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Solutions for Carboxylic Acids
12 (c) All steps are reversible, which is the reason the Principle of Microscopic Reversibility applies. 
Applying the steps as outlined on the previous page (abbreviating OCH2CH3 as OEt):
Step A proton on (resonance stabilization)
Step B nucleophile attacks
Step C proton off
Step D proton on
Step E leaving group leaves (resonance stabilization)
Step F proton off
C
OEt
O
H A is the acid catalyst
A is the conjugate base, although in
hydrolysis reactions, water usually removes H+.
H A
C
OEt
O H
C
OEt
O H
H
C C
OEt
O H
HC
C
OEt
O H
CH
C
OEt
O H
C
OEt
O H
C
OEt
O H
OH2 C
O H
OEt
O
H
H
OH2 C
O H
OEt
O
H
Step A
Step B Step C
H O
H
H
C
O H
O
O
HStep E
H
– EtOH
Step D
C
OH
O
Hsame series
of resonance
forms as above
Step F OH2
C
OH
O
The resonance forms with positive charge on the 
benzene ring are usually omitted. However, they 
still stabilize the (+) charge by delocalization, 
even though we may not draw them.
Et
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