Both m-bromoanisole on reaction with sodamine and liquied ammonia
Answers
explanation:
These are the reaction conditions for generating benzyne intermediates.
The reaction of ortho-bromoanisole with potassium amide in liquid ammonia (b. p. -33 °C) is extremely rapid.
Step 1. The amide ion attacks the
H
atom that is ortho to
C3
, generating a carbanion.
Step 1
Step 1
Step 2. Loss of
Br
-
to form a benzyne intermediate.
Step 2
Step 2
The elimination is by an E2cb pathway.
Step 3. Addition of
NH
-
2
The strain caused by a triple bond in a benzene ring can be relieved by a nucleophilic addition (
Ad
N
) of
NH
-
2
.
The methoxy group is electron-withdrawing by induction, so the nucleophile will attack
C3
to place the carbanion as close as possible to the methoxy group.
Step 3
Step 3
Step 4. Protonation of the carbanion.
Step 4
Step 4
The product is meta-methoxyaniline.
para-Bromoanisole
The reaction with para-bromoanisole also follows a benzyne mechanism.
Step 5
Step 5
The nucleophile can attack either end of the triple bond, and the methoxy group is far enough away that its inductive effects are minimal.
Step 6
Step 6
The product is a mixture of para- and meta-methoxyaniline.
Related questions
Why is the product of the addition of
C
l
2
to trans-2-butene a meso compound?
xplanation:
These are the reaction conditions for generating benzyne intermediates.
The reaction of ortho-bromoanisole with potassium amide in liquid ammonia (b. p. -33 °C) is extremely rapid.
Step 1. The amide ion attacks the
H
atom that is ortho to
C3
, generating a carbanion.
Step 1
Step 1
Step 2. Loss of
Br
-
to form a benzyne intermediate.
Step 2
Step 2
The elimination is by an E2cb pathway.
Step 3. Addition of
NH
-
2
The strain caused by a triple bond in a benzene ring can be relieved by a nucleophilic addition (
Ad
N
) of
NH
-
2
.
The methoxy group is electron-withdrawing by induction, so the nucleophile will attack
C3
to place the carbanion as close as possible to the methoxy group.
Step 3
Step 3
Step 4. Protonation of the carbanion.
Step 4
Step 4
The product is meta-methoxyaniline.
para-Bromoanisole
The reaction with para-bromoanisole also follows a benzyne mechanism.
Step 5
Step 5
The nucleophile can attack either end of the triple bond, and the methoxy group is far enough away that its inductive effects are minimal.
Step 6
Step 6
The product is a mixture of para- and meta-methoxyaniline.
Related questions
Why is the product of the addition of
C
l
2
to trans-2-butene a meso compound?