![Page 1: Organic Chemistry II: CHEM 2211xmshi.myweb.usf.edu/documents/teaching/2019-Spring/note/chapte… · 14.1 Structure of benzene: snake bits its own tail! • Early 19th century chemists](https://reader033.vdocuments.site/reader033/viewer/2022042402/5f116ebfc1421853e6645a12/html5/thumbnails/1.jpg)
Organic Chemistry II:CHEM 2211
Chapter 14
Aromaticity
![Page 2: Organic Chemistry II: CHEM 2211xmshi.myweb.usf.edu/documents/teaching/2019-Spring/note/chapte… · 14.1 Structure of benzene: snake bits its own tail! • Early 19th century chemists](https://reader033.vdocuments.site/reader033/viewer/2022042402/5f116ebfc1421853e6645a12/html5/thumbnails/2.jpg)
Chapter 14 Problem Set
14.1-14.15 (in chapter, help to understand materials);
14.16-29; 14.30-14.34; 14.38-14.42; Learning group problem #2,#3.
![Page 3: Organic Chemistry II: CHEM 2211xmshi.myweb.usf.edu/documents/teaching/2019-Spring/note/chapte… · 14.1 Structure of benzene: snake bits its own tail! • Early 19th century chemists](https://reader033.vdocuments.site/reader033/viewer/2022042402/5f116ebfc1421853e6645a12/html5/thumbnails/3.jpg)
13. Retrosynthesis!!!
• Please review Org I reactions!
• Reagents and their structures!
• Elimination: KOtBu; NaOEt; Pyridine
• Reduction: H2, Pd/C; LiAlH4; NaBH4; DIBAL
• Oxidation: PCC; KMnO4; Jone’s; Swern oxidation12.4B
• Ozonalysis: 8.16B
• Epoxidation: mCPBA
![Page 4: Organic Chemistry II: CHEM 2211xmshi.myweb.usf.edu/documents/teaching/2019-Spring/note/chapte… · 14.1 Structure of benzene: snake bits its own tail! • Early 19th century chemists](https://reader033.vdocuments.site/reader033/viewer/2022042402/5f116ebfc1421853e6645a12/html5/thumbnails/4.jpg)
14.1 Structure of benzene: snake bits its own tail!• Early 19th century chemists
derive benzene formula (C6H6)and molecular mass (78)
• Problems with Kekulé’sstructure
• If Kekulé’s structure were tohave two chloride substituentsreplacing two hydrogen atoms,there should be a pair of 1,2-dichlorobenzene isomers.
• benzene is fairly inert and failsto undergo reactions thatcharacterize normal alkenesKekulé’s structure
CCCCC
CH
H H
HH
H
CCCCC
CH
H H
ClCl
H
CCCCC
CH
H Cl
ClH
H
![Page 5: Organic Chemistry II: CHEM 2211xmshi.myweb.usf.edu/documents/teaching/2019-Spring/note/chapte… · 14.1 Structure of benzene: snake bits its own tail! • Early 19th century chemists](https://reader033.vdocuments.site/reader033/viewer/2022042402/5f116ebfc1421853e6645a12/html5/thumbnails/5.jpg)
14.3 Reactivity: not like C=C!
![Page 6: Organic Chemistry II: CHEM 2211xmshi.myweb.usf.edu/documents/teaching/2019-Spring/note/chapte… · 14.1 Structure of benzene: snake bits its own tail! • Early 19th century chemists](https://reader033.vdocuments.site/reader033/viewer/2022042402/5f116ebfc1421853e6645a12/html5/thumbnails/6.jpg)
14.5 Improved stability
+ H2
HH
ΔHo = -120 kJ/mol
+ H2
HH
ΔHo = -232 kJ/mol2H
H
+ H2
HH
ΔHo = -208 kJ/mol3H
H
H
H
![Page 7: Organic Chemistry II: CHEM 2211xmshi.myweb.usf.edu/documents/teaching/2019-Spring/note/chapte… · 14.1 Structure of benzene: snake bits its own tail! • Early 19th century chemists](https://reader033.vdocuments.site/reader033/viewer/2022042402/5f116ebfc1421853e6645a12/html5/thumbnails/7.jpg)
14.3 Reactivity: not like C=C!
Three pi bonds lying within a ring.
• Each atom is sp2 • Planarity.
• 6 pi electrons (4n +2 = 6, n = 1).
• “All C-C, bond lengths are equal,
and halfway between C-C and C=C.
All C-H bonds are equal.
