1. Organic Chemistry Chapter 24
Copyright © The McGraw-Hill Companies, Inc.  Permission required for reproduction or display.

2. Common Elements in Organic Compounds
24.1

3. The Bonding of Carbon
Organic chemistry is the chemistry of compounds containing carbon.
Because carbon can form single, double, and triple bonds, the following bonding combinations are possible for carbon:

4. Three types of hydrocarbons exist.
Saturated hydrocarbons: contain only carbon–carbon single bonds. They may be cyclic or acyclic.
Unsaturated hydrocarbons: contain at least one carbon–carbon double or triple bonds.
Aromatic hydrocarbons: contain benzene rings or similar features.
Hydrocarbons
The simplest organic compounds are made of carbon and hydrogen. They are called hydrocarbons.

5. Classification of Hydrocarbons
24.1

6. Alkanes Alkanes have the general formula CnH2n+2 where n = 1,2,3,…
only single covalent bonds
saturated hydrocarbons because they contain the maximum number of hydrogen atoms that can bond with the number of carbon atoms in the molecule
CH4
C2H6
C3H8
methane
ethane
propane
24.2

7. Structural isomers are molecules that have the same molecular formula but different structures
24.2

8. How many structural isomers does pentane, C5H12, have?
n-pentane C H
CH3
2,2-dimethylpropane
2-methylbutane
24.2

9. Alkane Nomenclature
The parent name of the hydrocarbon is that given to the longest continuous chain of carbon atoms in the molecule.
CH3
CH2 CH
4-methylheptane 1 2 3 4 5 6 7
An alkane less one hydrogen atom is an alkyl group.
CH4
methane
CH3
methyl
24.2

10. The alkanes constitute a homologous series, a series of compounds in which one compound differs from a preceding one by a fixed group of atoms.
Members of a homologous series have similar properties that vary systematically, as shown in Table 24.1.

11. Alkane Nomenclature
24.2

12. Alkane Nomenclature
When one or more hydrogen atoms are replaced by other groups, the name of the compound must indicate the locations of carbon atoms where replacements are made. Number in the direction that gives the smaller numbers for the locations of the branches.
CH3 CH
CH2 1 2 3 4 5
2-methylpentane
CH3
CH2 CH 1 2 3 4 5
4-methylpentane
24.2

13. Alkane Nomenclature
Use prefixes di-, tri-, tetra-, when there is more than one alkyl branch of the same kind.
CH3 CH
CH2 1 2 3 4 5 6
2,3-dimethylhexane
CH3 CH C
CH2 1 2 3 4 5 6
3,3-dimethylhexane
24.2

14. Alkane Nomenclature
Use previous rules for other types of substituents.
CH3 CH Br 1 2 3 4
NO2
2-bromo-3-nitrobutane
CH2 CH
CH3 Br 1 2 3 4
NO2
1-bromo-3-nitrobutane
24.2

15. What is the IUPAC name of the following compound?
CH3 CH
CH2
C2H5 1 2 3 4 5 6 7 8
2-methyl-4-ethyloctane
What is the structure of 2-propyl-4-methylhexane? 1 2 3 4 5 6
CH3 CH
CH2
C2H5
24.2

16. Give the IUPAC name for each of the following.1 2 6 5 4 3 7 2 3 a. b. 1 4 5 6
a. 2-methylhexane
b. 2,3-dimethyl-4-t-butylheptane

17. Write the condensed structural formula of 2,3,5-trimethylhexane.
Hexane is a six-carbon chain.
2,3,5-Trimethyl means three methyl groups: one each at the 2, 3, and 5 carbons.

