1. principles and modern applications
Chemistry 140 Fall 2002
ELEVENTH EDITION
GENERAL CHEMISTRY
principles and modern applications
PETRUCCI HERRING MADURA BISSONNETTE 26
Structures of Organic Compounds
PHILIP DUTTON
UNIVERSITY OF WINDSOR
DEPARTMENT OF CHEMISTRY AND BIOCHEMISTRY

2. Structures of Organic Compounds
Chemistry 140 Fall 2002
Structures of Organic Compounds
CONTENTS
26-1
Organic Compounds and Structures: An Overview
26-2
Alkanes
26-3
Cycloalkanes
26-4
Stereoisomerism in Organic Compounds
26-5
Alkenes and Alkynes
26-6
Aromatic Hydrocarbons
26-7
Organic Compounds Containing Functional Groups
26-8
From Molecular Formula to Molecular Structure

3. Representations of the methane molecule
Chemistry 140 Fall 2002
26-1 Organic Compounds and Structures: An Overview
FIGURE 26-1
Representations of the methane molecule

4. Chemistry 140 Fall 2002
FIGURE 26-2
The ethane molecule C2H6

5. The propane molecule, C3H8
Chemistry 140 Fall 2002
FIGURE 26-3
The propane molecule, C3H8

6. Constitutional Isomers in Organic Compounds
Chemistry 140 Fall 2002
Constitutional Isomers in Organic Compounds

7. Line-angle formulas or line structures

8. Nomenclature Select the longest continuous carbon chain.
Every branch is considered an alkyl group.
Number the base chain so substituents appear at the lowest numbers possible .
Name each substituent according to its identity, use di, tri, tetra, and so on.
Separate numbers with commas but no spaces and numbers from letters with hyphens.
List substituents alphabetically, prefixes are ignored.

10. Functional groups

13. 26-2 Alkanes Saturated hydrocarbons: Only single bonds.
Normal formula is CnH2n+2
Branching of chains affects properties.

14. Staggered conformation of ethane
Chemistry 140 Fall 2002
Conformations
FIGURE 26-5
Staggered conformation of ethane

15. Staggered and eclipsed conformations of ethane
Chemistry 140 Fall 2002
FIGURE 26-6
Staggered and eclipsed conformations of ethane

16. The dihedral angle, θ, refers to the angle of rotation about a carbon-carbon bond.

17. Chemistry 140 Fall 2002
The barrier to rotation is small enough a room
FIGURE 26-7
Potential energy diagram for the internal rotation of the methyl groups in ethane

18. Steric hinderance in a totally eclipsed conformation of butane
FIGURE 26-9
Steric hinderance in a totally eclipsed conformation of butane

19. FIGURE 26-8
Conformations and their potential energies of butane for rotation about the C2-C3 bond

20. Preparation of Alkanes
(26.1)
(26.2)
(26.3)

21. Alkanes from petroleum

22. 2,2,4-Trimethylpentane Octane rating: 100 n-Heptane Octane rating: 0
A catalytic cracking unit (cat cracker) at a petroleum refinery

23. 26-3 Cycloalkanes
CnH2n

24. Ring strain in cyclopropane
Chemistry 140 Fall 2002
Ring Strain in Cycloalkanes
FIGURE 26-10
Ring strain in cyclopropane

25. Newman projection for cyclopropane
FIGURE 26-11
Newman projection for cyclopropane

28. Two important conformations of cyclohexane
Chemistry 140 Fall 2002
Cis-Trans Isomerism in Distributed Cycloalkanes
FIGURE 26-12
Two important conformations of cyclohexane

29. Chemistry 140 Fall 2002

31. A Closer Look at Cyclohexane1. 4.
Points upward 2.
Points downward
Imaginary line through the
center of the ring 3. 5.

