Upload
vukien
View
249
Download
1
Embed Size (px)
Citation preview
1
Chapter 10 Introduction to Organic Chemistry: Alkanes
10.1 Organic Compounds
Copyright © 2009 by Pearson Education, Inc.
2
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.
3
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.
oil (organic) and water (inorganic)Copyright © 2009 by Pearson Education, Inc.
4
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?
Copyright © 2009 by Pearson Education, Inc.
5
Comparing Organic and Inorganic Compounds
Copyright © 2009 by Pearson Education, Inc.
6
Learning Check
Identify each characteristic as most typical of compoundsthat 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.
7
Solution
Identify each characteristic as most typical of compoundsthat are 1) inorganic or 2) organic.
1 A. has a high melting point. 2 B. is not soluble in water.2 C. has a formula CH3─CH2─CH3.1 D. has a formula MgCl2.2 E. burns easily in air.2 F. has covalent bonds.
8
Writing Formulas for Alkanes
In 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
9
Tetrahedral Structure of Carbon
VSEPR theorypredicts that a carbon atom with four single, covalent bonds has a tetrahedral shape.
10
Organic Molecules
In 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
11
Tetrahedral Structure of Carbon
In molecules with two or more carbon atoms, each carbon atom with four single bonds has a tetrahedral shape.
Copyright © 2009 by Pearson Education, Inc.
12
Chapter 10 Introduction to Organic Chemistry: Alkanes
10.2 Alkanes
Copyright © 2009 by Pearson Education, Inc.
13
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 CondensedH
H C H CH4 , methane
H
14
Expanded and Condensed Structures
Copyright © 2009 by Pearson Education, Inc.
15
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
16
Names of Alkanes
The 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
Ethane 2 CH3―CH3
Propane 3 CH3―CH2―CH3
Butane 4 CH3―CH2―CH2―CH3
17
Names of Alkanes
Alkanes with 5-10 carbon atoms in a chain use Greek prefixes.Name # Carbons Structural FormulaPentane 5 CH3CH2CH2CH2CH3
Hexane 6 CH3CH2CH2CH2CH2CH3
Heptane 7 CH3CH2CH2CH2CH2CH2CH3
Octane 8 CH3CH2CH2CH2CH2CH2CH2CH3
Nonane 9 CH3 CH2 CH2CH2CH2CH2CH2CH2CH3
Decane 10 CH3CH2CH2CH2CH2CH2CH2CH2CH2CH3
18
Learning Check
A. Write the condensed formula for:H H H H H
H C C C C C H
H H H H HB. What is its molecular formula?C. What is its name?
19
Solution
A. CH3─CH2─CH2─CH2─CH3
B. C5H12
C. pentane
20
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.
21
Some Structures for Butane
Copyright © 2009 by Pearson Education, Inc.
22
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.
Copyright © 2009 by Pearson Education, Inc.
23
Learning Check
Write the condensed structural formula for
A. ethane.
B. heptane.
24
Solution
Write the condensed structural formula for
A. ethane CH3─CH3
B. heptane CH3─CH2─CH2─CH2─CH2─CH2─CH3
25
Cycloalkanes
Cycloalkanes
• 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.
26
Cycloalkanes
The structural formulas of cycloalkanes are usually represented by geometric figures.
Copyright © 2009 by Pearson Education, Inc.
More Cycloalkanes
27
Copyright © 2009 by Pearson Education, Inc.
28
Learning Check
Name the following.
A. CH3─CH2─CH2─CH3
B.
C. CH3─CH2─CH2─CH2─CH2─CH2─CH2─CH3
D.
29
Solution
Name the following:
A. CH3─CH2─CH2─CH3 butane
B. cyclopropane
C. CH3─CH2─CH2─CH2─CH2─CH2─CH2─CH3 octane
D. cyclohexane
30
Chapter 10 Introduction to Organic Chemistry: Alkanes
10.3 Alkanes with Substituents
31
Isomers of Butane
Isomers• have the same
molecular formula.• have different atom
arrangements.• of butane (C4H10) are a
straight chain and a branched chain.
32
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
33
Naming Substituents
In the IUPAC system,• a carbon branch is
named as an alkyl group.
• halogen atoms are named as halo.
Guide to Naming Alkanes
34
35
Alkanes with Substituents
CH3
CH3 CH CH3 methylpropane
methyl groupsCH3 CH3
CH3 CH CH2 CH CH3 2,4-dimethylpentane
36
Naming Alkanes
Give the name of CH3 CH3
CH3─CH─CH─CH3
STEP 1: Name the longest continuous chain.
