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) Copyright © 2009 by Pearson Education, Inc.

Organic vs. Inorganic Propane, C 3 H 8, 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 Copyright © 2009 by Pearson Education, Inc.

Comparing Organic and Inorganic Compounds 5 Copyright © 2009 by Pearson Education, Inc.

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 CH 3 ─CH 2 ─CH 3. D. has a formula MgCl 2. E. burns easily in air. F. has covalent bonds. 6

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 CH 4, methane 7

Tetrahedral Structure of Carbon VSEPR theory predicts that a carbon atom with four single, covalent bonds has a tetrahedral shape. 8

Organic Molecules In organic molecules, valence electrons are shared. covalent bonds form between carbon atoms. H H H H H  C  C  HH C C H H H H H Ethane, CH 3 ─CH 3 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 Copyright © 2009 by Pearson Education, Inc.

Chapter 10 Introduction to Organic Chemistry: Alkanes 10.2 Alkanes 11 Copyright © 2009 by Pearson Education, Inc.

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 CH 4, methane H 12

Expanded and Condensed Structures 13 Copyright © 2009 by Pearson Education, Inc.

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 CH 3 ─CH 2 ─CH 2 ─CH 3 │ │ │ │ H H H H 14

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 Methane1CH 4 Ethane2CH 3 ―CH 3 Propane3CH 3 ―CH 2 ―CH 3 Butane4CH 3 ―CH 2 ―CH 2 ―CH 3 15

Names of Alkanes Alkanes with 5-10 carbon atoms in a chain use Greek prefixes. Name # Carbons Structural Formula Pentane 5CH 3 CH 2 CH 2 CH 2 CH 3 Hexane 6 CH 3 CH 2 CH 2 CH 2 CH 2 CH 3 Heptane 7 CH 3 CH 2 CH 2 CH 2 CH 2 CH 2 CH 3 Octane 8 CH 3 CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 CH 3 Nonane 9 CH 3 CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 CH 3 Decane 10 CH 3 CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 CH 3 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 Copyright © 2009 by Pearson Education, Inc.

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 Copyright © 2009 by Pearson Education, Inc.

Learning Check Write the condensed structural formula for A. ethane. B. heptane. 21

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. 22

Cycloalkanes 23 The structural formulas of cycloalkanes are usually represented by geometric figures. Copyright © 2009 by Pearson Education, Inc.

More Cycloalkanes 24 Copyright © 2009 by Pearson Education, Inc.

Learning Check Name the following. A. CH 3 ─CH 2 ─CH 2 ─CH 3 B. C. CH 3 ─CH 2 ─CH 2 ─CH 2 ─CH 2 ─CH 2 ─CH 2 ─CH 3 D. 25

Chapter 10 Introduction to Organic Chemistry: Alkanes 10.3 Alkanes with Substituents 26

Isomers of Butane Isomers have the same molecular formula. have different atom arrangements. of butane (C 4 H 10 ) 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. CH 3 methyl CH 3 CH 2 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 CH 3 CH 3 CH CH 3 methylpropane methyl groups CH 3 CH 3 CH 3 CH CH 2 CH CH 3 2,4-dimethylpentane 31

Naming Alkanes Give the name of CH 3 CH 3  CH 3 ─CH─CH─CH 3 STEP 1: Name the longest continuous chain. CH 3 CH 3  CH 3 ─CH─CH─CH 3 butane 32

Naming Alkanes Give the name of CH 3 CH 3  CH 3 ─CH─CH─CH 3 STEP 2: Number chain. CH 3 CH 3  CH 3 ─CH─CH─CH STEP 3: Locate substituents and name. 2,3-dimethylbutane 33

Learning Check Write the name of Cl CH 3  CH 3 ─CH 2 ─CH─CH─CH 3 34

Learning Check Give the IUPAC name for each of the following: A. CH 3 CH 3 | CH 3 ─CH─CH 2 ─CH─CH 3 B. Cl CH 3 | | CH 3 ─CH 2 ─CH─CH 2 ─C─CH 2 ─CH 3 | Cl 35

Guide to Drawing Alkane Formulas 36

Learning Check Draw the condensed structural formula for 2-chloropropane 3-bromo-1-chlorobutane 1,1,2,2-tetrabromopropane 37

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 STEP 3: Add hydrogen to complete 4 bonds to each C. Br  CH 3 ─CH─CH 2 ─CH 2 ─Cl 38

Naming Cycloalkanes with Substituents The name of a substituent is placed in front of the cycloalkane name. methylcyclobutane CH 3 chlorocyclopentane Cl 39

Learning Check Name each of the following. 1. CH 3 CH 2 ─CH

Chapter 10 Introduction to Organic Chemistry: Alkanes 10.4 Properties of Alkanes 41

Some Properties of Alkanes Alkanes are nonpolar. insoluble in water. less dense than water. flammable in air. 42 Copyright © 2009 by Pearson Education, Inc.

Some Properties of Alkanes Alkanes with 1-4 carbon atoms are methane, ethane, propane, and butane. gases at room temperature. used as heating fuels. 43 Copyright © 2009 by Pearson Education, Inc.

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. 44

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. 45 Copyright © 2009 by Pearson Education, Inc.

Combustion In combustion reactions, alkanes react with oxygen. CO 2, H 2 O, and energy are produced. Alkane + O 2 CO 2 + H 2 O + heat 46 Copyright © 2009 by Pearson Education, Inc.

Learning Check Write a balanced equation for the complete combustion of propane. 47 Copyright © 2009 by Pearson Education, Inc.

Chapter 10 Introduction to Organic Chemistry: Alkanes 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 Copyright © 2009 by Pearson Education, Inc.

Functional Groups 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. 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 Copyright © 2009 by Pearson Education, Inc.

Comparing Alkenes, Alkynes, and Aromatic Compounds 52 Copyright © 2009 by Pearson Education, Inc.

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 Copyright © 2009 by Pearson Education, Inc.

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—OH An ester contains the carboxyl group between carbon atoms. 55 Copyright © 2009 by Pearson Education, Inc.

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 Copyright © 2009 by Pearson Education, Inc. Amines An amide

Summary of Functional Groups 57 Copyright © 2009 by Pearson Education, Inc.

Learning Check Classify each of the following as: alcohol, ether, aldehyde, ketone, carboxylic acid, ester, amine, or amide. 1)CH 3 ─CH 2 ─CH 2 ─OH 2) CH 3 ─O─CH 2 ─CH 3 3) CH 3 ─CH 2 ─NH 2 O O ║ ║ 4) CH 3 ─C─OH 5) CH 3 ─C─O─CH 3 58