrocarbon
whose molecules have a closed ring
structure

CH3CH3

cyclohexane C6H12

alkene

1.2

ethyne

CHCH

benzene

C6H6

alkyl group a hydrocarbon group
derived from an alkane by the
removal of a hydrogen atom; often a
substitution group or branch on an
organic molecule

Aromatic

NEL

Organic Compounds

11


aromatic hydrocarbon a compound with a structure based on
benzene: a ring of six carbon atoms
IUPAC International Union of Pure
and Applied Chemistry; the organization that establishes the conventions used by chemists

Figure 2
Benzene, C6H6, is colourless, flammable, toxic, and carcinogenic, and
has a pleasant odour. Its melting
point is 5.5°C and its boiling point
80.1°C. It is widely used in the manufacture of plastics, dyes, synthetic
rubber, and drugs.

DID YOU

KNOW

?

Joined Benzene Rings

Like other hydrocarbons, benzene
rings can link together to form a
wide variety of compounds
(Figure 3), many of which are
quite smelly!
(a)

A fourth group of hydrocarbons with characteristic properties and structures is called
the aromatic hydrocarbons. The simplest aromatic hydrocarbon is benzene; all other
members of this family are derivatives of benzene. The formula for benzene is C6H6,
and the six carbon atoms form a unique ring structure. Unlike cyclohexane, C6H12, the
benzene ring has a planar (flat) structure, and is unsaturated (Table 1). As we will learn
later in this chapter and in Chapter 10, the bonds in the benzene ring have properties intermediate between single bonds and double bonds; the common structural diagram for
benzene shows a hexagon with an inscribed circle, symbolizing the presence of double
bonds in unspecified locations within the six-carbon ring (Figure 2). The unique structure and properties of compounds containing benzene rings have prompted their classification as a broad organic family of their own. Named historically for the pleasant
aromas of compounds such as oil of wintergreen, aromatic compounds include all
organic molecules that contain the benzene ring. All other hydrocarbons and their
oxygen or nitrogen derivatives that are not aromatic are called aliphatic compounds.

Nomenclature of Hydrocarbons
Because there are so many organic compounds, a systematic method of naming them is
essential. In this book, we will use the IUPAC system of nomenclature, with additional
nonsystematic names that you may encounter in common usage. It is especially important to have a good grasp of the nomenclature of hydrocarbons, as the names of many

organic molecules are based on those of hydrocarbon parent molecules.

Alkanes
All alkanes are named with the suffix -ane. The prefix in the name indicates the number
of carbon atoms in the longest straight chain in the molecule (Table 2). Thus a 5-C
straight-chained alkane would be named pentane.
Any alkyl branches in the carbon chain are named with the prefix for the branch, followed by the suffix -yl. Thus, a branch that contains a 2-C chain is called an ethyl group.
The name of a branched alkane must also indicate the point of attachment of the branch.
This is accomplished by assigning numbers to each C atom of the parent alkane, and pointing
out the location of the branch chain by the numeral of the C atom where the branching occurs.
The naming system always uses the lowest numbers possible to denote a position on the chain.
Finally, all numerals are separated by commas; numerals and letters are separated by hyphens;
and names of branches and parent chains are not separated.

(b)

Table 2 Alkanes and Related Alkyl Groups
Figure 3
(a) Naphthalene, C10H8, is a colourless solid with a pungent odour.
Its melting point is 80°C, and its
boiling point 218°C. However, it
sublimes on heating. It is the
main component of mothballs,
and is also used as an insecticide, in solvents, and in the synthesis of dyes.
(b) Anthracene, C14H10, is a colourless solid with melting and
boiling points of 218°C and
354°C. It is less well known, but
is also used in the synthesis of
dyes.
12

