SLIDE 1 YSU YSU
Organic Chemistry – The Functional Group Approach
alkane (no F.G.) non-polar (grease, fats) tetrahedral
OH
alcohol polar (water soluble) tetrahedral
Br
halide non-polar (water insoluble) tetrahedral alkene non-polar (water insoluble) trigonal alkyne non-polar (water insoluble) linear aromatic non-polar (water insoluble) flat aldehyde/ketone polar (water soluble) trigonal imine polar (water soluble) trigonal
O NH
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Carey Chapter 11 – Arenes and Aromaticity
Codeine Sildenafil
SLIDE 2
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11.1 – Increasing Unsaturation in 6-Membered Rings
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11.2 – Evidence of Structure for Benzene all C‐C bonds are the same length, all H’s are equivalent
Kekule (1866) – two rapidly interconverting isomers?
SLIDE 3
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11.2 – Evidence of Structure for Benzene all C‐C bonds are the same length, all H’s are equivalent
Robinson (1920) ‐ the two Kekule forms are resonance contributors
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11.2 – Evidence of Structure for Benzene all C‐C bonds are the same length, all H’s are equivalent
Robinson depiction : “Aromatic Sextet”
SLIDE 4 YSU YSU
11.4 Resonance energy of benzene as estimated from heats
Figure 11.2
Benzene is a lot more stable than “cyclohexatriene” YSU YSU
11.5 – The s bonds (a), the delocalized p system (b), and the electrostatic potential map (c) of benzene
i.e. each carbon experiences the same electron density, the six pi electrons are delocalized over the entire molecule
Figure 11.3
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11.6 – The molecular orbitals of benzene arranged in order
Figure 11.4
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Figure 11.4
SLIDE 6
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11.7 – Nomenclature of Substituted Benzenes
Many have common names, however IUPAC systematic names often easier to work out
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11.7 – Nomenclature of Disubstituted Benzenes
Br CH3 CH3 NO2 F NH2 Br CH3 CH3 CH2H3 F Br CH3 Can use numbering or o, m, p nomenclature systems
SLIDE 7
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Not Covering
11.8 11.9 11.11
11.12 – Free-Radical Halogenation of Alkylbenzenes
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C H H H C H H
+ H
C H H H
+ H
C H H C H H H
+ H
C H H
H = 91 kcal/mol H = 88 kcal/mol H = 85 kcal/mol
SLIDE 8
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11.12 – Free-Radical Halogenation of Alkylbenzenes
Figure 11.9 C H H H C H H
Br Br2
CCl4, 80 oC (+ HBr) 71% yield
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11.13 – Oxidation of Alkylbenzenes
SLIDE 9
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11.14 – Nucleophilic Substitution in Benzylic Halides
SN2 applies with good nucleophiles on 1o and 2o carbons SN1 applies with weak nucleophiles – good carbocation E2 competes with more basic nucleophiles on 2o and 3o
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11.15 – Preparation of Alkenylbenzenes
SLIDE 10
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11.16 – Addition to Alkenylbenzenes
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Not Covering 11.17 11.18
SLIDE 11
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11.19 – Hückel’s Rule
http://redandr.ca/vm3/Heme.jpg YSU YSU
11.19 – Hückel’s Rule
N S O
Aromatic = 4n+2 electrons and flat system
SLIDE 12
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11.19 – Hückel’s Rule
Figure 11.12
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Not Covering 11.20
SLIDE 13
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11.21 – Aromatic Ions
Cation is relatively easy to form: 4n + 2 = 6 system capable of being flat
Figure 11.13
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11.21 – Aromatic Ions
pKa of acid is ~16 since anion is aromatic: 4n + 2 = 6 system capable of being flat
Figure 11.14
SLIDE 14
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11.23 – Heterocyclic Aromatic Compounds – Hückel’s Rule
Figure 11.15
N N H pyridine pyrrole
.. ..
