Functional Classes II, Reactions - Organic Chemistry Concepts: An EFL Approach - page 117

FIGURE 7.23
Oxidation of 1°, 2°, and 3° alcohols.
FIGURE 7.24
Ether cleavage.
7.7 ALDEHYDES AND KETONES
In Chapter 2, the dipolar nature of the carbonyl group was shown as an elec-
trophilic carbon and a nucleophilic oxygen. Because the carbonyl group has a
double bond, addition is a major reaction type.
In Chapter 6, the carbonyl group was shown to increase the acidity of any hydro-
gens on the α-carbon atom. This allows the formation of a resonance-stabilized
enolate carbanion, and gives a second pathway for the reaction of aldehydes
and ketones.
7.7.1 Nucleophilic Addition
The carbonyl dipole controls the initial reaction site. As Figure 7.25 shows, the
reaction usually starts with nucleophilic attack at the electrophilic carbonyl car-
bon. Therefore, the process is called nucleophilic addition. Compare this with
the electrophilic addition reactions of alkenes in which the initial attack was by
the C ] C on an electrophile.