CH3 CH3
CH3─CH─CH─CH3
butane
37
Naming Alkanes
Give the name of CH3 CH3
CH3─CH─CH─CH3
STEP 2: Number chain. CH3 CH3
CH3─CH─CH─CH31 2 3 4
STEP 3: Locate substituents and name.2,3-dimethylbutane
38
Learning Check
Write the name of
Cl CH3
CH3─CH2─CH─CH─CH3
39
Solution
STEP 1: Longest chain is pentane.
STEP 2: Number chain from end nearest substituent.Cl CH3
CH3─CH2─CH─CH─CH35 4 3 2 1
STEP 3: Locate substituents and name alphabetically. 3-chloro-2-methylpentane
40
Learning Check
Give the IUPAC name for each of the following:
A. CH3 CH3| | CH3─CH─CH2 ─CH─CH3
B. Cl CH3| |CH3─CH2─CH─CH2─C─CH2─CH3|
Cl
41
Solution
A. CH3 CH3| | CH3─CH─CH2 ─CH─CH3 2,4-dimethylpentane1 2 3 4 5
B. Cl CH3 more substituents on C3| |
CH3─CH2─CH─CH2─C─CH2─CH3|Cl
7 6 5 4 3 2 1
3,5-dichloro-3-methylheptane
Guide to Drawing AlkaneFormulas
42
43
Learning Check
Draw the condensed structural formula for 3-bromo-1-chlorobutane.
44
Solution
3-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 ─ Cl4 3 2 1
STEP 3: Add hydrogen to complete 4 bonds to each C.Br
CH3─CH─CH2─CH2─Cl
45
Naming Cycloalkanes with Substituents
The name of a substituent is placed in front of thecycloalkane name.
methylcyclobutane CH3
chlorocyclopentane Cl
46
Learning Check
Name each of the following.
1. CH3
CH2─CH32.
47
Solution
Name each of the following.
1. methylcyclopropane
2. ethylcyclohexane
48
Chapter 10 Introduction to Organic Chemistry: Alkanes
10.4 Properties of Alkanes
49
Some Properties of Alkanes
Alkanes are• nonpolar.• insoluble in water.• less dense than water.• flammable in air.
Copyright © 2009 by Pearson Education, Inc.
50
Some Properties of Alkanes
Alkanes with 1-4 carbon atoms are
• methane, ethane, propane, and butane.
• gases at room temperature.
• used as heating fuels.
Copyright © 2009 by Pearson Education, Inc.
51
Some Properties of Alkanes
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.
52
Some Properties of Alkanes
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.
Copyright © 2009 by Pearson Education, Inc.
53
Combustion
In combustion reactions,• alkanes react with oxygen.• CO2, H2O, and energy are produced.• Alkane + O2 CO2 + H2O + heat
Copyright © 2009 by Pearson Education, Inc.
54
Learning Check
Write a balanced equation for thecomplete combustion of propane.
Copyright © 2009 by Pearson Education, Inc.
55
Solution
Unbalanced equationC3H8 + O2 CO2 + H2O
Balance CC3H8 + O2 3CO2 + H2O
Balance HC3H8 + O2 3CO2 + 4H2O
Balance OC3H8 + 5O2 3CO2 + 4H2O (Balanced)
56
Chapter 10 Introduction to Organic Chemistry: Alkanes
10.5 Functional Groups
57
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.
Copyright © 2009 by Pearson Education, Inc.
58
Functional 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.
Functional Groups
59
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.
Copyright © 2009 by Pearson Education, Inc.
Comparing Alkenes, Alkynes, and Aromatic Compounds
60
Copyright © 2009 by Pearson Education, Inc.
61
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.
Copyright © 2009 by Pearson Education, Inc.
62
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.
Copyright © 2009 by Pearson Education, Inc,
63
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.
Copyright © 2009 by Pearson Education, Inc.
64
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.
Copyright © 2009 by Pearson Education, Inc.
Amines
An amide
65
Summary of Functional Groups
Copyright © 2009 by Pearson Education, Inc.
66
Learning Check
Classify each of the following as: alcohol, ether, aldehyde, ketone, carboxylic acid, ester, amine, or amide.1) CH3─CH2─CH2─OH2) CH3─O─CH2─CH33) CH3─CH2─NH2
O O║ ║
4) CH3─C─OH 5) CH3─C─O─CH3
67
Solution
1) CH3─CH2─CH2─OH alcohol2) CH3─O─CH2─CH3 ether3) CH3─CH2─NH2 amine
O O║ ║
4) CH3─C─OH 5) CH3─C─O─CH3carboxylic acid ester