All C-C-C bond angles are equal,
and all H-C-C bond angles are equal at 120°
![Page 8: Organic Chemistry II: CHEM 2211xmshi.myweb.usf.edu/documents/teaching/2019-Spring/note/chapte… · 14.1 Structure of benzene: snake bits its own tail! • Early 19th century chemists](https://reader033.vdocuments.site/reader033/viewer/2022042402/5f116ebfc1421853e6645a12/html5/thumbnails/8.jpg)
14.2 Nomenclature: functional group and position
F
fluorobenzene
NO2
nitrobenzene
CH3
toluene
OH
phenol
NH2
aniline
COOH
benzoic acid
CHO
benzaldehyde styrene
CN
benzonitrile
![Page 9: Organic Chemistry II: CHEM 2211xmshi.myweb.usf.edu/documents/teaching/2019-Spring/note/chapte… · 14.1 Structure of benzene: snake bits its own tail! • Early 19th century chemists](https://reader033.vdocuments.site/reader033/viewer/2022042402/5f116ebfc1421853e6645a12/html5/thumbnails/9.jpg)
14.2 Nomenclature: di-substituted benzene
o-xylene m-xylene p-xylene
12
1
3
1
2
BrBr
1,2-dibromobenzene
o-dibromobenzene
Ortho- meta- para-
![Page 10: Organic Chemistry II: CHEM 2211xmshi.myweb.usf.edu/documents/teaching/2019-Spring/note/chapte… · 14.1 Structure of benzene: snake bits its own tail! • Early 19th century chemists](https://reader033.vdocuments.site/reader033/viewer/2022042402/5f116ebfc1421853e6645a12/html5/thumbnails/10.jpg)
14.2 Nomenclature: multi-substituted benzene
O2N
Br
COOH
3-bromo-5-nitrobenzoic acid
Br1-(3-bromo-5-(tert-butyl)phenyl)ethan-1-one
O
13
5
Br
H
O
Br
t-Bu
2-bromo-5-(tert-butyl)-1,3-dimethylbenzene
NO2
ClCH3
![Page 11: Organic Chemistry II: CHEM 2211xmshi.myweb.usf.edu/documents/teaching/2019-Spring/note/chapte… · 14.1 Structure of benzene: snake bits its own tail! • Early 19th century chemists](https://reader033.vdocuments.site/reader033/viewer/2022042402/5f116ebfc1421853e6645a12/html5/thumbnails/11.jpg)
14.6 Aromaticity
naphthalene
anthracene
Are they aromatic?
![Page 12: Organic Chemistry II: CHEM 2211xmshi.myweb.usf.edu/documents/teaching/2019-Spring/note/chapte… · 14.1 Structure of benzene: snake bits its own tail! • Early 19th century chemists](https://reader033.vdocuments.site/reader033/viewer/2022042402/5f116ebfc1421853e6645a12/html5/thumbnails/12.jpg)
14.6 Aromaticity!!!!
• Cyclic
• Conjugate
• Planar
• 4n+2= # of pi electron (n=0 or positive integer)
![Page 13: Organic Chemistry II: CHEM 2211xmshi.myweb.usf.edu/documents/teaching/2019-Spring/note/chapte… · 14.1 Structure of benzene: snake bits its own tail! • Early 19th century chemists](https://reader033.vdocuments.site/reader033/viewer/2022042402/5f116ebfc1421853e6645a12/html5/thumbnails/13.jpg)
14.7 Aromatic, anti-aromatic and non-aromatic
Cyclic?Yes
Conjugated?
No
Planar?
4n+2?
Yes
Yes
Yes
Aromatic!
Non-aromaticNo
No
NoAnti-aromatic
Examples:
N
NH N
HN
4n
![Page 14: Organic Chemistry II: CHEM 2211xmshi.myweb.usf.edu/documents/teaching/2019-Spring/note/chapte… · 14.1 Structure of benzene: snake bits its own tail! • Early 19th century chemists](https://reader033.vdocuments.site/reader033/viewer/2022042402/5f116ebfc1421853e6645a12/html5/thumbnails/14.jpg)
14.7 Aromatic, anti-aromatic and non-aromatic
Exception:
Examples:
[10]-annulene
![Page 15: Organic Chemistry II: CHEM 2211xmshi.myweb.usf.edu/documents/teaching/2019-Spring/note/chapte… · 14.1 Structure of benzene: snake bits its own tail! • Early 19th century chemists](https://reader033.vdocuments.site/reader033/viewer/2022042402/5f116ebfc1421853e6645a12/html5/thumbnails/15.jpg)
14.9 Hetero-Aromatic compounds
ONH
N
S
O
NH
indole furan thiophene
pyridine pyrrolepyrylium