Chapter 1

Prefix

IUPAC name

meth-

methane

eth-

Formula

Alkyl group

Alkyl formula

CH4(g)

methyl-

ethane

C2H6(g)

ethyl-

prop-

propane

C3H8(g)

propyl-

but-

butane

C4H10(g)

butyl-

pent-

pentane

C5H12(l)

pentyl-

hex-

hexane

C6H14(l)

hexyl-

hept-

heptane

C7H16(l)

heptyl-

oct-

octane

C8H18(l)

octyl-

non-

nonane

C9H20(l)

nonyl-

dec-

decane

C10H22(l)

decyl-

ϪCH3
ϪC2H5
ϪC3H7
ϪC4H9
ϪC5H11
ϪC6H13
ϪC7H15
ϪC8H17
ϪC9H19
ϪC10H21
NEL


Section 1.2

We will take a special look at naming propyl groups and butyl groups. When alkyl
groups have three or more C atoms, they may be attached to a parent chain either at
their end C atom, or at one of the middle C atoms. For example, Figure 4 shows two points
of attachment for a propyl group. The two arrangements are structural isomers of each
other, and are commonly known by their nonsystematic names. The prefix n- (normal)
refers to a straight-chain alkyl group, the point of attachment being at an end C atom.
The isomer of the n-propyl group is the isopropyl group. Figure 5 shows the common
names for isomers of the butyl group; in this book, we will not concern ourselves with
isomers of alkyl groups greater than 4 C atoms.
(a) CH3

CH2

CH2

CH2

(b)

CH3

CH

CH3

CH2

n-butyl (normal butyl)

(a)

CH3

CH2

CH2

n-propyl (normal propyl)
(b)

CH3

CH

CH3

isopropyl
Figure 4
Two isomers of the propyl group.
The coloured bond indicates where
the group is attached to the larger
molecule.

isobutyl
(c) CH3

CH

CH2

CH3

CH3

(d)

C

CH3

s-butyl (secondary butyl)

CH3

isomer a compound with the same
molecular formula as another compound, but a different molecular
structure

t-butyl (tertiary butyl)
Figure 5
Four isomers of the butyl group

Naming Alkanes
1.

SAMPLE problem

Write the IUPAC name for the chemical with the following structural diagram.

CH3

CH2

CH3

CH3

CH2

CH2

CH3

CH

CH

CH

CH3

First, identify the longest carbon chain. Note that you may have to count along what
appear to be branches in the structural diagram to make sure you truly have the longest
chain. In this case, the longest carbon chain is 6 C long. So the parent alkane is hexane.
Next, number the C atoms as shown.

CH3

CH3

CH2

CH2

6

5

CH3

6

CH2

5

CH
4

CH
3

CH3
1b

CH
2

CH3

1a

In this case, there are several possible six-carbon chains. Choose the one that gives the
lowest possible total of numbers identifying the location of the branches. Usually it is best
to start numbering with the end carbon that is closest to a branch. In this case, the first
branch is on C 2. Notice that it makes no difference whether we choose C 1a or C 1b to be
the actual C 1.

NEL

Organic Compounds

13


Name each branch and identify its location on the parent chain. In this example, there
is a methyl group on C 2 and an ethyl group on each of C 3 and C 4. Thus the branches
are 2-methyl, 3-ethyl, and 4-ethyl.
To check that you’ve got the lowest total, try naming the structure from the other ends
of the chain. If we had counted from either of the C 6 ends, we would arrive at 3-ethyl,
4-ethyl, and 5-methyl—a set of numbers with a higher total.
When the same alkyl group (e.g., ethyl) appears more than once, they are grouped as
di-, tri-, tetra-, etc. In this compound, the two ethyl groups are combined as 3,4-diethyl.
Finally, write the complete IUPAC name, following this format: (number indicating location)-(branch name)(parent chain). In this book, when more than one branch is present,
the branches are listed in alphabetical order. (Note that other sources may list the
branches in order of complexity.) Alphabetically, ethyl comes before methyl. So the name
begins with the ethyl groups, followed by the methyl group, and ends with the parent
alkane. Watch the use of commas and hyphens, and note that no punctuation is used
between the alkane name and the alkyl group that precedes it.
The IUPAC name for this compound is 3,4-diethyl-2-methylhexane.
2.

Write the IUPAC name for the following hydrocarbon.

