Copyright © 2009 by Pearson Education, Inc. 2. Organic Chemistry. An organic
compound ... by Pearson Education, Inc. 5. Comparing Organic and Inorganic.
Chapter 10 Introduction to Organic Chemistry: Alkanes
Organic Chemistry An organic compound
10.1 Organic Compounds
• • • •
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.
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Organic Compounds
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Organic vs. Inorganic
Typical organic compounds
• Propane, C3H8, is an organic compound used as a fuel.
• • • • •
have covalent bonds. have low melting points. have low boiling points. are flammable. are soluble in nonpolar solvents. • are not soluble in water.
• NaCl, salt, is an inorganic compound composed of Na+ and Cl− ions. Why is propane organic, but NaCl is not? oil (organic) and water (inorganic)
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Copyright © 2009 by Pearson Education, Inc.
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Comparing Organic and Inorganic Compounds
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Learning Check Identify each characteristic as most typical of compounds that are 1) inorganic or 2) organic. A. B. C. D. E. F.
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has a high melting point. is not soluble in water. has a formula CH3─CH2─CH3. has a formula MgCl2. burns easily in air. has covalent bonds.
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Solution
Writing Formulas for Alkanes In organic compounds, • carbon has 4 valence electrons and hydrogen has 1.
Identify each characteristic as most typical of compounds that are 1) inorganic or 2) organic. 1 2 2 1 2 2
A. B. C. D. E. F.
• •C• •
has a high melting point. is not soluble in water. has a formula CH3─CH2─CH3. has a formula MgCl2. burns easily in air. has covalent bonds.
H•
• carbon achieves an octet by forming four bonds. H H ••
H:C:H
H
••
H
C
H
H
CH4, methane
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Tetrahedral Structure of Carbon
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Organic Molecules In organic molecules, • valence electrons are shared. • covalent bonds form between carbon atoms.
VSEPR theory predicts that a carbon atom with four single, covalent bonds has a tetrahedral shape.
H
••
H
••
H:C:C:H ••
H
••
H
H
H
H
C
C
H
H
H
Ethane, CH3─CH3
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Chapter 10 Introduction to Organic Chemistry: Alkanes
Tetrahedral Structure of Carbon
10.2 Alkanes
In molecules with two or more carbon atoms, each carbon atom with four single bonds has a tetrahedral shape.
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Copyright © 2009 by Pearson Education, Inc.
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Expanded and Condensed Structures
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 H H
C
Condensed
H
CH4 , methane Copyright © 2009 by Pearson Education, Inc.
H
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Structural Formulas
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:
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 │ │ │ │ H H H H
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Name CH3─CH2─CH2─CH3
# Carbons
Condensed Structural Formula CH4
1
Methane Ethane
2
CH3―CH3
Propane
3
CH3―CH2―CH3
Butane
4
CH3―CH2―CH2―CH3
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Names of Alkanes
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Learning Check
Alkanes with 5-10 carbon atoms in a chain use Greek prefixes. # Carbons Structural Formula Name Pentane
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Hexane
6
CH3CH2CH2CH2CH2CH3
Heptane
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CH3CH2CH2CH2CH2CH2CH3
Octane
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CH3CH2CH2CH2CH2CH2CH2CH3
Nonane
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CH3 CH2 CH2CH2CH2CH2CH2CH2CH3
Decane
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A. Write the condensed formula for: H H H H H
CH3CH2CH2CH2CH3
H
C
C
C
C
C
H
H H H H H B. What is its molecular formula? C. What is its name?
CH3CH2CH2CH2CH2CH2CH2CH2CH2CH3
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Solution
Writing Structural Formulas
A. CH3─CH2─CH2─CH2─CH3
Carbon atoms in a chain
B. C5H12
• • • •
C. pentane
maintain tetrahedral shape. are connected in a zigzag pattern. are drawn as 2-dimensional. can be written in several conformations.
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Some Structures for Butane
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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.
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Learning Check
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Solution
Write the condensed structural formula for
Write the condensed structural formula for
A. ethane.
A. ethane
B. heptane.
B. heptane CH3─CH2─CH2─CH2─CH2─CH2─CH3
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CH3─CH3
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Cycloalkanes
Cycloalkanes The structural formulas of cycloalkanes are usually represented by geometric figures.
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.
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More Cycloalkanes
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Learning Check Name the following. A. CH3─CH2─CH2─CH3 B. C. CH3─CH2─CH2─CH2─CH2─CH2─CH2─CH3 D.
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Chapter 10 Introduction to Organic Chemistry: Alkanes
Solution Name the following: A. CH3─CH2─CH2─CH3 B.
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10.3 Alkanes with Substituents
butane cyclopropane
C. CH3─CH2─CH2─CH2─CH2─CH2─CH2─CH3 octane D. cyclohexane
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Isomers of Butane
Alkyl groups Alkyl groups are • alkanes that are missing one H. • substituents attached to carbon chains. • named with a –yl ending.
Isomers • have the same molecular formula. • have different atom arrangements. • of butane (C4H10) are a straight chain and a branched chain.
