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©Kevin Burgess, April 10, 2017 1 Ester Hydrolysis And Transesterification from chapter(s) _____________ in the recommended text A. Introduction
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Transcript of from chapter(s) in the recommended text - Inquisition … Ester...from chapter(s) _____ in the...
©Kevin Burgess, April 10, 2017 1
EsterHydrolysisAndTransesterificationfrom chapter(s) _____________ in the recommended text
A. Introduction
©Kevin Burgess, April 10, 2017 2
B. Reactivity less less do not more more unlikely.
are not
C. Acid-mediated Hydrolysis
O
O+
O
O+
+H2NH+
H
H2N-H+
O
O H+
OHH
H2O HO O+HH
OO
+OH
O+
HO OH
H
-H+, +H+ -HOMe
-H+
OH
+OH
OH
O
©Kevin Burgess, April 10, 2017 3
carboxylic acids water.
O
O+
H3O+
OH
OHOMe
O
O+
H3O+OH
O
HOMe
O PhO
+H3O+
OH
OHOPh
O Ph
O+
H3O+
HO Ph
OHOEt
©Kevin Burgess, April 10, 2017 4
reversible,
O
O H3O+
OH
O
HO
H3O+
OO
OO
OOH
OHO + 2 HOEt
H+HOOH
O+ O
O
OHClHO+
O
H+
OCl
O
©Kevin Burgess, April 10, 2017 5
HO+OHOH
O
O excess
H+
OO
O
O
+HO
excessOH
AcOHH+
O O
OO
OH
O
OH
H+
O
O
H+HO OH
O
O
O
©Kevin Burgess, April 10, 2017 6
O
O
OH
O
HO+
O OO
OOH
O
HO OH+
excess
OO
OHO
OH
Ph O
O
HO
O
+Ph OH
©Kevin Burgess, April 10, 2017 7
possibilities: forming a five-membered ring is more favorable than three- or four-membered ring due to
ring strain of sp3 carbons.
HydrolysisOftert-ButylEstersOccursViaADifferentMechanism stable without
O O
O O
HO OH
O O+
HO OH
O
OHO
HOOH
OHO
HOOH
O
O H+tBu ++O
+OtBu
H
OH
O
©Kevin Burgess, April 10, 2017 8
carbocation.
H+-H+Nu-
HNu
MeCOOtBuH+ H+
H2NO
OtBu
alanine
MeCOOH H2NO
OH
H+ TFA
glycine
tert-butylglycineCOOtBu
OH
lactic acid
COOH
OHH2N OH
O
H+H2N
O
OtBu
valine
H+H2N
O
OtBu
leucine
H2NO
OH H3+NO
O-
©Kevin Burgess, April 10, 2017 9
D. Base-mediated Hydrolysis Mechanism
irreversible reversible.
O OMeO
3
O
O
2
O
O
4OMe
O
O
5
O
O
1
O
O
6OMeNO2
OMe
NO2
NO2
O
O-OH
O
-O OHO H
O
-O++
O-
OO+ H
©Kevin Burgess, April 10, 2017 10
likely.
unlikely.
unlikely.
O
O-OH
O
-O OH H+
O+
-O OH
H
OH
O
HO+
O HO
-OH+O-
OOH+ H
O HO
-OH+OH
-O OH
OH
-O ORO R
O-OH+
©Kevin Burgess, April 10, 2017 11
Et OPh
O -OH+Et OPh
-O OHEt OH
OHOPh
+ HOBnOH
-O OBn (i) -OBn
(ii) -H+/+H+
HO-
OBn
O
OH
O
©Kevin Burgess, April 10, 2017 12
18O
would not
would not
can
soaps
O
O-OH+
O-
O
HO+
O
O-OH+
O-
O OH+
O
O
O-
O+ +
HO-
O-
O+
OH
O OO
O
OO
+NaOH
H2OHO OH
OH+ Na+ O-
O3
©Kevin Burgess, April 10, 2017 13
are: Particles that aggregate in the solution with the hydrophilic "head" regions in contact with
surrounding solvent and the hydrophobic single-tail regions are in the micelle center.
NaOH
H2O
OAc
OCOnPr
OCOnBu
OH
OH
OH
+ +Na-O
O
+Na-O nPr
O+Na-O nBu
O
NaOH
H2O
O
O
O
O
O
O ( )11
( )21
OH
OH
OH
+ +Na-O
O
+Na-O
O+Na-O
O
( )11
( )21
cartoon of a micelle
©Kevin Burgess, April 10, 2017 14
E. Transesterification Reactions MechanismUnderAcidicConditionsanother ester.
O
OH++ OH
EtO
+OH OHO
+OEtH
+H+
OEtHO O+
H-H+ OHO
OEt
HO+ O++ H
H
OEt
+O H
OEt
O
©Kevin Burgess, April 10, 2017 15
ExamplesOfTransesterificationsalkoxide
HO+O
O H+HO+O
O
HO+Ph O
O H+HO+Ph O
O
OHO
OH+
O
O
HO
O O
O O+ EtOH
H+O O
O O+ MeOH
©Kevin Burgess, April 10, 2017 16
+ EtOHO O
O O H+
O
O+ HO OH
OO
HO
O
check by assigning (R)- or (S)-configurations
H+
cat. H2OO
O
O
OH(S) (S)
(S)
(S)
OMe
OOEt
O
EtOHH+
MeOHH+
OEt
OOMe
O
Et17OHH+
OEt
OOH
AcOMeH+
MeOH AcOHOMe
OO
O
©Kevin Burgess, April 10, 2017 17
MechanismUnderBasicConditionsalkoxides.
ExamplesOfBase-MediatedTransesterifications
O
Cl OMe-OMe
-O ClOMe
O+ Cl-+
O
OMe-OEt
show arrows
OEt
-O OMeOEt
O+ -OMe
-OEt
HOEt
CO2Me
MeO OMe
O O -OEt
HOEt
CO2Et
EtO OEt
O O
-OMe
HOMe
-OEt
HOEtHCOOBn
O
OnBuHCOOMe
O
OEt
©Kevin Burgess, April 10, 2017 18
more sp3- would not
F. Ester Hydrolyses In Biochemistry InTheCentralNervousSystemesterases. acetylcholinesterase. acetylcholine receptors choline. ACHE paralysis. nerve gases.
©Kevin Burgess, April 10, 2017 19
InTheDigestiveSystemlong chain alkyl groups triglyceride catalysts. neutral nucleophiles electrophiles. can metabolism of triglycerides transesterifications. lipases.