CH3

CH3

CH2

CH3

CH2

CH

CH2

CH2

CH2

CH2

CH3

First, identify the longest carbon chain: 8 C atoms. So the molecule is an octane.
Next, number the C atoms as shown.

CH3
CH3

1

2

CH2

CH2
CH
3

CH3
CH2

4

CH2

5

6

CH2

CH2

7

CH3

8

If we start counting at C 1, the branch group attached to C 3 contains 3 C atoms, so it is
a propyl group. However, the propyl group is attached to the parent chain at its middle C
atom, not at an end C atom. This arrangement of the propyl group is called isopropyl
(Figure 4(b)).
One possible name for this compound is 3-isopropyloctane.
However, a different name results if we number this hydrocarbon from the top branch.
1

2

CH3 — CH — CH3
CH3 — CH2 — CH — CH2 — CH2 — CH2 — CH2 — CH3
3

4

5

6

7

8

This shows a methyl group on C 2 and an ethyl group on C 3, giving the name
3-ethyl-2-methyloctane. Where more than one name is correct, we use the one that
includes the lowest possible numerals.
The correct name of this compound is 3-ethyl-2-methyloctane.

CH3

3.

1CH
5CH 2
4CH2

14

Chapter 1

2CH 2
3CH

CH3

Draw a structural diagram for 1,3-dimethylcyclopentane.

The parent alkane is cyclopentane. Start by drawing a ring of 5 C atoms single-bonded to
each other, in the shape of a pentagon.
Next, number the C atoms in the ring, starting anywhere in the ring.
Then attach a methyl group to C 1 and another to C 3.
Finally, add H atoms to the C atoms to complete the bonding and the diagram.

NEL


Section 1.2

Example
Write the IUPAC name for the following hydrocarbon.

CH3
CH3

CH2

CH

C

CH

CH3

CH3 CH2
CH3

Solution
This alkane is 3,4,4-trimethylheptane.

Naming Branched Alkanes

SUMMARY

Step 1 Identify the longest carbon chain; note that structural diagrams can be
deceiving—the longest chain may travel through one or more
“branches” in the diagram.
Step 2 Number the carbon atoms, starting with the end that is closest to the
branch(es).
Step 3 Name each branch and identify its location on the parent chain by the
number of the carbon at the point of attachment. Note that the name
with the lowest numerals for the branches is preferred. (This may
require restarting your count from the other end of the longest chain.)
Step 4 Write the complete IUPAC name, following this format: (number of
location)-(branch name)(parent chain).

LEARNING

TIP

The structure of an organic molecule can be represented in many
different ways: some representations give three-dimensional detail;
others are simplified to show only
the carbon backbone and functional groups. The following structural diagrams all show the same
molecule—pentanoic acid—but in
slightly different ways.
O

(a)

CH3 — CH2 — CH2 — CH2 — C — OH

(b)

Step 5 When more than one branch is present, the branches are listed either in
alphabetical order or in order of complexity; in this book, we will follow
the alphabetical order.
Note:

When naming cyclic hydrocarbons, the carbon atoms that form the ring
structure form the parent chain; the prefix cyclo- is added to the parent
hydrocarbon name, and the naming of substituted groups is the same as
for noncyclic compounds.

(c)

O
OH

(d)

Practice
Understanding Concepts
1. Write IUPAC names for the following hydrocarbons.

CH3

(a)

CH3
CH3

CH

CH2
CH
CH3

CH

CH

CH2

CH3

CH3

4-ethyl-2,3,5-trimethylheptane

NEL

Organic Compounds

15


(b) CH
3

(c)

CH

CH2

CH2

CH3

CH2

CH2

CH

CH3

CH2

CH3

CH2CH3
CH3 — CH — CH2 — CH — CH2 — CH — CH3
CH3

CH2CH2CH3

CH3

(d)

CH

CH3

CH 2

CH

CH2

CH2
CH2

2. Draw a structural diagram for each of the following hydrocarbons:

(a)

(b)
(c)
(d)
(e)

3,3,5-trimethyloctane
3,4-dimethyl-4-ethylheptane
2-methyl-4-isopropylnonane
cyclobutane
1,1-diethylcyclohexane

Alkenes and Alkynes
The general rules for naming alkenes and alkynes are similar to those for alkanes, using
the alkyl prefixes and ending with -ene or -yne respectively.

