1. Christopher G. Hamaker, Illinois State University, Normal IL © 2008, Prentice Hall Chapter 19 Organic Chemistry INTRODUCTORY CHEMISTRY INTRODUCTORY CHEMISTRY Concepts & Connections Fifth Edition by Charles H. Corwin

2. Chapter 19 2 Organic chemistry is the study of carbon and its compounds. The major sources of carbon are the fossil fuels petroleum, natural gas, and coal. Currently, about 7 million organic compounds account for about 90% of all known substances. Each year, over 50,000 new organic compounds are synthesized. Introduction

3. Chapter 19 3 A hydrocarbon is a compound that contains only carbon and hydrogen. A hydrocarbon derivative is a compound derived from a hydrocarbon but containing other elements, such as fluorine, nitrogen, and oxygen. There are two types of hydrocarbons: –saturated hydrocarbons –unsaturated hydrocarbons Introduction

4. Chapter 19 4 A saturated hydrocarbon has only single bonds between the carbon atoms. Carbon can form four single covalent bonds to other atoms. A saturated hydrocarbon with only single bonds belong to the alkane family. Saturated Hydrocarbons

5. Chapter 19 5 An unsaturated hydrocarbon has either a double or triple bond between two carbon atoms. –If it has a double bond, it is an alkene (b). –If it has a triple bond, it is an alkyne (c). An aromatic hydrocarbon has a benzene ring. A benzene ring is a 6-membered ring of carbon atoms with alternating single and double bonds (d). Unsaturated Hydrocarbons

6. Chapter 19 6 Below is a flowchart for the classification of hydrocarbons. Classification of Hydrocarbons

7. Chapter 19 7 Alkanes are a family of compounds whose names end in the suffix -ane. They are saturated hydrocarbons. They each have the same general molecular formula: C n H 2n+2. –The fifth member of the alkane family, pentane, has 5 carbon atoms and 12 (2 × 5 + 2 = 12) hydrogen atoms, C 5 H 12. Alkanes

8. Chapter 19 8 The lighter alkanes (1 – 10 carbons) are used as fuels, while the larger alkanes (20 – 40 carbons) are solids used to make waxes and candles. Alkane Family

9. Chapter 19 9 Two compounds with the same molecular formula but different structural formulas are isomers. Butane has the formula C 4 H 10. We can draw the formula in two ways: CH 3 CH 2 CH 2 CH 3 and CH 3 CH(CH 3 )CH 3 The two isomers have different physical properties. Structural Isomers

10. Chapter 19 10 When a hydrogen is removed from an alkane, an alkyl group results. CH 4 – H = CH 3 – methane methyl group CH 3 -CH 3 – H = CH 3 -CH 2 – ethane ethyl group When we remove the hydrogen atom, the name -ane suffix is changed to -yl. Alkyl and Aryl Groups

11. Chapter 19 11 Alkyl and Aryl Groups

12. Chapter 19 12 1.Name an alkane for its longest continuous carbon chain regardless of the branches. 2.Number the longest continuous chain starting from the end closest to the first branch on the chain. 3.Indicate the position of the alkyl groups by name and number. 4.If there are two or more of the same group attached to the chain, use the prefixes di-, tri-, tetra-, etc. Guidelines for Naming Alkanes

13. Chapter 19 13 What is the name of the following alkane? The longest chain has 5 carbons, so it is a pentane derivative. The methyl group is in the 2 position. The name is 2-methylpentane. Nomenclature of Alkanes

14. Chapter 19 14 What is the name of the following alkane? The longest chain has 6 carbons, so it is a hexane derivative. The methyl groups are in the 2, 4, and 4 positions. The name is 2,4,4-trimethylhexane. Nomenclature of Alkanes

15. Chapter 19 15 The C-C and C-H bonds in alkanes are very strong and unreactive at room temperature. At high temperatures, alkanes burn rapidly in the presence of oxygen. This is a combustion reaction. CH 4 (g) + 2 O 2 (g) → CO 2 (g) + 2 H 2 O(g) The products of a combustion reaction are carbon dioxide and water. Alkane Reactions