18. Alkane Reactions Combustion
CH4 (g) + 2O2 (g) CO2 (g) + 2H2O (l) DH0 = kJ
Halogenation
CH4 (g) + Cl2 (g) CH3Cl (g) + HCl (g)
light
Cl2 + energy Cl• + Cl•
Cl• + C H C H •
+ HCl C H • C Cl H
+ Cl Cl
+ Cl•
24.2

19. achiral
chiral
24.2

20. Cycloalkanes
Alkanes whose carbon atoms are joined in rings are called cycloalkanes. They have the general formula CnH2n where n = 3,4,…
24.2

21. Sources of Alkanes and Cycloalkanes
Petroleum, or crude oil, is a mixture of alkanes and cycloalkanes with small amount of aromatic hydrocarbons.
Crude oil from different regions differ in their compositions of these compounds.
1. Oil from the Canadian north slope contain molecules composed of 20 to 40 carbon atoms.
2. Oil from Saudi Arabia contain molecules composed of 5 to 20 carbon atoms. This oil is more desirable as a source because it is easier to transport crude oil containing low molecular mass molecules.
Hydrocarbon mixtures in crude oil are separated by a process known as fractional distillation. This process separates molecules according to molecular mass.

22. Cycloalkanes
24.2

23. Alkenes and Alkynes
Alkenes and alkynes are unsaturated hydrocarbons.
Alkenes contain carbon–carbon double bonds. They have the general formula CnH2n.
Alkynes contain carbon–carbon triple bonds. They have the general formula CnH2n-2.

24. Alkenes and Geometric Isomers
In an alkene, all of the atoms connected to the double-bonded carbons are in one plane.
Rotation around the carbon–carbon double bond is restricted due to the side-to-side overlap of the p orbitals to form the p bond. This makes geometric isomers—that is, cis and trans isomers—possible.

25. This is illustrated below for 2-pentene.

26. Alkenes Alkenes have the general formula CnH2n where n = 2,3,…
contain at least one carbon-carbon double bond
also called olefins
CH2 CH
CH3
CH3 CH
1-butene
2-butene C Cl H C Cl H
cis-dichloroethylene
trans-dichloroethylene
24.2

27. Cis-Trans Isomerization in the Vision Process
24.2

28. Addition Reactions of Alkenes
Alkenes are more reactive than alkanes owing to the presence of the double bond. Many reactions add to the double bond.
In an addition reaction, parts of a reactant are added to each carbon atom of a carbon–carbon double bond, which converts it to a carbon–carbon single bond.

29. Alkene Reactions Cracking C2H6 (g) CH2 CH2 (g) + H2 (g)Pt
catalyst
Addition Reactions
CH2 CH2 (g) + HBr (g)
CH3 CH2Br (g)
CH2 CH2 (g) + Br2 (g)
CH2Br CH2Br (g)
24.2

30. 2-bromopropane 1-bromopropane
Unsymmetrical reactants such as HBr and HCl add to unsymmetrical alkenes to give two products.
2-bromopropane
1-bromopropane

31. The two products are not formed in equal amounts
The two products are not formed in equal amounts. Markovnikoff’s rule is a generalization that states that the major product formed by the addition of an unsymmetrical reactant, such as H—Cl, H—Br, or H—OH, is the one obtained when the hydrogen atom of the reactant adds to the carbon atom of the multiple bond that has the greater number of hydrogen atoms attached to it.
The major product is then 2-bromopropane.

32. Alkynes Alkynes have the general formula CnH2n-2 where n = 2,3,4,…
contain at least one carbon-carbon triple bond CH C
CH2
CH3
CH3 C
1-butyne
2-butyne
Production of acetylene
CaC2 (s) + 2H2O (l) C2H2 (g) + Ca(OH)2 (aq)
24.2

33. Alkynes
Alkynes are unsaturated hydrocarbons containing a carbon–carbon triple bond. The general formula is CnH2n-2.
The simplest alkyne is acetylene, C2H2. It is very reactive with oxygen, so it is used in torches for welding to give a very hot flame (~3000°C).

34. Here acetylene is prepared by the reaction of water with calcium carbide, CaC2.
The acetylene produced burns with a sooty flame.