SAMPLE problem

Naming Alkenes and Alkynes
1.

Write the IUPAC name for the hydrocarbon whose structural diagram and
ball-and-stick model are shown.

CH3

CH

CH

CH2

CH3
First, find the longest C chain that includes the multiple bond. In this case, it is 4 C long,
so the alkene is a butene.
Number the C atoms, beginning with the end closest to the double bond.
The double bond is between C 1 and C 2, so the alkene is a 1-butene.

CH3

4

3

CH

CH

2

CH2

1

CH3

4

Next, identify any branches: A methyl group is attached to C 3, so the branch is
3-methyl.
Finally, write the name, following the conventions for hyphenation and punctuation.

Since a number precedes the word butene, hyphens are inserted and the alkene is
3-methyl-1-butene.

16

Chapter 1

NEL


Section 1.2

2.

Draw a structural diagram for 2-methyl-1,3-pentadiene.

First, draw and number a 5 C chain for the pentadiene.

C— C— C— C— C
1

2

3

4

5

Now insert the double bonds. The name “diene” tells us that there are two double

bonds, one starting at C 1 and another starting at C 3.

C

C— C

1

2

3

C— C
4

5

Draw a methyl group attached to C atom 2.

CH3
C

C— C

C— C

1

2

4

3

5

Finally, write in the remaining H atoms.

CH3
C — CH

CH2
3.

CH — CH3

Write the IUPAC name for the compound whose structural diagram and balland-stick model are shown.

CH3
First, identify the ring structure, which contains 6 C atoms with one double bond. The
parent alkene is therefore cyclohexene.
1
Next, number the C atoms beginning
6
2
with one of the C atoms in the double
bond. The numbering system should
3
5
result in the attached group having the

CH3
4
lowest possible number, which places
the methyl group at C 3 .
The IUPAC name for this compound is 3-methylcyclohexene.

Example 1
Draw a structural diagram for 3,3-dimethyl-1-butyne.

Solution
CH3
CH

C

C

CH3

CH3

NEL

Organic Compounds

17


Example 2
Write the IUPAC name for the following compound.

CH2

CH

C

CH

CH3

CH

CH2

CH3

CH3

Solution
The compound is 3-isopropyl-1,3-hexadiene.

LEARNING

TIP

Some alkenes and alkynes
have common names.
IUPAC
name

Common
name

ethene

ethylene

propene

propylene

ethyne

acetylene

Naming Alkenes and Alkynes

SUMMARY

Step 1. The parent chain must be an alkene or alkyne, and thus must contain
the multiple bond.
Step 2. When numbering the C atoms in the parent chain, begin with the end
closest to the multiple bond.
Step 3. The location of the multiple bond is indicated by the number of the C
atom that begins the multiple bond; for example, if a double bond is
between the second and third C atoms of a pentene, it is named
2-pentene.
Step 4. The presence and location of multiple double bonds or triple bonds is
indicated by the prefixes di-, tri-, etc.; for example, an octene with

double bonds at the second, fourth, and sixth C atoms is named
2,4,6-octatriene.

Practice
Understanding Concepts
3. Explain why no number is used in the names ethene and propene.
4. Write the IUPAC name and the common name for the compound in Figure 6.

Figure 6
When this compound combusts, it transfers
enough heat to melt most metals.
5. Write IUPAC names for the compounds with the following structural diagrams:

(a)

CH3
CH3

18

Chapter 1

C

C

CH

CH3
CH

CH2

CH2

CH3

NEL


Section 1.2

(b)

CH2
CH

CH3

C

CH2

CH3

CH2

CH3

(c) CH3CH

CH CH2
CH CH CH2
(d) CH2
CH
CH CH
CH
CH3

CH3

CH2

CH2

CH

CH2

(e)
CH3
CH3
6. Draw structural diagrams for each of the following compounds:

(a)
(b)
(c)
(d)
(e)