16. Chapter 19 16 Alkenes contain one or more double bonds. The general molecular formula for an alkene with one double bond is C n H 2n. –The fifth member of the alkene family, pentene, has 5 carbon atoms and 10 (2 × 5 = 10) hydrogen atoms, C 5 H 10. Alkynes contain one or more triple bonds. The general molecular formula for an alkyne with one double bond is C n H 2n-2. –The fifth member of the alkyne family, pentyne, has 5 carbon atoms and 8 (2 × 5 – 2 = 8) hydrogen atoms, C 5 H 8. Alkene and Alkyne Formulas

17. Chapter 19 17 Butene, C 4 H 8, has two structural isomers. The double bond can be between the first and second carbon or between the second and third carbon. Alkene Family

18. Chapter 19 18 1.Name an alkene for its longest continuous carbon chain that contains the double bond. The name is the same as the alkane with the -ane suffix changed to -ene. 2.Number the longest continuous chain, starting from the end closest to the double bond. 3.Indicate the position of the attached alkyl groups by name and number. 4.If there are two or more of the same group attached to the chain, use the prefixes di-, tri-, tetra-, etc. Guidelines for Naming Alkenes

19. Chapter 19 19 What is the name of the following alkene? The longest chain with the double bond has 6 carbons, so it is a hexene derivative. The double bond is the second bond, so it is a 2-hexene. The methyl groups are in the 5 position. The name is 5,5-dimethyl-2-hexene. Nomenclature of Alkenes

20. Chapter 19 20 Butyne, C 4 H 6, has two structural isomers. The triple bond can be between the first and second carbon or between the second and third carbon. Alkyne Family

21. Chapter 19 21 1.Name an alkene for its longest continuous carbon chain that contains the triple bond. The name is the same as the alkane, with the -ane suffix changed to -yne. 2.Number the longest continuous chain, starting from the end closest to the triple bond. 3.Indicate the position of the attached alkyl groups by name and number. 4.If there are two or more of the same group attached to the chain, use the prefixes di-, tri-, tetra-, etc. Guidelines for Naming Alkynes

22. Chapter 19 22 What is the name of the following alkyne? The longest chain with the triple bond has 4 carbons, so it is a butyne derivative. The triple bond is the first bond, so it is a 1-butyne. The methyl group is in the 3 position. The name is 3-methyl-1-butyne. Nomenclature of Alkynes

23. Chapter 19 23 In addition to combustion reactions, alkenes and alkynes also undergo addition reactions. The double or triple bond can add atoms. There are two types: hydrogenation and halogenation. Hydrogenation –CH≡CH(g) + H 2 (g) → CH 2 =CH 2 (g) Halogenation –CH 2 =CH 2 (l) + Br 2 (l) → CH 2 Br-CH 2 Br(l) Reactions of Alkenes and Alkynes

24. Chapter 19 24 A polymer is a giant molecule made up from many small molecules (monomers) joined in a long chain. Ethylene, CH 2 =CH 2, can react to give polyethlyene. We represent the polymer as [-CH 2 -CH 2 -] n. n CH 2 =CH 2 → [-CH 2 -CH 2 -] n monomer polymer Polymerization Reactions

25. Chapter 19 25 Arenes contain a benzene ring. Arenes are also called aromatic compounds because of their fragrant smell. The formula for benzene is C 6 H 6, and it has a cyclic structure. The double bonds are delocalized, and benzene is often written with a circle in the middle. Arenes

26. Chapter 19 26 If we replace two of the hydrogens on benzene with chlorines, we have dichlorobenzene, C 6 H 4 Cl 2. The chlorine atoms can be arranged in three different ways: Isomers of a Disubstituted Benzene

27. Chapter 19 27 If the chlorines are on adjacent carbons, we have ortho-dichlorobenzene. If the chlorines are separated by one carbon, we have meta-dichlorobenzene. If the chlorines are opposite each other, we have para-dichlorobenzene. Isomers of a Disubstituted Benzene

28. Chapter 19 28 There are millions of organic compounds. We can categorize them into classes of compounds. Each of the classes has a specific functional group. A functional group is a set of atoms that gives a class of compounds its characteristics. There are 10 classes: five without a carbonyl group and five with a carbonyl group (C=O). Hydrocarbon Derivatives

29. Chapter 19 29 Here are the basic hydrocarbon classes. R is an alkyl group and Ar is an aryl group. Non-Carbonyl Hydrocarbon Derivatives

