20 Characteristics of Enols And Enolates answers Characteristics of... · Keto-Enol Tautomers Of...
15
©Kevin Burgess, May 3, 2017 1 Characteristics Of Enols and Enolates from chapter(s) _____ in the recommended text A. Introduction B. Enols Form Under Acidic Conditions Mechanism Of Formation protonation enol. O +H + H -H + protonated carbonyl enol form + OH H OH O +H + H -H + protonated carbonyl enol form + OH H OH Ph O +H + -H + enol Ph + OH Ph OH
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Transcript of 20 Characteristics of Enols And Enolates answers Characteristics of... · Keto-Enol Tautomers Of...
©Kevin Burgess, May 3, 2017 1
CharacteristicsOfEnolsandEnolatesfrom chapter(s) _____ in the recommended text
A. Introduction
B. Enols Form Under Acidic Conditions MechanismOfFormationprotonation enol.
O +H+
H
-H+
protonated carbonyl enol form
+OH
H
OH
O +H+
H
-H+
protonated carbonyl enol form
+OH
H
OH
Ph
O +H+ -H+
enol
Ph
+OH
Ph
OH
©Kevin Burgess, May 3, 2017 2
O OH2-H3O+H+
+OH OH
H
©Kevin Burgess, May 3, 2017 3
DeuteriumExchangedeuterons.
tBu
O +D+ -H+
deuterated carbonyl enol form
tBu
+OD
tBu
O
H
D
D+
+D+, -D+
deuterated product
tBu
O
D
O +D+ -H++OD
H
OD
D+
+D+, -D+ O
D
©Kevin Burgess, May 3, 2017 4
tautomerism;
Ph
O +D+ -H+
O-deuterated carbonyl O-deuterated enol
Ph
+OD
Ph
OD
+D+, -D+
C-deuterated ketone
+D+ -H+
O-deuterated carbonyl
Ph
O
DPh
+OD
D
enol form
+D+, -D+
dideuterated ketone
Ph
OD
DPh
O
D D
O O
CHCl2
O O O O O O O
O
©Kevin Burgess, May 3, 2017 5
EnolsOf1,2-And1,3-DicarbonylCompoundsketo form 106 : 1. enol
reason: Enolization of 1,3-cyclohexanedione forms conjugation between carbonyl and C=C which is
stabilized by resonance, while the acetone does not have resonance effect.
reason: Compared to acetone, one carbonyl group in the 2,3-butanedione acts as electron withdrawing
group that enhances acidity of a-H.
.
O+H+ -H+
protonated carbonyl enol form
O +OHO OHO
O
O
+H+ -H+ O
OH
O
+OH
©Kevin Burgess, May 3, 2017 6
conjugates
In the print the question above right will be changed to the following:
OOO
O
O
OH
O OH
N+O-
OOO
O
O
O
O
OH
N+O-
OOH
OO
O O
OHO
H
O O
OOOO
O O
HOH
OH
NO O O
OH
N OH
O
N
best second best
©Kevin Burgess, May 3, 2017 7
O O
HOH NO O O N
©Kevin Burgess, May 3, 2017 8
EnolsOfOtherCarbonylCompounds
O
O OH2-H3O+H+
O
+OH
H
H2O
O
OH
OH2-H3O+H+
NMe2
O
NMe2
+OH
H
H2O
NMe2
OH
O
OOOH2-H3O+H+
O
+OHO
HO
OOH
HO
O OH2-H3O+H+
HO
+OH
HHO
OH
©Kevin Burgess, May 3, 2017 9
Keto-EnolTautomersOfOtherCompoundTypes
incorrect they are not resonance structures.
SMe
O
NH
enol keto
SMe
OH
N
OH OOH
keto keto
O OO
NH
O N
SH
enol keto
N OH N
S
OH
O
N+OH
O-
keto enol
N+O
O-OH
OH
©Kevin Burgess, May 3, 2017 10
C. Enolates Form Under Basic Conditions MechanismOfFormation
H OEt
OHO- +
enolate enol
H OH
-HO-OEt
O-
OEt
OH
H OMe
OMeO- +
H OH
-HO-OMe
O-
OMe
OH
H OMe
ONa+ H- +
H OH
-HO-OMe
O-
OMe
OH
H CNNa+ NH2- +
Ph
H OH
-HO-
Ph
N-
Ph
NH
©Kevin Burgess, May 3, 2017 11
ResonanceStructuresOfEnolates
HNa+ NH2- +
Ph
O
NMe2
H OH
-HO-Ph
O-
NMe2Ph
OH
NMe2
N
O- O
O-N
O-
O
O-
CO2Me
O-
N-CO2Me
O-
N
-
O
O
-
O
O
O-O
O
O-O
©Kevin Burgess, May 3, 2017 12
more more It is not easy N-anions.
D. Effects Of Enolization Racemization
N+O-
O
-
O
Ph N+O-
O-O
Ph N+O-
O-O
Ph
optically active
Ph
O
Ph
OH
achiral
Ph
O
Ph
OH
Ph
OOMe
optically active
Ph
OHOMe
H2N NH2
O
NH2
O
NH
O
NH
O
O
©Kevin Burgess, May 3, 2017 13
can racemize
DoubleBondMigration Migration
Ph
OOMe
optically active
Ph
OHOMe
enol
H+ H+
O
OH
O
OH
ibuprofen
OH
OH
enol
Ph
O
keto
Ph
O
Ph
OH
H+
©Kevin Burgess, May 3, 2017 14
enol
O
keto
OH O
enol enol
O OH OH
keto enol
O OH
©Kevin Burgess, May 3, 2017 15
O O
OHHO
HO
HO H
keto
H+
β
O O
OHO
HO
HO
β
enol
HOOH
OH
OH
OHO
H+
glucose
HOOH
OH
OH
OHOH
HOOH
OH
OH
OOH
H+
fructose
