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Solutions for Condensations and Alpha Substitutions of Carbonyl Compounds
3 (f) continued
O
CH2
C
O
CH2
HH
O
CH2
H
C
O
H
H
C
O
H
H
O
H
H
4
(a) Sodium ethoxide is not a strong enough base to deprotonate cyclohexanone more than a tiny amount:
CH2
O
+ NaOEt CH
O
+ HOEt
Na+
pKa ≈ 16
pKa ≈ 20
A difference of 4 pKa units means 
an equilibrium constant of ≈ 10–4, 
meaning 0.01% of the 
cyclohexanone is deprotonated.
Since ≈ 99.99% of the NaOEt is still present when benzyl bromide is added, these two react by Williamson 
ether synthesis. Unreacted cyclohexanone will remain in the reaction solution.
CH2Br + NaOEt CH2OCH2CH3 + NaBr
(b) Two changes are needed to make the desired reaction feasible: (1) use a strong, non-nucleophilic base 
such as LDA that will completely deprotonate cyclohexanone, and (2) use an aprotic solvent such as THF 
or diethyl ether so that cyclohexanone cannot find a proton from solvent. These conditions will work fine.
O O CH2CH3
O
CH3CH2
O CH3
(b)
5 New carbon-carbon bonds are shown in bold.
(a) (c)
+
minor major
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