1. Organic Chemistry Chapter 24
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2. Common Elements in Organic Compounds
24.1

3. Classification of Hydrocarbons
24.1

4. 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

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

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

7. 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

8. Alkane Nomenclature
24.2

9. 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

10. 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

11. 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

12. 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

13. Alkane Reactions Combustion
CH4 (g) + 2O2 (g) CO2 (g) + 2H2O (l) DH0 = kJ
Halogenation – the replacement of one or more hydrogen atoms by halogen atoms
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

14. Optical Isomerism
Optical isomers are compounds that are nonsuperimposable mirror images of each other
The mirror images of CH2ClBr are superimposable: achiral
A molecule is achiral if it is superimposable on its mirror image. Most achiral molecules do have a plane of symmetry or a center of symmetry.
The mirror images of CHFClBr are not superimposable, no mater how we rotate the molecules: chiral
A molecule is chiral if it is not superimposable on its mirror image. Most chiral molecules can be identified by their lack of a plane of symmetry or a center of symmetry. 

15. achiral
chiral
Most simple chiral molecules have at least one asymmetric carbon atom – a carbon atom bonded to four different atoms or groups of atoms
24.2

16. Are the following molecules chiral or achiral?
a) Cl |
H-C-CH2-CH3
CH3
b) Br
I-C-CH2-CH3 Br

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

18. Cycloalkanes
Chair form is more stable than boat form because the electron densities are further apart
24.2

19. 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

20. Cis-Trans Isomerization in the Vision Process
24.2

21. 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

22. 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

23. 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

24. Chemistry In Action: Ice That Burns

25. Aromaticity Pleasant odor Unusually low reactivity Unusually stable
Substitution, not addition
Unusually stable
Characteristic ring structure with delocalized pi bonding

26. Aromatic Hydrocarbons
24.3

27. Benzene - stability C6H6 No typical C=C reactions
Unreactive with HX, X2, KMnO4
Reaction requires extreme conditions
When reaction does occur, it is substitution, not addition

28. Benzene - structure All C are sp2 (trigonal planar - 120° angles)
Ideal for a planar hexagon
All C-C bonds are the same (139 pm)
Compare C-C (154 pm) C=C (135 pm)
Cyclic conjugated pi bonds unusually stable (resonance)

29. 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

30. Nomenclature of Aromatics
Monosubstituted benzenes
Fuctional group name + benzene
Ex. Chlorobenzene, nitrobenzene, aminobenzene
If more than one substituent is present, we must indicate the location of the second group relative to the first
ortho (1,2-), meta (1,3-), para (1,4)

31. Common names of monosubstituted benzenes

32. 2-chloronitrobenzene, or o-chloronitrobenzene
3-chloronitrobenzene, or m-chloronitrobenzene
4-chloronitrobenzene, or p-chloronitrobenzene

33. A benzene ring less one H is called a phenyl group:
2-phenylpentane

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

35. Polycyclic Aromatic Hydrocarbons
24.3

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

37. 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

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

39. 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

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

41. 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

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

43. 24.4

44. Chemistry In Action: The Petroleum Industry
Crude Oil