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Hofmann rearrangement In the Hoffmann ...

Hofmann rearrangement
In the Hoffmann rearrangement an unsubstituted amide is treated with sodium hydroxide and bromine to give a primary amine that has one carbon lesser than starting amide.
`R-oversetoverset(O)(||)C-NH_2+NaOH+Br_2toR-N=underset("isocyanate")(C=O)overset("hydrolysis")toR-NH_2`
Mech :

If the migrating group is chiral then its configuration is retained . Electron releasing effects in the migrating group increases reactivity of Hofmann rearrangement.
`H_3C-H_2C-undersetundersetunderset((R))(CH_3)(|)overset(**)CH-oversetoverset(O)(||)C-NH_2+CH_3-CH_2-undersetundersetunderset((S))(CH_3)(|)oversetoverset(D)(|)C-oversetoverset(O)(||)C-overset(15)(NH_2)overset(Br_2//KOH)to`Products

A

B

C

D

B & C both are correct

Text Solution

Verified by Experts

The correct Answer is:
B
In Hofmann rearrangement configuration of central atom remain uncharged as the rearragement is through cross over.
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Hofmann rearrangement In the Hofmann rearrangement an unsubstituted amide is treated with sodium hydroxide and bromide to give a primary amine that has one carbon lesser than starting amide. In the migrating group is chiral then is configuration is retained. Electron releasing effects in the migrating group increases reactivity of Hofmann rearrangement. Arrange the following amides according to their relative when reacted with Br_(2) in excess of strong base :

PhCH_(2)-overset(CH_(3))overset(|)(CH)-CH_(2)-overset(O)overset(||)C-NH_(2)overset(Br_(2),NaOH)toX, X is

CH_(3)-overset(O)overset(||)(C)-CH_(2)-Br

Me-overset(O)overset(||)C-O-CH_(2)-CH_(2)-overset(o+)NH_(2)overset(NaOH)rarr Q

CH_(3)-overset(O)overset(||)(C)-CH_(2)-underset(CH_(3))underset(|)overset(CH_(3))overset(|)(C)-CHOoverset(KOH,H_(2)O)to(A) , product A is

Knowledge Check

  • Hofmann rearrangement In the Hoffmann rearrangement an unsubstituted amide is treated with sodium hydroxide and bromine to give a primary amine that has one carbon lesser than starting amide. R-oversetoverset(O)(||)C-NH_2+NaOH+Br_2toR-N=underset("isocyanate")(C=O)overset("hydrolysis")toR-NH_2 Mech : If the migrating group is chiral then its configuration is retained . Electron releasing effects in the migrating group increases reactivity of Hofmann rearrangement. Which of the following compound cannot give Hofmann rearrangement :

    A
    B
    `CH_3-CH_2-oversetoverset(O)(||)C-NH-Ph`
    C
    D
    `Ph-oversetoverset(O)(||)C-NH_2`

  • Hofmann rearrangement In the Hoffmann rearrangement an unsubstituted amide is treated with sodium hydroxide and bromine to give a primary amine that has one carbon lesser than starting amide. R-oversetoverset(O)(||)C-NH_2+NaOH+Br_2toR-N=underset("isocyanate")(C=O)overset("hydrolysis")toR-NH_2 Mech : If the migrating group is chiral then its configuration is retained . Electron releasing effects in the migrating group increases reactivity of Hofmann rearrangement. Arrange the following amides according to their relative reactivity when react with Br_2 in excess of strong base

    A
    IVgtIgtIIgtIII
    B
    IIgtIgtIIIgtIV
    C
    IIgtIVgtIIIgtI
    D
    IIgtIgtIVgtIII

  • Hofmann rearrangement In the Hofmann rearrangement an unsubstitued amide is treated with sodium hydroxide and bromine to give a primary amine that has one carbon lesser than starting amide. Gneral reaction: If the migrating group is chiral then its configuration is retained. Electron releasing effects in the migrating group increase reactivity of Hofmann rearangement. Arrange the following amides according to their relative reactivity when reacted with Br_(2) in excess of strong base:

    A
    `IV gt I gt II gt III`
    B
    `II gt I gt III gt IV`
    C
    `II gt IV gt III gt I`
    D
    `II gt I gt IV gt III`
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