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Chapter 17 591
Copyright © 2017 Pearson Education, Inc.
85.
The benzoin condensation requires the aldehyde hydrogen to be removed. This hydrogen cannot be
removed unless the electrons left behind can be delocalized onto an electronegative atom. The nitrogen of
the cyano group serves that purpose. Therefore, the reaction will not occur if hydroxide ion is used instead
of cyanide ion because the electrons left behind if the hydrogen were to be removed cannot be delocalized.
C H
O
+
C N
−
C H
C
−
CH
3
O
−
H
C H
C
O
+
CH
3
O
−
C
C
O
−
CH
O
C CH
O
C
O
H
C CH
O OH
+
C N
−
N
N
N
N
−
86.
To arrive at the final product, three equivalents of malonyl thioester are needed. (See page 840 in the text.)
Because only one acetate ion was used, only one carbon is labeled in the product.
*
+ 3
CH
3
C
SR
C
SR
O
_
O
O
C
O
* CH
3
SR
C
O
C
O
C
O
C
O
OH
HO
CH
3
O
OH
OH
HO
HO
CH
3
O
SR
O
O
O
CH
3
SR
O
O
O
CH
3
SR
HCl
H
2
O
tautomerization
H
2
SO
4