23.1 introduction to functional groups 1 > copyright © pearson education, inc., or its...

23.1 Introduction to 23.1 Introduction to Functional GroupsFunctional Groups

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Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Chapter 23Functional Groups

23.1 Introduction to Functional Groups

23.2 Alcohols, Ethers, and Amines23.3 Carbonyl Compounds23.4 Polymers


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From a distance, all the musicians look nearly identical. But are they?

CHEMISTRY & YOUCHEMISTRY & YOU

How can you tell the difference between one organic compound and another?


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Functional Groups

How are organic compounds classified?

Functional GroupsFunctional Groups


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In most organic reactions, the saturated hydrocarbon skeletons of molecules are chemically inert, or non-reactive.

• So how, then, can there be hundreds of different kinds of organic reactions?


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Most organic chemistry involves substituents, which are groups attached to hydrocarbon chains or rings.

• The substituents of organic molecules often contain oxygen, nitrogen, sulfur, and/or phosphorus.



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Most organic chemistry involves substituents, which are groups attached to hydrocarbon chains or rings.

• The substituents of organic molecules often contain oxygen, nitrogen, sulfur, and/or phosphorus.

• They are called functional groups because they are the chemically functional parts of the molecules.



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A functional group is a specific arrangement of atoms in an organic compound that is capable of characteristic chemical reactions.



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A functional group is a specific arrangement of atoms in an organic compound that is capable of characteristic chemical reactions.

• Note that the double and triple bonds of alkenes and alkynes are chemically reactive.

• Therefore, they are also considered functional groups.



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Organic compounds can be classified according to their functional groups.



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Interpret DataInterpret Data

Organic Compounds Classified by Functional Group

Compound type

General structure

Functional group

Compound type

General structure

Functional group

Halocarbon Halogen Carboxylic acid Carbonyl

Alcohol Hydroxy

Ether EtherEster Ester

Amine Amino

Aldehyde Carbonyl Amide Amide

KetoneCarbonyl

• In each general structure listed, the symbol R represents any carbon chains or rings attached to the functional group.


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• In some cases, R can be a hydrogen atom.


Compound type

General structure

Functional group

Compound type

General structure

Functional group


Alcohol Hydroxy


Amine Amino


KetoneCarbonyl


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• When more than one R group is shown in the structural formula, the groups do not need to be the same.


Compound type

General structure

Functional group

Compound type

General structure

Functional group


Alcohol Hydroxy


Amine Amino


KetoneCarbonyl


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Are functional groups always substituents on a hydrocarbon?


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Are functional groups always substituents on a hydrocarbon?

No. Alkenes and alkynes are also chemically reactive. Therefore double and triple bonds can be considered functional groups, but they are not substituents.


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Halocarbons

What is the general formula of a halocarbon?

HalocarbonsHalocarbons


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Halocarbons

What is the general formula of a halocarbon?


• A halocarbon is an organic compound that contains at least one covalently bonded fluorine, chlorine, bromine, or iodine atom.


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The general formula of a halo carbon is RX, where X is a halogen substituent.



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The IUPAC rules for naming halocarbons are based on the name of the parent hydrocarbon.

• The halogen groups are named as substituents.



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Chloromethane


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Chloroethene


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Chlorobenzene


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Common names of halocarbons consist of two parts.

• The first part names the hydrocarbon portion of the molecule as an alkyl group, such as methyl- or ethyl-.

• The second part names the halogen with an -ide ending.


Methyl chloride Vinyl chloride Phenyl chloride


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• On the basis of their common names, a halocarbon in which a halogen is attached to a carbon of an aliphatic chain is called an alkyl halide.

• A halocarbon in which a halogen is attached to a carbon of an arene ring is called an aryl halide.



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Some Common Substituent Groups

Name Group structure Name Group structure

IsopropylTertiary butyl (tert-butyl)

Isobutyl Vinyl

Secondary butyl (sec-butyl)

Phenyl


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The attractions between halocarbon molecules are primarily the result of weak van der Waals interactions.


• Generally, these attractions increase with the degree of halogen substitution.


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Comparing Methane and Chloromethanes

Molecular formula Name Molar mass (g) Boiling point (°C)

CH4 Methane 16.0 –161

CH3Cl Chloromethane (methyl chloride)

50.5 –24

CH2Cl2Dichloromethane (methylene chloride)

85.0 40

CHCl3Trichloromethane (chloroform)

119.5 61

CCl4Tetrachloromethane (carbon tetrachloride)

154.0 74

More highly halogenated organic compounds have higher boiling points.


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Very few halocarbons are found in nature, but they can be readily prepared and used for many purposes.

• For example, hydrofluorocarbons (HFCs) are used as refrigerants in automobile air-conditioning systems.

