conjugation which of the following compounds is conjugated?
TRANSCRIPT
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Conjugation
• Which of the following compounds is conjugated?
O O O OH
A B C D
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Conjugation
• Which of the following compounds is not conjugated?
N
A B C D
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• Slides 4 and 5 are part of the same question.
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Butadiene
• 2 conformations possible, both overall planar
s-ciss-cis-1,3-butadiene
s-transs-trans-1,3-butadiene
C
C C
C
HH
H
HH
H C
C C
CH
H
H
H
H
H
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Butadiene
• Which conformation appears to be more stable?
a. s-cis
b. s-trans
c. neither
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Butadiene
• Would forms A, C, and D contribute significantly?
a. yes b. no
This would be one explanation for the low degree of delocalization in dienes.
A B C
D
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• Slides 8 9 and 12 pertain to the questions on slides 10 and 11.
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SpectroscopyUltraviolet-Visible (UV-Vis)
• Many organic compounds absorb light at wavelengths below 300 nm.
• e.g. ethylene, - * transition, E = 173
kcal/mole, = 165 nm
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SpectroscopyUltraviolet-Visible (UV-Vis)
• As conjugation is extended, what is happening to the the HOMO-LUMO energy gap?
a. increases b. decreases c. nothing
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SpectroscopyUltraviolet-Visible (UV-Vis)
• As conjugation is extended, what will happen to the wavelength of absorption increases?
a. increases b. decreases c. nothing
• (E = hc/)
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165 217 251 304
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Reactions of Conjugated Compounds Dienes: 1,2- vs. 1,4-Addition
• Which ion is more likely to form and why?
H BrC
HH
H
H
H
CH
H
H
+
vs.
A B
A
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Reactions of Conjugated Compounds Dienes: 1,2- vs. 1,4-Addition
• The numbering in this case has nothing to do with nomenclature. Instead the numbering indicates where the “pieces” of the electrophile attached.
• Which alkene would be more stable, the 1,2 or 1,4
addition product?
a. 1,2 addition product b. 1,4 addition product
c. neither
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Reactions of Conjugated Compounds Dienes: 1,2- vs. 1,4-Addition
• Which C would be expected to have more partial positive charge?
a. Y b. Z c. neither
(Y)
(Z)
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Reactions of Conjugated Compounds Dienes: 1,2- vs. 1,4-Addition
• Which product will form faster?
a. 1,2 addition product
b. 1,4 addition product
c. neither
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Diels-Alder Reaction
• Could another product have formed?
a. yes b. no
OO
+150º
O
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Diels-Alder Reaction
• Diels-Alder reaction : addition of dienophile to diene is syn or anti? a. syn b. anti c. both d.neither
CO2CH3
H3CO2C
CO2CH3
CO2CH3
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Diels-Alder Reaction
• Can the reaction occur in the s-trans conformation? a. yes b. no
+ ?
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• How many isoprene units are present in nepetalactone?
O
O
CH3
CH3H
H
2
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• Predict the major product of
the following reaction. Cl2low temperature
a. b. c. d. e.Cl
Cl
Cl
Cl
Cl Cl
Cl
Cl
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What is the major product for the following reaction?
a. b. c. d. e.
R1
+
O
O
R2
R1O
O
H
H
R2
R1O
O R2
H
H
O
O
R1
R2
H
H
O
O
R1
R2
H
H
O
O
R1
R2
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Which of the following is not a p molecular
orbital if 1,3-butadiene?
a. b. c.
d. e.
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Which p molecular orbital reduces the p bonding character between C2 and C3 of 1,3-butadiene (and is still a bonding
MO)?
a. b. c.
d. e.