34. The interconversion of two chair conformations in cyclohexane
Chemistry 140 Fall 2002
In the figure, two of the H atoms are shown in red to emphasize that when the cyclohexane ring converts from one chair conformation to another, the equatorial hydrogen atoms are converted into axial hydrogen atoms and vice versa. The interconversion of the two chair forms proceeds through other conformations, including the boat form.
FIGURE 26-13
The interconversion of two chair conformations in cyclohexane

36. 26-4 Stereoisomerism in Organic Compounds
FIGURE 26-14
Isomerism summarized

37. Chirality

38. Nonsuperimposable mirror images of 3-methylhexane
Chemistry 140 Fall 2002
FIGURE 26-15
Nonsuperimposable mirror images of 3-methylhexane

39. Assignment of R and S configuration at a tetrahedral stereocenter
Chemistry 140 Fall 2002
Naming Enantiomers: The R, S System of Nomenclature
FIGURE 26-16
Assignment of R and S configuration at a tetrahedral stereocenter

40. Rules for Assigning Priorities to Substituents
Rule 1: Substituent of higher atomic number takes precedence over one of lower atomic number:

41. Rule 2: If two substituents attached to the stereocenter have the same priority, proceed along the chains to the first point of difference:

42. Rule 3: Double and triple bonds count as if they were single and the atoms are duplicated or triplicated at the other end of the double or triple bond:

43. 26-5 Alkenes and Alkynes

44. Stereoisomerism in Alkenes

45. Preparation and Uses of Alkenes and Alkynes
Elimination reaction

47. Simple qualitative test for an alkene
(26.8)
The test tube on the left contains cyclohexene and the one on the right contains cyclohexane. When bromine, Br2, is added to the tube containing cyclohexene, the red-brown color disappears because Br2adds across the double bond.

48. Chemistry 140 Fall 2002
Naming the Stereoisomers of Highly Substituted Alkenes: The E,Z System of Nomenclature

50. 26-6 Aromatic Hydrocarbons
Kekulé structures
Simplified molecular orbital representation
Toluene
o-Xylene
Napthalene
Anthracene

51. Characteristics of Aromatic Hydrocarbons
Planar (flat) cyclic molecules.
Conjugated п systems (4n + 2)
August Kekulé ( ) who proposed the hexagonal ring structure for benzene in His representation of this molecule is still widely used.

52. Naming Aromatic Hydrocarbons

53. 26-7 Organic Compounds Containing Functional Groups
Chemistry 140 Fall 2002
26-7 Organic Compounds Containing Functional Groups
Alcohols and Phenols

55. Preparation and Use of Alcohols

56. Ethers Preparation and Uses of Ethers
Chemistry 140 Fall 2002
Ethers
Preparation and Uses of Ethers
conc. H2SO4
CH3CH2OH + HOCH2CH CH3CH2OCH2CH3 + H2O
140°C

57. Aldehydes and Ketones carbonyl group Chemistry 140 Fall 2002
The carbonyl group

58. 3-chloro-2-methylbutanal
4-chloro-3-methylpentan-2-one

59. Preparation and Uses of Aldehydes and Ketones
Oxidation of alcohols.
(26.13)
ethanol
(a primary alcohol)
acetaldehyde
(an aldehyde)
acetic acid
(an acid)
(26.14)
propane-2-ol
(an secondary alcohol)
acetone
(a ketone)

60. Extract from natural sources

61. Reduction to alcohol

62. Carboxylic Acids
carboxyl group

64. Preparation and Uses of Carboxylic Acids
(26.16)
(26.17)

66. Esters
The distinctive aroma and flavor of oranges are due in part to the ester octyl acetate, CH3CO2CH2(CH2)6CH3

68. Amides

69. Resonance in an amide.

70. Preparation and Uses of Amides

71. Amines

73. Morphine , a very powerful and addictive painkiller, can be isolated from the opium poppy (Papaver somniferum).

74. Amines are weak bases

75. Quaternary ammonium ions

76. Heterocyclic Compounds
Chemistry 140 Fall 2002
Heterocyclic Compounds
FIGURE 26-17
Pyridine

77. 26-8 From Molecular Formula to Molecular Structure
C5H10
If an organic molecule with n carbon atoms has fewer than 2n+2 hydrogen atoms, then it contains elements of unsaturation, such as π bonds or ring structures

78. Alcohol
Ether
Ketone (or aldehyde)

79. C3H6O
C3H8O
C3H6O2

80. End of Chapter