Chemistry Reference
In-Depth Information
8. Addition reactions and conjugate addition reactions, to be discussed in Chapter 7, are
related to S
N
2 and S
N
2
0
reactions, respectively. We can make these comparisons if we
recognize that the carbonyl double bond contains a leaving group. Specifically, if a
nucleophile adds to the carbon of a carbonyl, the carbonyl double bond becomes a
carbon-oxygen single bond with a negative charge residing on the oxygen.
Additionally, the trigonal-planar geometry of the carbonyl carbon is converted to tetra-
hedral geometry. With these points in mind, predict the products of the following reac-
tions and explain your answers. For Problem 8(b), the nucleophile is a methyl anion
associated with the illustrated cuprate.
The first stage of this reaction is deprotonation of acetone by LDA in a manner ana-
logous to that demonstrated in Problem 7(i).
The second stage of the reaction is addition of the acetone anion to formaldehyde as
shown below.
Protonation of the resulting alkoxide anion leads to the alcohol illustrated below.
This reaction is known as an aldol condensation.
The copper-based reagent shown in the above reaction is known as a cuprate. This
specific compound is dimethyl lithiocuprate and is an excellent carrier of methyl