2-methyl-5-ethyl-2-heptene

1,3,5-hexatriene
3,4-dimethylcyclohexene
1-butyne
4-methyl-2-pentyne

Aromatic Hydrocarbons
In naming simple aromatic compounds, we usually consider the benzene ring to be
the parent molecule, with alkyl groups named as branches attached to the benzene.
For example, if a methyl group is attached to a benzene ring, the molecule is called
methylbenzene (Figure 7). Since the 6 C atoms of benzene are in a ring, with no beginning or end, we do not need to include a number when naming aromatic compounds
that contain only one additional group.
When two or more groups are attached to the benzene ring, we do need to use a numbering system to indicate the locations of the groups. We always number the C atoms so
that we have the lowest possible numbers for the points of attachment. Numbering may
proceed either clockwise or counterclockwise. As shown in the examples in Figure 8,
we start numbering with one of the attached ethyl groups, then proceed in the direction
that is closest to the next ethyl group.
C2H5
C2H5
C2H5
1
1
6

C2H5
2

5

3
4

(a) 1,2-diethylbenzene

NEL

1
6

6

2

5

3

CH3

Figure 7
Methylbenzene, commonly called
toluene, is a colourless liquid that is
insoluble in water, but will dissolve in
alcohol and other organic fluids. It is
used as a solvent in glues and lacquers and is toxic to humans. Toluene
reacts with nitric acid to produce the
explosive trinitrotoluene (TNT).

2

5

3
4

C2H5

(b) 1,3-diethylbenzene

4

C2H5
(c) 1,4-diethylbenzene

Figure 8
Three isomers of diethylbenzene

Organic Compounds

19


Section 1.2

Solution
(a) 1-ethyl-2,4-dimethylbenzene
(b) 4-phenyl-3-propyl-1-hexene

Naming Aromatic Hydrocarbons

SUMMARY

1. If an alkyl group is attached to a benzene ring, the compound is named as an
alkylbenzene. Alternatively, the benzene ring may be considered as a branch
of a large molecule; in this case, the benzene ring is called a phenyl group.
2. If more than one alkyl group is attached to a benzene ring, the groups are
numbered using the lowest numbers possible, starting with one of the added
groups.

Practice
7. Write IUPAC names for the following hydrocarbons.

(a) CH3 — CH2 — CH — CH — CH3

C2H5

(b) CH2 — CH

CH — CH —

C2H5
(c) CH

(d)

CH3
C — CH2 — CH — CH3

CH3

CH2CH2CH3

8. Draw structural diagrams for the following hydrocarbons:

(a)
(b)
(c)
(d)
(e)

NEL

1,2,4-trimethylbenzene
1-ethyl-2-methylbenzene
3-phenylpentane
o-diethylbenzene
p-ethylmethylbenzene

Organic Compounds

21


Physical Properties of Hydrocarbons

Figure 10
The nonpolar hydrocarbons in gasoline are insoluble in water and
remain in a separate phase.

fractional distillation the separation
of components of petroleum by distillation, using differences in boiling
points; also called fractionation

Since hydrocarbons contain only C and H atoms, two elements with very similar electronegativities, bonds between C and H are relatively nonpolar. The main intermolecular interaction in hydrocarbons is van der Waals forces: the attraction of the electrons
of one molecule for the nuclei of another molecule. Since these intermolecular forces are
weak, the molecules are readily separated. The low boiling points and melting points of
the smaller molecules are due to the fact that small molecules have fewer electrons and
weaker van der Waals forces, compared with large molecules (Table 3). These differences in boiling points of the components of petroleum enable the separation of these
compounds in a process called fractional distillation. Hydrocarbons, being largely nonpolar, generally have very low solubility in polar solvents such as water, which is why
gasoline remains separate from water (Figure 10). This property of hydrocarbons makes
them good solvents for other nonpolar molecules.
Table 3 Boiling Points of the First 10 Straight Alkanes
Formula

Name

b.p. (°C)

