Hofman degradation application

2009-01-07 1:32 am

1.Can anyone tell me that whether hoffman degradation can be applied to urea using Br2/OH- other than NaOCl/OH-?
###### O
###### | |
2. H2N-C - N - phenyl-(NO2)2 <-----------nitro group attached on 2,4
######### H

Is is possible for the above compound to undergo such reaction in
order to prepare 2,4-DNP ? If yes ,then , what reagent(s) can be used?

更新1:

1.Is it applicable to those compound like RCONHR and RCONR2 ,etc ? 2. Does only benzamide need to be heated in this degradation ???Also , how can we judge whether a certain compound should be heated?

回答 (1)

cheungwaito

2009-01-07 10:25 pm

✔ 最佳答案

1. i don't think it is possible.

the first step :
RCONH2 + Br2---> HBr + RCONHBr

since Cl2 has a higher dissociation energy, you may heat up the reactants.

2.not too possible for preparation of 2,4-DNP by hofmann rearrangement.

mecahnism:
1.RCONH2 + Br2---> HBr + RCONHBr
2.RCONHBr+ OH- ---->H2O + RCONBr-

3.rearrangement:
RCONBr- -------->Br- + R-N=C=O

4.hydrolysis
R-N=C=O------>CO2 + RNH2

in your case, during the third step,
RNHCONBr- -------->Br- + R-NH-N=C=O
requires high activation energy as the migration group is nitrogeneous compound

2009-01-08 20:35:49 補充：
2. every compound need to be heated
1. hofmann rearrangement only applicable to RCONH2

RCONHR or RCOHRR' can't do it

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