Review Of Organic Chemistry Page 31
ADVERTISEMENT
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34Organic Chemistry I Review: Highlights of Key Reactions, Mechanisms, and Principles
31
Donor
The Situation with an Electron
/Cation Stabilizer (Ortho-Para Director) (Section 17-6)
E
H
E
Ortho
H
E
H
Boxed form is especially good
D
D
Addition
D
electronically.
Relative to a
Ortho addition often has some steric
Donor
destabilization.
E
E
E
Meta
D
D
D
None of the three resonance forms
Addition
H
benefits from the electron donor.
H
H
with a
Donor
D
D
D
Para
Boxed resonance form
Addition
E
is especially benefitted
E
E
Relative to a
electronically.
Donor
H
H
H
Summary: Electronic Factor: An electron donor (cation stabilizer) is especially beneficial
electronically when the electrophile adds ortho or para relative to the donor.
Thus donors are ortho/para directors.
Steric Factor: Ortho addition relative to the donor is always destabilized somewhat by steric
interactions. Thus, when addition para relative to the donor does not involve any steric
interactions, (usually but not always the case), para addition is faster than ortho addition.
Withdrawer
The Situation with an Electron
/Cation Stabilizer (Ortho-Para Director) (12.13)
E
H
E
H
E
Ortho
H
W
W
Addition
W
Boxed form is especially bad
Relative to a
electronically.
Withdrawer
E
E
E
Meta
None of the three resonance forms
W
W
W
Addition
suffers badly from the electron
H
H
H
Relative to a
donor.
Withdrawer
W
Para
W
W
Addition
Boxed form is especially bad
E
E
E
Relative to a
electronically.
Withdrawer
H
H
H
Summary: An electron withdrawer (cation destabilizer) is especially harmful electronically
when the electrophile adds ortho or para relative to the withdrawer. Thus withdrawers are meta
directors. Not because meta is that good; it’s just not as bad as ortho or para.
Note: Meta is still deactivated somewhat, it’s just not as slow as ortho or para addition.
ADVERTISEMENT
0 votes
Related Articles
Related forms
Related Categories
Parent category: Education