CH4(g)

methane

C2H6(g)

ethane

–89

C3H8(g)

propane

–44

C4H10(g)

butane

–0.5

C5H12(l)

pentane

36

C6H14(l)

hexane

68

C7H16(l)

heptane

98

C8H18(l)

octane

125

C9H20(l)

nonane

151

C10H22(l)

decane

174

–161

Section 1.2 Questions
Understanding Concepts
1. Draw a structural diagram for each hydrocarbon:

(a)
(b)
(c)
(d)
(e)
(f)
(g)
(h)
(i)
(j)

(k)
(l)

22

2-ethyloctane
2-ethyl-3-isepropylnonane
methylcyclopentane
3-hexyne
3-methyl-1,5-heptadiene
1,2,4-trimethylbenzene
4-s-butyloctane
2-phenylpropane
3-methyl-2-pentene
n-propylbenzene
p-diethylbenzene
1, 3-dimethylcyclohexane

Chapter 1

2. For each of the following names, determine if it is a correct

name for an organic compound. Give reasons for your
answer, including a correct name.
(a) 2-dimethylhexane
(b) 3-methyl-1-pentyne
(c) 2,4-dimethylheptene
(d) 3,3-ethylpentane
(e) 3,4-dimethylhexane
(f) 3,3-dimethylcyclohexene

(g) 2-ethyl-2-methylpropane
(h) 2,2-dimethyl-1-butene
(i) 1-methyl-2-ethylpentane
(j) 2-methylbenzene
(k) 1,5-dimethylbenzene
(l) 3,3-dimethylbutane

NEL


Section 1.2

3. Write correct IUPAC names for the following structures.

(a) CH3CH2CH

CHCHCH
CH3CHCH3

(b)

CHCH3

(e) CH3CHCH3

CH3CCH

CH2

CH3CHCH2CH3

CH2CH3

4. Draw a structural diagram for each of the following com-

CH3
(c)

CH3
CH3CH2CHCHCH3

pounds, and write the IUPAC name for each:
(a) ethylene
(b) propylene
(c) acetylene
(d) toluene, the toxic solvent used in many glues
(e) the o-, m-, and p- isomers of xylene (dimethylbenzene), used in the synthesis of other organic compounds such as dyes
Making Connections
5. (a) Use the information in Table 3 to plot a graph showing

(d)

CH2CH3
CH2CH3

the relationship between the number of carbon atoms
and the boiling points of the alkanes. Describe and
propose an explanation for the relationship you
discover.
(b) Research a use for each of the first 10 alkanes, and

suggest why each is appropriate for this use.

GO

NEL

www.science.nelson.com

Organic Compounds

23


1.3

Reactions of Hydrocarbons
All hydrocarbons readily burn in air to give carbon dioxide and water, with the release
of large amounts of energy (Figure 1); this chemical reaction accounts for the extensive use of hydrocarbons as fuel for our homes, cars, and jet engines. In other chemical
reactions, alkanes are generally less reactive than alkenes and alkynes, a result of the
presence of more reactive double and triple bonds in the latter. Aromatic compounds,
with their benzene rings, are generally more reactive than the alkanes, and less reactive
than the alkenes and alkynes. In this section, we will examine this trend in the chemical
reactivity of hydrocarbons.
When we are representing reactions involving large molecules, it is often simpler to use
a form of shorthand to represent the various functional groups. Table 1 shows some of
the commonly used symbols. For example, RϪØ represents any alkyl group attached
to a benzene ring, and RϪX represents any alkyl group attached to any halogen atom.
Table 1 Examples of Symbols Representing Functional Groups

Figure 1

Hydrocarbons are found as solids,
liquids, and gases, all of which burn
to produce carbon dioxide and
water, and large amounts of light
and heat energy.

