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Functional Groups
REACTIONS
23.1 Introduction to
Functional Groups
Essential Understanding
Most organic compounds contain chemically reactive components
called functional groups.
Reading Strategy
Compare and Contrast Organizing information in a table helps you compare and
contrast several topics at one time, such as the types of functional groups. As you read, ask
yourself, “How are they similar? How are they different?”
As you read Lesson 23.1, use the compare and contrast table below to differentiate among
functional groups.
Compound type
General structure
Functional group
halocarbon
R—X (X = F, Cl, Br, or I)
halogen
EXTENSION Write an example for each type of compound based on ethane (C2H6).
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Lesson Summary
Functional Groups A functional group is a chemically functional part of an organic
compound.
Substituents called functional groups are often attached to hydrocarbon chains or rings.
Organic compounds can be classified according to their functional groups.
Halocarbons A halocarbon is an organic compound that contains a halogen as its
functional group.
The general formula of a halocarbon is RX, where X is a halogen substituent.
When a halogen is attached to an aliphatic chain, it is called an alkyl halide; when
attached to an arene ring, it is an aryl halide.
Common names of halocarbons begin with the name of the alkyl or aryl group and end
with the name of the halogen with an -ide ending.
Substitution Reactions A substitution reaction can be used to introduce functional
groups into organic compounds.
A halocarbon is produced when a halogen atom replaces a hydrogen atom on an alkane.
A catalyst, such as iron, is often used in the halogenation of aromatic compounds.
Halocarbons can be converted to other halocarbons, amines, or ethers by similar
substitution reactions.
Type of reaction
General reaction
specific reaction
R—H + X2 → R—X + HX
CH4 + Cl2 → CH3Cl + HCl
2R—X + 2OH− → 2R—OH + X−
CH3I + KOH → CH3OH + KI
Alkane halogenation
Aromatic halogenation
Formation of alcohol
After reading Lesson 23.1, complete the following questions.
Functional Groups
1. Is the following sentence true or false? The saturated hydrocarbon skeletons of organic
molecules are chemically reactive.
2. What is a functional group?
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Use Table 23.1 to answer Questions 3 and 4.
3. Name the functional group for each general structure.
a. R—O—R
b. R—OH
c. R—NH2
4. Name two compound types that have a carbonyl group as a functional group.
a.
b.
Halocarbons
5. What are halocarbons?
6. Give the IUPAC and common names for the following halocarbons.
a. CH3—CH2—CH2—Br
b.
7. A halogen attached to a carbon of an aliphatic chain produces a halocarbon called a(n)
.
8. The second part of a halocarbon common name ends with
.
9. Highly halogenated organic compounds have higher
because of van der Waal interactions.
10. What uses do halogenated hydrocarbons have?
11. What is an aryl halide?
Substitution Reactions
12. Why do reactions involving organic compounds often proceed more slowly than those
involving inorganic molecules and ions?
13. Is the following sentence true or false? The products of organic reactions are often a
complex mixture of compounds.
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14. Organic reactions that involve the replacement of one atom or group of atoms with
another atom or group of atoms are called
reactions.
15. Label the compounds in this generalized halogenation reaction.
R—H
+
X2
R—X
→
+
HX
16. Hydroxide ions can displace most halogens on carbon chains to produce a(n)
.
23.2 Alcohols, Ethers,
and Amines
Essential Understanding
Three of the most important types of compounds with functional
groups are alcohols, ethers, and amines.
Lesson Summary
Alcohols Organic compounds with the general formula R—OH are alcohols.
Aliphatic alcohols belong to different structural groups according to the number of
carbons attached to the carbon with the hydroxy group.
Many alcohols are soluble in water and have high boiling points.
Naming Alcohols
Type of compound
Naming rules
Example
1 hydroxy group attached to
an alkyl group
Name longest chain
Drop -e, add -ol
Write number at beginning
to show where the OH is
attached
butanol (OH at end)
common name: butyl alcohol
2-hydroxy-butane
2 or 3 hydroxy groups
attached to an alkyl group
Use numbers
Add endings -diol or -triol
1,3-propanediol
1,2,3-propanetriol
Hydroxy group attached
directly to an aromatic ring
Use the word phenol
Place other attached groups
before the word phenol
methylphenol
diethylphenol
Addition Reactions New functional groups can be added to an organic molecule at the
site of a double or triple bond.
In an addition reaction, a substance is added at the double or triple bond of an alkene or
alkyne.
Water and halides can be inserted through hydration or halogenation addition reactions.
A catalyst is used to enable a hydrogen to be added to a carbon-carbon double bond in a
hydrogenation reaction.
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