Organic Chemistry

669

The three chaptersin Part Six focus on

the reactions of compounds that contain a

carbonyl group. Carbonyl compounds can

be placed in one of two classes: those that

contain a group that can be replaced by an-

other group (Class I) and those that do not

contain a group that can be replaced by an-

other group (Class II).

Class I carbonyl compounds undergo nucleophilic acyl
substitutionreactions. These reactions are discussed in
Chapter 17, where you will see that all Class I carbonyl
compounds react with nucleophiles in the same way—
they form an unstable tetrahedral intermediate that col-
lapses by eliminating the weakest base. So all you need to
know to determine the product of a reaction—or even
whether a reaction will occur—is the relative basicity of
the groups in the tetrahedral intermediate.

The first part of Chapter 18compares Class I and Class
II carbonyl compounds by discussing their reactions with
good nucleophiles—carbon nucleophiles and hydride
ion. You will see that while Class I carbonyl compounds
undergo nucleophilic acyl substitution reactions with
these nucleophiles, Class II carbonyl compounds undergo
nucleophilic acyl additionreactions. The chapter goes on
to discuss the reactions of Class II carbonyl compounds
with poorer nucleophiles—nitrogen and oxygen nucle-
ophiles. You will see that Class II carbonyl compounds
undergo nucleophilic addition–eliminationreactions with
these nucleophiles, forming unstable tetrahedral interme-
diates that preferentially eliminate the weakest base. In
other words, what you learned about the partitioning of
tetrahedral intermediates formed by Class I carbonyl
compounds is revisited with Class II carbonyl com-
pounds. The reactions of Class I and
Class II carbonyl compounds is also discussed.

Many carbonyl compounds have two sites of reactivity:
the carbonyl group andthe Chapter 17 and
Chapter 18 discuss the reactions of carbonyl compounds
that take place at the carbonyl group. Chapter 19exam-
ines the reactions of carbonyl compounds that take place
at the

You have seen a variety of redox reactions in previous
chapters. Chapter 20introduces you to more redox re-
actions. Chapter 21extends the coverage of amines that
has been presented in earlier chapters and discusses the
chemistry of heterocyclic compounds

a-carbon.

a-carbon.

a,b-unsaturated

Carbonyl

Compounds

and Amines

PA R T S I X

Chapter 17

Carbonyl Compounds I:

Nucleophilic Acyl Substitution

Chapter 18

Carbonyl Compounds II:

Nucleophilic Acyl Addition,

Nucleophilic Acyl Substitution,

and Nucleophilic Addition–

Elimination • Reactions of

-Unsaturated Carbonyl

Compounds

Chapter 19

Carbonyl Compounds III:

Reactions at the -Carbon

Chapter 20

More About Oxidation–

Reduction Reactions

Chapter 21

More About Amines •

Heterocyclic Compounds

a

a,b