LAB EXERCISE 1.3.1
Preparation of Ethyne (p. 84)
How close does the actual yield
come to the theoretical yield in the
reaction between calcium carbide
and water?

combustion reaction the reaction
of a substance with oxygen, producing oxides and energy
substitution reaction a reaction in
which a hydrogen atom is replaced
by another atom or group of atoms;
reaction of alkanes or aromatics
with halogens to produce organic
halides and hydrogen halides
alkyl halide an alkane in which one
or more of the hydrogen atoms have
been replaced with a halogen atom
as a result of a substitution reaction

Group

Symbol

alkyl group

R, RЈ, RЉ, etc. (R, R-prime, R-double prime)

halogen atom

X

phenyl group

Ø

Reactions of Alkanes
The characteristic reactions of saturated and unsaturated hydrocarbons can be explained
by the types of carbonϪcarbon bonds in saturated and unsaturated hydrocarbons.
Single covalent bonds between carbon atoms are relatively difficult to break, and thus
alkanes are rather unreactive. They do undergo combustion reactions if ignited in air,
making them useful fuels. Indeed, all hydrocarbons are capable of combustion to produce carbon dioxide and water. The reaction of propane gas, commonly used in gas barbecues, is shown below:
C3H8(g) ϩ 5 O2(g) → 3 CO2(g) ϩ 4 H2O(g)

While the CϪC bonds in alkanes are difficult to break, the hydrogen atoms may be substituted by a halogen atom in a substitution reaction with F2, Cl2, or Br2. Reactions with
F2 are vigorous, but Cl2 and Br2 require heat or ultraviolet light to first dissociate the
halogen molecules before the reaction will proceed. In each case, the product formed is
a halogenated alkane; as the halogen atom(s) act as a functional group, halogenated
alkanes are also referred to as an organic family called alkyl halides.
In the reaction of ethane with bromine, the orange colour of the bromine slowly disappears, and the presence of HBr(g) is indicated by a colour change of moist litmus paper
from blue to red. A balanced equation for the reaction is shown below.

H

H

H

C

C

H(g) + Br2( l )

H

H

Br

C

C

H

H

heat or UV light

H

H

H( l ) + HBr( l )
(substitution
reaction)

bromoethane,
(ethyl bromide)
24

Chapter 1

NEL


Section 1.3

As the reaction proceeds, the concentration of bromoethane increases and bromine
reacts with it again, leading to the substitution of another of its hydrogen atoms, forming
1,2-dibromoethane.
H

Br

C

C

H

H

H

H

H(g) + Br2(g)

heat or UV light

Br

Br

C

C

H

H

H(l) + HBr(g)
(substitution
reaction)

1,2-dibromoethane

Additional bromines may be added, resulting in a mixture of brominated products that
(because of differences in physical properties) can be separated by procedures such as distillation.

Reactions of Alkenes and Alkynes

Alkenes and alkynes exhibit much greater chemical reactivity than alkanes. For example,
the reaction of these unsaturated hydrocarbons with bromine is fast, and will occur at
room temperature (Figure 2). (Recall that the bromination of alkanes requires heat or
UV light.) This increased reactivity is attributed to the presence of the double and triple
bonds. This characteristic reaction of alkenes and alkynes is called an addition reaction as atoms are added to the molecule with no loss of hydrogen atoms.
Alkenes and alkynes can undergo addition reactions not only with halogens, but also
with hydrogen, hydrogen halides, and water, given the appropriate conditions. Examples
of these reactions are shown below.

Figure 2
The reaction of cyclohexene and
bromine water, Br2(aq), is rapid,
forming a layer of brominated
cyclohexane (clear).
addition reaction a reaction of
alkenes and alkynes in which a
molecule, such as hydrogen or a
halogen, is added to a double or
triple bond

Halogenation (with Br2 or Cl2)
H

C
H

C
H

Br

Br

H

C

C

room
temperature

H

H

H + Brz(g)

ethene

Table 2 Prefixes for Functional
Groups

H

(addition reaction)

1,2-dibromoethane

Hydrogenation (with H2)

H

H

catalyst

H

C

C

H + 2 Hz(g)

H

heat, pressure

C

C

H

H

H

(addition reaction)

ethane

ethyne

H

C
H
propene

NEL

CH

CH3 + HBr(g)

H

room
temperature

Br

C

CH

H

2-bromopropane

Prefix

–F

fluoro

–Cl

chloro

–Br

bromo

–I

iodo

–OH

hydroxy

–NO2

nitro

–NH2

amino

DID YOU

Hydrohalogenation (with hydrogen halides)
H

Functional group

CH3 (addition reaction)

KNOW

?

