chapter 10 introduction to organic chemistry: alkanes 10.1 organic compounds 1 copyright © 2009 by...

Chapter 10 Introduction to Organic Chemistry: Alkanes

10.1 Organic Compounds

1

Copyright © 2009 by Pearson Education, Inc.

Organic Chemistry

An organic compound

• is a compound made from carbon atoms.• has one or more C atoms. • has many H atoms.• may also contain O, S, N, and halogens.

2

Organic Compounds

Typical organic compounds

• have covalent bonds.

• have low melting points.

• have low boiling points.

• are flammable.

• are soluble in nonpolar solvents.

• are not soluble in water.

3

oil (organic) and water (inorganic)


Organic vs. Inorganic

• Propane, C3H8, is an organic compound used as a fuel.

• NaCl, salt, is an inorganic compound composed of Na+ and Cl− ions.

Why is propane organic,

but NaCl is not?

4


Comparing Organic and Inorganic Compounds

5


Learning Check

Identify each characteristic as most typical of compounds

that are 1) inorganic or 2) organic.

A. has a high melting point.

B. is not soluble in water.

C. has a formula CH3─CH2─CH3.

D. has a formula MgCl2.

E. burns easily in air.

F. has covalent bonds.

6

Writing Formulas for AlkanesIn organic compounds, • carbon has 4 valence electrons and hydrogen

has 1.

• • C • H • •

• carbon achieves an octet by forming four bonds. H H

H C H H C H

H H CH4, methane

7

Tetrahedral Structure of Carbon

VSEPR theory predicts that a carbon atom with four single, covalent bonds has a tetrahedral shape.

8

Organic MoleculesIn organic molecules, • valence electrons are shared.• covalent bonds form between carbon atoms.

H H H H • • • •

H C C H H C C H

• • • • H H H H

Ethane, CH3─CH3

9

Tetrahedral Structure of Carbon

In molecules with two or more carbon atoms, each carbon atom with four single bonds has a tetrahedral shape.

10



10.2 Alkanes

11


Structural Formulas

Alkanes are written with structural formulas that are

• expanded to show each bond.• condensed to show each carbon atom and its

attached hydrogen atoms.

Expanded Condensed H

H C H CH4 , methane

H

12

Expanded and Condensed Structures

13


Structural Formulas Condensed formulas are written for expanded

structural formula by showing each carbon and the attached hydrogen atoms.

Expanded Condensed H H H H │ │ │ │H─C ─C ─C ─C ─ H CH3─CH2─CH2─CH3

│ │ │ │ H H H H

14

Names of AlkanesThe names of alkanes • are determined by the IUPAC (International

Union of Pure and Applied Chemistry) system.• end in –ane.• with 1-4 carbons in a chain use prefixes as

follows:

Name # Carbons Condensed Structural Formula

Methane 1 CH4

Ethane2 CH3―CH3

Propane 3 CH3―CH2―CH3

Butane4 CH3―CH2―CH2―CH3

15

Names of AlkanesAlkanes with 5-10 carbon atoms in a chain use Greek prefixes.Name # Carbons Structural Formula

Pentane 5 CH3CH2CH2CH2CH3

Hexane 6 CH3CH2CH2CH2CH2CH3

Heptane 7 CH3CH2CH2CH2CH2CH2CH3

Octane 8 CH3CH2CH2CH2CH2CH2CH2CH3

Nonane 9 CH3 CH2 CH2CH2CH2CH2CH2CH2CH3

Decane 10

CH3CH2CH2CH2CH2CH2CH2CH2CH2CH3

16

Learning Check A. Write the condensed formula for:

H H H H H

H C C C C C H

H H H H H

B. What is its molecular formula?

C. What is its name?

17

Writing Structural Formulas

Carbon atoms in a chain

• maintain tetrahedral shape.• are connected in a zigzag pattern.• are drawn as 2-dimensional. • can be written in several conformations.

18

Some Structures for Butane

19


Hexane Has Six Carbon Atoms

Hexane • is an alkane with six carbon atoms in a

continuous chain.• has a “zigzag” look because each carbon

atom is at the center of a tetrahedron.• is represented by a ball-and-stick model as

shown below.

20


Learning CheckWrite the condensed structural formula for

A. ethane.

B. heptane.

21

CycloalkanesCycloalkanes

• are cyclic alkanes.

• have two hydrogen atoms fewer than the open chain.

• are named by using the prefix cyclo- before the name of the alkane chain with the same number of carbon atoms.

22

Cycloalkanes

23

The structural formulas of cycloalkanes are usually represented by geometric figures.


More Cycloalkanes

24


Learning CheckName the following.

A. CH3─CH2─CH2─CH3

B.

C. CH3─CH2─CH2─CH2─CH2─CH2─CH2─CH3

D.

25


10.3 Alkanes with Substituents

26

Isomers of Butane

Isomers• have the same

molecular formula.

• have different atom arrangements.

• of butane (C4H10) are a straight chain and a branched chain.

27

Alkyl groups Alkyl groups are• alkanes that are missing one H. • substituents attached to carbon chains.• named with a –yl ending.