• Halocarbons are also used as solvents and as ingredients of stretchable polymers.



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What is the difference between an alkyl halide and an aryl halide?


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What is the difference between an alkyl halide and an aryl halide?

An alkyl halide is a halocarbon in which a halogen is attached to a carbon of an aliphatic chain. An aryl halide is a halocarbon in which a halogen is attached to a carbon of an arene ring.


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Substitution Reactions

How are substitution reactions used in organic chemistry?

Substitution ReactionsSubstitution Reactions


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Organic reactions often proceed more slowly than inorganic reactions because organic reactions commonly involve the breaking of relatively strong covalent bonds.

• They often require catalysts.

• Many organic reactions are complex, and they usually produce a mixture of products.


– The desired product must then be separated by distillation, crystallization, or other means.


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A common type of organic reaction is a substitution reaction, in which an atom, or a group of atoms, replaces another atom or group of atoms.



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Substitution reactions are an important method of introducing new functional groups to organic molecules.


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A halogen atom can replace a hydrogen atom on an alkane to produce a halocarbon.


• The symbol X stands for a halogen in this generalized equation.

R—H + X2 → R—X + HX Alkane Halogen Halocarbon Hydrogen halide


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A halogen atom can replace a hydrogen atom on an alkane to produce a halocarbon.


• The symbol X stands for a halogen in this generalized equation.

R—H + X2 → R—X + HX Alkane Halogen Halocarbon Hydrogen halide

• This type of reaction is also called a halogenation reaction because the reaction introduces a halogen atom into the molecule.


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UV light

CH4 + Cl2 → CH3Cl + HClMethane Chlorine Chloromethane Hydrogen

chloride


Sunlight or another source of ultraviolet radiation usually serves as a catalyst.


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UV light

CH4 + Cl2 → CH3Cl + HClMethane Chlorine Chloromethane Hydrogen

chloride


Sunlight or another source of ultraviolet radiation usually serves as a catalyst.

• Even under the most controlled conditions, this simple substitution reaction produces a mixture of mono-, di-, tri-, and tetrachloromethanes.


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Halogenation of benzene in the presence of a catalyst causes the substitution of a hydrogen atom on the ring.

• Iron compounds are often used as catalysts for substitution reactions in aromatic compounds.


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Halocarbons can be converted to other types of compounds by substitution reactions.

• Hydroxide ions can displace halogen atoms on carbon chains to form an alcohol.



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Chemists usually use aqueous solutions of sodium hydroxide or potassium hydroxide as the source of hydroxide ions.



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Halocarbons can also be converted to other halocarbons, amines, or ethers by similar substitution reactions.



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Earlier you learned that adding a halogen substituent to a hydrocarbon affects certain physical properties. How can you distinguish between hydrocarbons and halocarbons in terms of structures and properties?



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Earlier you learned that adding a halogen substituent to a hydrocarbon affects certain physical properties. How can you distinguish between hydrocarbons and halocarbons in terms of structures and properties?

A halocarbon will contain at least one covalently bonded fluorine, chlorine, bromine, or iodine atom. Halocarbons are more reactive than hydrocarbons, and have higher boiling points.



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Name two kinds of substitution reactions used in organic chemistry.


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Name two kinds of substitution reactions used in organic chemistry.

There are substitution reactions in which a halogen reacts with an alkane to produce a halocarbon, and substitution reactions in which a hydroxide ion reacts with a halocarbon to form an alcohol.


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Organic compounds can be classified according to their functional groups.

The general formula of a halocarbon is RX, where X is a halogen substituent.

Substitution reactions are an important method of introducing new functional groups to organic molecules.

Key ConceptsKey Concepts


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• functional group: a specific arrangement of atoms in an organic compound that is capable of characteristic chemical reactions; the chemistry of an organic compound is determined by its functional groups

• halocarbon: any member of a class of organic compounds containing covalently bonded fluorine, chlorine, bromine, or iodine

Glossary TermsGlossary Terms


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• alkyl halide: a halocarbon in which one or more halogen atoms are attached to the carbon atoms of an aliphatic chain

• aryl halide: a halocarbon in which one or more halogens are attached to the carbon atoms of an arene ring

• substitution reaction: a common type of organic reaction; involves the replacement of an atom or group of atoms by another atom or group of atoms

Glossary TermsGlossary Terms


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• Functional groups affect the physical and chemical properties of organic compounds.

• Chemical reactions can be used to change the structure of organic molecules, often by introducing a new functional group.

• Substitution reactions are commonly used in organic chemistry.

BIG IDEABIG IDEA

Carbon Chemistry and Reactions


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END OF 23.1END OF 23.1

23.1 introduction to functional groups 1 > copyright © pearson education, inc., or its...

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