30. Chapter 19 30 Carbonyl Hydrocarbon Derivatives

31. Chapter 19 31 If a halogen atom (F, Cl, Br, I) replaces a hydrogen atom in a hydrocarbon, the new compound is an organic halide. Organic halides are used primarily as household and industrial solvents. They are found in many pesticides. They are essentially nonpolar molecules with low boiling points and properties similar to those of alkanes. Organic Halides

32. Chapter 19 32 When an –OH group replaces a hydrogen atom on an alkane, the result is an alcohol. When an –OH replaces a hydrogen atom on a arene, the resulting molecule is a phenol. The –OH group is called a hydroxyl group. The names of alcohols are derived from the parent alkane by changing the -ane ending to an -ol suffix. –For example, CH 3 CH 2 OH is ethanol. Alcohols and Phenols

33. Chapter 19 33 Most alcohols are quite water soluble because of the polar –OH group, which allows for hydrogen bonding. Alcohols have higher boiling points than their parent alkanes. Alcohols and Phenols

34. Chapter 19 34 Organic molecules with two hydrocarbon groups attached to an oxygen are ethers, R-O-R. Ethers are usually named by indicating the two groups attached to the oxygen. Ethers do not hydrogen bond, and their properties lie between those of alkanes and alcohols. Ethers

35. Chapter 19 35 If an alkyl or aryl group replaces a hydrogen in ammonia, an amine results: R-NH 2. Amines are often referred to by their common names, indicating the alkyl group present. Most amines are polar due to their ability to hydrogen bond. Amines

36. Chapter 19 36 Aldehydes contain a carbonyl (C=O) group and are polar. In an aldehyde, the carbonyl group is attached to a hydrogen and an alkyl or aryl group, RCHO. The name of an aldehyde is derived from its parent alkane by changing the -ane to an -al suffix. Aldehydes

37. Chapter 19 37 Ketones also contain the carbonyl group and are generally polar. Ketones have two alkyl or aryl groups attached to the carbonyl group. Ketones are named for their parent alkane. Ketones

38. Chapter 19 38 In a carboxylic acid, a hydroxyl group and alkyl or aryl group is bonded to a carbonyl group, RCOOH. This group, -COOH, is a carboxyl group. Acetic acid, CH 3 COOH, is a major component of vinegar and gives it its sour taste. Carboxylic acids are named from their parent alkane by dropping the -ane ending and replacing it with a -oic acid suffix. Carboxylic Acids

39. Chapter 19 39 Carboxylic acids are polar since the carboxyl group, –COOH, can form hydrogen bonds. They have similar properties to alcohols with high boiling points and good water solubility. Carboxylic Acids

40. Chapter 19 40 An ester has an –R and an –OR group bonded to a carbonyl group, RCOOR. Esters typically have a pleasant, fruity odor. They are slightly polar. They are typically formed from the reaction of an alcohol with a carboxylic acid. Esters

41. Chapter 19 41 In amides, a carbonyl group is attached to an alkyl or aryl group and an –NH 2 group. Amides are formed from the reaction of a carboxylic acid with ammonia. They are polar molecules with properties similar to those of carboxylic acids. Amides

42. Chapter 19 42 Chemistry Connection: Polymers A polymer is a giant molecule made up of many small molecules. There are two basic types: addition polymers and condensation polymers. Addition polymers are derived from alkenes, such as polyethylene and polystyrene. Polyethylene is used in plastic wrap and plastic bags.

43. Chapter 19 43 Chemistry Connection: Polymers Condensation polymers are synthesized from hydrocarbon derivatives. Polyesters and polyamides are two of the most important types of condensation polymers. Polyesters are produced from an acid and an alcohol. Polyamides (such as nylon) are produced from an amine and an acid.

44. Chapter 19 44 Organic chemistry is the study of compounds that contain carbon. Hydrocarbons contain only hydrogen and carbon. Saturated hydrocarbons have only single carbon- carbon bonds. Unsaturated hydrocarbons have double or triple carbon-carbon bonds. Aromatic hydrocarbons have a benzene ring. Chapter Summary

45. Chapter 19 45 Alkenes have at least one carbon-carbon double bond. Alkynes have at least one carbon-carbon triple bonds. Arenes contain a benzene ring. Hydrocarbon derivatives have a functional group in addition to the hydrocarbon function. They are summarized on the next slide. Chapter Summary, continued

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