CH3 methyl

CH3 CH2 ethyl

28

Naming Substituents

In the IUPAC system,

• a carbon branch is named as an alkyl group.

• halogen atoms are named as halo.

29

Guide to Naming Alkanes

30

Alkanes with Substituents CH3

CH3 CH CH3 methylpropane

methyl

groups

CH3 CH3

CH3 CH CH2 CH CH3 2,4-dimethylpentane

31

Naming AlkanesGive the name of CH3 CH3

CH3─CH─CH─CH3

STEP 1: Name the longest continuous chain.

CH3 CH3

CH3─CH─CH─CH3

butane

32

Naming AlkanesGive the name of CH3 CH3

CH3─CH─CH─CH3

STEP 2: Number chain. CH3 CH3

CH3─CH─CH─CH3

1 2 3 4STEP 3: Locate substituents and name.

2,3-dimethylbutane

33

Learning CheckWrite the name of

Cl CH3

CH3─CH2─CH─CH─CH3

34

Guide to Drawing Alkane Formulas

36

Learning CheckDraw the condensed structural formula for 2-chloropropane3-bromo-1-chlorobutane1,1,2,2-tetrabromopropane

37

Solution3-bromo-1-chlorobutaneSTEP 1: Longest chain has 4 carbon atoms.

C─C─C─CSTEP 2: Number chain and add substituents.

Br

C ─ C ─ C ─ C ─ Cl 4 3 2 1

STEP 3: Add hydrogen to complete 4 bonds to each C. Br

CH3─CH─CH2─CH2─Cl

38

Naming Cycloalkanes with Substituents

The name of a substituent is placed in front of the

cycloalkane name.

methylcyclobutane CH3

chlorocyclopentane Cl

39

Learning Check

Name each of the following.

1. CH3

CH2─CH3

2.

40


10.4 Properties of Alkanes

41

Some Properties of Alkanes

Alkanes are• nonpolar.• insoluble in water.• less dense than water.• flammable in air.

42



Alkanes with 1-4 carbon atoms are

• methane, ethane, propane, and butane.

• gases at room temperature.

• used as heating fuels.

43



Alkanes with 5-8 carbon atoms are• liquids at room temperature.• pentane, hexane, heptane, and octane.• very volatile.• used to make gasoline.

Alkanes with 9-17 carbon atoms • are liquids at room temperature• have higher boiling points.• are found in kerosene, diesel, and jet

fuels.

44


Alkanes with 18 or more carbon atoms

• have high molar masses.• are waxy solids at room

temperature.• used in waxy coatings of fruits and

vegetables.

45


Combustion

In combustion reactions,

• alkanes react with oxygen.

• CO2, H2O, and energy are

produced.

• Alkane + O2 CO2 + H2O +

heat

46


Learning Check

Write a balanced equation for the

complete combustion of propane.

47



10.5 Functional Groups

48

Elements in Organic Compounds

In organic molecules, carbon atoms bond • with four bonds.• mostly with H and other C atoms.• sometimes to O, N, S. • sometimes to halogens F, Cl, and Br.

49


Functional GroupsFunctional groups are• a characteristic feature of organic molecules

that behave in a predictable way. • composed of an atom or group of atoms. • groups that replace a hydrogen atom in the

corresponding alkane.• a way to classify families of organic

compounds.

50

Alkenes, Alkynes, and Aromatic Compounds

Alkenes contain a double bond between adjacent carbon atoms.Alkynes contain a triple bond.Aromatic compounds contain a ring of six carbon atoms called benzene.

51


Comparing Alkenes, Alkynes, and Aromatic Compounds

52


Alcohols and Ethers

An alcohol contains the hydroxyl (-OH) functional group.

A thiol contains the thiol (-SH) functional group.

An ether contains an oxygen atom bonded to two carbon atoms.

53


Aldehydes and Ketones

An aldehyde contains a carbonyl group (C=O), which is a carbon atom with a double bond to an oxygen atom. The carbonyl is attached to a hydrogen.

In a ketone, the carbon of the carbonyl group (C=O) is attached to two carbon atoms.

54

Copyright © 2009 by Pearson Education, Inc,

Carboxylic Acids and Esters

Carboxylic acids contain the carboxyl group, which is a carbonyl group attached to a hydroxyl group.

O ║

— C—OHAn ester contains the carboxyl group between carbon atoms.

55


Amines and Amides

In amines, the functional group is a nitrogen atom. |

—N —

In amides, the hydroxyl group of a carboxylic acid is replaced by a nitrogen group.

56


Amines

An amide

Summary of Functional Groups

57


Learning Check

Classify each of the following as: alcohol, ether, aldehyde, ketone, carboxylic acid, ester, amine, or amide.

1) CH3─CH2─CH2─OH

2) CH3─O─CH2─CH3

3) CH3─CH2─NH2

O O ║ ║

4) CH3─C─OH 5) CH3─C─O─CH3

58

chapter 10 introduction to organic chemistry: alkanes 10.1 organic compounds 1 copyright © 2009 by...

Documents