Logo Passei Direto
Buscar
Material
páginas com resultados encontrados.
páginas com resultados encontrados.
left-side-bubbles-backgroundright-side-bubbles-background

Crie sua conta grátis para liberar esse material. 🤩

Já tem uma conta?

Ao continuar, você aceita os Termos de Uso e Política de Privacidade

Prévia do material em texto

Solutions for Amines
OCH3Cl
N
NH2
Br
HC
N
NH2N
C
N
Cl OCH3
H
N
Br
NH2
OCH3
N
C
N
Cl OCH3
H
CH
N
Br
NH2
OCH3
NH2
N Br
N
Cl
GOOD
– Cl–
13 The middle resonance form demonstrates how the negative charge is distributed onto the more 
electronegative nitrogen atom.
14
(a)
GOOD
– Br–
C
N
NH2
N
C NH2
H
NH2
H
N
H
NH2
N
NH3
NH3 NH3
NH2
N
C
NH2
N
NH2
NH2
NH2
N
H
Br
H
N
(b)
+
+
This is a benzyne-type mechanism. (For simplicity above, two steps of benzyne generation are shown as 
one step: first, a proton is abstracted by amide anion, followed by loss of bromide.) Amide ion is a strong 
enough base to remove a proton from 3-bromopyridine as it does from a halobenzene. Once a benzyne is 
generated (two possibilities), the amide ion reacts quickly, forming a mixture of products. 
Why does the 3-bromo follow this extreme mechanism while the 2-bromo reacts smoothly by the addition- 
elimination mechanism? Stability of the intermediate! Negative charge on the electronegative nitrogen 
makes for a more stable intermediate in the 2-bromo substitution. No such stabilization is possible in the 3-
bromo case.
stabilized by induction 
from nitrogen
Amide ion will not attack at C-2 
because the anion at C-3 is not as 
stable as the anion at C-2.
two steps
two steps
456

Mais conteúdos dessa disciplina