35. Alkyne Reactions Hydrogenation CH CH (g) + H2 (g) CH2 CH2 (g)
Addition Reactions
CH CH (g) + HBr (g)
CH2 CHBr (g)
CH CH (g) + Br2 (g)
CHBr CHBr (g)
CH CH (g) + 2Br2 (g)
CHBr2 CHBr2 (g)
24.2

36. IUPAC Rules for Naming Alkenes and Alkynes
Identify the longest chain containing the multiple bonds. Alkenes have contain carbon-carbon double bond(s) and alkynes contain carbon-carbon triple bond(s).
The longest chain provides the stem name followed by the ending –ene for alkenes or –yne for alkynes.
Number the longest chain from the end neared the multiple bond. The multiple bond is given the number of the first carbon atom involved in the multiple bond. This number is written in front of the alkene or alkyne name, separating the number from the name by a dash.
Branched chains are named using the same method used in naming alkanes.
If the multiple bond is in the middle of the longest chain, number the chain from the end that gives the branches the lowest number.
The simplest alkene, CH2CH2, is ethene and has a common name of ethylene. The simplest alkyne, CHCH, is ethyne and has a common name of acetylene.

37. Give the IUPAC name for each of the following compounds:
a. 2,4-dimethyl-2-hexene
b. 3-propyl-1-hexene

38. Give the IUPAC name for each of the following alkynes:
a. 1-propyne
b. 3-methyl-1-pentyne

39. Chemistry In Action: Ice That Burns

40. Aromatic Hydrocarbons
Aromatic hydrocarbons usually contain benzene rings: six-membered rings of carbon atoms with alternating carbon–carbon single and carbon–carbon double bonds.
The molecular orbital description of benzene utilizes a p molecular orbital that is delocalized across the entire molecule. The result is that the double bonds in benzene do not behave as isolated double bonds.

41. Aromatic Hydrocarbons
24.3

42. Aromatic Compound Nomenclature
CH2CH3
ethylbenzene
NH2
aminobenzene Cl
chlorobenzene
NO2
nitrobenzene Br Br 1 2 3 4 5 6
1,2-dibromobenzene
1,3-dibromobenzene
24.3

43. Aromatic Compound Reactions
Substitution reaction H Br
+ HBr
+ Br2
FeBr3
catalyst H
CH2CH3
+ HCl
+ CH3CH2Cl
AlCl3
catalyst
24.3

44. Polycyclic Aromatic Hydrocarbons
24.3

45. The term aromatic indicates that compounds containing a benzene ring have aromas. Flavoring agents that can be made in the lab or are found in nature and that contain benzene rings include cinnamaldehyde, which is the source of the cinnamon flavor, and methyl salicylate, which is the source of the wintergreen flavor that is used in candies and gum.
Benzene rings are also found in pain relievers such as acetylsalicylic acid (aspirin), acetaminophen (Tylenol), and the illegal drug mescaline.

46. Functional Group Chemistry
Alcohols contain the hydroxyl functional group and have the general formula R-OH.
24.4

47. Biological production of ethanol
C6H12O6 (aq) CH3CH2OH (aq) + 2CO2 (g)
enzyme
Commercial production of ethanol
CH2 CH2 (g) + H2O (g) CH3CH2OH (g)
H2SO4
Metabolic oxidation of ethanol
CH3CH2OH CH3CHO + H2
alcohol dehydrogenase
24.4

48. Functional Group Chemistry
Ethers have the general formula R-O-R’.
Condensation Reaction
CH3OH + HOCH CH3OCH3 + H2O
H2SO4
catalyst
24.4

49. Functional Group Chemistry
Aldehydes and ketones contain the carbonyl ( ) functional group. O C
R C H O
aldehydes have the general formula
R C R’ O
ketones have the general formula
H C H O
H C O
CH3 C O
CH3
H3C
formaldehyde
acetaldehyde
acetone
24.4

50. Give the IUPAC name of the following compound:
3-ethyl-3-hexanol

51. Give the common name of each of the following compounds:
b. Ethyl methyl ether
a. Dimethyl ether

52. Functional Group Chemistry
Carboxylic acids contain the carboxyl ( -COOH ) functional group.
24.4

53. Functional Group Chemistry
Esters have the general formula R’COOR, where R is a hydrocarbon group.
CH3COOH + HOCH2CH CH3 C O CH2CH3 + H2O O
ethyl acetate
24.4

54. Functional Group Chemistry
Amines are organic bases with the general formula R3N.
CH3NH2 + H2O RNH3+ + OH-
CH3CH2NH2 + HCl CH3CH2NH3+Cl-
24.4

55. 24.4

56. Chemistry In Action: The Petroleum Industry
Crude Oil