Organic Chemistry

632 CHAPTER 16 Reactions of Substituted Benzenes

Table 16.1 The Effects of Substituents on the Reactivity of a Benzene Ring

Toward Electrophilic Substitution

NH 2

NHR

NR 2

OH

OR

NHCR

O

OCR

R

Ar

CH CHR

H

Activating substituents Most activating

Strongly

activating

Ortho/para

directing

Moderately

activating

Weakly

activating

Weakly

deactivating

Strongly

deactivating

Moderately

deactivating

Standard of comparison

F

Cl

Br

I

Deactivating substituents

O

CH

O

CR

O

COR

O

COH

O

CCl

CN

SO 3 H

NR 3

NO 2

Most deactivating

O

NH 2 R

+

Meta directing

NHR 2

+

NH 3

+

+

The moderately activating substituentsalso donate electrons into the ring by reso-

nance and withdraw electrons from the ring inductively. Because they are only moder-

ately activating, we know that they donate electrons into the ring by resonance less

effectively than do the strongly activating substituents.