1. INTRODUCTORY CHEMISTRY INTRODUCTORY CHEMISTRY Concepts and Critical Thinking Sixth Edition by Charles H. Corwin 1 Chapter 19 © 2011 Pearson Education, Inc. Chapter 19 Organic Chemistry by Christopher Hamaker

2. 2 Chapter 19 © 2011 Pearson Education, Inc. Introduction 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.

3. 3 Chapter 19 © 2011 Pearson Education, Inc. Introduction, Continued 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: 1.Saturated hydrocarbons 2.Unsaturated hydrocarbons

4. 4 Chapter 19 © 2011 Pearson Education, Inc. Saturated Hydrocarbons 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 belongs to the alkane family.

5. 5 Chapter 19 © 2011 Pearson Education, Inc. Unsaturated Hydrocarbons 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 six-membered ring of carbon atoms with alternating single and double bonds (d).

6. 6 Chapter 19 © 2011 Pearson Education, Inc. Classification of Hydrocarbons Below is a flowchart for the classification of hydrocarbons.

7. 7 Chapter 19 © 2011 Pearson Education, Inc. Alkanes 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 x 5 + 2 = 12) hydrogen atoms, C 5 H 12.

8. 8 Chapter 19 © 2011 Pearson Education, Inc. Alkane Family The lighter alkanes (1–10 carbons) are used as fuels, whereas the larger alkanes (20–40 carbons) are solids used to make waxes and candles.

9. 9 Chapter 19 © 2011 Pearson Education, Inc. Structural Isomers 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.

10. 10 Chapter 19 © 2011 Pearson Education, Inc. Alkyl and Aryl Groups 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.

11. 11 Chapter 19 © 2011 Pearson Education, Inc. Alkyl and Aryl Groups, Continued

12. 12 Chapter 19 © 2011 Pearson Education, Inc. Guidelines for Naming Alkanes 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.

13. 13 Chapter 19 © 2011 Pearson Education, Inc. Nomenclature of Alkanes What is the name of the following alkane? The longest chain has five carbons, so it is a pentane derivative. The methyl group is in the 2 position. The name is 2-methylpentane.

14. 14 Chapter 19 © 2011 Pearson Education, Inc. Nomenclature of Alkanes, Continued What is the name of the following alkane? The longest chain has six 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.

15. 15 Chapter 19 © 2011 Pearson Education, Inc. Alkane Reactions The C–C and C–H bonds in alkanes are very strong and are 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.

16. 16 Chapter 19 © 2011 Pearson Education, Inc. Alkene and Alkyne Formulas 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 x 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 x 5 – 2 = 8) hydrogen atoms, C 5 H 8.

17. 17 Chapter 19 © 2011 Pearson Education, Inc. Alkene Family 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.

18. 18 Chapter 19 © 2011 Pearson Education, Inc. Guidelines for Naming Alkenes 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.

19. 19 Chapter 19 © 2011 Pearson Education, Inc. Nomenclature of Alkenes What is the name of the following alkene? The longest chain with the double bond has six 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 3, 3, and 5 positions. The name is 3,3,5-trimethyl-2-hexene.

20. 20 Chapter 19 © 2011 Pearson Education, Inc. Alkyne Family 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.

21. 21 Chapter 19 © 2011 Pearson Education, Inc. Guidelines for Naming Alkynes 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.

22. 22 Chapter 19 © 2011 Pearson Education, Inc. Nomenclature of Alkynes What is the name of the following alkyne? The longest chain with the triple bond has four 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.

23. 23 Chapter 19 © 2011 Pearson Education, Inc. Reactions of Alkenes and Alkynes In addition to combustion reactions, alkenes and alkynes also undergo addition reactions. The double or triple bond can add atoms. There are two types: 1.Hydrogenation CH≡CH(g) + H 2 (g) → CH 2 =CH 2 (g) 2.Halogenation CH 2 =CH 2 (l) + Br 2 (l) → CH 2 Br-CH 2 Br(l)

24. 24 Chapter 19 © 2011 Pearson Education, Inc. Polymerization Reactions 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

25. 25 Chapter 19 © 2011 Pearson Education, Inc. Arenes 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.

26. 26 Chapter 19 © 2011 Pearson Education, Inc. Isomers of a Disubstituted Benzene 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 the following three different ways:

27. 27 Chapter 19 © 2011 Pearson Education, Inc. Isomers of a Disubstituted Benzene, Continued 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.

28. 28 Chapter 19 © 2011 Pearson Education, Inc. Hydrocarbon Derivatives 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).

29. 29 Chapter 19 © 2011 Pearson Education, Inc. Non-Carbonyl Hydrocarbon Derivatives Here are the basic hydrocarbon classes. R is an alkyl group and Ar is an aryl group.

30. 30 Chapter 19 © 2011 Pearson Education, Inc. Carbonyl Hydrocarbon Derivatives

31. 31 Chapter 19 © 2011 Pearson Education, Inc. Organic Halides If a halogen atom (F, Cl, Br, and 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.

32. 32 Chapter 19 © 2011 Pearson Education, Inc. Alcohols and Phenols When an –OH group replaces a hydrogen atom on an alkane, the result is an alcohol. When an –OH replaces a hydrogen atom on an 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.

33. 33 Chapter 19 © 2011 Pearson Education, Inc. Alcohols and Phenols, Continued 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.

34. 34 Chapter 19 © 2011 Pearson Education, Inc. Ethers 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.

35. 35 Chapter 19 © 2011 Pearson Education, Inc. Amines 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.

36. 36 Chapter 19 © 2011 Pearson Education, Inc. Aldehydes 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, R–CHO. The name of an aldehyde is derived from its parent alkane by changing the -ane to an -al suffix.

37. 37 Chapter 19 © 2011 Pearson Education, Inc. Ketones Ketones also contain the carbonyl group and are generally polar. Ketones have two alkyl or aryl groups attached to the carbonyl group, R–COR'. Ketones are named for their parent alkane.

38. 38 Chapter 19 © 2011 Pearson Education, Inc. Carboxylic Acids 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.

39. 39 Chapter 19 © 2011 Pearson Education, Inc. Carboxylic Acids, Continued 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.

40. 40 Chapter 19 © 2011 Pearson Education, Inc. Esters 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.

41. 41 Chapter 19 © 2011 Pearson Education, Inc. Amides 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.

42. 42 Chapter 19 © 2011 Pearson Education, Inc. Chapter Summary 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.

43. 43 Chapter 19 © 2011 Pearson Education, Inc. Chapter Summary, Continued 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.

44. 44 Chapter 19 © 2011 Pearson Education, Inc.