14: Substituent Effects

(9/94)(11,12/96)(11,12/04,01/05) Neuman Chapter 14
Table 14.15. Approximate Relative Reactivity and Directive Effects
of Various Substituents (S)
S Reactivity Directive Effect
(Reactivity Order)
O - (most reactive) Activator o,p
NR2 A o,p
O R A o,p
NH(C=O)R* A o,p
OC(=O)R* A o,p
CR3 A o,p
Ar A o,p
(H) - -
F, I Deactivator o,p
Br, Cl D o,p
CCl3 D m
C(=O)NH2* D m
C(=O)OR* D m
C(=O)R D m
SO3H D m
C≡N D m
CF3 D m
NO2 D m
NR3 + (least reactive) D m
Figure 14.37 [next page] is a graphical summary of the reactivity and directive effects of
substituents shown in Table 14.15.
In order to make it less complicated, we have gathered substituents together into general
groups. For example, NR2 also includes NH(C=O)R, OR includes OC(=O)R, C(=O)Y
includes C(=O)NH2, C(=O)OR, and C(=O)R, while F, Cl, Br, and I are designated X.
CH2-Y Groups. We see a delicate balance between I and R effects on reactivity and product
distribution in rate and product data for electrophilic substitution on benzene rings with various S
= CH2Y (Table 14.16).
Table 14.16. Electrophilic Substitution on Some Substituted Benzenes (S = CH2-Y).
CH2-Y kS/kH %-o %-p %-o + %-p %-m
CH2-H 25 56 41 97 3
CH2-OCH3 6 51 42 93 7
CH2-Cl 0.7 34 52 86 14
CH2-C≡N 0.3 24 56 80 20
CH2-NO2 0.1 22 23 45 55
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