Margarine
Vegetable oils consist of molecules
with long hydrocarbon chains containing many double bonds; these
oils are called “polyunsaturated.”
The oils are “hardened” by undergoing hydrogenation reactions to
produce more saturated molecules, similar to those in animal
fats such as lard.

Organic Compounds

25


Hydration (with H2O)
H2SO4
catalyst

H

CH3 + HOH

CH

CH

propene

H

OH

H2C

CH

CH3

(addition reaction)

2-hydroxypropane (an alcohol)

Markovnikov’s Rule
When molecules such as H2, consisting of two identical atoms, are added to a double
bond, only one possible product is formed; in other words, addition of identical atoms
to either side of the double bond results in identical products.
When molecules of nonidentical atoms are added, however, two different products are

theoretically possible. For example, when HBr is added to propene, the H may add to C
atom 1, or it may add to C 2; two different products are possible, as shown below.
CH CH3
H2C
CH3 or H2C
CH
H CH CH
CH3 + HBr
H
propene

Br

Br

H

1-bromopropane

2-bromopropane
(main product)

Experiments show that, in fact, only one main product is formed. The product can be
predicted by a rule known as Markovnikov’s rule, first stated by Russian chemist V. V.
Markovnikov (1838–1904).
Markovnikov’s Rule
When a hydrogen halide or water is added to an alkene or
alkyne, the hydrogen atom bonds to the carbon atom within
the double bond that already has more hydrogen atoms. This
rule may be remembered simply as “the rich get richer.”

As illustrated in the reaction of propene above, the first C atom has two attached H
atoms, while the second C atom has only one attached H atom. Therefore, the “rich” C1
atom “gets richer” by gaining the additional H atom; the Br atom attaches to the middle
C atom. The main product formed in this reaction is 2-bromopropane.

SAMPLE problem

Predicting Products of Addition Reactions
What compound will be produced when water reacts with 2-methyl-1-pentene?
First, write the structural formula for 2-methyl-1-pentene.

CH3CH2CH2C
5

4

3

2

CH2
1

CH3
Next, identify the C atom within the double bond that has more H atoms attached.
Since carbon 1 has two H atoms attached, and carbon 2 has no H atoms attached, the
H atom in the HOH adds to carbon 1, and the OH group adds to carbon 2.
We can now predict the product of the reaction.

OH
CH3CH2CH2C
5

4

3

2

CH3

CH2 + HOH
1

CH3CH2CH2C
5

4

3

2

H
CH2
1

CH3

The compound produced is 2-hydroxy-2-methylpentane.

26

Chapter 1

NEL


Section 1.3

Example
Draw structural diagrams to represent an addition reaction of an alkene to produce
2-chlorobutane.

Solution
H
H2C

Cl

H2C — CHCH2CH3

CHCH2CH3 + HCl

1-butene

Practice
Understanding Concepts
1. What compounds will be produced in the following addition reactions?

(a)

CH3CH

CCH2CH3 ϩ H2

Pt catalyst
500°C

CH2CH3
(b) CH3CH

CCH2CH3 ϩ HBr
CH3

(c)

CH3CH2CHCH

CH2 ϩ H2O

H2SO4

CH2CH3
(d)

ϩ Cl2

Synthesis: Choosing Where to Start

Addition reactions are important reactions that are often used in the synthesis of complex organic molecules. Careful selection of an alkene as starting material allows us to
strategically place functional groups such as a halogen or a hydroxyl group (ϪOH) in
desired positions on a carbon chain. As we will see later in this chapter, the products of
these addition reactions can in turn take part in further reactions to synthesize other
organic compounds, such as vinegars and fragrances.

Practice
Understanding Concepts
2. Explain the phrase "the rich get richer" as it applies to Markovnikov’s rule.
3. Draw structural diagrams to represent addition reactions to produce each of the

following compounds:
(a) 2,3-dichlorohexane
(b) 2-bromobutane
(c) 2-hydroxy-3-methylpentane
(d) 3-hydroxy-3-methylpentane

NEL

Organic Compounds

27