CH3 CH3
methyl CH2
ethyl
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Naming Substituents
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Guide to Naming Alkanes
In the IUPAC system, • a carbon branch is named as an alkyl group. • halogen atoms are named as halo.
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Alkanes with Substituents
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Naming Alkanes Give the name of
CH3 CH3 CH
methylpropane
CH3
STEP 1:
CH3 CH3 ⎢ ⎢ CH3─CH─CH─CH3
Name the longest continuous chain.
methyl groups CH3
CH3 CH3 ⎢ ⎢ CH3─CH─CH─CH3
CH3
CH3 CH CH2 CH CH3
2,4-dimethylpentane
butane
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Naming Alkanes Give the name of
Learning Check
CH3 CH3 ⎢ ⎢ CH3─CH─CH─CH3
Write the name of Cl CH3 ⎢ ⎢ CH3─CH2─CH─CH─CH3
Number chain.
CH3 CH3 ⎢ ⎢ CH3─CH─CH─CH3 1 2 3 4 STEP 3: Locate substituents and name. 2,3-dimethylbutane
STEP 2:
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Solution
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Learning Check
STEP 1:
Longest chain is pentane.
Give the IUPAC name for each of the following:
STEP 2:
Number chain from end nearest substituent. Cl CH3 ⎢ ⎢ CH3─CH2─CH─CH─CH3 5 4 3 2 1
A.
CH3 CH3 | | CH3─CH─CH2 ─CH─CH3
B.
Cl CH3 | | CH3─CH2─CH─CH2─C─CH2─CH3 | Cl
STEP 3: Locate substituents and name alphabetically. 3-chloro-2-methylpentane
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Guide to Drawing Alkane Formulas
Solution A.
CH3 CH3 | | CH3─CH─CH2 ─CH─CH3 1
B.
2
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3
4
2,4-dimethylpentane
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Cl CH3 more substituents on C3 | | CH3─CH2─CH─CH2─C─CH2─CH3 | Cl 7
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5
4
3
2
1
3,5-dichloro-3-methylheptane
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Learning Check
Solution 3-bromo-1-chlorobutane STEP 1: Longest chain has 4 carbon atoms. C─C─C─C STEP 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
Draw the condensed structural formula for 3-bromo-1-chlorobutane.
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Naming Cycloalkanes with Substituents
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Learning Check Name each of the following.
The name of a substituent is placed in front of the cycloalkane name.
1.
2. chlorocyclopentane
CH3
CH3
methylcyclobutane
CH2─CH3
Cl
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Chapter 10 Introduction to Organic Chemistry: Alkanes
Solution Name each of the following.
10.4 Properties of Alkanes
1. methylcyclopropane 2. ethylcyclohexane
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Some Properties of Alkanes
Some Properties of Alkanes
Alkanes are • nonpolar. • insoluble in water. • less dense than water. • flammable in air.
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.
Copyright © 2009 by Pearson Education, Inc.
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Some Properties of Alkanes
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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.
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.
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Combustion
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Learning Check Write a balanced equation for the complete combustion of propane.
In combustion reactions, • alkanes react with oxygen. • CO2, H2O, and energy are produced. • Alkane + O2 CO2 + H2O + heat
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Chapter 10 Introduction to Organic Chemistry: Alkanes
Solution
10.5 Functional Groups
Unbalanced equation C3 H8 + O 2
CO2 + H2O
Balance C C3 H8 + O 2
3CO2 + H2O
Balance H C3 H8 + O 2
3CO2 + 4H2O
Balance O C3H8 + 5O2
3CO2 + 4H2O (Balanced)
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Elements in Organic Compounds
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Functional Groups
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.
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.
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Comparing Alkenes, Alkynes, and Aromatic Compounds
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.
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Alcohols and Ethers
Aldehydes and Ketones
A thiol contains the thiol (-SH) functional group.
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.
An ether contains an oxygen atom bonded to two carbon atoms.
In a ketone, the carbon of the carbonyl group (C=O) is attached to two carbon atoms.
An alcohol contains the hydroxyl (-OH) functional group.
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Copyright © 2009 by Pearson Education, Inc.
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Carboxylic Acids and Esters
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Amines and Amides
Carboxylic acids contain the carboxyl group, which is a carbonyl group attached to a hydroxyl group. O ║ — C—OH An ester contains the carboxyl group between carbon atoms.
In amines, the functional group is a nitrogen atom. | —N — Amines
In amides, the hydroxyl group of a carboxylic acid is replaced by a nitrogen group.
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Copyright © 2009 by Pearson Education, Inc.
An amide
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Summary of Functional Groups
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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 ║ 4) CH3─C─OH
O ║ 5) CH3─C─O─CH3
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Solution 1) CH3─CH2─CH2─OH 2) CH3─O─CH2─CH3 3) CH3─CH2─NH2
alcohol ether amine
O ║ 4) CH3─C─OH carboxylic acid
O ║ 5) CH3─C─O─CH3 ester
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